did i kill it?

[MisterRoboto]

this is my first centrifugal clutch. its a hilliard extreme duty clutch 41 chain 11t. jackshaft has 10t in 10t out axle has 60t.
so anyway i got it all put together as the kart came with a torque converter but it was pretty old and missing the weight/spring pack so i put my clutch on and converted to chain.

anyway when i get on and put the gas down it doesnt get moving quickly, but when it gets moving it goes pretty darn well... we were going up and down a dirt road and when i would turn around it would be hard to get going again so i stopped and the clutch was bubbled on the outside and was smoking

 

[Russ2251]

Overloaded.

 

[MisterRoboto]

thanks...

 

[Badot]

Did the clutch start out working well and then stop working as well?

Also, do you have your drive tire diameter and engine spec? That'll help in determining if your ratio is wrong or if there's some other problem. Switching from a cvt to a clutch without regearing/checking your ratio is a good candidate for burning up a clutch though.

 

[MisterRoboto]

it did not start out well... when i got it all put together i noticed it not working well so i took it apart and there was some oily stuff inside so i cleaned that out.. and tried to take a lil slack out of the js to engine chain. got it to work ok... but not good on take off. the tires are 18inch and the engine is an hf 6.5

 

[Badot]

That puts you at around 35 mph at 3600 rpm. I only have experience with very light high speed things on roads, so other people should probably chime in, but you're probably pushing it even if your kart weighed 350 lbs (with rider) and you were driving on paved roads. Personally, I'd put a larger sprocket on the input of the jackshaft.

If the clutch still runs the same way it did when you first started out, it should be fine. I don't see anything too out of the ordinary there, but I've never burned up a clutch before either.

Another thing, make sure your throttle arm stop screw is backed out far enough to where your engine reaches proper RPM. If it can't rev high enough, the clutch can't fully engage and it'll burn up real quick. Gearing is probably your issue though.

 

[Russ2251]

As I've stated in other posts, clutch should not get so hot that you cannot touch it.
I will demonstrate within the next few days if the weather holds.

 

[MisterRoboto]

thanks badot i think that unfortunately as im just getting used to karting and what not i made a mistake in my ratios going down from 11 clutch sprocket to 10 js when i should have gone up -.-

 

[MisterRoboto]

As I've stated in other posts, clutch should not get so hot that you cannot touch it.
I will demonstrate within the next few days if the weather holds.

obviously you dont want to burn up your clutch... was looking for more helpful info

 

[landuse]

As I've stated in other posts, clutch should not get so hot that you cannot touch it.
I will demonstrate within the next few days if the weather holds.

Hey Russ, are you going to do a vid??

 

[Russ2251]

was looking for more helpful info

What is you final drive ratio and tire diameter?

Hey Russ, are you going to do a vid??

If weather cooperates...it isn't at the moment.

 

[sportcoupe88]

Right now he has it setup with 11t clutch sprocket to 10t jackshaft sprocket, then a 10t sprocket to 60t axle sprocket. Tires are 18"
I believe with those sprockets it equals ~5.45:1 ratio, if I did the math correctly.. The problem came when I flipped the clutch sprocket teeth and jackshaft sprocket teeth in my head before he picked up the jackshaft sprocket..
I am MisterRoboto's brother btw...

 

[Badot]

If you replace the jackshaft input with a 14t sprocket your top speed will be around 25 mph which I feel would be more suitable.

Yeah, that's a 5.45 ratio. Ratio alone isn't what you want to look at though. Typically you want to look at peak power at a given rev count, and choose a speed based on that. From there you take the revs from the engine and the size of your tire and calculate the needed gearing.


Usually what I'll do -- Say I want 40 mph at 3600 rpm on 6" dia wheels, the setup on my drift trike...


Take your target speed and convert it to inches per minute instead of miles per hour. Multiply it by 1056, so 40x1056=42240

Take your wheel diameter and find the circumference - this is how far the kart will travel per each rev of the wheel. 6x3.14=18.84

Divide the inches per minute speed by the circumference of your wheel to get the required RPM of your wheel for the given speed. 42240/18.84=2242.04

Divide the engine revs by the wheel revs to get the required gearing ratio. 3600/2242.04=1.61

Figure out your sprockets from that point. My trike doesn't need a jackshaft so with the 11 tooth sprocket on the clutch, 11*1.61=17.71, and round that up to an 18 tooth rear sprocket.

 

[sportcoupe88]

Thanks Badot. Now his question is what will be best overall? He wants it to have some decent take off. Would the 14t on the jackshaft be enough to help with low speed take off or should he look for a 15t or 16t? And which would be the best compromise as far as take off, top speed, and making sure the clutch doesnt slip or overheat?

 

[MisterRoboto]

ordered a 14t sprocket today from fastenal so hope that will work out well i think it will help alot thanks for your help guys

 

[Badot]

Let us know how it works out for you.

And the clutch is always going to slip, that's what it's meant to do... to an extent. I'm not sure off the top of my head, but I think the standard 'lockup' for a centrifugal clutch is around 2200 RPM, running the kart/engine at anything below that (including accelerating) will cause it to slip and heat up appreciably. You just want to minimize this. Obviously if the clutch is not engaged at all (idling) this won't be an issue.

 

[sportcoupe88]

Well guys it turns out i got the tire size mixed up between the two karts he has.. so the tires he has on this kart are 22's now do you think a 14t will be sufficient or should he step up to a 15t or maybe a 16t? Dont want to kill the top end would like to be around 27-30mph
Seems like he just cant catch a break with these karts Ive been tryin to help but I live 9hrs away so i cant help in person...

 

[Doc Sprocket]

22's? No wonder the clutch roasted!
You've either got to gear that thing a lot lower (say goodnight to speed) or put a CVT back on it. Those tires are basically too big for a centrifugal clutch. I really think you're going to have to be up around 8:1 to get away with that.

 

[MisterRoboto]

k ima go with 8.18:1 ratio... and either 22's or 20s and i think i will be ok for now. the kart actually had 18s on it when i was roasting the clutch but they were pretty bald, and the other tires i have are atv tires either 20 inch front atv tires or 22 inch rear tires... so im going with 22s to see how it works if that doesnt work well, ill go for the 20s.

id like to go back to a tav at some point if i can either rehabilitate the one that came with it or maybe find one cheap eventually

 

[anderkart]

Those tires are basically too big for a centrifugal clutch.

As long as his jackshafts gearing was setup to compensate for the taller tires, why wouldnt a centrifugal clutch work and hold up just as well as the same kart with short tires?

If the final-drive gearing was exactly the same, it seems like the only additional strain on the clutch would be the additional weight of the taller tires/rims...