All-Terrain Electric Scooter

At the beginning of the 2011/2012 school year, my school's robotics team decided to finally dismantle some old FRC robots that had been collecting dust for six or seven years. We had no use for all the parts we stripped off the robots, so 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 this, which at one point used a pair of CIM motors. That vehicle then led me to these. By an interesting coincidence, only a few weeks after I discovered those vehicles, I went to the Atlanta Mini Maker Faire, and guess what I saw there. After seeing the vehicles in action, I decided to build my own electric vehicle, and so the idea for my scooter was born.

The scooter is geared for a top speed of about 25 mph, has around 3 horsepower, and can go 8-12 miles per charge.

Step 1: Parts and Tools

Here is a basic overview of the most important components used.  As much as possible I built the scooter with parts that I reused or already had on hand, so some of these exact parts are may be hard to find.

• Donor kick scooter frame - mine was a Royce Union Transit
• Wheels - I used 12.5" low-speed pneumatic wheels from Northern Tool
• Motor(s) - 3x CIM motors, which are generally used in FIRST robots
• Gearbox - CIM motors are fairly high speed/low torque motors, so a gearbox was required in addition to the reduction from the chain drive.  My franken-gearbox is a mashup of two Andy Mark Toughboxes from 2005.
• Motor Controller + throttle- I went a bit overkill, and chose a Kelly KDS72200E, 72V, 120 A continuous, 200A peak controller.
• Batteries - 8 x Turnigy 5000 mAh 4s LiPo packs
• Aluminum - angle channel and flat bar in a variety of sizesd
• Shock absorbers - 2x mountain bike rear shocks, 2x mountain bike fork shocks
• Nuts and bolts - too many and of too many different varieties to list here
• 1/2" threaded rod with matching nuts
• 1/2" and 8mm stainless steel rods + shaft collars- for the pivot points in the suspension
• Large power switch
• Fuse/Fuse holder
• High current terminal connectors

Tools

• Drill - with lots of large bits, up to at least 1/2"
• Hack Saw - if you have a bandsaw with metal cutting blades, please save yourself and use that
• Drill Press - Not strictly necessary, but it makes drilling precisely aligned holes much easier than with a hand drill
• File - for smoothing sharp corners and enlarging holes
• Propane torch and aluminum-zinc brazing rods
• An assortment of clamps
• Bench vice - mine was literally a workbench that was a vice, but the kind that bolts onto a bench would be even better
• Soldering iron + solder - one with a very heavy tip for soldering large power connectors and battery leads
• Lithium Polymer battery charger with power supply
• At least two adjustable wrenches

Comments

[Luigi_pl]

Wow ! I'm impressed !
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 ?

[Adnan Fahim]

how much did it costs

[Ralphxyz]

How did you do the aluminum brazing?

That would make a good instructable.

Great scooter nice job.

Where are you gong to school now?

thanks

Ralph

[ben_k]

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/

It's nowhere near as strong as welding, but all it takes is a propane torch and a stainless steel wire brush.

Thanks!

I am now a freshman at MIT

[Trike Lover]

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 "scrap" 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....

(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).

[ben_k]

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.

You could get the batteries from HobbyKing's international warehouse, although shipping will take longer and be more expensive.

[Trike Lover]

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 "international" shipping rates, the stuff comes domestic parcel post here, at least.
Years ago, I worked in an engineering research lab. It was amazing what we used to get for the price of disassembling it.

Thanks for your interesting article. Cheers.

[AudioMaximus]

Is your robotics team a FIRST team? I'm on one as well, team 1676 the Pascack Pi-Oneers

[AudioMaximus]

nvr mind i just saw ur an FRC team. Good to see another FRC member here

[ben_k]

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.

[AudioMaximus]

Ah gotcha.

[Wingloader]

If you round the corners of your steel plates, it would up the sexy factory by 10.

You could seriously make and sell these. Don't pass up an opportunity to make money foo.

[M3G]

I NEED one of these!

[WWC]

Nice build.
Have you noticed anything getting hot?
Connectors ect from the current.

How did you determine the springs to use. Maybe you used my high tech method of best guess.

W

[ben_k]

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.

I arbitrarily decided that I wanted the suspension to compress about 1/2" 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.

[ben_k]

Sorry, 3000 lbs/in, not in/lb

[AndrewryanSears]

Can i buy one from u

[triumphman]

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.

[Arghus]

i want one , so jealous :D

[NickGriffin]

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?

[ben_k]

I weigh about 145 lbs, so it would take 150 no problem. It's also handled a 175 lb rider just fine.

[nissan0712]

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.

[Edgar]

Pro work, if you ask me! =)

Gone to my Portuguese Gizmo Blog post,

http://faz-voce-mesmo.blogspot.pt/2012/09/3d-em-faianca-metal-fluido-rostok-mais.html

and since China treatens to make a new Gold-based Currency, I've gone and downloaded the Pdf...
Might come handy!

[trrydms]

Awesomey awesomeness.

[paininthebutt]

COOL ! PHERB I KNOW WHAT WE ARE GOING TO DO TODAY!

[dfergemann]

Very cool. I'm glad to see that you eventually put on shoes and a helmet.

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?

[ben_k]

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.

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.

[scolton]

This gearbox is epic.

[ride on toy dude]

H. O. L. Y. C.O. W.!!!!!!!