tag:blogger.com,1999:blog-65553640955868040462024-03-19T00:08:42.813-04:00BuildItsBen Katzhttp://www.blogger.com/profile/15816221191617788028noreply@blogger.comBlogger52125tag:blogger.com,1999:blog-6555364095586804046.post-67232424609637156462019-12-15T21:36:00.007-05:002022-04-20T19:27:21.526-04:00The Mini Cheetah RobotBack during my second year of undergrad I started scheming about building legged robots out of cheap hobby brushless motors. Two years later as a senior, I finally made a first-pass at building some of the hardware - <a href="https://build-its-inprogress.blogspot.com/2016/03/new-boards.html">motor controllers</a>, <a href="https://build-its-inprogress.blogspot.com/2016/02/planetary-gearboxes.html">gearboxes</a>, and a two-degree of freedom <a href="https://build-its-inprogress.blogspot.com/2016/05/slow-motion-jump.html">leg</a>. Things look promising, so I stayed at MIT to do a masters in <a href="http://biomimetics.mit.edu/">Sangbae's lab</a> continuing the project. The Mini Cheetah robot is the result of that work:<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgIAt_UpMWXTWrasIV_B8yPjwOQAxWPo6pgLlXQer9GpbQHO6xen9twk3R-o1-OkIEZiLbluthU21TWMyc1_Udio91eLiPmR1u3x6DjHAWaN2Y0iJCewisVZMDL6AsSLtNtxlIclYjY89U/s1600/cheetah_bv16_crop.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="1067" data-original-width="1600" height="426" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgIAt_UpMWXTWrasIV_B8yPjwOQAxWPo6pgLlXQer9GpbQHO6xen9twk3R-o1-OkIEZiLbluthU21TWMyc1_Udio91eLiPmR1u3x6DjHAWaN2Y0iJCewisVZMDL6AsSLtNtxlIclYjY89U/s640/cheetah_bv16_crop.jpg" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Photo: Bryce Vickmark</td></tr></tbody></table><div class="separator" style="clear: both; text-align: center;">
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The first version of the robot was put together in March 2018. I spent the summer after finishing my Masters helping get the robot fully up and running (literally). When we saw how well everything worked, we decided to build a <a href="https://www.youtube.com/watch?v=G6fMV1UPzkg&feature=emb_title">handful </a>more of the robots, both for our lab and to loan out to other research groups to experiment on. I spent about a year doing some design revisions and building <a href="https://build-its-inprogress.blogspot.com/2019/11/building-all-robots.html">10 more of the robots</a>.</div>
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The robot is probably best documented in my <a href="https://dspace.mit.edu/handle/1721.1/118671">masters thesis</a>, but there are also <a href="https://build-its-inprogress.blogspot.com/search/label/Mini%20Cheetah">several blog-posts</a> as well.</div><div><br /></div><div>Here are several papers (in no particular order) published about the robot or using it. I'll keep updating this list as I hear about more publications using the robot</div><br /><ul style="text-align: left;"><li><a href="https://ieeexplore.ieee.org/abstract/document/8793865/">Mini cheetah: A platform for pushing the limits of dynamic quadruped control</a></li><ul><li>Benjamin Katz, Jared Di Carlo, Sangbae Kim</li></ul><li><a href="https://arxiv.org/abs/1909.06586">Highly Dynamic Quadruped Locomotion via Whole-Body Impulse Control and Model Predictive Control</a></li><ul><li>Donghyun Kim, Jared Di Carlo, Benjamin Katz, Gerardo Bledt, Sangbae Kim</li></ul><li><a href="https://ieeexplore.ieee.org/abstract/document/9196777/">Vision aided dynamic exploration of unstructured terrain with a small-scale quadruped robot</a></li><ul><li>D Kim, D Carballo, J Di Carlo, B Katz, G Bledt, B Lim, S Kim</li></ul><li><a href="https://arxiv.org/abs/2006.08102">Hybrid Systems Differential Dynamic Programming for Whole-Body Motion Planning of Legged Robots</a></li><ul><li>He Li, Patrick M. Wensing</li></ul><li><a href="https://arxiv.org/abs/2010.08881">Model Hierarchy Predictive Control of Robotic Systems</a></li><ul><li>He Li, Robert J. Frei, Patrick M. Wensing</li></ul><li><a href="https://dspace.mit.edu/handle/1721.1/125485">Regularized predictive control framework for robust dynamic legged locomotion</a></li><ul><li>Bledt, Gerardo.</li></ul><li><a href="https://ieeexplore.ieee.org/document/9197488">Extracting Legged Locomotion Heuristics with Regularized Predictive Control</a></li><ul><li>Gerardo Bledt; Sangbae Kim</li></ul><li><a href="https://ieeexplore.ieee.org/abstract/document/9033976">Variational-Based Optimal Control of Underactuated Balancing for Dynamic Quadrupeds</a></li><ul><li>M Chignoli, PM Wensing </li></ul><li><a href="https://www.researchgate.net/publication/344892717_Robust_Autonomous_Navigation_of_a_Small-Scale_Quadruped_Robot_in_Real-World_Environments"> Robust Autonomous Navigation of a Small-Scale Quadruped Robot in Real-World Environments. </a></li><ul><li>Dudzik, Thomas & Chignoli, Matthew & Bledt, Gerardo & Lim, Bryan & Miller, Adam & Kim, Donghyun & Kim, Sangbae. </li></ul><li><a href="https://arxiv.org/abs/2202.05481">Concurrent Training of a Control Policy and a State Estimator for Dynamic and Robust Legged Locomotion</a></li><ul><li>Gwanghyeon Ji, Juhyeok Mun, Hyeongjun Kim, Jemin Hwangbo</li></ul><li><a href="https://arxiv.org/abs/2110.15344">Learning to Jump from Pixels</a></li><ul><li>Gabriel B. Margolis, Tao Chen, Kartik Paigwar, Xiang Fu, Donghyun Kim, Sangbae Kim, Pulkit Agrawa</li></ul><li><a href="https://sites.google.com/view/model-free-speed/">Agile Locomotion via Model-free Learning</a></li><ul><li>Gabriel Margolis*, Ge Yang*, Kartik Paigwar, Tao Chen, Pulkit Agrawal</li></ul></ul><div><br /></div>Ben Katzhttp://www.blogger.com/profile/15816221191617788028noreply@blogger.com3tag:blogger.com,1999:blog-6555364095586804046.post-76412718252425964282019-12-15T21:36:00.005-05:002021-07-28T20:30:10.259-04:00The Rubik's ContraptionJared Di Carlo and I built a machine that can solve a Rubik's cube really fast, and it became kind of internet-famous:<br />
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<a href="https://build-its-inprogress.blogspot.com/search/label/Rubik%27s%20Cube%20Solver">See my hardware and low-level control build-log here</a></div>
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and<a href="http://cactus-zone.blogspot.com/2018/03/rubiks-solver-software.html"> Jared's software blog here</a></div>
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Ben Katzhttp://www.blogger.com/profile/15816221191617788028noreply@blogger.com0tag:blogger.com,1999:blog-6555364095586804046.post-52888545246582543082019-12-15T21:36:00.001-05:002019-12-15T21:36:05.629-05:00Planar Magnetic HeadphonesI built a pair of planar magnetic headphones - basically just because I though the operating principle was interesting. After several catastrophically bad-sounding attempts, I eventually built a version that sounded decent and looks pretty good:<br />
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The drivers are meticulously hand-etched from the thinnest flex-pcb material I could find. The driver membrane is sandwiched between an arrangement of magnets embedded in the aluminum grill that makes up most of the structure of the headphones.<br />
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<a href="https://build-its-inprogress.blogspot.com/search/label/Planar%20Magnetic%20Headphones">See the build-log here for details</a>Ben Katzhttp://www.blogger.com/profile/15816221191617788028noreply@blogger.com0tag:blogger.com,1999:blog-6555364095586804046.post-90839507660239633172019-12-15T21:35:00.003-05:002019-12-15T21:35:50.433-05:00Furuta PendulumsIn the summer of 2016 I built a desktop <a href="https://en.wikipedia.org/wiki/Furuta_pendulum">furuta pendulum</a> out of random parts I had lying around:<br />
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Recently, I redesigned it to <i>not</i> be built out of scraps, sent out for all the machined parts, and assembled a handful more:<br />
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<a href="https://build-its-inprogress.blogspot.com/search/label/Pendulum">See the build logs here</a></div>
Ben Katzhttp://www.blogger.com/profile/15816221191617788028noreply@blogger.com4tag:blogger.com,1999:blog-6555364095586804046.post-60233357914689754832019-12-15T21:35:00.002-05:002019-12-15T21:35:41.826-05:00Motor DynamometerIn 2016 I built an electric motor dynamometer - a device for characterizing the performance of electric motors and motor controllers<br />
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The dynamometer is controlled by a <a href="https://github.com/bgkatz/Dyno-Software">Python and QT-based interface </a>which provides manual control of the torque, speed, voltage, and current, simulates loads, or runs through sequences of test points.<br />
The dyno lets me characterize electric motors to generate useful data like efficiency maps:<br /><br />
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<a href="https://build-its-inprogress.blogspot.com/search/label/Motor%20Dyno">See the build log here:</a>Ben Katzhttp://www.blogger.com/profile/15816221191617788028noreply@blogger.com0tag:blogger.com,1999:blog-6555364095586804046.post-18776206053891930232019-12-15T21:35:00.001-05:002019-12-15T21:35:29.488-05:00Machined Electric Travel UkuleleIn December 2015 (4 whole years ago!) I machined an electric ukulele out of some aluminum, stainless steel, and brass. The whole thing was built over the course of less than a week, with no computer aided design save for the fret-board.<div>
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It's a headless design with the tuners built into the body. Under the carbon fiber cover at the center is a home-made low profile pickup. The body was hand-shaped using a combination of a bandsaw, manual milling machine, and hand-filing.</div>
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<a href="https://build-its-inprogress.blogspot.com/search/label/Electric%20Ukulele">See here for the build-log</a></div>
Ben Katzhttp://www.blogger.com/profile/15816221191617788028noreply@blogger.com0tag:blogger.com,1999:blog-6555364095586804046.post-27449993862329735332015-12-21T15:15:00.003-05:002015-12-21T15:15:57.258-05:00Benchtop LatheAfter stumbling upon the bed, carriage, and tailstock from a <a href="http://www.taigtools.com/mlathe.html">Taig</a> lathe, I rebuilt the lathe, making all the parts I didn't have already. This includes new cross slide and compound slide, a new headstock and spindle with integrated taper for ER32 collets, and brushless spindle motor with a DC custom power supply.<br />
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<a href="http://build-its-inprogress.blogspot.com/search/label/Mini%20Lathe">Here's the build log</a> (and many more pictures), which will be occasionally updated as I add features like auto feed and chucks.<br />
<br />Ben Katzhttp://www.blogger.com/profile/15816221191617788028noreply@blogger.com0tag:blogger.com,1999:blog-6555364095586804046.post-55987278524694616852014-12-29T12:25:00.000-05:002015-03-03T20:51:41.088-05:002014 East Campus Roller Coaster<br />
Since working on the <a href="http://build-its.blogspot.com/2013/09/rotating-climbing-wall.html">rotating climbing wall</a> last year, I've been interested in trying to revive the <a href="http://eastcamp.us/">East Campus</a> roller coaster. Fellow MechE 2016's <a href="http://kriste11er.blogspot.com/">Jaguar K</a>. and Wesley L. were similarly enthusiastic about the roller coaster, so we started coming up with ideas over that fall semester. We got an early start on the approval process for the ride, and, thanks to lots of hard work from our Rush chairs and others, we were able to get the permitting and approval from MIT and Cambridge in time. <br />
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After <a href="http://build-its-inprogress.blogspot.com/2014/12/east-campus-roller-coaster-actually.html">a week of construction</a>, we had a working roller coaster:<br />
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<tr><td class="tr-caption" style="text-align: center;">Photo credit to the folks at <a href="http://monograph.io/eastcampus/2014-mit-east-campus-coaster">monograph.io</a></td></tr>
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More documentation of the roller coaster's design and construction can be found <a href="http://build-its-inprogress.blogspot.com/search/label/Wooden%20Roller%20Coaster">here</a>.Ben Katzhttp://www.blogger.com/profile/15816221191617788028noreply@blogger.com0tag:blogger.com,1999:blog-6555364095586804046.post-28444278216278991572014-09-30T14:48:00.001-04:002014-09-30T14:49:57.750-04:00iPad Retina Display External MonitorTwo summers ago I bought an iPad 3 LCD off ebay. These are 9.7" 2048 x 1536 IPS panels, which use an internal DisplayPort interface. In May, I finally got around to building an external display out of the panel, which can be clipped directly onto the side of my Macbook Pro's screen, and is powered by a USB port.<br />
