[Exco] had been playing around with the idea of building an electric scooter for a while now, and over the holidays he decided to just do it.
Similar to the motorized long board we shared last month, this scooter makes use of an RC hobby motor — in this case, a 63mm 3kW brushless outrunner (for a RC plane), coupled with a 100A ESC. He bought the scooter (“kick board”) off eBay for cheap, and spent a few days in the machine shop modifying it. It has better wheels now, and custom milled aluminum brackets for mounting the motor. The drive system uses a belt and pulley with a sliding rail to provide tensioning.
To power it, he bought a bunch of 2.5Ah, 18V LiPo packs on eBay originally from a Makita drill set. He then sorted out the cells, removed the dead ones, and soldered everything together for his own Frankenstein pack to balance them. The final configuration features twenty-one 18650 lithium cells. He even shrink wrapped it, which makes it look relatively professional!
It’s controlled by a push-button potentiometer hooked up to the ESC. Theoretical top speed is about 27km/h @ 1285RPM, and they managed to get it up to 25km/h in a real test. There’s more info over at the Endless Sphere forum, and we’ve got two test videos for you after the break.
[Thanks Momo!]
Reminds me of combat robot style (think Battle Bots) drives and motors.
Would I be mistaken if I’m skeptical of the implied 4 hp. produced by such a physically small motor? Even if it’s it’s for brief peak I can’t see how such a spec could be useful, other than for marketing. I’m understand James is reporting what he was given, and I’m not blaming him for anything.
The thing about RC airplane/helicopter motors, as far as I’ve always understood it, is that they CAN produce the rated power output but in doing so they are running much closer to their absolute physical limits than motors in most other industries. As such, it’s much easier to burn them up by accident and they aren’t expected to have as long of a service life.
Also, I believe you are expected to almost always run them extremely close to their optimal RPM.
No, brushless motors can be run at a really wide range of speed while keeping high torque, at least compared to DC motors.
The RC motor rating is based on the assumption that they are “air over” design. Even in HVAC application, the motors which drive the fan directly (and hence gets cooled), have higher ratings. I am not sure as how this motor will behave in scooter, which do not have forced cooling of motor.
He also makes porn.
The “we make porn” sticker is next to pedo bear sticker…
“We make porn” is the moto of Tetalab, a hacker’s space in Toulouse, southern France.
I’m sure they’ll be glad to trade stickers : http://tetalab.org/
Or they let you print your own : http://wemakeporn.tetalab.org/WMP_STICK_RECT.pdf
Well that’s my summer holiday sorted out.
I’m pretty sure neither that belt nor that wheel can actually take 3kW … the belt is going to stip pretty quickly.
A bike chain would be a better choice, but would probably also not last very long.
*strip
The speed record achieved with this thing is at around 25 kph. I know, because i was the one who did it.
The belt is close to dead, the motor has way too much torque :(
35 roller chain is where it’s at. take in your tensioner all the way before sizing because it WILL stretch!
3kw is only the rating of the motor – which it could produce @10s.
I’m only running it at 7s – and the max recorded power to the controller was ~1kw (38A @28V (-voltage drop)) – which is still pretty much power. It even does wheelies.
The belt wore down really fast because my 1st motor mount wouldn’t hold up to the torque.
It’ll be upgraded from T5 to AT5 and I expect it to last longer than I’m interested in riding it ;-)
35 rollerchain
It’s good to know the motor’s so versatile. Wonder what you could use instead of a belt, since it’s handy having the elasticity in something that jiggles a lot. Maybe a bigger belt I suppose! Or maybe 2 belts.
Motor cycle chain would be best yet. You can put a couple hundred HP through some of those.
Better yet would be HI-Vo chain you find on some motorcycle camshafts. It’s very compact and is good with small sprockets with few teeth. It would need to be encased ideally though.
Cool sticker collection.
Good luck with the project.
Nice project. Scooters can be difficult depending on your parts available. I built one with a “300W” brushed DC motor I overvolted to ~32V running off LiPos and a homebuilt speed controller. When it wasn’t smoking FETs it’d do ~37km/h. Anything more than a KW on these things is generally overkill – you can’t accelerate very fast on a push scooter safely without losing control in one way or another, generally by popping the front wheel due to the high torque. Gear down more and you could go a lot faster with that power. Though, I have melted wheels before on mine. It’s a tough design game!
Well the max recorded power to the motor was ~1 kw (38A @ 28V (-voltage drop)).
The belt wore out because my first motor mount bent.
I’m upgrading from a T5 to AT5 belt and think it will hold longer than I’ll be interested in riding it ;-)