[skinnyR1]

Hello,

I have a 24V set up with a PWM ECM in my kids jeep powerwheels. I have run a variety of motors in the past. Stock to HPI 550's to the Titan 775's. They have all ran fine until they went up in smoke or slowed down from use. I have now made adapters to run Dewalt 802's. They are DeWalt 396505-21SV. These are big motors with replaceable brushes.

The problem I am encountering is that they have very little power. They spin up to speed then slow down. They won't move the power wheels with a kid in them. The only thing I can think of is they need a capacitor. The Titan's have a small cap soldered onto them that I have noticed. Are these big Dewalts drawing too much and the pulsing of the ECM is not enough to run them without a cap?

Do these need a capacitor too? How big and what size if so? Is my theory here sound correct or is there possibly something else I am missing?

[DOHC20]

Hi
these should have enough power to run the jeep. im in the process of doing my own conversion with two of these in my daughters range rover. HOWEVER...these motors have advanced timing which is not adjustable meaning they will rotate in the forward direction faster than they do backwards which means if you use 2 of them ( 1 on each side of the car ) one will rotate slower when moving forwards! i had to open one of the motors and reverse the timing back the other direction. they have plenty of power, depends on how you are driving them??

[thisdave]

Would you guys share pictures of your set up with these motors? Apart from reversing the timing is it pretty trivial to swap these motors to fit on a powerwheel gearbox.

How much are you paying for these ? $40 each ?
cheers.

[DOHC20]

they are fairly easy to fit to the gearboxes, i just brought the ML toys motor mounting kit which basically made it a straight fit, the only thing i had to do was put a slight schamfer on the outer edge of the mounting spacers to clear the motor just slightly, this can be done with a grinder if you dint have a lathe. and just elongate the holes in the gearbox and spacers because the 820s have a slightly wider mounting hole spacing, its all easy done with basic tools. the hardest part is the timing adjustments..

[thisdave]

Be interested to hear your verdict once you have these up and running.
and how they compare to the 775 motors http://www.mltoys.com/product-p/matched-775s.htm
Seeing as they are a similar price. pros and cons etc.

I'm hoping to swap the motors out on a PW Jeep Wrangler soon... initially running at 12volts but once my daughter gets the hang of it upgrading to 24volts and an ESC accelerator etc.
Cheers for the response.

Did you get the timing figured out? how involved is it ?

[DOHC20]

yeah the timing does require some cutting of the motor can for clearance of the brushes. and i brought a digital rmp meter to measure the rpms against the other motor so that was my method of timing matching/rpm matching ill try and get some pics the next time im out doing some work on it if i remember..

[skinnyR1]

I don't have timing issues, they just have very little power.

Do you have the small caps on these motors to make them work?

[DOHC20]

nope, no caps at all. and ive got heaps of torque. It has so much torque that it can drag me behind it with no issues.

[thisdave]

@DOHC20, would you share what you had to do to the motors with pictures if possible cheers.

I haven't bought the motors yet and am on the fence as to whether I'll be able to get them to work..

Cheers.

[DOHC20]

so here is a few pics of the motor in the gearboxes, i think they are worth it. i was testing the car on the weekend and it has heaps of torque, so much so that it has no problems spinning the wheels on takeoff. Im running them off a motion dynamics 50A bi-directional controller via RC transmitter and a 29v lipo.

[thisdave]

Thanks.. they look pretty awesome.
when you said "! i had to open one of the motors and reverse the timing back the other direction."
Was this trivial? and obvious... as in did you just have to open one up and flip something over ? or more involved ?

[DOHC20]

It was a little bit involved but if you put your mind to it its doable. In the photos you can see where I cut the motor can to make way for the brush springs, that's all I had to cut but it also ment that the motor didn't close up again so I had to make my own mounts out of angle plate alloy that mounted inside the motor can so I could screw the end bell back in. That was a little tricky not knowing what to do but now that I've done it you guys can just copy what I've done. I brought a digital rpm meter from Ebay to calibrate the two motors to the same rpm so now they both spin at exactly the same rpm. I also forgot to mention that I did damage the bronze bearing when I took it apart because I cocked it over so it became elongated and didn't sound right when I ran it all low rpms so I brought ball bearings from ebay which ended up being an upgrade anyway

[Hammer-fm]

What kind of RPM are these running at 29V? It sounds like these may be a good candidate for bypassing 1st gear, ala: this design. The original prototype I did of that involved a single 24V motor -- there's nothing about it that requires multiple motors, though using 2x 12-18V motors has proven to be very reliable. Given that you've done quite a bit of modification anyway, this would probably be a very simple conversion.

Given that it's about a 2.8x speed increase when bypassing 1st gear(if you keep the motor gear as-is), you'd likely have to move down to a 13-15T gear instead of the 22T(?) one you are using. It would allow you to run lower RPMs: to get the equivalent of the gearing I set up in the Pink Rocket Mustang (2nd-gear drive, 14T, ~22000 RPM motors @ 18V/ea), you would have to spin a 22T 1st-gear drive motor at 40,000 RPM.

[DOHC20]

I'm not 100% sure on the rpms but I may recall about 35000rpm from when I was using the rpm meter to match rpms.
A first gear bypass would be interesting with these motors as they have heaps of torque even with the 22t pinion. I guess if you kept the 22t and did the 1st gear delete it would go like a rocket...

[Hammer-fm]

I think the 2.8x increase in speed (and corresponding decrease in torque) would probably be too much. It'd be great for something like the FIRST (robotics) CIM motors -- 3x the torque of the standard 775 motors and 1/3 the speed. I can't tell how big the case is on the one you're using but it looks only slightly larger than a 775 motor, and if it's spinning that kind of RPM it's been designed to put the power out at high RPM.

However, slap a 11, 12, or 13T gear on there and now you're talking about something that's about 60% faster than your current implementation, and that would seriously haul the mail. Plus you get the benefit of the motor driving a wider gear (6mm wide vs. 4mm) -- less likely to break at the motor:gearbox interface.

Whether anyone should be driving a Power Wheels at that kind of speed would be a different discussion