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I have been using the display on a daily basis for the last four months, and it has held up beautifully. It took a little while for my eyes to get used to the tiny 264 pixels-per-inch pixel density, but I can now comfortably use it at native resolution.<br />
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<a href="http://build-its-inprogress.blogspot.com/search/label/iPad%20Monitor">The display's build log can be found here.</a><br />
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The back of the display was cut from the side panel of an old Power Mac G5 case, and it attaches to the side of my laptop with a pair of 3D-printed clips that friction-fit onto my laptop's screen.<br />
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<br />Ben Katzhttp://www.blogger.com/profile/15816221191617788028noreply@blogger.com1tag:blogger.com,1999:blog-6555364095586804046.post-30702201378008205342013-12-02T16:58:00.001-05:002013-12-02T16:58:51.620-05:00All Terrain Scooter ReduxThe <a href="http://build-its.blogspot.com/2012/07/all-terrain-electric-scooter.html">original version</a> of my all-terrain electric scooter suffered from a number of problems, the most important of which was in the motors I used. The <a href="https://lh6.googleusercontent.com/-mLRLZQpRTjU/T3iNfmxH28I/AAAAAAAABOY/wzgYPOGGiWA/s640/DSCN4161.JPG">triple CIM motors</a> were just not capable of providing both the top speed and acceleration I wanted out of the vehicle. Actually they could, but just not for very long before the insulation on their windings turned into a melty black mess. <br />
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After some attempted snow-scootering during the northeast snowstorm last year, I decided I was sick of the freshly roasted motor smell, and stored away the scooter until the summer. A full teardown of the scooter revealed enough unnoticed or impending failures that I decided to scrap pretty much the entire mechanical end of the original scooter.<br />
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Version 2 features the same HobbyKing LiPo battery pack and Kelly 72V 200A brushed motor controller as the original, but nearly everything else is new. Replacing the CIMs are a pair of Magmotor S28-200's, which are slightly larger than the <a href="http://www.robotmarketplace.com/products/0-A28-150.html">S28-150's of battlebot fame</a>. Like before, the motors are mechanically coupled to one output shaft through a gearbox reduction, and connected electrically in series.<br />
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This version also has even bigger wheels (because the old ones clearly weren't large enough...), and over a foot of clearance everywhere.<br />
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The scooter's <a href="http://build-its-inprogress.blogspot.com/search/label/ATS%20Redux">build log can be found here</a>.<br />
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"Lefty" type leading link fork, for no better reason than that I like how they look:<br />
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This version of the scooter also fixes the <a href="http://build-its-inprogress.blogspot.com/2012/08/chain-tensioner-v3-so-close.html">chain and chain tensioner problems</a> of the previous version. A pair of connected sprockets at the pivot of the rear swingarm ensure that chain length remains constant over the travel of the suspension. This way, I don't need to use any sort of chain tensioner.<br />
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The shock absorber on the rear swingarm is a very fancy downhill mountain bike part. It is extremely adjustable, and damping in compression and extension directions are independently adjustable.<br />
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Here are the dual magmotor S28-200's. Right, now the Kelly controller is limited to 100A at 60V, meaning that each motor gets 100A at 30V. This works out to an acceleration of .54 g (at half the controller's current limit...). This acceleration is only actually reachable if you lean way over the handlebars. As I have experienced, you are simply thrown off if you throttle hard without doing this.<br />
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Ben Katzhttp://www.blogger.com/profile/15816221191617788028noreply@blogger.com3tag:blogger.com,1999:blog-6555364095586804046.post-56351649694826840642013-10-05T03:19:00.000-04:002013-10-05T03:19:18.756-04:00Gourd Ukulele<div class="separator" style="clear: both; text-align: left;">
Back in June, I returned to Atlanta for a couple weeks. While there, I took advantage of all the woodworking hand tools I had access to, and made this ukulele. The body of the instrument was made from a dried gourd. The neck is mahogany, which was scavenged from the desk in my old bedroom. The fretboard is burned oak, which was split off a stump in my back yard, and the soundboard was the bottom of a desk drawer.</div>
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The ukulele is about <a href="http://en.wikipedia.org/wiki/Ukulele#Types">Tenor sized</a>, and tuned with a low-G. Fret positions were determined using this handy <a href="http://www.stewmac.com/freeinfo/Fretting/i-fretcalc.html">online fret calculator</a>. All of the construction except drilling a couple of holes was done with hand tools. The neck was shaped mostly with a drawknife, except for the channel for the tuning pegs, which was chiseled out.</div>
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<a href="http://2.bp.blogspot.com/-x-gTx17JaNY/Ub_QcOuOGlI/AAAAAAAADiE/5jfVq4U-Qjc/s1600/20130616_234125.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="http://2.bp.blogspot.com/-x-gTx17JaNY/Ub_QcOuOGlI/AAAAAAAADiE/5jfVq4U-Qjc/s640/20130616_234125.jpg" width="640" /></a></div>
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The <a href="http://build-its-inprogress.blogspot.com/search/label/Gourd%20Ukulele">ukulele's build thread can be found here.</a><br />
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I don't have any audio or video clips of me playing it, so you'll have to take my word for it that it sounds pretty good. I think it does, at least. Not that I have much to compare it to.<br />
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You can see three holes in the bridge. These were from the original bridge and string mounting method, which started to pull apart from string tension. My final solution was to have the strings pass all the way down the length of the instrument to be fastened at the end, rather than at the bridge.<br />
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<a href="http://4.bp.blogspot.com/-LehaRAI7A-I/Ub_QYy2PnJI/AAAAAAAADgo/7FpXEjC2jLQ/s1600/20130616_233802.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="http://4.bp.blogspot.com/-LehaRAI7A-I/Ub_QYy2PnJI/AAAAAAAADgo/7FpXEjC2jLQ/s640/20130616_233802.jpg" width="640" /></a></div>
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The neck is pretty thick compared to a normal ukulele or guitar. I could have (and still could, I suppose) thin it out more while keeping the smooth profile. </div>
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<a href="http://3.bp.blogspot.com/-TNpkNMEy3UU/Ub_QY7rbX0I/AAAAAAAADgk/jU3GxxhZQRc/s1600/20130616_233748.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="http://3.bp.blogspot.com/-TNpkNMEy3UU/Ub_QY7rbX0I/AAAAAAAADgk/jU3GxxhZQRc/s640/20130616_233748.jpg" width="640" /></a></div>
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I originally planned on making my own tuning pegs, but realized I wouldn't have time if I wanted to finish in two weeks. I ended up ordering some cheap violin tuning pegs, and carving off some of the details. <br />
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<a href="http://1.bp.blogspot.com/-mUlyClNqsFc/Ub_QaAtTh9I/AAAAAAAADhY/wH70nY8mN2s/s1600/20130616_234009.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="http://1.bp.blogspot.com/-mUlyClNqsFc/Ub_QaAtTh9I/AAAAAAAADhY/wH70nY8mN2s/s640/20130616_234009.jpg" width="640" /></a></div>
<br />Ben Katzhttp://www.blogger.com/profile/15816221191617788028noreply@blogger.com2tag:blogger.com,1999:blog-6555364095586804046.post-73774561141713737592013-09-04T00:03:00.000-04:002013-09-04T00:03:58.426-04:00Rotating Climbing Wall<div style="text-align: center;">
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For <a href="http://web.mit.edu/dormcon/REX/">REX</a> this year at <a href="http://eastcamp.us/">East Campus</a>, I helped to design and build a rotating climbing wall. <br />
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The climbing wall consisted of a twelve-foot diameter by eight-foot wide wooden cylinder suspended on an axle. The surface of the cylinder was covered in climbing holds. As the climber progresses, their weight causes the cylinder to rotate opposite the climbing direction. </div>
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The entirety of the construction was done over the course of one week. Newly arrive freshman were enlisted and armed will drills to screw everything together. Trying to manage a large (up to ~10 people at times) group of workers, most of whom had never before used power tools was an interesting experience. For the most part, everything worked out fine. We were able to get through construction without running into any major problems.</div>
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The climbing wall went from this:</div>
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<a href="http://3.bp.blogspot.com/-QGrchqKgyYs/UceE5QfGAjI/AAAAAAAADjg/10OTUsVm_-k/s1600/1.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="388" src="http://3.bp.blogspot.com/-QGrchqKgyYs/UceE5QfGAjI/AAAAAAAADjg/10OTUsVm_-k/s640/1.JPG" width="640" /></a></div>
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To this:</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiTvB2uHJ36e3zaeEMQVBpIDNCnu-A3krv8ci6h_gAQ91KBN5fbIfq4apoDJ4kfHZaNYSkjoONFrjGtNppgi1pIAwIlqagwqgT9ZQP2aANeivP7xiZT93T5VKwiu3c2HUPUyf8FRgrQzjg/s1600/_IGP7602.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" height="424" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiTvB2uHJ36e3zaeEMQVBpIDNCnu-A3krv8ci6h_gAQ91KBN5fbIfq4apoDJ4kfHZaNYSkjoONFrjGtNppgi1pIAwIlqagwqgT9ZQP2aANeivP7xiZT93T5VKwiu3c2HUPUyf8FRgrQzjg/s640/_IGP7602.JPG" width="640" /></a></div>
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For non-beginners, the climbing wall worked surprisingly well. We found a setting for the brake that worked for a wide variety of climber weights. To prevent light (or really fast) climbers from getting too high off the ground, two helpers assisted in the rotation of the cylinder. The wall was a bit too hard for many people, however. You start climbing on an overhang, which was difficult to get past. Later on, we started people out on chairs, so that they could reach the roughly vertical part of the wall. </div>
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More photos and videos can be found in the <a href="http://build-its-inprogress.blogspot.com/search/label/Rotating%20Climbing%20Wall">build log.</a></div>
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Ben Katzhttp://www.blogger.com/profile/15816221191617788028noreply@blogger.com0tag:blogger.com,1999:blog-6555364095586804046.post-929718243207514462013-04-28T16:06:00.000-04:002013-05-01T23:47:50.718-04:00Zero-Dollar Carbon Fiber Bicycle<div class="separator" style="clear: both; text-align: left;">
<a href="http://build-its-inprogress.blogspot.com/2013/01/a-preview-of-upcoming-projects.html">Back in January</a>, I was presented with a large carbon fiber tube, in the form of an oar. Being who I am, I made the obvious decision to build a bicycle frame out of it. As I found out when building my <a href="http://build-its.blogspot.com/2010/09/building-bamboo-bike-frame.html">bamboo bike</a>, making a bicycle frame from scratch, especially when using composites, is not actually very hard, as long as you have a lot of patience. To make this project more interesting, more challenging, and cheaper, I built the entire frame and bicycle without spending any money on it. Every component (except the pedals, which used to live on the bamboo bike) I either made myself or scavenged.</div>
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<a href="http://3.bp.blogspot.com/-vHwoZSIAoT4/UX1m-xE61qI/AAAAAAAADP0/rNe6jpE0Yeg/s1600/20130427_151406.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="http://3.bp.blogspot.com/-vHwoZSIAoT4/UX1m-xE61qI/AAAAAAAADP0/rNe6jpE0Yeg/s640/20130427_151406.jpg" width="640" /></a></div>
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The frame started its life as a large oar. Apparently it showed up in in a trash pile on a loading dock sometime last year, and found its way to <a href="http://miters.mit.edu/">MITERS</a> from there. The carbon fiber tube that made up the shaft of the oar happened to be about the right length and diameter to build the front triangle of a bicycle frame.<br />
