P3PPY GRM+ Memberand HalfDork
6/22/20 3:49 p.m.

This will be my build thread for my kids' power wheels electric ride on cars.

My eldest has a 12 V Shelby Cobra and my second has a 6 V Mini Cooper S.

Mod #1: Rubber tires on the Cobra

After about 6 miles in the past 6 years the plastic wheels had come apart.

I taped them back into their correct shape and filled the void with Great Stuff in order to salvage them. I would have ordered new ones and still added rubber but no one has them in stock.

I cannot recommend this as it expressly states that it won't work well in closed spaces and they're correct. There were many hassles with this.

Then I got a few old bike tires from the local shop and cut them to the diameter of the wheel, splayed them out after removing the metal hoops and used some low profile wood screws to attach them to what was left of the wheel surface.

Ideally you're going to do this long before the mounting face of the wheel gets as thin as mine are.

Before going this route I also looked into lawnmower tires and go kart tires but they're just so expensive and would require even more modding to make work. I came across a couple used ones for free and they were too big. The clearance up front is very close at lock so I would have to be even more careful if I tried to put a real tire there.


Mod #2: Make the Cooper faster.

The Cooper was slower than the Cobra's slow mode so after looking into it I put a 12 V battery in the Cooper and now it's medium fast. On some 6 V cars they say it can fry this that or the other thing but it hasn't done anything untoward after over a week.


Mod #3: Cooper battery relocation to reduce "torque steer."

It's a one wheel wonder (back right) and whenever she accelerates it drags the zero traction front wheels laterally about 30 degrees to the left. I've advised her to lean forward on acceleration, which helps. In order to assist with front traction I mounted the battery onto the firewall. It helps, but not enough. The forward lean is still necessary. Before it's almost too late (as with the Cobra) I will add rubber tread to the tires which may help, too.


Mod#4: A real throttle pedal and brakes.

The next step is to use these donor scooters in order to provide variable throttle acceleration. I'm working through some questions since I have no idea how electronics work and I'm not sure if it's cool to use the twist throttles from these 24 V scooters with 12 V systems. Ideally they will "just work" and I can rig something up with cables to replicate the UX of using a pedal. My eldest can probably learn to use a brake but I'll have to see about using the resistance of the motor itself to stop the Cooper. This is not yet the right time to add any complexity to the driving experience on that one.

I got this pair for $50. One works fine but has a cracked frame. The other acts as if it turns on and has power but doesn't respond to throttle input-- although one time I was sure it did for just a moment. I haven't dug into them yet but I'm hopeful that since one was used hard enough to snap at a weld then the other one is just shaken loose somehow. In any event, the batteries in them when wired in parallel will keep me from having to buy a new riding mower battery, I hope, thus justifying the cost to Mrs. P3PPY.

After that gets to working I'll see about adding the motors to the cars. I expect I'll need to keep at least some of the power wheels OE motorwork in place since these scooters require a 3mph kickstart to get going. I also do not want them running these at the full 24 V yet because it's so silly fast. The cracked one keeps trying to launch out from under me. So then I'll also need to know if I can run 24 V motors at 12 V indefinitely without causing issues of some kind. For all I know the throttle control does just that by limiting the volts to the motor, but ???

TED_fiestaHP Reader
6/22/20 7:40 p.m.

   Have you seen the you tube films of the girl drifting one of these cars?

MrJoshua UltimaDork
6/22/20 8:29 p.m.

The best setup I had on one was rubber on the front tires and an 18V Ryobi battery hooked to the dual motor model. My daughter learned to use the off throttle rear wheel braking to step the rear end out and tighten her turns. She was quite impressive with her car control.

nderwater UltimaDork
6/22/20 11:51 p.m.

Like what I see so far. Never seen that cobra body before—nice score!

P3PPY GRM+ Memberand HalfDork
6/23/20 9:27 a.m.

Before doing the retread the Cobra would spin both tires on accel and lock them up at release. So since the age of 2 my daughter was learning to drive with a squirrely rear end, which makes me happy. Yeah I'm trying to not live vicariously through them, but if they DO happen to enjoy driving like that, they have an enabler dad waiting in the wings.

And yes I love that Cobra. It's the car she was named after and my sister in law found it at a garage sale right before Shelby was born. We have a friend in KC, Brian Pyle and his wife Cheryl, who have a Cobra who did a really cool photoshoot with her and her car:

I'll put in a plug for them while I'm at it -- if you're in the KC area and need HVAC work give the Pyles a call at Modern Air Cooling & Heating. He's far more of a car guy than I'll ever be.


Back to the matter at hand, while I'll be doing my own research, does anyone have experience with modding the kickstart function or know if it can run at 12 V all day? Or the principle behind how these throttles work?


Regarding the Ryobi - did you just replace one motor with the drill motor and leave the "gearbox" in place?

nderwater UltimaDork
6/23/20 10:09 a.m.

