M.L. Toys
M.L. Toys
HobbyMasters M.L. Toys
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Pre project note: I reused some of the original metal frame. It is galvanized. You MUST remove the coating with acid before welding. Use appropriate gauge wire, USE FUSES, solder connections and seal from elements.

This started out a few weeks ago as a $25 Craigslist dune racer. I have a 3 and 4 yo and they needed an upgrade from their old 6v ride on.

After taking apart and cleaning all the switch internals, cleaning and greasing, it ran perfectly. The only problem was the run time. 2 kids+ hills and 3 acres, meant unhappy campers when it ran out of juice. Added as many batteries that I could, but it wasn't doing what I needed it too.
I wanted to retain the auto braking, speed control and reverse (for now) that the power wheels had.

Version 1: 25cc
Not about to spend a bunch of money on batteries, forever, I started searching. I found, essentially, a string trimmer engine mated to an alternator.i decided this is how I would fight the battery.
Found a new (closeout/overstock) alternator locally for $25. I had a 25cc trimmer engine laying around, and slapped it together.
Did some welding and wiring, and the first version was done. The engine was running flat out, and was charging the car, and providing power. Except it only worked on slow. Going into fast would bog the engine and stall it.
Home brew (not mine) inspiration
2013-01-12-099.jpg (69.96 KiB) Viewed 4831 times
Commercial model 80-100amps 35cc 4-stroke
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Last edited by MyOtherRideIsUrMom on Sat Jul 14, 2018 11:34 am, edited 5 times in total.

Version 2: 79cc 4-stroke
Since my proof of concept worked, the only thing left to do is what I do best: go overboard.

IF I could find one, people wanted insane prices for 35cc, 4-strokes. Screw it. Harbor freight has a 79cc (3hp) 4 stroke for $99.

Using my observation skills, I noticed this engine was much larger and heavier (22lbs), and wouldn't "hang off the back". Only one thing to do: strip it and do the frame. 16ga x 48" was perfect, and the drill press took care of the holes.

Made a rear extension and some cross braces for the engine and strength. Engine is contained within the outer frame providing: a bumper, buffer from parts, and wheelie protection. Wheelie bars will be added if needed, I don't think they will though. All of the spinning mating adapters will be hidden in the rear "engine" cover.

My son wanted a hitch, so I took some of the tube, squished the end in a 20 ton press, grind it round, drill hole, weld end shut and done. Perfect hitch. Added a hook too, for general stuff.

Early mockups

Finished the frame. During a different project, I needed a big oven. So I build a big (6'x6'x6') walk in oven in my basement. Making use of the oven, I coated the whole thing, plus front axle and door bars with Prismatic Powders "blood red" that I had from a different project. After baking, I did a hot coat of clear and re baked.

Putting it back together ( for the hundredth time)

Along the way, I also did:
New back tires
Fix steering linkage slop, toe and camber
Shim out front panels to fit a motorcycle battery in front
A bunch of other stuff I'll update as I remember

My son wanted some lights like my tractor. So Amazon has 2 led "light bar" for $8 and I had a water proof switch. Wired, tucked and fused. They are the same ones I have and they've been great for me.

Tomorrow I will put in engine and finish up (hopefully) then test drive. If all goes well, I'll get a mouldable remote fuel cell, ESC and do a big electric motor/tranny upgrade. Ill also fab up a quiet, double insulated "blast" pipe style exhaust once it is running correctly. Probably electric start at some point too.
To make use of the hitch, I have a lawn mower (3'x4'?) Dump trailer that I'll put some wide tires on and make a quick hook up.
He, and sometimes his sister, want to drive around while I mow (2 hrs), pick up sticks, give sister rides to wild flower patch, etc. This should hopefully yield a great yard car for them.
Last edited by MyOtherRideIsUrMom on Thu Jul 12, 2018 2:20 am, edited 8 times in total.
ITS ALIVE (and works)

Just finished the build (so far) for my new proof of concept with the 79cc engine. I feel kind of bad, my son had just gone to sleep, but I promised him he could ride it today. So, I woke him up. In a foggy state, he was able to drive around the yard so I can see any adjustments. Ill get a better video of him driving tomorrow.

Not sure yet, being how it was used and I never checked the condition, I may have stripped the gears. Don't really care, was planning on upgrading anyway. Could also have been a operator error.