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<a href="http://build-its-inprogress.blogspot.com/search/label/OarCycle?max-results=20">The build log can be found here.</a><br />
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<tr><td style="text-align: center;"><a href="http://3.bp.blogspot.com/-yZ9V9a5OfhY/UQluD1VaCpI/AAAAAAAACwE/BFP1JrE0nI0/s1600/20130129_214040.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="640" src="http://3.bp.blogspot.com/-yZ9V9a5OfhY/UQluD1VaCpI/AAAAAAAACwE/BFP1JrE0nI0/s640/20130129_214040.jpg" width="480" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">From this to bicycle in four months</td></tr>
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I came up with the geometry of the bicycle by shamelessly copying the geometry of the 58cm Trek Madone. Using the lengths and angles provided on their website, I was able to create a fully constrained 2-D SolidWorks sketch of the frame. Using this model, I designed and built a <a href="http://build-its-inprogress.blogspot.com/2013/02/bike-frame-jig.html">simple frame jig</a> out of 80/20 extrusion and nylon stock.<br />
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<a href="http://3.bp.blogspot.com/-3Rnfg8kn4M4/UX1m-6nhSkI/AAAAAAAADP4/tiw1TJRZzWE/s1600/20130427_151413.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="http://3.bp.blogspot.com/-3Rnfg8kn4M4/UX1m-6nhSkI/AAAAAAAADP4/tiw1TJRZzWE/s640/20130427_151413.jpg" width="640" /></a></div>
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<a href="http://2.bp.blogspot.com/-DzNuQAa0h80/UX1m-TiiHFI/AAAAAAAADPo/mfe5rpEFzUE/s1600/20130426_202604.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="http://2.bp.blogspot.com/-DzNuQAa0h80/UX1m-TiiHFI/AAAAAAAADPo/mfe5rpEFzUE/s640/20130426_202604.jpg" width="640" /></a></div>
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<a href="http://2.bp.blogspot.com/-ifHDFTTx6F0/UX1m-CKrV2I/AAAAAAAADPg/pG0rkAANwQ4/s1600/20130426_202548.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="http://2.bp.blogspot.com/-ifHDFTTx6F0/UX1m-CKrV2I/AAAAAAAADPg/pG0rkAANwQ4/s640/20130426_202548.jpg" width="640" /></a></div>
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I have not weighed the entire bike yet, bur from earlier weighings it's probably something like 18 lbs. Not exactly light for a carbon fiber bike, but a good bit lighter than any other bike I've had. The vast majority of the weight is from the components I used. Since I got all the components for free, I did not really have super-light options to choose from. <br />
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The bike rides....like a bicycle. Believe it or not, taking 5 pounds or so of a bike does not make a huge difference. Not really surprising, as I make up 85-90% of the mass of the bike-human system. It does make it much more pleasant to carry up and down stairs though. Most of the improvements in this over other bikes I have ridden come from the fit, which is greatly improved over my <a href="http://build-its.blogspot.com/2010/09/building-bamboo-bike-frame.html">bamboo bike</a> and my <a href="http://2.bp.blogspot.com/-2PPlm5tKAQg/UCPI5djlP2I/AAAAAAAABhY/PT-X5MchIHE/s1600/DSCN0587.JPG">giant steel bike</a>. Ben Katzhttp://www.blogger.com/profile/15816221191617788028noreply@blogger.com1tag:blogger.com,1999:blog-6555364095586804046.post-43230204405739182902013-03-25T22:49:00.000-04:002013-03-25T22:49:32.565-04:00Electric Tricycle<div class="separator" style="clear: both; text-align: left;">
So I built another electric vehicle. This time around, I actually did some designing before I got any parts, so this was less of a "what do I do with this cool part" project than most of the things I build are. However, the actual construction of the vehicle <i>was</i> started due to the <a href="http://build-its-inprogress.blogspot.com/2012/11/soon-to-be-named-three-wheeled-electric.html">acquisition of a cool part</a>: the "melon" sized brushless motor that drives the tricycle. Getting the motor was a great excuse to implement a bunch of ideas for an electric vehicle I developed after building my <a href="http://build-its.blogspot.com/2012/07/all-terrain-electric-scooter.html">electric scooter</a>.</div>
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This was my first big project done with access to real machine tools (courtesy of <a href="http://miters.mit.edu/">MITERS</a>), so this was both my <i>learn how to machine things</i> and <i>learn how to Solidworks</i> project. Even with just a semester working with these tools, I was able to make this vehicle significantly more refined (while simultaneously even more ridiculous) than my scooter.</div>
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The design for the vehicle was inspired by the classic <a href="http://ecx.images-amazon.com/images/I/51B9cds5HfL._SX300_.jpg">Radio Flyer tricycle</a>. That vehicle geometry is not exactly intended for the high speed go-kart like performance I wanted, so I tried to optimize the design while retaining the tiny kids-trike aesthetic. </div>
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And now, a brief overview of the tricycle's specifications:</div>
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Motor: <a href="http://4.bp.blogspot.com/-Ej4wp1VUuLE/UQF4ys1dbAI/AAAAAAAACs8/tz5-Puor1Sc/s1600/20130123_010649.jpg">Turnigy C80100-130</a> brushless RC outrunner</div>
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Controller: <a href="http://kellycontroller.com/kbs4812150a24-48v-mini-brushless-dc-controller-p-528.html">Kelly KBS48121</a> 120A peak BLDC controller</div>
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Batteries: 39.6V 7.5 Ah A123 Systems Lithium Nanophosphate pack</div>
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Drivetrain: Manual <a href="http://www.shimano.com/publish/content/global_cycle/en/us/index/products/0/nexus/product.-code-SG-8C31.-type-..html">8-Speed Shimano internal gear hub</a>, custom spur gear differential</div>
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Chassis: Welded steel tubing and aluminum plate construction with side-to-side leaning</div>
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Top Speed: 45+ mph, if you're feeling brave</div>
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<a href="http://4.bp.blogspot.com/-axOFjM7agWo/UVCptKr3HsI/AAAAAAAADFk/erA6VXqdzGo/s1600/20130324_154714.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="http://4.bp.blogspot.com/-axOFjM7agWo/UVCptKr3HsI/AAAAAAAADFk/erA6VXqdzGo/s640/20130324_154714.jpg" width="640" /></a></div>
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More pictures, videos, and build log can be found after the break.<br />
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The tricycle's build log can be found <a href="http://build-its-inprogress.blogspot.com/search/label/Presently%20UnNamed%20Tricycle">here</a> (in reverse chronological order) or below:<br />
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<li><a href="http://build-its-inprogress.blogspot.com/2012/11/soon-to-be-named-three-wheeled-electric.html">Part 1</a></li>
<li><a href="http://build-its-inprogress.blogspot.com/2012/12/assorted-tricycle-updates.html">Part 2</a></li>
<li><a href="http://build-its-inprogress.blogspot.com/2012/12/building-differential.html">Part 3</a></li>
<li><a href="http://build-its-inprogress.blogspot.com/2012/12/improper-use-of-machinery.html">Part 4</a></li>
<li><a href="http://build-its-inprogress.blogspot.com/2013/01/mechanically-finished-tricycle.html">Part 5</a></li>
<li><a href="http://build-its-inprogress.blogspot.com/2013/01/battery-building-motor-woes-and.html">Part 6</a></li>
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The basic systems of the tricycle work as follows: <br />
Hidden beneath the black cover near the back left wheel is <a href="http://2.bp.blogspot.com/-rvgSzoNrLbc/UPykhJ0MykI/AAAAAAAACp0/SC3yZbrugZw/s1600/20130115_001713.jpg">300 Watt-hour battery pack</a> built from 36 A123 26650 cells. This pack feeds a <a href="http://kellycontroller.com/kbs4812150a24-48v-mini-brushless-dc-controller-p-528.html">Kelly KBS48121</a> controller, capable of outputting over 4 kW peak, controlled by a twist-grip throttle. This in turn controls a <a href="http://4.bp.blogspot.com/-Ej4wp1VUuLE/UQF4ys1dbAI/AAAAAAAACs8/tz5-Puor1Sc/s1600/20130123_010649.jpg">Turnigy C80100-130</a> brushless DC motor. The output from the motor (after a chain reduction) turns a <a href="http://www.shimano.com/publish/content/global_cycle/en/us/index/products/0/nexus/product.-code-SG-8C31.-type-..html">8-Speed Shimano internal gear hub</a>, which can be shifted with a trigger-shifter on the handlebars The output from the gearbox, after a second chain reduction, turns a <a href="http://build-its-inprogress.blogspot.com/2012/12/building-differential.html">spur gear differential</a>, splitting the torque between the two rear wheels. If you for some reason want to stop, a brake lever on the handlebars can actuate disk brakes on each rear wheel. Steering is accomplished very similarly to a bicycle or motorcycle. In addition to the handlebars turning the front wheel, the front half of the trike's frame also<a href="http://3.bp.blogspot.com/-KFtms8yGZtA/UMZekgm9l6I/AAAAAAAACYA/4wv8utA-q6M/s1600/20121209_023207.jpg"> tilts side to side</a>. The tilting motion allows for fast, stable turns, which would not be possible if the frame were rigid.<br />
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<a href="http://4.bp.blogspot.com/-IDockXrrM_M/UVCprf37w6I/AAAAAAAADEw/hkH-ciBPL_4/s1600/20130324_154636.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="http://4.bp.blogspot.com/-IDockXrrM_M/UVCprf37w6I/AAAAAAAADEw/hkH-ciBPL_4/s640/20130324_154636.jpg" width="640" /></a></div>
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<a href="http://4.bp.blogspot.com/-awo0xFypMCo/URB7-JDkvdI/AAAAAAAAC2o/z3noKZPFdvc/s1600/20130204_162809.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="http://4.bp.blogspot.com/-awo0xFypMCo/URB7-JDkvdI/AAAAAAAAC2o/z3noKZPFdvc/s640/20130204_162809.jpg" width="640" /></a></div>
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<a href="http://1.bp.blogspot.com/-YNxPhUuSHcE/URB79kuSMZI/AAAAAAAAC2Q/rsfXnkT5n5Q/s1600/20130204_162740.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="http://1.bp.blogspot.com/-YNxPhUuSHcE/URB79kuSMZI/AAAAAAAAC2Q/rsfXnkT5n5Q/s640/20130204_162740.jpg" width="640" /></a></div>
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Here you can see most of the inner workings of the drivetrain:</div>
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<a href="http://3.bp.blogspot.com/-mpAbEvCqNxo/UPGKA4FrpeI/AAAAAAAACmc/Oo974zEPHKI/s1600/20130111_004522.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="http://3.bp.blogspot.com/-mpAbEvCqNxo/UPGKA4FrpeI/AAAAAAAACmc/Oo974zEPHKI/s640/20130111_004522.jpg" width="640" /></a></div>
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Action shot:<br />
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<a href="http://3.bp.blogspot.com/-8qQilSQJAxY/UVC6zG1eQDI/AAAAAAAADGU/z5zJRhaAtQ0/s1600/Screen+Shot+2013-03-17+at+5.01.40+PM.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="359" src="http://3.bp.blogspot.com/-8qQilSQJAxY/UVC6zG1eQDI/AAAAAAAADGU/z5zJRhaAtQ0/s640/Screen+Shot+2013-03-17+at+5.01.40+PM.png" width="640" /></a></div>
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Large parking lots become excellent riding grounds at early hours of the morning:</div>
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Ben Katzhttp://www.blogger.com/profile/15816221191617788028noreply@blogger.com8tag:blogger.com,1999:blog-6555364095586804046.post-66761346417665850562013-01-29T14:42:00.000-05:002013-01-29T14:42:13.507-05:00Autonomous Anti-Mouse Sentry TurretFor <a href="http://bad-ideas.mit.edu/">Bad Ideas</a> I built a computer controlled anti-mouse sentry turret. The turret uses a video feed from a webcam and a slightly modified version of the <a href="http://projectsentrygun.rudolphlabs.com/">Project Sentry Gun</a> Processing code to track mouse-sized objects that move across the camera's field of view. It fires at the objects using a hacked electric airsoft gun on a pan/tilt servo platform.<br />
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<a name='more'></a>The servos arrived from HobbyKing an unfortunately short amount of time before the start of Bad Ideas, so I had only three days to build, test, and calibrate the sentry. </div>
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The pan-tilt assembly was made from scraps of aluminum I found around MITERS. I used as thin metal as possible to make the sentry light and responsive, and also easy to machine within my time constraints. The tilt axis is entirely supported by the servo's output shaft, while the panning is supported by a small set of lazy Suzanne bearings, with the servo in the center. </div>
