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Step 6: Gearbox

Because the CIM motors I used are relatively high-speed low-torque motors, a gearbox was needed to reduce the motors' output speed to a useable level.  I started out with two AndyMark Toughboxes, scavenged from my school.  These are two-motor, two-stage gearboxes, so I had to cut them apart and recombine them to make them useful.  First I removed one stage from each of the gearboxes, for a gear ratio of 14:50.   I cut down the gearboxes to get rid of as much wasted space as possible, and aluminum-zinc brazed the pieces back together to get a 3-motor gearbox with one output shaft.

The gearbox was mounted to the scooter using the original bolt holes built into the gearbox and some aluminum angle bolted to the scooter's frame.  Finally, a 21 tooth sprocket for #35 chain was fixed to the output shaft.
<p>Great design but one thing I think I will try for is to make one lighter and free wheeling. So that when you reach a pre determined speed the motors idle instead of, when the power shuts off, slowing the scooter so abruptly.</p>
<p>Gangster! </p>
Powerfull!! But me thinks it would cost the less-generous soul a couple of grand to duplicate what you have there! <br>God bless the dumpster-diver!
Powerfull!! But me thinks it would cost the less-generous soul a couple of grand to duplicate what you have there! <br>God bless the dumpster-diver!
Powerfull!! But me thinks it would cost the less-generous soul a couple of grand to duplicate what you have there! <br>God bless the dumpster-diver!
Powerfull!! But me thinks it would cost the less-generous soul a couple of grand to duplicate what you have there! <br>God bless the dumpster-diver!
Powerfull!! But me thinks it would cost the less-generous soul a couple of grand to duplicate what you have there! <br>God bless the dumpster-diver!
Powerfull!! But me thinks it would cost the less-generous soul a couple of grand to duplicate what you have there! <br>God bless the dumpster-diver!
Powerfull!! But me thinks it would cost the less-generous soul a couple of grand to duplicate what you have there! <br>God bless the dumpster-diver!
hey im from team 2974 walton robotics. if you live near atlanta have you ever gone to DE
Cool
This is bad ass, way to go. <br>http://www.kickstarter.com/projects/plasanator/the-eic-1-wireless-remote-control-training-lab
im somewhat concerned about how you intend to use the batteries. lithium polymer is well known for its ability to put out a continues currunt for long periods of time however not many people know that if one of the cells inside the battery falls below 3V its a dead battery and cannot be charged agian deppending on the lipo charger your using it will refuse to charge that battery for safety reasons (rapid combustion of the battery into a ball of fire 4ft wide) however if you were to intagrate a voltage limeter that cuts power to the motors at 96V-100V or 48V-50V if you want to use four sets of two batterys in parallel then connect the sets in series as for the volatges how i worked it out was the 4S batteries have four cells each 4x3v=12v 12v x 8 batteries 96v cut off or 12v parallel x 4 set = 48v double the run time
Wow ! I'm impressed ! <br>I want to build ev scooter myself and i'm wondering how much powerful motor i have to use. Can You tell me how powerful are this CMI motors ?
how much did it costs <br>
How did you do the aluminum brazing? <br> <br>That would make a good instructable. <br> <br>Great scooter nice job. <br> <br>Where are you gong to school now? <br> <br>thanks <br> <br>Ralph <br> <br>
I did aluminum-zinc brazing, using Alumiweld brazing rods, which can be found on ebay. It's pretty much the same as Durafix: http://durafix.com/ <br> <br>It's nowhere near as strong as welding, but all it takes is a propane torch and a stainless steel wire brush. <br> <br>Thanks! <br> <br>I am now a freshman at MIT
This is a really interesting, imaginative and entertaining build. The only downside (for me, at least) is that none of the major components except the wheels and the controller are readily available to buy, and I am not lucky enough to have a source of &quot;scrap&quot; motors, gearboxes, etc. I'm currently building a recumbent trike with electric assist, so I was especially interested in your choice of lightweight high capacity batteries. Being more gravitationally challenged, and building a much larger vehicle poses different challenges, but your project is nonetheless very interesting. Just wish I had access to your scrap bin.... <br> <br>(Ironic sidelight - the HobbyKing web site says these batteries are available for shipping to the U.S. only. The irony is that Hobby King's warehouse is close to where I work - in Canada, and shipments to U.S. customers go out from there. How do I know that.? Their parcel pickup is the same truck as ours. Go figure). <br>