Wow that’s a hot car, awesome pic

Placemotorsports GRM+ Memberand Reader
6/23/20 10:11 a.m.

I was going to do a dual battery set up in a Jeep Hurricane years back but never got time to mess with it and sold it

stylngle2003 GRM+ Memberand Reader
6/23/20 2:52 p.m.

you can put a resistor on one of the wires from the pedal to the motors to lessen the locking effect when off-throttle.  ML Toys sells it as a Brake Reduction Module.  I call it: https://www.amazon.com/uxcell-Aluminum-Resistor-Wirewound-Resistors/dp/B07DNB7Q5X/ref=sr_1_2?dchild=1&keywords=Wirewound+Resistor%2C+25W+0.47+Ohm+5%25&qid=1592941662&sr=8-2 


Re: the drill battery, i think he means he basically ran 18v through the stock wiring/motors.  Good for a little while, anyway.  Hard on gearboxes, especially with rubber tires.

Mndsm MegaDork
6/23/20 3:22 p.m.
TED_fiestaHP said:

   Have you seen the you tube films of the girl drifting one of these cars?

That's Josh Kalis' daughter- he is a pro skater and all around car nut. Ran a Dinan 5 series in a cannonball back in the early 2000s. 

MrJoshua UltimaDork
6/23/20 4:05 p.m.

Re: the drill battery, i think he means he basically ran 18v through the stock wiring/motors.  Good for a little while, anyway.  Hard on gearboxes, especially with rubber tires.

Yep, chopped the battery mount off of a drill so I could hot swap it. It had a better run time than the stock battery but it would melt the plastic around the drill battery terminals a bit. I never broke a gearbox but I never went to rubber rear tires either.

P3PPY GRM+ Memberand HalfDork
6/23/20 8:30 p.m.

In reply to stylngle2003 :

Is the one you linked to the exact one I’d need? And, does it still result in a stopped car, just not as suddenly? Or does it result in a slower car?

also, I’d read that for the OE pedal setup there’s a third wire there that is there to “short” the motor into stopping whenever the pedal is released— is that the wire you’re talking about putting this inline on? 16 gauge wire, FWIW. 

Thanks, by the way, stuff like this is super helpful. 

P3PPY GRM+ Memberand HalfDork
6/23/20 8:32 p.m.
nderwater said:

Wow that’s a hot car, awesome pic

I believe it’s for sale now. $160k, IIRC. He took me for a ride after the photo shoot. 427. He only really hit it once and it was ...hard to describe, just - I’m at a loss for words, really. It seemed like so much power and I wondered where in the world you could reasonably make use of it. It was incredible. 

P3PPY GRM+ Memberand HalfDork
6/25/20 8:27 a.m.

Well, first snag with the scooters is that the batteries in one are kaput, which was not altogether unanticipated. Happily the throttle and motors in both. FWIW they're 2x 12 V 6 Ah

Second snag: throttle on these is on/off, not variable. I'm not sure how I missed that. Looking into other options now.

P3PPY GRM+ Memberand HalfDork
12/5/20 8:16 p.m.

So after months of deliberating I finally just cracked into it the other night, starting with the slower of the two, the single motor 6V Cooper (that has a 12V battery in it). I pulled out the motor from the Razor - there’s nothing complicated about the “power core” setup. Very tiny snap rings that I didn’t notice at first and so I couldn’t tell how it was all put together though. 

The body of the 24V Razor motor is the same size as the powerwheels 6, same as the 12Vs. I was going to just swap it straight in but the gear on the shaft is about a mm wider and wouldn’t quite mate up with the first gear in the stock gearbox. I couldn’t get it to come off the shaft either. If I tried softening the plastic gearbox gear with heat and was careful, I might make it happen. Else, casting it from aluminum might get the right shrinkage. 

Anyway I looked on Amazon and came across this whole 12 V dual motor setup for only $36.


A couple days later I got it in the Mini Cooper. I was even able to reuse all of the Cooper’s controls by just plugging the new stuff into them. Instead of the key being on/off now it’s for the fast/slow toggle - something the original setup didn’t have - and I left the power button turned on and hidden under the body, pulling the LED power wire first. 

To get the motor on the driver’s side of the shaft, I used a sledge to beat flat these little tabs on the bar that the wheels and gearboxes slide onto. I cut a 2” hole for the motor to go thru but was just barely off so softened it with a butane torch and stretched the hole out that way. 

I even soldered her headlight power cords onto the new wiring.

It works great. Her car is exactly the same speed as her big sister’s Cobra. The Cobra takes off with a kick but intentional or not there’s a slow start smoothness to the Cooper’s new motors when they start. She’s so happy now, she was crying to herself driving alongside her sister. 

nderwater UltimaDork
4/12/21 6:18 p.m.

Time for an update!  How did your mods work out?

Our Preferred Partners