Im not even sure how many times I took this apart and put back together to test fit; it was a lot. Motor and alternator are mounted on rubber vibration isolators, alternator exciter switch on back cover, back "engine" cover fits perfectly to conceal the alternator. Dynamat was added to back of seat for a "firewall"/heat shield, mostly because I had it laying around and I was waiting on my oven. Air intake for cooling alternator was added, ill be adding dc fans. Ordering the new gears and motors tonight and will install asap. Ill also order a new header pipe and building a kid safe, quite exhaust.

Image Image
Last edited by MyOtherRideIsUrMom on Wed Jul 18, 2018 8:43 am, edited 1 time in total.
The next thing to take care of was the exhaust. It is super loud, and exits right behind the driver. I'd rather build it than buy it. Especially when it was around $20-$25 to build.
Started with an arnold lawn mower muffler from Wal-Mart for $5. It was sealed, so it opened it. I re did the inside and made it so I could unscrew to open it (to change the packing) $10 in pipe, a vibration mount for an engine, paint etc. It's all in the oven now, when it's done I'll wrap it with some DEI exhaust wrap and install. Muffler detaches quickly now, and I'll be trying different ceramic and glass packing.


I just noticed that the hook on the hitch was making a bunch of sound. I'll have to redo video. No hook
Last edited by MyOtherRideIsUrMom on Wed Jul 18, 2018 3:37 pm, edited 5 times in total.
Very cool/interesting build, cant wait to see how well it works.
Got the kids in it after messing with the exhaust. Still trying different packing.
Worked well, but with 2 kids/ or 1 kid and big hill, it needs more torque. Time for electric motor upgrade.

I would also like the throttle on the engine to be variable, not just 100% all the time.
Havent decided yet
1. ESC with a stepper motor that controls throttle and is triggered before electric motors
2. ESC with a lawn mower type control where the shifter went.

anyways, they rode around for an hour or so. I had my son doing hills as I was making adjustments. the gas usage after this was maybe 1/5th tank or so. That will all change after the new electric motors and other adjustments

After an hour of driving, then 8 hours of sitting, I ran it for a few minutes (on battery) before testing battery voltage. It was showing 12.63Vdc. Just to make sure, I put it on a .08amp tender, and within a few minutes it showed the battery as fully charged. So the alternator is providing all the energy the car is using; and if it runs out of gas somewhere, they still have a full battery charge to keep driving.

1 Kid 2 Kids
So many options for the 775. I want to leave the accelerator alone (for now) and the auto brake. I'm trying to find an adjustable acceleration ramp controller., and leave everything else alone.

In the mean time, I think the motors are having a rough time and building up too much heat. I'm sure being packaged with the alternator doesn't help. I got a small radiator/heat exchanger, pumps,etc. I'll be wrapping the motors with copper coil in an effort to exchange heat more easily. Once I do the new motors, I'll wrap some new coil to integrate them.
Didn't expect Amazon to come so quickly, but looks like I'll be doing this sooner rather than later.
50a relays
10gauge wire
2 pumps
1 (so far) radiator.
12v waterproof fans are more than I though, may stack radiators on back engine plastic and use a small radiator fan.
Going to wrap the motors and maybe get a cooling block for the alternator regulator.
We will see once I start doing it.
Also going to have some copper tube with the wires to help dissipate heat.

Got the water cooling hooked up and then decided I might as well just do the rest.
Just ordered
2x 775 motors with 16t pinion
100a PWM ESC +reverse/auto brakes/soft start
10g wiring
Circuit breaker, distro blocks, cooling blocks, etc

As soon as it comes in, I'll install it, switch water cooling over and call it done for now. Pictures to follow.

I was probably a bit hasty in ordering the 775 motors. They were cheap, and should work well, but I've ordered something else now.

After many hours of reading, I think I found my perfect motor. It's a mabuchi RS-755VC-8514. Note that it is NOT the 775, or 755WC.
No one seems to sell that model, but it is used in Hitachi 14.4v li-ion drills ds14dfl and ds14dvf3, and is Hitachi replacement part 324-483.
I managed to get one for super cheap, but the others are ~$32. I ended up buying a new bare drill to take apart and ended up being cheaper.

Kysan also makes the 755VC-8514, under their sku of 1112191. ... ordID=8552

I emailed to inquire, but it doesn't show as an active product.
Last edited by MyOtherRideIsUrMom on Thu Jul 26, 2018 12:56 pm, edited 1 time in total.

This will be the cooling system. I'll be making a reservoir out of 1" pvc that will sister the frame rail underneath. Pumps mounted somewhere in there.
I originally coiled the copper 1/4" tubing assuming the radiator was copper. I double checked, and it's aluminum. Cu+al=galvanic corrosion, so I had to switch to all aluminum.