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<a href="http://1.bp.blogspot.com/-6q_tZh2171I/UQgfBwr68kI/AAAAAAAACt4/ppOcaLr4_tU/s1600/20130129_140058.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="http://1.bp.blogspot.com/-6q_tZh2171I/UQgfBwr68kI/AAAAAAAACt4/ppOcaLr4_tU/s640/20130129_140058.jpg" width="640" /></a></div>
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I removed all the unnecessary parts from the airsoft gun, like the trigger, handle, sights, and other decorative plastic bits.<br />
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To control the small DC motor that fires the airsoft gun, I just wired some small NPN transistors I had in parallel and added a diode across the motor output. I heatshrinked over the whole thing to make it look like a <a href="http://www.hobbyking.com/hobbyking/store/__61__182__Speed_Controllers-All_Speed_Controllers.html">real motor controller.</a><br />
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<a href="http://3.bp.blogspot.com/-_3kT9atJDG0/UQgfCyG6_JI/AAAAAAAACuU/fi3iqJ9R_Hc/s1600/20130129_140441.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="http://3.bp.blogspot.com/-_3kT9atJDG0/UQgfCyG6_JI/AAAAAAAACuU/fi3iqJ9R_Hc/s640/20130129_140441.jpg" width="640" /></a></div>
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I used the webcam from a 2006 iMac computer. Although these webcams are internal, they run over USB. I spliced its four wires to those of a standard USB cable, and stuck the camera just below the pan-tilt assembly.</div>
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To get the Project Sentry Gun code to work for my setup, I had to make a few minor modifications. First, I completely erased the stock firing code and replaced it with one line to simply turn the fire pin on the Arduino to HIGH. Also, by default, the motion tracking bit of the software has a lower limit for the size of moving objects it will target. It locks onto the largest moving object above this threshold. In addition to the lower limit, I added in an upper limit, so the turret will track things that are roughly mouse-sized, but will ignore larger things like people. <br />
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With no target, the crosshairs on the webcam overlay are thin:<br />
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<a href="http://3.bp.blogspot.com/-9O8oF8ouNBg/UQgitpJCwaI/AAAAAAAACu8/aYFthcajK2U/s1600/blank.PNG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="504" src="http://3.bp.blogspot.com/-9O8oF8ouNBg/UQgitpJCwaI/AAAAAAAACu8/aYFthcajK2U/s640/blank.PNG" width="640" /></a></div>
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When there is a small target, the crosshairs are thick and the target is boxed in red:</div>
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<a href="http://1.bp.blogspot.com/-MBwma9Gjslw/UQgitkTAS0I/AAAAAAAACu4/kWP-IWQXi3k/s1600/target.PNG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="504" src="http://1.bp.blogspot.com/-MBwma9Gjslw/UQgitkTAS0I/AAAAAAAACu4/kWP-IWQXi3k/s640/target.PNG" width="640" /></a></div>
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If the object is too large, it is ignored:<br />
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Ben Katzhttp://www.blogger.com/profile/15816221191617788028noreply@blogger.com5tag:blogger.com,1999:blog-6555364095586804046.post-38477382112986845952013-01-16T13:43:00.000-05:002013-01-16T13:43:38.622-05:00Motorized Projector Screen<div class="separator" style="clear: both; text-align: left;">
After the winter break, I brought a projector I got from old high school's recycling pile back to my dorm with me. I made a screen for the projector from some blackout fabric, and motorized the raising and lowering of the screen with a small gear motor and some other parts I found.</div>
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<a name='more'></a>The screen's controls were mounted to an aluminum plate left over from the <a href="http://build-its-inprogress.blogspot.com/2012/09/scooter-accessories.html">cargo rack</a> I made for my scooter. Flipping the red toggle switch up raises the screen, flipping it down lowers the screen.<br />
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<a href="http://4.bp.blogspot.com/-Zh86qHDpQpo/UPbwet1_qCI/AAAAAAAACoc/WC2FkHavgeM/s1600/20130112_172408.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="http://4.bp.blogspot.com/-Zh86qHDpQpo/UPbwet1_qCI/AAAAAAAACoc/WC2FkHavgeM/s640/20130112_172408.jpg" width="640" /></a></div>
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The upper and lower limits of the screen are controlled by two limit switches and a wing nut on a threaded rod. One end of the rod is pressed onto the motor shaft, while the other is tightly threaded into the bit of hex stock that couples the screw to the steel rod the screen is wound around. The DPDT toggle switch forms a mechanical H-bridge to reverse the direction of the motor. <br />
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<a href="http://3.bp.blogspot.com/-xSaPxPxcylg/UPbweitEkxI/AAAAAAAACog/oV99-2Rbya0/s1600/20130112_172435.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="http://3.bp.blogspot.com/-xSaPxPxcylg/UPbweitEkxI/AAAAAAAACog/oV99-2Rbya0/s640/20130112_172435.jpg" width="640" /></a></div>
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The opposite side of the screen is supported by an aluminum bracket with a bearing pressed into it.</div>
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Ben Katzhttp://www.blogger.com/profile/15816221191617788028noreply@blogger.com0tag:blogger.com,1999:blog-6555364095586804046.post-81933355851524564512013-01-03T22:06:00.000-05:002013-04-29T17:19:57.775-04:00PocketBoard<div class="separator" style="clear: both; text-align: left;">
PocketBoard is a 14.5" long skateboard designed to be the opposite of my <a href="http://build-its.blogspot.com/2012/07/all-terrain-electric-scooter.html">electric scooter</a>: It is a small, simple and reliable vehicle for going short distances quickly. At roughly 5% the weight of the scooter and some small fraction of the volume, I can easily store it in a backpack or even my laptop bag when I'm not riding it. It has a solid oak deck with inlayed aluminum plates, and (what I assume to be) standard skateboard trucks, along with some soft 60mm diameter wheels.</div>
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PocketBoard V2 keeps the same shape and footprint, but has an aluminum deck made from the side panel of a PowerMac G5 case.</div>
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<a href="http://4.bp.blogspot.com/-sE-jywbK1Wk/UOYDGSAnY6I/AAAAAAAACj8/uPrKdWlIimU/s1600/20130103_163641.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="http://4.bp.blogspot.com/-sE-jywbK1Wk/UOYDGSAnY6I/AAAAAAAACj8/uPrKdWlIimU/s640/20130103_163641.jpg" width="640" /></a></div>
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PocketBoard's rather short build thread can be found <a href="http://build-its-inprogress.blogspot.com/search/label/PocketBoard">here</a>.</div>
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<a href="http://1.bp.blogspot.com/-K5oZLZSR2R0/UVXGNNtA2MI/AAAAAAAADIs/1r4lPstvEhQ/s1600/20130324_170710.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="http://1.bp.blogspot.com/-K5oZLZSR2R0/UVXGNNtA2MI/AAAAAAAADIs/1r4lPstvEhQ/s640/20130324_170710.jpg" width="640" /></a></div>
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<a href="http://1.bp.blogspot.com/-RXrywJyW2FI/UVXGNTEEsOI/AAAAAAAADIw/b7euM0H7Fc8/s1600/20130328_142041.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="http://1.bp.blogspot.com/-RXrywJyW2FI/UVXGNTEEsOI/AAAAAAAADIw/b7euM0H7Fc8/s640/20130328_142041.jpg" width="640" /></a></div>
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Resting on the stump from which it was fashioned:</div>
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<a href="http://2.bp.blogspot.com/-Qm8HgvraZIw/UOYDGyv-SrI/AAAAAAAACkM/wGhELG8tYWc/s1600/20130103_163926.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="http://2.bp.blogspot.com/-Qm8HgvraZIw/UOYDGyv-SrI/AAAAAAAACkM/wGhELG8tYWc/s640/20130103_163926.jpg" width="640" /></a></div>
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This thing is really tiny. I can get approximately 1.5 of my feet on it. Despite its very short length it does not have an great turning radius, due to the skateboard stiff trucks I used.</div>
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<a href="http://4.bp.blogspot.com/-nLQkgNaXFQg/UOYDHJ2ZOsI/AAAAAAAACkI/KIcuNadfETE/s1600/20130103_164817.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="http://4.bp.blogspot.com/-nLQkgNaXFQg/UOYDHJ2ZOsI/AAAAAAAACkI/KIcuNadfETE/s640/20130103_164817.jpg" width="640" /></a></div>
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Me, when I realize I don't know how to ride a skateboard:<br />
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<br />Ben Katzhttp://www.blogger.com/profile/15816221191617788028noreply@blogger.com1tag:blogger.com,1999:blog-6555364095586804046.post-48945035509855319142012-11-04T13:58:00.001-05:002012-11-04T13:58:51.954-05:00Monitor ArmBy a combination of luck and keeping a close eye on the reuse mailing list, I have acquired a pair of nice, large computer monitors: A 24" 1920 x 1200 SyncMaster 245BW and a 25" 1920 x 1080 HP 2509m. Both screens were easily repaired by replacing dead capacitors on their power supply and inverter boards. Due to the small size of the stock dorm room desks, the two monitors plus my laptop could not actually fit on my desk with space left for anything else, so I built a monitor arm that bolts to my loft out of some 80/20 extrusion.<div>
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<a href="http://3.bp.blogspot.com/-cCFGNc-dTxQ/UJawQwQiPLI/AAAAAAAACJs/xvp4p6PNIvY/s1600/20121103_023537.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="http://3.bp.blogspot.com/-cCFGNc-dTxQ/UJawQwQiPLI/AAAAAAAACJs/xvp4p6PNIvY/s640/20121103_023537.jpg" width="640" /></a></div>
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I found most the parts of the arm in the stock pile at <a href="http://miters.mit.edu/">MITERS</a>. The basets of the pivoting blocks were milled flat, so that they would not lock into the slots on the 80/20. </div>
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The monitor can't move freely like expensive arms that use springs to counterbalance the weight of the monitor, so it has to be adjusted by loosening the joints with a hex key. The part the monitor attaches to came from Samsung's original stand, and can tilt as well as rotate 90 degrees.</div>
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Here's the final 9,561,600 pixel monitor setup:</div>
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Ben Katzhttp://www.blogger.com/profile/15816221191617788028noreply@blogger.com0tag:blogger.com,1999:blog-6555364095586804046.post-12043141924769319292012-10-28T14:43:00.000-04:002012-10-30T16:13:40.522-04:00Nyan HatI present Nyan Hat, possibly my silliest and most useless project yet. Nyan Hat was spawned from a late-night discussion involving at various times Halloween, hats, and Nyan Cat, and went from idea to completion in just over two weeks.<br />
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Despite the short timeframe over which Nyan Hat was designed and built, as surprising amount of thought was put into it's design, especially on the mechanical end of things. Nyan Hat features cam-actuated linkage plates, laser cut gears, and more acrylic and polycarbonate than any hat should have. </div>
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Nyan Hat is relatively simple electrically, at least compared to its mechanical bits. The 60 white LEDs that make up the stars are controlled by two two-transistor oscillators. Audio is provided by an old iPod Nano connected to the amplifier and driver from a stripped down set of computer speakers, and the entire hat is powered by a 9.9V, 2.3 Ah A123 lithium nanophosphate battery pack.</div>
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<a href="http://build-its-inprogress.blogspot.com/search/label/Nyan%20Hat">Click here for Nyan Hat's build log.</a></div>
Ben Katzhttp://www.blogger.com/profile/15816221191617788028noreply@blogger.com13tag:blogger.com,1999:blog-6555364095586804046.post-84363419870588980402012-09-15T17:22:00.000-04:002012-09-15T17:22:45.535-04:00LoftUsing wood left over from the REX shenanigans in the <a href="http://ec.mit.edu/">East Campus</a> courtyard, my roommate and I built a double loft in our room. We put up the loft in record time - we only had to sleep in our institute-provided beds for a total of one night before we could sleep in the loft. The design we used was based on another loft down the hall. It spans the entire room, so there are no supports in the middle of the floor, and it is tall enough to walk under without having to duck. It also includes integrated speaker mounts, a cruft shelf, and LED strip lighting.<br />