Most of the parts can be bought, other than the gearbox and the particular scooter frame I used, just I happened to have a source for free ones. All the raw materials like aluminum and polycarbonate, as well as hardware and sprockets can be sourced from the likes of McMaster. The motors can be purchased a number of sites like AndyMark, Vex, and a few others. The mountain bike parts like the fork and springs, handlebars are all easy to find as well. <br> <br>You could get the batteries from HobbyKing's international warehouse, although shipping will take longer and be more expensive.
Ben, you are correct of course - most all can be bought. I'm just cheap - also poor - but I like to find major components as part of a good scrounge. Princess Auto locally have all the driveline parts and wheels, and periodically their surplus section will get in some suitable motors. Springs I've gotten for the trike from the Internet, and disc brake components also. As for Hobby King, their warehouse is just down the road, and although they charge &quot;international&quot; shipping rates, the stuff comes domestic parcel post here, at least. <br>Years ago, I worked in an engineering research lab. It was amazing what we used to get for the price of disassembling it. <br> <br>Thanks for your interesting article. Cheers. <br> <br>
Is your robotics team a FIRST team? I'm on one as well, team 1676 the Pascack Pi-Oneers
nvr mind i just saw ur an FRC team. Good to see another FRC member here
Actually my school did VEX. They had a FIRST team ~7 years ago, which is where I got the motors and other parts from. Also, I graduated, so I'm no longer on the team.
Ah gotcha.
If you round the corners of your steel plates, it would up the sexy factory by 10. <br> <br>You could seriously make and sell these. Don't pass up an opportunity to make money foo.
I NEED one of these!
Nice build. <br>Have you noticed anything getting hot? <br>Connectors ect from the current. <br> <br>How did you determine the springs to use. Maybe you used my high tech method of best guess. <br> <br>W
Yes, the motors can get quite hot. Riding on flat ground, they usually just get a little warm, but frequent hard acceleration or hills make them anywhere from quite warm to too hot to touch. I actually managed to burn out two motors going up a long hill at full throttle. The connectors near the motors get warm as well, but it's probably mostly because they sink some of the heat from the motors. <br> <br>I arbitrarily decided that I wanted the suspension to compress about 1/2&quot; with just my weight on it, so I did some rough calculations based on the length of the lever ams involved in the suspension mechanism to get around 3000 in/lb for the total spring constant of the parallel springs.
Sorry, 3000 lbs/in, not in/lb
Can i buy one from u
Nice machining! Very cool. Would love one of these! Scooters lookout here I come!
This is really cool. I share your experience with the bearings. With my electric GoKart, I find that the drive system, and in particular the bearings, are almost always the components that fail.
i want one , so jealous :D
Did I miss a weight limit? If not, how much weight have you tried on this little monster? (Love it, BTW) would it take 150 Lbs or thereabouts?
I weigh about 145 lbs, so it would take 150 no problem. It's also handled a 175 lb rider just fine.
i have 2 of these scooter frames to start with. WOOHOO. cant wait to make one of these for car meets and car shows to zoom around on.
Pro work, if you ask me! =) <br> <br>Gone to my Portuguese Gizmo Blog post, <br> <br>http://faz-voce-mesmo.blogspot.pt/2012/09/3d-em-faianca-metal-fluido-rostok-mais.html <br> <br>and since China treatens to make a new Gold-based Currency, I've gone and downloaded the Pdf... <br>Might come handy! <br>
Awesomey awesomeness.
COOL ! PHERB I KNOW WHAT WE ARE GOING TO DO TODAY! <br>
Very cool. I'm glad to see that you eventually put on shoes and a helmet. <br> <br>Why not wire both the batteries and the motors in parallel to keep the motors at 14.8V, where they're unlikely to burn out?
If I wired the motors in parallel and used a lower voltage battery pack, I would need a motor controller that could handle 3 times the current as with the batteries in series and a high voltage battery pack. It was much easier to find a high voltage/low current controller than a low voltage/high current controller. <br> <br>I could get the same effect if I just removed one of the four modules from the battery pack, making a 44.4V pack split across 3 motors in series, for 14.8V per motor. But, assuming the motors have similar efficiency at 14.8 and 20 volts, the motors should put out about twice as much mechanical power when running at 20V vs 14.8V, and I'd rather just avoid long hills than sacrifice top speed and acceleration.
This gearbox is epic.
H. O. L. Y. C.O. W.!!!!!!!

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