Making the cooling coils is easy.
1. Wrap 1/4 flexible tubing around motor to figure out length. Use the tubing to cut the aluminum to length, adding about an inch extra.
2. Crush or tape one end, and fill completely with table salt. Crush other end after settling and refilling salt.
3. Hold with pliers and wrap around motor, or same size socket.
4. Slide perfectly formed coil off of motor, cut ends, flush salt with water or air.

I got 2x 120mm ip55 waterproof fans to attach to the radiator.
Radiator is 18 row, and will mount somewhere on the back.
Did a bunch of wiring. This is stuff I had laying around from other projects. Distribution block, ANL 160 on alternator, 100breaker for rest. I used 4 and 8 awg because I had it. Had to put conduit underneath. The Watercooling reservouir will be U shaped and loop back to plastic motor.
Waiting on motors to finish.

Shifter slop fix with heat shrink tubing

Elbow of white PVC elbow in back ground. Wraps around shifter (underside molding) and back to pumps on each end.
Mostly finished wiring for ESC, distribution block, motors etc.

Going to wire up speed and direction. Keeping shifter and stock pedal and have low adjustable through the dial. F/r will be selectable with gear lever, and reverse will have a 40 or 50k resistor.
Slow start is automatic and the foot pedal will be used as interrupt for soft start and braking.
Unit was jumpered to auto on with breaker.

So I got one of these cheap 100amp esc. It has soft start, auto braking, and reverse. Image

For $35, I'll take a shot. I kept the stock foot pedal and shifter switch system. I still have to take it apart, route, loom, attach plastic harness connectors etc.
I removed the power leads from the potentiometer, and jumpered the switch. It will turn on with the breaker.
The other two inputs were basically just extended and replaced with the shifter switches. F/R switch has the foot switch in between switch and esc. H/L, the high connects black to yellow, slow is just the potentiometer wired in.
Function is now the same as a stock power wheels. It will have soft start and auto brake, and reverse.

If anyone wants me to do a real diagram, I can probably pull something off. For now, it's screen write. Image

Pot located in "dashboard"? For on the fly, slow speed adjustment. Image
Screenshot_20180803-192958.jpg (318.63 KiB) Viewed 4422 times
I was curious what specifically you found most compelling about this particular motor:
"After many hours of reading, I think I found my perfect motor. It's a mabuchi RS-755VC-8514. Note that it is NOT the 775, or 755WC."

It's a shorter case (and thus lower heat capacity and dissipation) than the 775 motors, and typically they're lower torque per amp, so I hadn't really looked much at them.

Also very interested in how the 100A PWM controller works out. Should be a better overall design than my homebrew one and a decent price, so I probably will end up buying instead of building on the next vehicle I install a controller in...
I'm still at 12-14v, so this motor would work for others that might want more torque without upping voltage.
The 755 has a 14v nominal, where the 775 is 18v. The 755 will give more torque, while maintaining reasonable speed at 12-14v. The 775 would be too slow until I up the voltage.

The ESC seems ok so far, wiring to stock shifter and pedal was super easy.
There are other better Motors, in theory, but obtaining them is a lot harder. Many of the mabuchi motors exist but we're never produced unless someone like Hitachi orders one and calls it a different part number. There are two Motors that I would love to get my hands on but as far as I can tell they were never put into production or at least under nothing I can find, and a minimum order would be 100 Motors
Ok, given that you're limited to 12-14V (standard 12V alternator output), that's a pretty good fit. I wonder if you could just get away with a 550-motor at that voltage (not extremely stressed). There are some decent 22-24k RPM 12V motors in a 550 can size that can be had for a few ($4) bucks each. Then again, given that you've already got the 755s, it'd probably be better off just stepping up to a 19T or 22T gearbox if you want more speed.

For 775 there are a few other options: the Johnson datasheets I have show a 12v, 21000 RPM motor. This listing appears to be a real one (but they're expensive): ... 0#shpCntId

Vex Robotics has a very efficient 12V/18.7k RPM 775 motor. The Vex one is a great drop-in when you have an ESC w/overcurrent protection. Otherwise it's too hard on the gearboxes and wiring, as the stall current and torque is very high. They're very efficient too (mostly because of the ball-bearings -- will make a limited difference in a Power Wheels). ... gLZC_D_BwE

Curves/datasheet here:

Ebay has a bunch of 12V/18.5k RPM Johnson motors, but they all list a 4mm output shaft, which I can't find gears for. Wierd...
Thanks for the info on those, I'll have to check it out. As I've been searching I've been finding that a lot of companies overstate their Motors or they're selling a standard spec motor, but they're changing some of the info. I don't like not being able to see a model number where I can look up specifications online.