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The orange sign was taken from one of the amusement park rides in the courtyard, which was a four-person spinning rope swing. Don't worry, it's not structural.</div>
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<a href="http://4.bp.blogspot.com/-VgBh31bb5ts/UFTuh7nsxnI/AAAAAAAAB38/WGrSUkXhwDw/s1600/20120901_165514.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="http://4.bp.blogspot.com/-VgBh31bb5ts/UFTuh7nsxnI/AAAAAAAAB38/WGrSUkXhwDw/s640/20120901_165514.jpg" width="640" /></a></div>
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Speaker mounts were attached between the corners and the braces:</div>
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We made a shelf for scavenged parts, or "cruft", using a left over shield from the East Side vs West Side water war:</div>
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The inner edges of both beds were lined with white LED strips, which actually make the room substantially brighter:</div>
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<br />Ben Katzhttp://www.blogger.com/profile/15816221191617788028noreply@blogger.com1tag:blogger.com,1999:blog-6555364095586804046.post-66548917824260089022012-08-19T00:30:00.000-04:002012-08-19T00:38:13.182-04:00Blacksmithing: Year 3<div class="separator" style="clear: both; text-align: left;">
For the third year running, I spent a week in the blacksmithing shop at the John C. Campbell Folk School in North Carolina. Following the trend I set during my last two visits, I continued working on cool but useless mechanical things. This time around, I made gears. </div>
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Because the gears were so time consuming to make, the final piece doesn't include the puzzle-like assembly or end goal (ringing the bell) of the <a href="http://build-its.blogspot.com/2011/08/more-blacksmithing.html">gizmo I made last year</a>. The gears started out as a 3" long, 1.5" x 3/8" bar of mild steel. Using the shop's 55 ton hydraulic press and a 7/16" square punch, I punched a hole every inch along the center of the bar. I split the bar down the center with a bandsaw, to make two square toothed rack gears. The rack gear bars were then heated in a coal forge and bent around circular forms. The gear's hubs were made from 3/4" flat bar of the same thickness, reworked to remove the sharp edges, and with holes drifted in their centers. The hubs were MIG welded in place. Getting the gears to run smoothly was an extremely long process of finding the ideal distance between the gears, beveling the gear teeth with a bench grinder, and filing down high and low spots around the circumference of the large gear to prevent teeth from sticking. Lots of help with the gears, including the idea of punching and bending flat bar to make them, came from <a href="http://www.ironhouseforge.com/">Lucas House,</a> the class's instructor.<br />
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I drifted a square hole in the center of the drive gear, so it would interface with with the hand crank.</div>
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The handle was forged from a 1" pipe, and it spins freely on the crank.</div>
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I built a ratcheting mechanism into the crank, so that the gears cannot be back-driven. The spring was made from the bristle of a heavy-duty wirebrush. </div>
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Here's the frist gear I made. I ended up not using it, because the teeth stretched too far apart when I bent the gear into a circle. For the small gear I ended up using, I halved difference between the outer and inner diameters of the gear (minus the teeth), so that the metal would stretch less when I bent it. The edges were smoothed and given a worn look by wire brushing them with an angle grinder.</div>
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In a little bit of extra time I had, I ground this useless but nicely shaped knife blade out of a scrap of rusted tool steel lying around the shop. Once the rust was ground away, it left a nice pitted surface finish.</div>
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<a href="http://1.bp.blogspot.com/-8lbesSM0tTk/UDBjRopHswI/AAAAAAAABlg/aRHBZt_safM/s1600/20120818_172459.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="http://1.bp.blogspot.com/-8lbesSM0tTk/UDBjRopHswI/AAAAAAAABlg/aRHBZt_safM/s640/20120818_172459.jpg" width="640" /></a></div>
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Here's some of the interior fo the shop:</div>
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A circle of power hammers:</div>
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Here's the forge where I worked:</div>
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The old shop. It still has a few forges in it, but it's mostly used for grinding, welding and cutting.</div>
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The exterior of the old part of the shop:</div>
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<br />Ben Katzhttp://www.blogger.com/profile/15816221191617788028noreply@blogger.com1tag:blogger.com,1999:blog-6555364095586804046.post-981355047973011702012-07-23T17:19:00.000-04:002012-07-23T17:19:30.153-04:00Site Change<span style="font-family: inherit;">Until now, this site has been organized so that all my projects have exactly one post associated with them. I started out posting that way because my early projects on here were ported over from Instructables I had written, rather than posted here initially. I've gotten a bit fed up with writing one massive post when I finish a project, so from now on I will be posting about projects all along the way, instead of just at the end. </span><div>
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<span style="font-family: inherit;">...which can also be found by clicking the "In Progress" tab under the header image.</span></div>
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<span style="font-family: inherit;">Since Blogger doesn't support having two blogs within one website, the In Progress page is actually a completely different website, with the same template as the main site. </span></div>
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<span style="font-family: inherit;">The main page of this site will not change. When a project is more or less finished (as I've learned from my electric scooter project, some builds may never be truly finished), I'll make a post on the main page with final pictures and details, but without any of the normal "how to" I used to include. All the "how to" will be under the In Progress portion of the site.</span></div>
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<span style="font-family: inherit;"><br /></span></div>
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<span style="font-family: inherit;">In Progress posts will be labeled by specific project (e.g. "All-Terrain Electric Scooter"), rather than type of project (<a href="http://build-its.blogspot.com/search/label/Mechanical">Mechanical</a>, <a href="http://build-its.blogspot.com/search/label/Programming">Programming</a>, etc), as they are on the main page, so that one will be able to easily find the entire build log of one project by clicking that project's unique label. </span></div>
</div>Ben Katzhttp://www.blogger.com/profile/15816221191617788028noreply@blogger.com0tag:blogger.com,1999:blog-6555364095586804046.post-30184089955083192092012-07-05T22:42:00.003-04:002015-03-27T19:40:09.157-04:00All-Terrain Electric Scooter<span style="font-family: inherit;">As seems to be the case <a href="http://build-its.blogspot.com/2010/07/birch-and-mahogany-home-theater-pc.html">with</a> <a href="http://build-its.blogspot.com/2010/09/battery-powered-ipod-box-speakers.html">many</a> <a href="http://build-its.blogspot.com/2011/09/imac-mini.html">of</a> <a href="http://build-its.blogspot.com/2011/04/bench-psu.html">my</a> <a href="http://build-its.blogspot.com/2011/11/retro-rechargeable-usb-booster.html">projects</a>, for this one, I acquired the parts first, and then designed a project to fit the parts I had. Here is the back story of how I got the parts, and what drove me to use them to build the vehicular monstrosity this post is about.</span><br />
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<span style="font-family: inherit;">But first, a brief overview of the scooter's specs:</span><br />
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<span style="font-family: inherit;">Motors: <a href="http://www.andymark.com/product-p/am-0255.htm">3x CIM motors</a></span><br />
<span style="font-family: inherit;">Batteries: 8x<a href="http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=18631&aff=695820"> Turnigy 5000 mAh 4s LiPo packs</a>, 16s2p configuration (59.2V, 10 Ah)</span><br />
<span style="font-family: inherit;">Controller: Kelly <a href="http://kellycontroller.com/kds72200e200a24v-72v-mini-brushed-controller-p-762.html">KDS72200E</a>, 72V, 120 A continuous, 200A peak</span><br />
<span style="font-family: inherit;">Wheels: 12.5" with knobby pneumatic tires</span><br />
<span style="font-family: inherit;">Deck: Hand laminated carbon fiber with polycarbonate top</span><br />
<span style="font-family: inherit;">Frame: Royce Union Transit kick scooter, with about 200% more aluminum added</span><br />
<span style="font-family: inherit;">Brake: Pedal actuated rear disk (sprocket) brake</span><br />
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<span style="font-family: inherit;">Videos are at the bottom of the post.</span><br />
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<span style="font-family: inherit;"><img src="https://lh6.googleusercontent.com/-C_vl5uv80rA/T_XzCYZjQII/AAAAAAAABV4/A5SDwozmpIg/s640/20120705_154151.jpg" /> </span></div>
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<span style="font-family: inherit;">At the beginning of this past school year, <a href="http://robotics.paideiaschool.org/">my school's robotics team</a> decided to finally dismantle some old FRC robots that had been collecting dust for six or seven years. Since we now compete in VEX, not FIRST, we had no use for all the parts we stripped off the robots. Therefore, I generously relieved the team of some of these parts, including six Victor 884's, six CIM motors (4x 2.5", 2x 3"), 2 AndyMark Toughbox gearboxes, some #35 roller chain, and assortment of sprockets, some steel shafts and shaft collars, a 1/4" by 4" by 3' aluminum plate, 1" aluminum U channel, 1/8" polycarbonate sheet.... Anyways, while looking up the CIM motor curves, and trying to figure out by how much I could over-volt them, I ran into <a href="http://www.etotheipiplusone.net/?page_id=1216">this</a>, which at one point used a pair of CIM motors. That vehicle then led me to<a href="http://www.etotheipiplusone.net/?page_id=943"> these</a>. By an interesting coincidence, only a few weeks after I discovered those vehicles, I went to the Atlanta Mini Maker Faire, and guess <a href="http://www.etotheipiplusone.net/?p=1563">what I saw there</a>. After seeing the vehicles in action, I had to have one of my own, and thus my scooter was born.</span><br />
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<span style="font-family: inherit;">I started on the actual construction of project part way through my second term senior year, and have continued it into the summer. It is still a work in progress, and updates will be posted <a href="http://build-its-inprogress.blogspot.com/search/label/All-Terrain%20Electric%20Scooter">HERE</a></span><span style="font-family: inherit;">. Also, I plan on taking it up to Boston with me for school next year, where it will be my first (and probably not last) entry to the MIT branch of the "</span><a href="http://www.etotheipiplusone.net/?p=1972" style="font-family: inherit;">Collegiate Silly Vehicle League</a><span style="font-family: inherit;">."</span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">The scooter started out as my old kick scooter, a Royce Union Transit, which was a small step above the classic Razor scooters in terms of quality - for instance, it has front and rear wheel suspension that uses actual springs and shock absorbers rather than rubber blocks, and it has a more elegant folding mechanism.</span><br />
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<span style="font-family: inherit;">Scooter:</span><br />
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<span style="font-family: inherit;"><img src="https://lh3.googleusercontent.com/-QCk9WlEakq0/T3iMF7PTmOI/AAAAAAAABM0/mKDHTde45TI/s640/1.JPG" /> </span><br />
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<span style="font-family: inherit;">Front suspension. The actual spring and shock absorber are hidden withing the steering column:</span><br />
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<span style="font-family: inherit;"><img src="https://lh5.googleusercontent.com/-0w7mJWFx7Kc/T3iMGAP8K_I/AAAAAAAABM0/tYkt9HZkGyA/s640/4.JPG" /> </span><br />
