Crazy "knee" scooter.

[Jayls5]

Ok, so modified a mobility scooter a while back:

https://www.youtube.com/watch?v=Ib5SEWjYTJ0

I machined out the wheel hubs to fit larger wheels and slight over-volted it with a 8S LIPO setup.

It lasted for years, but the controller finally died the other day after hours of kids off-road abusing it. The motor & trans-axle is still good though, so I pulled it off.

So here's my plan: I recently broke my foot, so I've got one of those ultralight knee scooters. This is what I will be working with:

https://www.amazon.com/gp/product/B00I471EI8

I also have a Kelly KDS-72200E controller. Specs:

http://kellycontroller.com/kds72200e200a24v-72v-mini-brushed-controller-p-762.html?osCsid=5m0m5sqeueobdtdb35tu337v71

Does anyone happen to know the relatively safe capabilities of the old "Pride Victory" scooter motors?

I can control both the end voltage as well as the current the motor will see. It's a 24v brushed DC motor.

Questions: I'm wondering what kind of current & voltages I should feed it before I have to worry about arcing. I was thinking of doing 100A max and 35v. Reasonable?

Should I do rear or FWD? I'm leaning towards front at the moment to slightly widen the wheel base and make turns less abrupt, plus the brake is already in the rear.

Thoughts/comments/concerns please!

 

[liveforphysics]

Being brushed, it's a complex crap shoot of how much humidity and conductive brush debris powder you've got around the commutator.

Trial and error, while being quick to let off the throttle is perhaps the best option. Good luck!

 

[amberwolf]

There are a lot of different motors various mobility stuff uses. Which specific one do you have?

I can say that the "300w" 24v brushed motors I used on the original CrazyBike2 can handle up to at least around 48v ok, but they'll overheat quickly if you keep putting a lot of current thru them--I'd guess they might be able to shed the heat of about 300-400w of motor power (assuming you are using them at at least their rated RPM), without additional cooling.

The "600w" motors were larger and could probably shed the heat of 600-750w of motor power, I'd guess.


They can survive momentary bursts at much higher currents; IIRC I've put something like 2.5Kw (according to the wattmeter) thru one before the 4QD controller blew it's FETs, when I had a chain jam (which bent the rear axle and destroyed the rear wheel, and some chainrings along the way). But that was at most a few seconds.

I've also burned the commutator on one at much lower power.... :/


FWIW, 100A and 35v is 3500w, which is going to smoke that motor from overheating if you repeatedly hit that frequently.

But realistically, with as little load as the knee scooter has on it (unless you weigh half a ton or something ), that will be some massive torque (it might even damage the transaxle if it's slammed on repeatedly, so you might want to ramp up the throttle), and I am not sure you can actually use that much power on that little knee scooter.


Given the wheelbase, FWD is your only safe option at any significant torque, unless you want to break something else when it wheelies and flips you over on your back.

 

[Jayls5]

Awesome. FWD it is.

It was an older "Pride Victory" scooter. The stock controller was 70A model. The old scooter probably weighed 80 pounds and supported 350+ lb people in stock format, able to climb slight hills. This knee scooter probably weighs about 30 pounds.

The Kelly does have a ramp function, so that can be used to keep the initial torque from ripping you off the scooter. This is going to be interesting.