I would love to find a hc785lp-025. It's like the 755, but has more of everything @ 12v.

The gearboxes are interesting too, 2 or 3 running one shaft.
If only they weren't so expensive I'd love to run a bunch of high-speed 550's. But of the price for everything it would be better just to up the voltage, or in my case remove the regulator and run on AC Motors.
Yeah, I've looked at the VEX and Andymark gearboxes. In the end I am too cheap and they'd require a fair bit of customization to work with the stock PW tires (and I didn't want to spend $100 on rubber tires and lose drift capability). But you can mount two motors to each of the Power Wheels gearboxes if you want more power and heat dissipation capability -- just look at the thread linked in my signature... By bypassing the 1st gear in the gearbox you get 2.8x the speed, so you don't have to run 35000 RPM to get huge speed out of it. I make up the torque loss by having two motors (wired in series) driving that gear, so 2x the torque, and then they're higher-torque motors than stock. And I can decide what reduction I want by switching out the motor gears and repositioning the plate, at least within a range (13-17T).

Modeled peak net power output for this type of setup (36V, dual Nichibo 7013F per gearbox) with a hefty (80+ amp) controller and a good battery (I'm running 3s2p 9Ah SLA) is around 1500 watts, vs. about 200 for a stock power wheels. And it only cost me about $50 in parts to make a pair of them -- most of that cost being the pinion gears for the motors.

I suspect it would be pretty easy for you to fab up the plates. I did mine on my drill press using a paper template that I built in AutoCAD. I've thought about getting a bunch of them water-jetted, but I don't know that I really want to be in a business doing it.
in-car.jpg (133.47 KiB) Viewed 4390 times
Yeah, the only reason I went with the 7 series is because of the extra torque. The engine and all the stuff weigh a lot with 2 kids.
I saw your post only after I had ordered the motors. I would have loved to try quad motors.

My oldest is only 4, and hasn't mastered 12v yet. Once he does, I'll end up upping the power. There's so many options for these, but not much off the shelf. I'm fabbing most of the stuff I'm doing, and pulling parts from everywhere.
At this point I'll be happy to get it out of my workshop. At least everything is oversized and easily upgradeable now.
Water reservoir glued up and finished. Maybe paint?

Radiator mockup. Couldn't think of anyway to mount how I want, and be expandable; ended up building a frame. I might end up putting another heat exchanger in front of the fans, hooked up to a loop around the alternator. For now, I'll be mounting it on the back. Wanted to do vertical, but I'm afraid it will suck in hair. I have grill covers coming and will mount with the top leaning forward. I'll powder coat it red or black to match, or a blue maybe for water parts.

Got the remaining parts in, except for 1 60mm fan for alternator cooling.
Finished radiator mount.
Before powder:
Screwed up and grabbed a super dark blue that I thought was black. Oh well.

It looks like the fan would be very loud behind the passengers, but with dual ball bearings, it's all but silent. Hoping the radiator and fans will act as a sound barrier from motor.

Hopefully I'll have it back together tomorrow or Thursday.
spencergs wrote:You are a crazy person. Love it. LOL
I love doing this kind of stuff. So many options, so much to consider; it's like a game

Had a heck of a time with the water system. Kept leaking, had to thread a barb onto both pump inlets.also thought the low pressure would be fine just clamping on to coil. I was wrong and had to bubble flare all of them. Last leak, the outlet on one pump was crushed and dripping, then broke off. Going to replace the double push/pull setup with a larger single

Finally, after removing a pull-pump, I was able to stop the leaking, and put the back-half back. Going to wait until morning to finish assembling; assuming there is no puddle. The loop is just for bleeding.


Tested the esc while it's up. Works as it should with stock gas/brake switch, H/L F/R shifter. Has soft start, and the potentiometer is mounted to adjust "slow" speed.

Hopefully tomorrow is just seat, front hood/fenders and test drive.
potentiometer for slow and reverse
Going to make a grill for the front.

