Clutch Clipping on Level Ground

[mudduck]

Hello.

I have a go kart with a 10 hp Briggs engine. The gokart drive system is configure as follows:

1. I have connected a heavy duty clutch (8-18 hp clutch) to the engine shaft. The clutch has 12 sprockets.

2. I have that clutch chained to a 12T spocket on a jackshaft.

3. On the other end of the jackshaft (tire end) is another 12T sprocket.

4. The sprocket on the tire end of the jackshaft is connected to a 72T sprocket which is connected to a live axe.

Engine is running fine, but as configured that gokart is barely inching along. Oh, and even that inching along (2-3mph) is at the cost of much slipping in the clutch.

Was looking for some advice on gear ratios, etc... before I end up burning out my 110.00 clutch.

Thanks!

​

 

[Kenny_McCormic]

Tire size? Weight?

 

[jr dragster T]

I want a video of that! It sounds ridiculous!

 

[oscaryu1]

Unless your 10HP peak rev's at 2200RPM or so... then you shouldn't be slipping, unless you have a 200000lb. frame.

 

[2or3wheels]

that car probly came with a T/C. Get a 24 tooth sproket on the jackshaft, the one the clutch is connected to and you will feel the difference, you may need even bigger.

 

[mudduck]

Thanks Kenny and 2or3wheels.

More info on kart:

-Weighs about 200lbs with the engine attached. With me attached it is about 400lbs.

-Wheel is 17inches (includes tread).

Yes, the kart did come with a T/C which was gone when I purchased it. I am a complete novice, but I was thinking 10hp should be able to move 400lbs +.

I am hoping that the new gear ratio would help?? However, I am having trouble finding one that goes on my 5/8 in jackshaft.


Thanks.

-Morgan

 

[Kenny_McCormic]

Wheels too big, the TC was there for a reason.

 

[mudduck]

I knew the T/C would work and can get one at northern tools, but I was hoping to avoid having to spend the 250+ on a TC.

I guess I could go with the larger sprocket on the jackshaft but then would I be looking at low end torque with no speed??

Thanks.

 

[2or3wheels]

no it would get you moving. If you went with a 24 you will still have a lot of speed. You can always get new gears if you dont like it.

 

[modelengineer]

Even with the large wheels and weight, the 10hp with clutch should still get you going at a fair clip with reasonable acceleration. Something is not set up right. Is the clutch keyed, or otherwise attached to the crankshaft? If it wasn't then you would have the problem you're describing because the clutch could grab but not actually move the kart.

 

[mudduck]

Howdy modelengineer.

Thanks for the reply. I took a good look and the clutch s properly keyed to the engine shaft.

During the process of checking the clutch I noticed that the number of teeth on the clutch sprocket is actually 20T. This changes my gear ratio from what I thought was about 1:6 to about 1:3.5.

Could that be an improper ratio for the 17in tires?? I think that is what 2or3wheels is suggesting.

Thanks!

 

[mudduck]

photos

Thanks for the input guys. Here are a few pics.

 

[Kenny_McCormic]

Wood is not a good engine mount. I would gear around 7:1.
Speed calc is on the diy go carts root page.

 

[modelengineer]

Ditto on the wood engine mounts. They will work OK for testing but eventually might want to think about metal ones.

1:3.5, that's a little bit steep. I know it sounds stupid but try pushing the kart as fast as you can and then hop on it and go. If it goes OK then it's just the gear ratio being too high. If it doesn't go then it could still be the ratio, but it could still be something else as well.

Since you're running a jackshaft could you run double reduction? i.e on the input side of the jackshaft run a much bigger sprocket so you are gearing it down twice. Easy way of getting the gearing without having to buy another clutch.

 

[2or3wheels]

back to getting the 24 tooth. the torque converter gave it a nice low start so it could pull that gearing, with a cent clutch no, get a 24 and you will be ok. that'll get you to a 7:1

 

[2or3wheels]

Also something to think about, you may have also burnt up your clutch if you've drivin it to much to slow.

 

[mudduck]

Thanks guys.

As a complete newbie it is good to be able to talk to some people who know what they are doing. I went ahead and purchased a larger sprocket for the input side of the jackshaft. I am going to try to get that on sometime today. I will update this thread once I try that out.


Thanks.

-M

 

[mudduck]

PS.

Modelengineer.

The wooden mount is actually bolted to a metal one. I had to shift the engine over a bit since the engine shaft is so long.

That being said I am hoping to take up welding soon. Once I feel comfortable with that I will definately replace what I have with a metal mount. Geez. Seems like my couple hundred dollar budget just keeps expanding and expanding...

Thanks.

-M

 

[2or3wheels]

yeah let us know, how many teeth did u get?

 

[mudduck]

Hello 2or3wheels.

I ended up going with 40T since that is all I cound find that would go on my 5/8 shaft (other than the 12 I already had).

Just as you said that worked like a champ! Hit the gas and was off to the races. Was also able to go up some hills which was great since I have plenty on my property. Top speed seems to be about 20-25mph or so.

Overall I am pleased but there are some things I want to address:

1. wooden engine mount
2. at some point a T/C

Thanks Experts!

-M