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<span style="font-family: inherit;">Rear suspension:</span><br />
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<span style="font-family: inherit;"><img src="https://lh4.googleusercontent.com/-rW3rIrgMQso/T3iMcDqz91I/AAAAAAAABM0/XgP6gLizZ3M/s640/DSCN3991.JPG" /> </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">For use on softer and less regular terrains than asphalt, the original wheels needed to go. I got new ones from Norther Tool. They sell a version with a 60t sprocket included, but I managed to scavenge a 60t sprocket with the same bolt hole pattern from school. The best part of these wheels is that I can later upgrade the tires to these <a href="http://www.northerntool.com/shop/tools/product_200331371_200331371">epic snowblower tires</a> if I want to use the scooter in snow:</span><br />
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<span style="font-family: inherit;"><img src="https://lh6.googleusercontent.com/-3-INIr6BllQ/T3iMmlOXr_I/AAAAAAAABM0/Ln7W8fk3VSw/s640/DSCN3993.JPG" /> </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">To accommodate the larger wheels, I built a completely new fork and rear suspension assembly out of aluminum. I found some cheap mountain bike shock absorbers on ebay, and bought two with 1500 lb/in springs. Here they are next to the scooter's original rear shock absorber:</span><br />
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<span style="font-family: inherit;"><img src="https://lh3.googleusercontent.com/-GNk8FMP86FI/T3iMhRmdM7I/AAAAAAAABOY/NVFLKTmrcN0/s640/DSCN4029.JPG" /> </span><br />
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<span style="font-family: inherit;">I made the rear swingarm of 1/4" x 4", 1/4" by 2", 1" angle, and 1" U channel aluminum, plus an assortment of nuts and bolts:</span><br />
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<span style="font-family: inherit;"><img src="https://lh3.googleusercontent.com/-BenCgEoc2hU/T3iMqN5SLoI/AAAAAAAABOY/T74E9RAn1aM/s640/DSCN4057.JPG" /> </span><br />
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<span style="font-family: inherit;"><img src="https://lh6.googleusercontent.com/-2Vj-SbSReTM/T3iMuVu4ClI/AAAAAAAABOY/EltAoXqq7H0/s640/DSCN4063.JPG" /> </span><br />
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<span style="font-family: inherit;"><img src="https://lh5.googleusercontent.com/-oYuxh6T5FmI/T3iMvbk_y9I/AAAAAAAABOY/QwQ_LJf2HSs/s640/DSCN4066.JPG" /> </span><br />
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<span style="font-family: inherit;"><img src="https://lh6.googleusercontent.com/-qq6md6gM36Y/T3iMwbtgxnI/AAAAAAAABOY/wZHtNbQ7w4U/s640/DSCN4070.JPG" /> </span><br />
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<span style="font-family: inherit;">Yes, I know one side is longer than the other one.</span><br />
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<span style="font-family: inherit;">For the new fork, I started out by tearing apart the fork from an old mountain bike. Fortunately, the scooter used a 1" threaded headset, which I was easily able to replace with the mountain bike's 1" threadless headset. </span><br />
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<span style="font-family: inherit;"><img src="https://lh6.googleusercontent.com/-scqmitMQzsk/T3iMyqQ_2HI/AAAAAAAABOY/oMhTEkiwUww/s640/DSCN4081.JPG" /> </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">Using the MTB fork's springs, damper, some steel tube and solid rod, and U aluminum, I built two new shock absorbers:</span><br />
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<span style="font-family: inherit;"><img src="https://lh4.googleusercontent.com/-XJiTn1SWBkc/T3iM46YMTzI/AAAAAAAABOY/2ryhrtNOiY4/s640/DSCN4092.JPG" /> </span><br />
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<span style="font-family: inherit;"><img src="https://lh5.googleusercontent.com/-bDpCF7qjN5w/T3iM48-5tWI/AAAAAAAABOY/Kx5aZj9wl9s/s640/DSCN4094.JPG" /> </span><br />
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<span style="font-family: inherit;">These were then bolted to some more aluminum and the fork crown, to make a leading link suspension arm:</span><br />
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<span style="font-family: inherit;"><img src="https://lh4.googleusercontent.com/-_udQ7lNFuOA/T3iNBfouXxI/AAAAAAAABOY/8cDTIwY1IFQ/s640/DSCN4121.JPG" /> </span><br />
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<span style="font-family: inherit;">I cut dropouts in the aluminum, so the wheel could be removed easily. I cut horizontal dropouts in the rear suspension arm:</span><br />
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<span style="font-family: inherit;"><img src="https://lh3.googleusercontent.com/-dZizlzkqprc/T3iNFHc-MpI/AAAAAAAABOY/efz8O7PVi7k/s640/DSCN4131.JPG" /> </span><br />
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<span style="font-family: inherit;">I sued a 1/2" threaded rod for the axle, but the I.D. of the wheel's bearings was 5/8". To make up for the difference, I filed down some 1/2" nuts, so the fit inside the wheel bearings:</span><br />
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<span style="font-family: inherit;"><img src="https://lh6.googleusercontent.com/-mxqusROyU-c/T3iND2HC-XI/AAAAAAAABOY/PCHwAbiRIFI/s640/DSCN4129.JPG" /> </span><br />
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<span style="font-family: inherit;"><img src="https://lh5.googleusercontent.com/-fpGzsfJbq2o/T3iNFPkwNSI/AAAAAAAABOY/HrKG7kwh0h4/s640/DSCN4130.JPG" /> </span><br />
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<span style="font-family: inherit;">To test handling, I pretended it was still a normal kick scooter, and pushed it around my driveway a bit:</span><br />
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<span style="font-family: inherit;"><img src="https://lh4.googleusercontent.com/-3CzcD8fHAhY/T3iNPAWzNiI/AAAAAAAABOY/0I-zZR4Py40/s512/DSCN4148.JPG" /> </span><br />
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<span style="font-family: inherit;"><img src="https://lh3.googleusercontent.com/-iKaZia2jxPQ/T3iNMBCqwfI/AAAAAAAABOY/gG96RevZJyw/s512/DSCN4144.JPG" /> </span><br />
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<span style="font-family: inherit;">It handled okay, but not great, due to the forward offset of the front wheel. This made it impossible to lean while turning, because if you lean into a turn, the wheel naturally wants to swivel away from the turning direction. Hardly ideal. Additionally, at higher speeds I realized that there would be the risk of the front wheel "castering" - trying to swivel around 180 degrees. </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">In the above pictures, you may notice that one side of the rear suspension arm has been bent to accommodate the sprocket on the rear wheel. I managed to bend the massive piece of aluminum by heating both sides of the bend lines simultaneously with two propane torches, while the piece was clamped in a vice, and applying force to the metal via clamps clamped to it.</span><br />
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<span style="font-family: inherit;">To improve the steering geometry, I rebuilt a new fork out of the metal used in the old one. It does raise the height of the front of the scooter, so the platform is no longer parallel to the ground. Notice how if you draw a line down the center of the steering column, it intersects the ground where the wheel touches the ground. This means that the wheel will not have a tendency to either aim straight ahead or be flipped around:</span><br />
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<span style="font-family: inherit;"><img src="https://lh4.googleusercontent.com/-3g7m9DooKsg/T6qbEKNFreI/AAAAAAAABOI/vgynlNrOaEU/s512/DSCN5235.JPG" /> </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">This scooter is powered by 3 CIM motors. To interface all three of these motors with a single drive sprocket and reduce the speed of the drive sprocket, I built a new gearbox out of the two Toughbox's I scavenged. I removed one stage from each gearbox, so that the input:output ratio was 14:50, rather than (14:50)^2. I chopped up the gearboxes and aluminum-zinc brazed the pieces back together, to get a 3 motor 1 stage gearbox:</span><br />
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<span style="font-family: inherit;"><img src="https://lh6.googleusercontent.com/-mLRLZQpRTjU/T3iNfmxH28I/AAAAAAAABOY/wzgYPOGGiWA/s640/DSCN4161.JPG" /> </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">I had to order the third pinion gear (not pictured) from AndyMark, the manufacturer of these particular gearboxes. Unfortunately, the newer version of these gears do not have a set screw, so I had to lock it to the shaft with a layer of CA glue to keep it from sliding off while riding.</span><br />
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<span style="font-family: inherit;"><img src="https://lh3.googleusercontent.com/-_MRDJTjgD-k/T3iNaMfuK7I/AAAAAAAABOY/pHZaHm6KGKg/s640/DSCN4164.JPG" /> </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">I built a structure to attach the gearbox to the frame out of some angle aluminum and 1/4" scrap:</span><br />
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<span style="font-family: inherit;"><img src="https://lh5.googleusercontent.com/-C_ewwLyflYI/T4CNXjAmvMI/AAAAAAAABOU/1MiRkKILBxA/s640/DSCN4183.JPG" /> </span><br />
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<span style="font-family: inherit;"><img src="https://lh3.googleusercontent.com/-K28sEEmmF0E/T4CNWP6mk-I/AAAAAAAABOU/xmayeOD1_PQ/s640/DSCN4179.JPG" /> </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">Because of the shape of the rear swingarm, there is not a direct line from the sprocket on the gearbox to the sprocket on the wheel. To address this, I added an idler attached to the swingarm. Since the sprocket on the gearbox is not located at the pivot point of the rear swingarm, as the suspension is compressed, the effective chain length increases. To take up the slack in the chain, I added a chain tensioner:</span><br />
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<span style="font-family: inherit;"><img src="https://lh3.googleusercontent.com/-WS2pjrc2Xoo/T4oSMuXG6rI/AAAAAAAAAuE/qgcILV4lqWs/s640/DSCN4191.JPG" /> </span><br />
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<span style="font-family: inherit;"><img src="https://lh4.googleusercontent.com/-gft5dvDrcEI/T4oSM9dKCwI/AAAAAAAAAt8/zh9bziJ9Fms/s640/DSCN4193.JPG" /> </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">Motors and drivechains are nice, but being able to stop is nice too. Since the rotors of disk brakes are simply large rotating metal disks bolted to a wheel, I decided to simply use the wheel's drive sprocket as the rotor for a disk brake. I built a caliper to grip the sprocket out of an aluminum block that used to support the scooter's original suspension, some aluminum U channel, two road bike brake pads, a spring, and some bolts.</span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">The right brake pad is fixed to the rod that passes through the caliper, springs, and aluminum frame of the suspension, and the pad and rod can slide through all those bits. Since the spring is split in the middle, the brake is applied, and the brake cable pulls the two halves of the caliper towards eachother, both halves move equally in opposite directions, so that they both move towards the sprocket. </span><br />
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<span style="font-family: inherit;"><img src="https://lh6.googleusercontent.com/-6_mked8yRY0/T7z2hS04lOI/AAAAAAAAA0E/XIirQVIwRlo/s640/DSCN5314.JPG" /> </span><br />
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<span style="font-family: inherit;"><img src="https://lh5.googleusercontent.com/-mnBwepmDVM0/T7z2i9vdtFI/AAAAAAAAA0k/JZ9R8dony1Y/s640/DSCN5316.JPG" /> </span><br />
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<span style="font-family: inherit;"><img src="https://lh4.googleusercontent.com/-yvrijkn3T3c/T7z2knbZEJI/AAAAAAAAA04/4j5JoWqTn_0/s640/DSCN5320.JPG" /> </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">Normally on kick scooters, you brake by pushing down a lever above the back wheel with your foot. THe lever rubs against the wheel, slowing the scooter down. I wanted the disk brake to be actuated the same way, so I built a brake pedal out of some 1" U and angle aluminum. Two pivoting segments are attached to the brake pedal, which, when fixed to the scooter frame, form a kite shape with hinged joints. When pressure is applied to the pedal, the kite is deformed, which lengthens its long diagonal. Since the brake cable is attached across the long diagonal, the cable's housing is pushed up the cable when the pedal is actuated:</span><br />
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<span style="font-family: inherit;"><img src="https://lh6.googleusercontent.com/-XV9VFUclPIA/T7z2kQh0aSI/AAAAAAAAA08/aJWXlsEPgnc/s640/DSCN5359.JPG" /> </span><br />
