Add Coasting to Kids Powered Ride On Jeep

Discussion in 'Electronics & Electrics' started by always.all.in, Mar 13, 2020.

  1. always.all.in

    always.all.in Member

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    Been working on the kids battery powered ride on Jeep, and I can't for the life of me figure out to get it to coast when it's not accelerating.

    The accelerator is a SPDT (going to replace it with a sewing machine speed control pedal), and when it's released, it jerks to a sudden stop.

    The current set up is two 12v DC motors in series running off a 18v power tool battery.

    How would you go about wiring it to coast instead of stopping sharply?

    Had a look on the interwebs, and I can't quite get the right search terms.

    Cheers
     
  2. Hater

    Hater Member

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    I suppose you'd need some sort of sprag clutch between the motor output shaft and the wheels?
     
  3. Technics

    Technics Member

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    It depends on what is causing the hard braking. It could be electrical, caused by the motor being shorted when not powered (presumably in which case the motor would be centre on the SPDT switch with positive on one side and negative on the other in which case you would simply need to remove the connection to the "off" side of the switch) or it could be because of the type of gear train being used (some, such as worm drives brake without input power). You could use a real electric speed control which would allow the throttle to be slowly released rather than instantly snapped off.

    It might help to take some pics of the wiring if you can.
     
  4. philquad

    philquad Member

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    i take its not the original battery setup
    dont they normally have 1 or 2 6 volts in them? 20 yrs ago lol they did
    6v was low speed, high speed was 12v, if its designed for that maybe the extra herbs are causing it.
    didnt think they had variable speed. ie its on or off power.
     
  5. ShadowBurger

    ShadowBurger Member

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    it'll be a tiny, high RPM motor geared low for some usable torque. If that's the case, there's not much you could do about it without swapping out the motor and gears for something with a lower KV rating not requiring so much reduction. Which wouldn't be a terrible idea since the stock setup will be plastic gears anyway
     
  6. OP
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    always.all.in

    always.all.in Member

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    That's a good idea. In this yum cha set up, they use an off the shelf gearbox and I'm not sure there's space to add a sprag clutch. Wish it was that easy.

    [​IMG]

    I've done exactly what you described - disconnected the negative on the SPDT switch. Didn't see a noticeable difference in deceleration characteristics, which brings us to:

    [​IMG]

    This is what it looks like inside. Would the gearbox have such heavy reduction that it'll realistically be unable to coast?

    I'll take a shot of the wiring next chance, though it's a rats nest threaded through the body and sleeved with heat shrink.

    You're right, it was originally powered by a 12v SLA which was rather gutless. Cheap 18v Ozito lithium battery and an eBay buck/boost unit fixed that (the front wheels lift off if the kids aren't leaning forward at full voltage takeoff!). These ride ons don't have variable speed, though I want to have a crack at adding speed control.
     

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  7. Technics

    Technics Member

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    Yep. Combined with the losses involved it probably would. The backlash from sloppy tolerances probably makes it seem worse too. Without mechanical mods you would need to something to allow the motor to spin down more slowly but there's also the safety considerations if braking is less effective.
     
  8. ShadowBurger

    ShadowBurger Member

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    I'm guessing there's also the issue of it being a one-wheel-drive?

    I'd be buying a $20 hand trolley from bunnings and rebuilding the whole rear axle with a new motor if I was serious about it
     
  9. Technics

    Technics Member

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    Plus the bonus of having enough tube left over for a roll cage. :lol:
     
    blue520 and ShadowBurger like this.
  10. mtma

    mtma Member

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    If you're replacing it with some linear pwm box thing then you could cheat and make the vehicle creep slightly until the brake is pressed.

    Safety considerations though, kid getting out of the car and it just running down a hill etc. I guess you could add a seat switch for that but... lol
     
  11. philquad

    philquad Member

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    always.all.in the 1 my kids had 20 yrs ago (trike)
    i hacked out the battery box a bit bigger @ put a 12v motor bike battery in it instead of the 2x6v crappy originals
    forget whether or not it had more power but it didnt go flat for a lot longer, & i rigged the foot power to a push button on the handle bars As the 3yr old was too short
     
  12. merlin13

    merlin13 Member

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    If the gearing is such to have a small motor spinning at ultrasonic speeds to drive the wheel(s) at sane revolutions, then look at it backwards.

    As in the wheels slowing down from max speed will be thence trying to drive the motor back up, initially keeping it at ultrasonic revs.

    Think you'd need to either have a clutch setup to completely disconnect the gearbox output or the motor itself from the drive mechanism.

    Or swap the motor and gearbox combination out with a single grunty/slow-spinning motor, that has enough torque to directly handle the final drive without any gear reduction. But that'll kill a small battery setup...

    Other option - drop in a suitable electronic speed control and have a variable foot throttle, same sort of setup like on the powered scooters the Old Farts tootle around on.

    Was thinking more a space frame for the bodywork.

    Or more appropriately perhaps, even a small child-sized emergency stretcher... ;)
     
  13. OP
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    always.all.in

    always.all.in Member

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    It's getting pretty obvious that a simple electrical mod isn't going to cut it, and a clutch isn't happening with some real engineering (which is beyond the happy hack job I'm willing to have fun with).

    Actually, that makes a lot of sense. Looks like a whole new gearbox with 775 motors are actually pretty reasonably priced for when the gears eventually strip form the full throttle starts and stops.

    :upset:

    Luckily our block is levelish, otherwise rolling would be a non trivial consideration.

    Knowing my kids, they'd spoof the seat switch with a brick, or leave the two year old on it to see what would happen :wired:


    Yah that makes sense.

    Looking at the interwebs, seems like an ESC is the way to go.
     
    Last edited: Mar 15, 2020
  14. OP
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    always.all.in

    always.all.in Member

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