go kart gearing

[crash]

My son and I built a go kart, it only has a 5.5hp engine. I am using a friction drive on the belt for engaging the drive belt (due to the throttle control on the engine and cost of centrifugal drive went with friction drive).
I have a 3" pulley on the motor and a 9" on the axle with about 12" tyres.
The trouble I am having is the engine will bog down and stall when you first start to drive, but once up and going seems to go Okay. It is a lot easier to change the pulley on the motor than the axle, would I be better going to either a 4 or 5" pulley on the motor to get a bit more torque out of the motor?

It has been a 3 year project as the rule was my son had to be there when I / we worked on it, and it was fun trouble shooting things together and he had an input into the design. It has been a lot of fun and to see it come to fruition has been great - even with its flaws.

[bee utey]

Wrong way, you need a smaller pulley on the motor, around 1.5" to 2". With your 12" wheels it'll cover approx one metre per revolution. With the engine at 3000rpm (rated power speed) and 3:1 gearing you'd be covering 1000m per minute ie 60km/h. With 6:1 gearing it'll still hit around 30km/h, plenty fast enough in a single speed go-kart.

[crash]

Wrong way, you need a smaller pulley on the motor, around 1.5" to 2". .

I was thinking back to front for some reason. The smallest I can get is a 2" pulley with a 3/4" shaft. Will try that and see how we go. If that does not work may try some smaller wheels or find a bigger motor :twisted:

[crash]

Put on a 2" pulley on the motor - pulls away without stalling now and is still plenty fast enough. Just have to sort the braking, move the kill switch and stop the drive belt sticking once it gets warmed up, probably go to a longer belt giving a bit more slack, and hopefully slipping a bit more.

[MR LR]

Awesome project!

As a kid I had a Swiss Hutless chassis that I put about 4 or 5 different motors on over the years, was great fun and learnt heaps.

Then at 15 I built my first dune buggy, and now I'm stuck playing with bloody LR's!

Step the belt up one size and it should solve your sticking issue, when I had the stationary engines on mine I used a leaf spring that pushed on the engine cradle which was on a pivot. I had a handle coming forward off this and that was the clutch.

Your gearing sounds pretty spot on from what I've played with, mine may have been slightly lower still.

The kill switch was generally the foot brake and I'd just let it cut out.

Used to terrorize the neighbours and one guy threatened to call the police several times... (he's scared of us all now we are adults, lol).

For braking, try and find either gokart or motorcycle parts, mechanical (cable) brakes are probably easiest...

[crash]

Went with the next size length belt, has stopped the belt from sticking and driving when you do not want it to.
Plenty of fun has been had already - a few laughs as well - while making a turn in the paddock one of the rear wheels came flying off (amazing how far he went on three wheels). I thought it must have sheared the drive pin - but no the wheel broke at the hub itself - back to the work shop all welded up and already to go again.
I think I got my value out of it already, best of all my son is enjoying it and can not wait to show it off to our neighbours son.