suggestions? unconventional drive system

[getting kart smart]

My dad is building a go kart for our upcoming race on April 21st. He is going a bit unconventional as far as the drive system goes and I am not sure if it will work. He is using a 2 pulley belt system from the engine to the axle. Instead of spending money on a clutch he is using a belt tensioner which will be controlled by a lever under the seat when he comes to an idle. He has a 18 horse briggs motor on it and is currently running at a 2.75 to 1 ratio. The kart weighs over 400 lbs and the tires are 22" diameter. I think he will smoke the belts trying to get going with this ratio and he thinks he will be just fine. Who is right??

 

[r_chez_08]

I think you are Belts are not very good at taking sudden loads of torque, and that ratio would be steep with chain.

I would say 5:1 tbh. He is currently geated for 86mph with a governed motor. With 5:1 he would be geared for 47mph. That would be more realistic. Make sure he is using a large belt. I would reccomend a 'c' belt or larger. I get belt slip on a 5.5hp with 'a' belt
http://www.gizmology.net/pulleysbelts.htm

 

[ghostdog]

How long is the race because those belts will get tore up quick with that load.

 

[getting kart smart]

It's a 4 mile race. Going around the section on gravel

 

[B man]

It's a 4 mile race. Going around the section on gravel

he could go two speed. two tennsioners two pulley for each. he could get up to speed with the low ratio and then use the high ratio.

 

[fowler]

Belt tensioners are not uncommon on smaller farm machinery
They can take the load fine
But they use 2 or sometimes 4 belts together

 

[Orange Krate]

he could go two speed. two tennsioners two pulley for each. he could get up to speed with the low ratio and then use the high ratio.

Ah, the elusive two speed belt tensioner, why have you not come to fruition? Must I build you myself?

 

[slideways]

I tried it on a yerf dog with a 16hp clone. I only had 16" tires too. It was awful. I had about 2"/5" pulleys with a 10/60t gear. Still destroyed the belts even totally locked down.

He is going to be royally screwed. And the money he spent on belts and pulleys would have gotten him a good $100 clutch that can handle a 1" shaft

 

[devino246]

Ah, the elusive two speed belt tensioner, why have you not come to fruition? Must I build you myself?

I feel like that was directed at me. It will get finished...one of these days. When I move up to VA, the kart is going with me, and it will reside at the farm. I'll probably end up tearing the kart apart and doing a sidewinder type build.

I tried it on a yerf dog with a 16hp clone. I only had 16" tires too. It was awful. I had about 2"/5" pulleys with a 10/60t gear. Still destroyed the belts even totally locked down.

He is going to be royally screwed. And the money he spent on belts and pulleys would have gotten him a good $100 clutch that can handle a 1" shaft

The 2" pulley is probably what got you. Need at least a 3".

 

[slideways]

I honestly can't remember the sizes of the pulleys. But it was definetely a reduction drive.

 

[getting kart smart]

Well, I was right. He had it on jackstands and it was awesome. He put it on the ground and he burned the belts up. He had 4 inch engine pulley and 7 inch axle pulley. Feels great to school the old man!!!!!! I told him to replace the axle pulley with a 12 inch and he would be close to a 4.75 to 1 ratio and it should go like hell. Any comments?

 

[Bluethunder3320]

it might still be high. i wouldnt go higher than a 6:1 ratio

 

[klicky96]

I would reduce the engine pulley to a 3", and run a jackshaft. 3"(engine) to 5"(jackshaft input), then 3"(JAckshaft output) to 7"(Axle). That would give you, I believe, around a 6:1. Im not good with finding the ratio with the jackshaft. But either way, a jackshaft would be a good thing to use.

 

[augidog]

take my idea...please!

Ah, the elusive two speed belt tensioner, why have you not come to fruition? Must I build you myself?

i thunk this up several years ago, but nothing ever came of it. since then, i've concluded the tensioner needs to be on the outside of the loop, but i think it could work.

 

[iswim_reelyfast]

^^ I like the design, I woild think it should work fine provided you could get the correct engagement(something to hold lever locked in) and still have a neutral. I use a riding mower at work to tow in trailers full of tires, belt drive works well and i would like to think the trailers are over the towing cpacity of the mower lol!

 

[getting kart smart]

Ok, so he took my suggestion and he went with a 12 inch pulley on the axle. He is now at a 4 to 1 ratio but he didn't want to spend anymore on pulleys so he just went with a single drive belt. It's still slipping. Keep in mind he has a 16 horse motor pushing it and he wants some speed. Other than a torque converter (VST) which is around 200 bucks, does anybody think a 3 pulley system would work at a 4 to 1?

 

[Doc Sprocket]

I think 4:1 is still too steep. While a cost factor is involved, I would suggest a jackshaft for compound gear reduction. 22" tires and that much weight is a he//uva lot to ask of that poor belt. Switching to dual "B" section belts at 4:1 might extend belt life, but engagement will be less than subtle. (Think whiplash)

 

[ryf]

to reduce slippage, increase tension and pulley size, bigger pulleys mean more surface area to spread the grip needed. I use a belt tensioner off a cheverolet 4.3 serpentine belt system (pushes on the back of the belt which also helps increase surface contact!)

 

[Doc Sprocket]

to reduce slippage, increase tension and pulley size, bigger pulleys mean more surface area to spread the grip needed. I use a belt tensioner off a cheverolet 4.3 serpentine belt system (pushes on the back of the belt which also helps increase surface contact!)

I'm glad to see someone is having success with that. I suggested it (for chain, mind you) here- http://www.diygokarts.com/vb/showthread.php?t=9991 but I've never tried it.

 

[ryf]

its been there for 4-5 years lol, other than a heavy clutch its great