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<span style="font-family: inherit;">The pedal fits between the two shock absorbers:</span><br />
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<span style="font-family: inherit;"><img src="https://lh5.googleusercontent.com/-znuEA1cAJMU/T7z2oO6IrfI/AAAAAAAAA14/GAVTaMckhyY/s640/DSCN5369.JPG" /> </span><br />
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<span style="font-family: inherit;"><img src="https://lh4.googleusercontent.com/-Q5wl7vR147Q/T7z2s9-4wfI/AAAAAAAAA2o/uLrwdABawlI/s640/DSCN5384.JPG" /> </span><br />
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<span style="font-family: inherit;">Here's what the mechanism looks like with the brake lever released:</span><br />
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<span style="font-family: inherit;"><img src="https://lh5.googleusercontent.com/-TUi38be8XBg/T7z2t2-NrVI/AAAAAAAAA2w/579_IYD4Ntk/s640/DSCN5385.JPG" /> </span><br />
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<span style="font-family: inherit;">And pushed:</span></div>
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<span style="font-family: inherit;"><img src="https://lh4.googleusercontent.com/-XVwbvOD1O3M/T7z2uAVb4nI/AAAAAAAAA20/dVUPP6AH3uc/s640/DSCN5386.JPG" /> </span><br />
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<span style="font-family: inherit;"><img src="https://lh4.googleusercontent.com/-2a2Ag0OT18M/T7z2wHUzBVI/AAAAAAAAA3E/sLdgZW3HLSQ/s640/DSCN5388.JPG" /> </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">To control the motors, I originally planned to use the Victor 884's I got from school, which are rated for 40 amps continuously and about 16V. I decided, however, that I wanted to try and get some more power out of the motors, and run them at around 20V, rather than the 12V they were rated for. At that voltage, and the extra current that would result, the 884's would probably have quickly released their magic smoke, so I bought a proper vehicle oriented motor controller. So I could use a lower current controller, I wired all three motors in series, for use with a 60 volt battery pack. It's easier to get a high voltage low current controller than a low voltage high current controller. I got a Kelly <a href="http://kellycontroller.com/kds72200e200a24v-72v-mini-brushed-controller-p-762.html">KDS72200E</a> controller, which is rated for 120A continuous and 200A peak at up to 72V.</span><br />
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<span style="font-family: inherit;">Here's one of the Victors:</span><br />
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<span style="font-family: inherit;"><img src="https://lh3.googleusercontent.com/-9z4vUiZOZnA/T6qbFDkEp5I/AAAAAAAAAzg/DOJoIXGnVkA/s640/DSCN5239.JPG" /> </span><br />
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<span style="font-family: inherit;">And the Kelly, next to a DVD for size reference:</span><br />
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<span style="font-family: inherit;"><img src="https://lh4.googleusercontent.com/-MG8CyoEQWUk/T8eaafqDMZI/AAAAAAAABCA/pXWMBcQyWXw/s640/DSCN5429.JPG" /> </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">Along with the controller, I got a hall effect twist grip throttle, which fit perfectly onto the mountain bike handlebars I fitted to the steering column. </span><br />
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<span style="font-family: inherit;"><img src="https://lh4.googleusercontent.com/-gfK7TeIs8ZU/T8eaal-68ZI/AAAAAAAABCE/E7_Ol1m4Gok/s640/DSCN5431.JPG" /> </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">Getting the mountain bike stem to fit the scooter's steering column involved a lot of shimming with aluminum flashing:</span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;"><img src="https://lh6.googleusercontent.com/-FZeWKF9ZcJ0/T8eabDkm6UI/AAAAAAAABCU/yET9SzwM0AE/s640/DSCN5432.JPG" /> </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">One problem with the original frame of the scooter is that its tiny deck is impractical for anything other than people with very small feet riding on very smooth surfaces. To fix this, I built a brand new deck, that is about three times the width of the original. I could have just ordered some 1/8" aluminum from McMaster, and with a little jigsawing and filing it would have made a great deck. I didn't think that approach was very interesting, though, so I took a much longer and more tedious route. Using the carbon fiber tow and resin left over from my<a href="http://build-its.blogspot.com/2010/09/building-bamboo-bike-frame.html"> bamboo bicycle</a>, I made a sheet of carbon fiber by wrapping the tow around a wooden frame, soaking it in resin, and compressing it between two pieces of plywood. Six times. Since carbon fiber is strong, but not particularly impact or abrasion resistant, I bonded the carbon fiber deck to a layer of 1/8" polycarbonate. </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">Here's the roughly made sheet of carbon fiber, along with the roll of tow and some resin. I still probably have a few kilometers of tow left, of the 5 km I originally got:</span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;"><img src="https://lh6.googleusercontent.com/-kv6thchjdiw/T8eaYggQzOI/AAAAAAAABBk/uCmCz1jYvRo/s640/DSCN5427.JPG" /> </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">Cut to shape:</span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;"><img src="https://lh6.googleusercontent.com/-6YUxCgWo8nM/T8eaaTN1pxI/AAAAAAAABB8/4kB_DQBofAE/s640/DSCN5428.JPG" /> </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">Plus the polycarbonate. The cutout is for the folding mechanism:</span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;"><img src="https://lh6.googleusercontent.com/-Fvx_fEgmTg8/T8eaYeQN1LI/AAAAAAAABBs/pRCgBFNEjuY/s640/DSCN5425.JPG" /> </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">The new deck was screwed to the original one with some countersunk stainless steel bolts:</span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;"><img src="https://lh3.googleusercontent.com/-uKELFRU21z8/T95zbairBNI/AAAAAAAABHo/BLcHsXf_yAw/s640/DSCN5504.JPG" /> </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">Here is the entire deck pictured, along with the <a href="http://www.amazon.com/HELLA-002843011-Series-Rating-Battery/dp/B0000AYAFE">Hella master power switch</a> that I used for, well, the master power switch.</span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;"><img src="https://lh4.googleusercontent.com/--nD6jLpr3dg/T95zbJCVdDI/AAAAAAAABHg/jG6NP1JeXqc/s640/DSCN5503.JPG" /> </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">To maximize battery space, I mounted the motor controller to the gearbox, via some aluminum angle:</span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;"><img src="https://lh4.googleusercontent.com/-pSD8QmUGe3Q/T95zY-aKnjI/AAAAAAAABGw/DKzA-uglmC4/s640/DSCN5496.JPG" /> </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;"><img src="https://lh5.googleusercontent.com/-RVM_Hv0G3cU/T95zYlcM21I/AAAAAAAABGo/O1oh3HHKwig/s640/DSCN5497.JPG" /> </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">I wired the motors in series using some large bullet connectors:</span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;"><img src="https://lh3.googleusercontent.com/-lB9ZRQSBh_Q/T95zYoZGvbI/AAAAAAAABGs/TiBtTDAUmy0/s640/DSCN5498.JPG" /> </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">The main power terminals were connected to the controller parallel to its top, to conserve space:</span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;"><img src="https://lh4.googleusercontent.com/-BDKob-qOuQU/T95zacS0iII/AAAAAAAABHY/rzPr8h3-a5Y/s640/DSCN5502.JPG" /> </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">I attached a power fuse to the deck with some more aluminum:</span><br />
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<span style="font-family: inherit;"><img src="https://lh4.googleusercontent.com/-adgfFfU6NS0/T95zdebssXI/AAAAAAAABIM/5dgPN3ABAm0/s640/DSCN5509.JPG" /> </span><br />
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<span style="font-family: inherit;"><img src="https://lh4.googleusercontent.com/-OU4MyEZrnvI/T95zfNLNgSI/AAAAAAAABIg/AvKlX6E-y0s/s640/DSCN5512.JPG" /> </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;"><img src="https://lh4.googleusercontent.com/-XhXWi1G0vuk/T95zfDrR4qI/AAAAAAAABIk/MoMN6Cti-iE/s640/DSCN5513.JPG" /> </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">While testing the suspension, I noticed that the 8mm stainless rod that I used as the pivot point for the rear suspension arm flexed significantly under load (e.g. me jumping up and down on it). To fix this, I drilled out all the 8mm holes to 1/2", and replaced the rod with a 1/2" stainless rod scavenged from an old scanner:</span><br />
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<span style="font-family: inherit;"><img src="https://lh6.googleusercontent.com/-rPjl-bpbD4E/T95zhSTm5KI/AAAAAAAABJE/IaDyRRZ1VeU/s640/DSCN5520.JPG" /> </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;"><img src="https://lh4.googleusercontent.com/-OhE74I-rZA4/T95zigrfMLI/AAAAAAAABJQ/ZSyXTrMmdNU/s640/DSCN5521.JPG" /> </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">For batteries, I ordered 9 4S 5 Ah hardcase LiPo packs from HobbyKing, which happen to be the best value in terms of Wh/$ you can find on the site. The 9th battery was an extra, since HK's quality control is not highly regarded. I used 8 of them to make a 16S2P pack, at a nominal 59.2V 10 Ah pack. That's around 600 watt hours. My poor 50 watt charger will need to be upgraded soon:</span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;"><img src="https://lh4.googleusercontent.com/-29JCjtcjQDE/T-EAgyYbt-I/AAAAAAAABJ0/BTOzi_Uy51U/s640/DSCN5523.JPG" /> </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">I paired off the battery packs, and wired the pairs in parallel, including the balance connectors:</span><br />
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<span style="font-family: inherit;"><img src="https://lh4.googleusercontent.com/-OjVrXwaD4hQ/T-o8zqqnvwI/AAAAAAAABLM/ZH59DFrA-1Q/s640/DSCN5531.JPG" /> </span><br />
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<span style="font-family: inherit;"><img src="https://lh3.googleusercontent.com/-ofEAP2ezCEo/T-o8yMzY4iI/AAAAAAAABKg/rCgaGGeqc_E/s640/DSCN5529.JPG" /> </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">I made a battery case out of some more aluminum angle, which I brazed together:</span><br />
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<span style="font-family: inherit;"><img src="https://lh3.googleusercontent.com/-UO7i6nfD1OM/T-o8zTf7cNI/AAAAAAAABK4/z4hHdlO1oOw/s640/DSCN5530.JPG" /> </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;"><img src="https://lh3.googleusercontent.com/-JD-GCSZCmnc/T-o8yBGkZEI/AAAAAAAABKo/tbxy4uk6NYc/s640/DSCN5527.JPG" /> </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">The front cover of the case can be removed by thumbscrews, for easy access to the charging connectors:</span><br />
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<span style="font-family: inherit;"><img src="https://lh4.googleusercontent.com/-CVD6ndAlHrg/T-o8zpOf8NI/AAAAAAAABK8/JBWzIu9-k0I/s640/DSCN5532.JPG" /> </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">Not shown is a polycarbonate bottom to the case, which holds the batteries up. Eventually, I'll plate the entire case in some sort of plastic.</span><br />
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<span style="font-family: inherit;"><img src="https://lh6.googleusercontent.com/-jSMBD28wmts/T-o82DqX-HI/AAAAAAAABLg/z9TeZZSaj8U/s640/DSCN5535.JPG" /> </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;"><img src="https://lh5.googleusercontent.com/-oFC3XIyl_-0/T-o82mp8pWI/AAAAAAAABLo/HId7uof1VW0/s640/DSCN5537.JPG" /> </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;"><img src="https://lh5.googleusercontent.com/-suXbnZYrgSc/T-pO8VrBr6I/AAAAAAAABMA/ziicI748W-8/s640/DSCN5553.JPG" /> </span></div>
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<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">When riding the scooter over bumps, I found that the chain frequently came off the drive sprocket. To fix this, I made a chain guard around the drive sprocket out of some angle aluminum. I cut out triangular wedges of the metal, so that I could bend it, and then brazed over the seams:</span><br />