Waiting for nap time and the rain to be done to try it out. I already know that the poti ometer has problems because it doesn't give full range of speed so I have to replace that. Since it only affects low and reverse it doesn't really matter, it just won't slow crawl yet. High/low/reverse and throttle/brake all work like stock. Still have some wires to loom once I know it all works, and some other changes too
Ack, at 14V? Sorry to hear that, especially after all that work. Even with higher-torque motors I'm a bit surprised -- assuming the ESC is limiting to 100A, the overall torque isn't going to be much more than stock, and you have soft start. Were there any big impacts (bumps/hills)?
Hammer-fm wrote:Ack, at 14V? Sorry to hear that, especially after all that work. Even with higher-torque motors I'm a bit surprised -- assuming the ESC is limiting to 100A, the overall torque isn't going to be much more than stock, and you have soft start. Were there any big impacts (bumps/hills)?
I cant really say im suprised, its like any other project. just keep fixing until it works. It did have soft start, and esc is on the 100amp breaker, so im assuming things worked as they should. It was a used craigslist score, so im not sure of previous use. For now, ill replace the gear and see what happens. If not, ill have to figure something else out.

while it was running, seemed pretty fun. Made some adjustments, still making adjustments. the extra weight of engine on the back made it swing like a pendulum, especially when it wound up to full power.
So, I ordered replacement gears, but fear I will keep having this problem. So I started sending out emails to gear makers to see what they suggest as material, and approximate cost.

While searching, I found this guy that cast his own parts. ... er-wheels/
Not sure how it turned out, but I started looking into it. Not sure of the material yet, but maybe carbon fiber reinforced resin or something.
I broke a final gear a few months after I got my first vehicle (Hurricane w/13T gearbox), doing an experiment to try to reduce the amount of slop between the wheel driver and the gearbox gear. I broke a few other gears over a few months after that, but haven't broken any in about a year. Amazingly, that was the only final gear that broke, even with substantially more power and torque vs. stock, in the F150 and Mustang (granted, the Mustang has somewhat "slippy" tires).

I don't know whether to chalk your gear failure up to too much torque, bad luck, or a defective gear (someone - I think GloryDays -- had posted one of his and there was a large bubble in the gear material at the breakpoint -- clearly a casting failure at the plant). I do think generally the factory plastic is pretty tough. Casting anything stronger may be somewhat difficult.

I have a stash of 6 brand-new gearboxes in the garage to use for spares and I haven't had to use any -- knock on wood. It's nice that all of the gears interchange with each other (as long as it has the 7R boxes).
Hammer-fm wrote: (someone - I think GloryDays -- had posted one of his and there was a large bubble in the gear material at the breakpoint -- clearly a casting failure at the plant). .
After you said that I checked. What do you know? A massive bubble under 3 gears. At least I feel there is hope for the stock gears now.
Another option to consider for the future -- if you determine that you have plenty of torque to spare (which I think should be the case) -- is to move up to a larger motor pinion. The Dune Racer is 15 or 16T stock, right? You could buy a case for a Mustang (18-19-20T) or Corvette (21-22-23T) and swap gears over -- or get a whole gearbox so you have more spares. Then buy the appropriate (19/22T) gear for your motor and bore out the axle hole. This will decrease the torque at the gearbox (less stress) and get you more speed.
Hammer-fm wrote:Another option to consider for the future...
Definitely going to do that in the future. Right now kids are still learning how to drive it as is. During the testing, my son ran into a tree. Instead of reversing, he tried going forward. Ended up having enough torque that the front end started climbing.

I got, well one at a time (20% coupon), harbor freight 13x5 tires with rim for the front. 7/16x5/8 sleeve bearings to mate up. I'm only going to do the front, try and control the torque steer and push. I think I can saw the back off the stock rim, use the piece as a spacer, and mount the cap on the rim. This should give it a more stock look. I may end up filling them with windshield washer fluid for more weight in the front.

New gearboxes should be here Saturday.
installed the new gearboxes and the kids drove around for an hour +. So far no problems, still adjusting throttle and other small things. Left off the hub caps on the front, but the rubber tires make a huge (HUGE) difference in handling. He swallowed a bug or spider and was trying to spit it out, almost ran into a tree; you can see him swerve at the last minute.
Through all this, im still on the original tank of gas. ~2 hours so far?
Looks good! Hopefully the new gears will last for a good while. Great to have a large yard and a way for the kids to help while still having fun!

We showed up last Christmas a the nearest tree lot with the PW truck one day with a hacked-together trailer on the back. It was pretty funny to see the reactions... (the trailer was a bit small for the tree, so I got to stabilize it all the way back to the house... glad it had a variable-speed controller).
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