- Tue Nov 21, 2017 1:45 am
15mph is a pretty aggressive goal for these plastic chassis vehicles -- you'll want to make sure the front end is in good shape first (no camber/toe-out problems, no sloppy steering, etc).
24V on stock motors will get you ~8-9mph for a short period of time (then smoke); smoke will happen much sooner if you add traction aids to the tires. You can certainly get new gearboxes with a higher tooth count pinion and a larger (775) motor, run it at 30000 RPM and get 12-14mph (depending on the tire size), but you also have to deal with the fact that unless you're running a variable-speed controller of some type (scooter controller or PWM motor controller), an on-off "zero or 14mph" switch is pretty hard to handle. My boys are used to having modified vehicles but when I set up our Mustang with a modified gearbox and 36V (16-17mph at full speed) with just the stock on/off switch, even the older child had a hard time really controlling it well -- we run out of cul-de-sac very quickly at that speed and you can't modulate the throttle. At 11mph (24V) it was reasonably driveable, but that's still above where we'd normally be comfortable for the cases where there are 2-3 ride-on vehicles in the area.
I think that if you really wanted to get >10mph, you're going to want:
(A) A variable-speed controller. Even the "Easy ESC" from East Coast Products would be helpful -- you'd have a soft-start function and a dial that could set the maximum speed (which could be installed where the driver could reach it).
(B) A modified gearbox with at least a decent 775-class motor and appropriate gearing, OR
(C) A larger scooter-style motor, chain drive, and solid rear axle (fairly major surgery).
To get 15mph out of one of those Jeeps without a scooter motor and chain drive, you need one of the 21/22/23T gearboxes, a 22T pinion for a 7-series motor, and a 7-series motor that will run at least 35000 RPM semi-reliably. Or you need a 'quad damage' setup (you can look in the gearbox section), though that's a lot more customization.
If you're willing to limit it to ~9mph, you can probably try out the cheapie Nichibo 775-7013F motors and run them at 24V (31000 RPM) in your current gearbox. They won't last forever at that speed but they'll long outlive the stock ones and they're <$5/each shipped to your door (though you do have to pay another $10-$15 to get 2 19T pinion gears). You could get another 2mph by going to 22T pinions but then that requires buying 2 new gearboxes ($100). I'd prioritize the ESC over that.
Absent other upgrades, running 24V risks burning out the switches if used with most motors -- including stock, the Nichibo I listed, and especially models like the Banebots 18V where the stall current is 50% higher than stock. You would need to go to an ESC setup (which limits the maximum current) OR upgrade the wiring and use relays. Otherwise the startup current @ 24V is going to be extremely high.
Look around in the gearbox and the rest of the speed forum to get some additional ideas, and if you're looking for drop-in options I'd definitely look at the East Coast Powerups offerings. The 7013F upgrade plus an Easy ESC should come in just over $150.
F-150 - 24-36V with homebrew 100A variable-speed motor controller, 4x 775 motors (no, it's NOT all-wheel-drive--look HERE
for more details!)
Pink Rocket Princess Mustang - 15mph, 36V, 4x 775 motors, homebrew PWM controller rev 2....
Hurricane - 24V w/50A step-down controller, 775 motors