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<span style="font-family: inherit;"><img src="https://lh6.googleusercontent.com/-lBdhTRCUFPU/T_Xy3QCjTVI/AAAAAAAABTA/tRgUle85kzA/s640/20120705_152905%2520-l.jpg" /> </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;"><img src="https://lh3.googleusercontent.com/-S1YU2mqDSe0/T_Xy3ZCMrPI/AAAAAAAABTE/JRkZx2TsJig/s640/20120705_153011.jpg" /> </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">The chain guard worked great, until I broke it. I went over a massive bump going down a trail, and the chain pushed up against it, breaking a brazed joint:</span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;"><img src="https://lh6.googleusercontent.com/-xCXiWHK78j8/T_YUDhJdhgI/AAAAAAAABYo/JVRqBT_jZvw/s640/20120705_180122.jpg" /> </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">I've since re-brazed the joints, and will be securing the chain guard at the other end as well.</span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">Here are some final pictures of the scooter:</span><br />
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<span style="font-family: inherit;"><img src="https://lh4.googleusercontent.com/-7o8vLAj14p4/T_Xy4ToVR0I/AAAAAAAABTc/LYwulLa2Gkk/s640/20120705_153614.jpg" /> </span><br />
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<span style="font-family: inherit;"><img src="https://lh5.googleusercontent.com/-ncxj9UrkcRc/T_Xy62IUhRI/AAAAAAAABTs/k7J1N_wgPlo/s640/20120705_153630.jpg" /> </span><br />
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<span style="font-family: inherit;"><img src="https://lh6.googleusercontent.com/--gsqLfsu9n0/T_Xy8Uaz4HI/AAAAAAAABUM/H406mBMKMKU/s640/20120705_153932.jpg" /> </span><br />
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<span style="font-family: inherit;"><img src="https://lh4.googleusercontent.com/-WUmE6dgc268/T_Xy9UitoFI/AAAAAAAABUY/6gbU4Jqr38A/s640/20120705_154005.jpg" /> </span><br />
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<span style="font-family: inherit;"><img src="https://lh5.googleusercontent.com/-JqytrRTG-qM/T_Xy-d86yHI/AAAAAAAABUk/BfykIh1_zAM/s640/20120705_154012.jpg" /> </span><br />
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<span style="font-family: inherit;"><img src="https://lh3.googleusercontent.com/-XnIkoWMSFC8/T_Xy--WKiLI/AAAAAAAABU0/OuXec4qOd5I/s640/20120705_154019.jpg" /> </span><br />
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<span style="font-family: inherit;"><img src="https://lh5.googleusercontent.com/-sZnbaHh5uXc/T_Xy_iHBsVI/AAAAAAAABVA/58yDy0fBJJo/s640/20120705_154027.jpg" /> </span><br />
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<span style="font-family: inherit;"><img src="https://lh3.googleusercontent.com/-IoDfCuW4I74/T_XzA90Wv2I/AAAAAAAABVc/PArgUR11E38/s640/20120705_154102.jpg" /> </span><br />
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<span style="font-family: inherit;"><img src="https://lh3.googleusercontent.com/-HfvGyROcZOA/T_XzCnrD3uI/AAAAAAAABWE/0PqXo8bQ1jw/s640/20120705_154201.jpg" /> </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;"><img src="https://lh6.googleusercontent.com/-C_vl5uv80rA/T_XzCYZjQII/AAAAAAAABV4/A5SDwozmpIg/s640/20120705_154151.jpg" /> </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">To make the scooter more convenient to charge, I made some modifications to my charger. I put the charger, along with the 12V power supply from a 2006 iMac desktop, into the shell of an old ATX power supply, so that I would not have to carry aroudn a separate pwer supply along with the charger. Also, I made a charging harness that will let me charge all the battery packs in parallel, for convenience.</span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;"><img src="https://lh5.googleusercontent.com/-vEXhzKRqsPc/T_Xzk-qAU-I/AAAAAAAABYY/eUeMu-mgzqA/s640/20120629_205932.jpg" /> </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">The charger is held down by some clips that were meant to secure wires inside a PC case.</span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;"><img src="https://lh3.googleusercontent.com/-Z89Q67Iu35w/T_XzhcyIQHI/AAAAAAAABWw/JK79_hN_pfI/s640/20120629_205205.jpg" /></span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;"><img src="https://lh6.googleusercontent.com/-tCF2leNRxs8/T_XzhSv_32I/AAAAAAAABW4/GpvmwWY6mIg/s640/20120629_205215.jpg" /> </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;"><img src="https://lh3.googleusercontent.com/-utb7QDQHta8/T_XzjhyrPTI/AAAAAAAABXU/_7v4bECguW0/s640/20120629_205630.jpg" /> </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;"><img src="https://lh6.googleusercontent.com/-chonLhlKA0s/T_XzkeBjvLI/AAAAAAAABXo/jHmfJ0QdTTs/s640/20120629_205643.jpg" /> </span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">Finally, here are some videos of riding the scooter:</span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">This first one is from before I added the chain guard. I went pretty light on the throttle for most of this video, and the only point at which I maxed it out is right at the end.</span></div>
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<span style="font-family: inherit;"><br /></span></div>
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<span style="font-family: inherit;"><iframe allowfullscreen="" frameborder="0" height="360" src="http://www.youtube.com/embed/KeNypuEwUJc" width="640"></iframe></span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">Here's a video taken with a camera attached just below the handlebars. This is where I broke the chain guard, and later on the master link of the chain. Average speed for the run was 15 mph, with a top speed of 24 mph. The scooter should be able to hit a little bit over that, give a long flat:</span><br />
<span style="font-family: inherit;"><br /></span></div>
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<span style="font-family: inherit;"><iframe allowfullscreen="" frameborder="0" height="360" src="http://www.youtube.com/embed/_6e4MBaeqxo" width="640"></iframe></span><br />
<span style="font-family: inherit;"><br /></span>
<span style="font-family: inherit;">Test with the camera attached to my helmet. The video is much smoother than the previous one as a result, even though it covers the same course. Also, in this run I broke even more things. I toasted two of the CIM motors. Honestly, I kind of deserved it for trying to go full throttle up a long steep hill... On taking them apart, one has some blackened windings, and while it spins, it does so slowly and unevenly. The other looks okay, but exhibits the same behavior. Also, I'm redoing the idler arrangement to keep the chain on track:</span><br />
<span style="font-family: inherit;"><br /></span>
<iframe allowfullscreen="" frameborder="0" height="360" src="http://www.youtube.com/embed/8MvDYclN7J0" width="640"></iframe></div>
Ben Katzhttp://www.blogger.com/profile/15816221191617788028noreply@blogger.com25tag:blogger.com,1999:blog-6555364095586804046.post-56749621771944584892012-05-31T23:11:00.000-04:002012-06-03T10:41:16.183-04:00Graduation GlassesFor my high school graduation, students walk onto the stage in pairs, and are expected to do something interesting (most do some variation of a dance move or handshake) when they meet in the middle, before going to their seats. Having been to my sister's graduation last year, I knew ahead of time that I wanted to make my entrance more interesting and less awkward than the ones I had seen. <br />
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I built two pairs of glasses - one for me, one for my walk in partner - that, when turned on, display "2012" across the two pairs. </div>
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<img height="480" src="https://lh4.googleusercontent.com/-jj40ILdWuLM/T8gqPjchHGI/AAAAAAAABD4/BEFJCrn_z6s/s640/DSCN5434.JPG" width="640" />
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I started out by getting two cheap plastic shutter glasses, 100 super bright 30 degree red LED's, and four 1x2 AAA battery holders:</div>
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<img height="480" src="https://lh6.googleusercontent.com/-Jx1FS6_VweY/T8gqKjfn8yI/AAAAAAAABCo/zCCBR9ir_GU/s640/DSCN5241.JPG" width="640" />
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LED layout:</div>
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<img height="480" src="https://lh3.googleusercontent.com/-qNBBge8jFEU/T8gqKoTQsaI/AAAAAAAABCk/yoat2-dq8vI/s640/DSCN5242.JPG" width="640" />
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Soldered "1":</div>
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<img height="480" src="https://lh3.googleusercontent.com/-qs0l_klY4fs/T8gqKrXo20I/AAAAAAAABCs/i-M-YTPQbCs/s640/DSCN5244.JPG" width="640" />
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<img height="480" src="https://lh6.googleusercontent.com/-_u9nRWcISNM/T8gqMKA5-wI/AAAAAAAABC8/AAaNW9Npuk8/s640/DSCN5245.JPG" width="640" />
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<img height="480" src="https://lh3.googleusercontent.com/-GQ9GW5SMZIY/T8gqMRwZmlI/AAAAAAAABDE/QmiPApk6eQc/s640/DSCN5250.JPG" width="640" />
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<img height="480" src="https://lh4.googleusercontent.com/-YQ7n0O_Vpww/T8gqNJGfEhI/AAAAAAAABDU/VmlEjh2C8lY/s640/DSCN5251.JPG" width="640" />
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All wired up:</div>
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<img height="480" src="https://lh5.googleusercontent.com/-R9kmNPcR67U/T8gqN3lV7QI/AAAAAAAABDc/5NWZYhUfHb4/s640/DSCN5252.JPG" width="640" />
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<img height="480" src="https://lh3.googleusercontent.com/-nqagoFsdnT4/T8gqNyh7EyI/AAAAAAAABDg/XYvhh7NheQw/s640/DSCN5255.JPG" width="640" />
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Both done:</div>
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<img height="480" src="https://lh6.googleusercontent.com/-VXdJvEmyLtY/T8gqOL59u2I/AAAAAAAABDo/CN0wBqO3qJQ/s640/DSCN5256.JPG" width="640" />
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I scavenged some switches from broken power supplies, and attached them to the frame:</div>
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<img height="480" src="https://lh4.googleusercontent.com/-L2TWLnAnhAA/T8gqPsrZRWI/AAAAAAAABD8/9gEGwGuhV5c/s640/DSCN5258.JPG" width="640" />
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<img height="480" src="https://lh6.googleusercontent.com/-99WntJ2F8Fg/T8gqQ-YqGyI/AAAAAAAABEQ/0zJqeWuxAmw/s640/DSCN5440.JPG" width="640" />
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<img height="480" src="https://lh4.googleusercontent.com/-jj40ILdWuLM/T8gqPjchHGI/AAAAAAAABD4/BEFJCrn_z6s/s640/DSCN5434.JPG" width="640" />
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<img height="480" src="https://lh5.googleusercontent.com/-4s0Z-lHtGwo/T8gqSzu53bI/AAAAAAAABEs/SXFqIuqbChw/s640/DSCN5435.JPG" width="640" />
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Apparently the graduation photographer's camera wasn't set up to capture bright lights well, but I've been told the looked good in person:</div>
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<img height="514" src="https://lh5.googleusercontent.com/-LaPvfKpoYyM/T8gxWq-qDcI/AAAAAAAABE8/UeuOb8Pu6sA/s640/graduation.jpg" width="640" />
</div>Ben Katzhttp://www.blogger.com/profile/15816221191617788028noreply@blogger.com1tag:blogger.com,1999:blog-6555364095586804046.post-39456459672463804242012-03-18T16:18:00.000-04:002012-06-27T19:56:26.989-04:00MIT Tube Hack<span style="font-family: inherit;"><iframe allowfullscreen="" frameborder="0" height="360" src="http://www.youtube.com/embed/rQvnmbdVYF0" width="640"></iframe></span><br />
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<span style="font-family: inherit;">This year in their early acceptance tubes, in honor of the 30th anniversery of the <a href="http://vimeo.com/33791625">great balloon hack</a>, the MIT admissions office sent a note encouraging us to hack our tubes. Since there were an number of balloons included in the tube, I decided to make my tube hack a tribute to the the great balloon hack. To fill the balloon, I built an electrolytic cell out of stainless steel washers. When the cell is placed in water (with baking soda added to increase its conductivity), the current splits the water into oxygen and hydrogen. This gas then fills the balloon. When the oxygen-hydrogen mixture in the balloon comes in contact with a flame, the oxygen and hydrogen very quickly combust back into water, producing a very satisfying explosion.</span><br />
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<a name='more'></a><span style="font-family: inherit;">Adjacent plates are insulated from each other by plastic spacers, to prevent short circuits. I used stainless steel rather than steel or zinc coated washers because otherwise the metal would combine with the pure oxygen on the oxygen producing plates, causing them to rust very quickly.</span><br />
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<span style="font-family: inherit;">You can find more hacks here:</span><br />
<a href="http://hackthetubes.mitadmissions.org/"><span style="font-family: inherit;">http://hackthetubes.mitadmissions.org/</span></a>Ben Katzhttp://www.blogger.com/profile/15816221191617788028noreply@blogger.com0