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Gruber
KidsWheels
Anything that doesn't fit somewhere else & general forum updates
User avatar
By MyOtherRideIsUrMom
#149271
I couldn't find anything like this, hopefully someone will have some ideas.
Trying to find a way to extend run time on a dune racer. Kids are too young for gas conversion, so I got started thinking. I found, basically, a string trimmer engine mounted to an alternator. The "pro" models are pushing 80amps.

Planning on mounting the alternator inside the former battery compartment, a 12v10ah battery and maybe capacitor will be mounted under back compartment or in front. For exhaust, I'll do a double wall blast pipe setup with muffler for sound and heat management.
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By TinCanTomCat
#149289
Would it not be just as safe/unsafe as using a mower engine and the self propelled gearing.
Then just limit the throttle?

Or did you want the electronic control and motor torque? Hybrid style.
User avatar
By dlgg7
#149318
I'd worry about the heat from a gas motor running on the back, especially inside that battery compartment. Why not think of something similar to the small generators that used to be used against the side of a bike tire that ran lights? Now you've got me thinking of a couple rigged up to do that!
User avatar
By MyOtherRideIsUrMom
#149328
I wanted something that could be removable in case we wanted to continue with battery packs and I didn't want to make any permanent changes. My kids are also three and four so I wanted to maintain the stock motor and gearing and automatic braking that the Power Wheels have. Plus I wanted something that I could switch to different Vehicles as they grow.

now that I have everything mocked up, if it works the way it should, I'll end up redoing it and making it look better and function better with electric start etc. I'll probably end up doing a dune buggy blast pipe style setup that's insulated and probably double wall for sound control and to make sure no one Burns themselves. Right now it's over braced so I can't close the battery cover completely but with the brace removed it looks stock for the most part. I have a 15ah (I think) battery in the front, and will add a capacitor if needed. The switch hanging down is to turn the alternator on

Tomorrow I'm going to have my son drive it for as long as possible and see what happens. do a little tuning on the engine and if everything works out I'll probably switch it to a 4-stroke and try and make it as good as it can be

So far, my costs (approximately)
$25 For dune racer (craigslist)
$30 For engine to alternator mating
$25 for new remain alternator (local find)
Free trimmer engine
All the metal, wiring and other stuff I had laying around

Also please ignore the mess I kept bringing things out without putting things away trying to finish this

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Last edited by MyOtherRideIsUrMom on Fri Jul 06, 2018 12:24 am, edited 1 time in total.
By TinCanTomCat
#149330
Looking good.

I'm assuming the engine turns fast enough to get decent output from the alternator?

Also, you'd probably get away with a 7ah battery - smaller, but will be enough to keep a proper reference for the alternator and run for a while without the engine.
And unless the alternator is faulty, you shouldn't need a switch (generates when turned, blocking when not)
User avatar
By MyOtherRideIsUrMom
#149332
The engine spins at 5-7k (ish) so I should be able to get 40-60amps. I only chose that battery because it's what I have laying around. Also gives some runtime in silent electric only mode.

The alternator is internally regulated, but needs an exciter to initially charge the magnet. There is a 12v ignition jumper on the alternator that is either keyed, or in my case, switch selectable.

When my son comes home, I'll have him give it a go. I'm not 100% about my 2-stroke I really like something 4-stroke that spins slower but we'll see what happens.
User avatar
By MyOtherRideIsUrMom
#149336
So I got to running today after a few hiccups it was able to nicely cruise on low speed. high speed the 25 cc 2 stroke, I have it running it probably maximum power, just can't keep up. So for now my next step will be to get a four stroke engine. I have a mini bike engine that's 49cc 2 stroke electric start that I'll try and if not I'll probably just end up going for a harbor freight 79cc. It weighs 22 pounds so I'll have to build an external support.
User avatar
By MyOtherRideIsUrMom
#149339
Got engine. 79cc 4-stroke. Going to replace frame with thicker gauge, longer tubing. The extra tubing will go out the back and turn into the engine mount. Fuel cell and battery in front. Probably wheelie bars too, just in case, and the 7xx motors to handle extra weight.
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I'll do a project thread if anyone is interested.
User avatar
By MyOtherRideIsUrMom
#149350
MyOtherRideIsUrMom wrote:Mockup
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User avatar
By toycrusher
#149358
That's some really cool out-of-the-box thinking there. Naturally at the end of the day you'll realize it was better and easier to just pack spare batteries... but that's never the point! :lol: :lol: :lol:

If you get this going, it will be perfect for the future, you can convert to AC motors and an AC controller and use that alternator to generate raw juice for motivation. :twisted:
User avatar
By MyOtherRideIsUrMom
#149379
Yeah, I usually get wrapped up in projects and tend to go overboard. That's how I ended up building a 6'x6'x6' walk in oven in my basement for powdercoating and paint. Speaking of that, I finished the frame and have it in the oven now. Came out nice. Ended up coating +clear the front cross bar and side door bars too.
Once it cools, I'll be reassembling to a rolling chassis, and finishing up engine. Ended up squishing some square tube to make a tow hook, adding led headlights and some other stuff.
This quickly ballooned into a huge project, but hopefully it will fix the range/charging/crying issue.
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User avatar
By MyOtherRideIsUrMom
#149389
Mounting engine tonight. Should be running tomorrow
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