gearing options on a small 4 wheeled buggy

[87jeepwrangler]

i'm starting a small 4 wheeled go-kart sized vehicle and have some gearing questions, but i'll preface it with this...

im 95% done with my last project which was a built-from-scratch 4 wheel drive remote control rock crawling buggy/stroller for my 1 year old. it used dual 24volt geared motors (one for each axle), locking hubs so i can lock and unlock each wheel independently, full suspension, actuator controlled steering, and is completely remote control since my 1 year old doesn't know how to drive yet. it currently has batteries for almost exactly 1.5 hours of run time, which works perfectly for cruising the neighborhood.

here's a picture and video just for reference:

[youtube]yPp-JDBu2T8[/youtube]
here's a link to the build thread if you are interested (link)


anyway, on to my next project...

i need something to follow my little guy around in when he cruises the neighborhood, so i want to build something for myself. i also want to be able to go as fast as i can reasonably go when i'm messing around without my little guy, without giving up too much torque. i will probably also occasionally drive this across grassy type fields with hills and small rocky like parking lots, so i'm willing to give up speed to make that happen.

this vehicle will be made out of a small, light steel frame with a slightly modified powerwheels body on top. it will have 13" turf style tractor wheels for now, and 1 live rear tire. i've already decided on 36 volt because i came across 3 new free 12volt 35 amp hour SLA's. so this will be a heavy car, but should still have long run times. i also already grabbed up a yk48 36volt controller with reverse and 36 volt 450 watt geared motor, all from tnc (link to motor).

and just to throw out a few more numbers, in my little guys buggy i used 24volt 250 watt geared motors (7.18 built in gearing) with a 9 tooth drive gear and 22 tooth gear on the wheels. that gives me a final ratio of 17.5:1. with 10" diameter wheels, i can sit on the roof while he's in it and with only 1 motor on, it can pull us up small grassy hills no problem.

what i'm kind of stuck on is deciding what gearing options to run to get this to happen. the 36volt geared motor i plan on using has a built in gearing of 79:11(7.182), with a 9 tooth pinion gear and 13" OD tires. any advice?

 

[Electroddy]

You may be disappointed by your choice of motor. An adult size buggy/cart needs more than 450W. Mine has 2300W, 9:1 reduction, 22"-12-8 tires and maxes at about 20mph. Of course it weighs approximately 650lbs with me aboard.

As you already have the motor; check the actual output RPM. If it in the 400-420 range then 1:1 will give around 15mph. If it is the 3000rpm then 6:1 will give around 19mph IF the motor can handle it.

 

[87jeepwrangler]

thanks for your input Electroddy. even though i am hoping to get reasonably fast speeds (15mph ish), im certainly not expecting acceleration like a similarly powered minibike or go kart.

i guess a better question would be, with 36 volts and a single 450 watt motor, weighing in around 300lbs with driver, do you think its possible to achieve 15 mph top end on flat ground, while still being able to drive up small hills?

 

[Electroddy]

"i guess a better question would be, with 36 volts and a single 450 watt motor, weighing in around 300lbs with driver, do you think its possible to achieve 15 mph top end on flat ground, while still being able to drive up small hills?"

If the gearing is correct you should be able to get to 15 on the flats. That said whats your definition of small hills :wink: ? The only thing to do at this point is to determine the gearing for the speed you want and build the kart. Then test it on the hills. Alter gearing as needed to get adequate results.

 

[87jeepwrangler]

If the gearing is correct you should be able to get to 15 on the flats. That said whats your definition of small hills :wink: ? The only thing to do at this point is to determine the gearing for the speed you want and build the kart. Then test it on the hills. Alter gearing as needed to get adequate results.

sounds good. i think that's what i'll do. i'll start a project thread once i get underway. thanks.

 

[winchmeup]

I built a little kart for the kids. it had 900w 24v. With me in it top speed was around 24kmh (with kids 28kmh)
It would take a while to get up to speed but would hold most of it around sharp corners and slight rises.
I think if you gear it so 15kmh is top speed it should do it.