Kanedog discovers a Clutching CATastrophy, again. Pics!

[Caper11]

Look at any Cat or Polaris clutch and you will see a few drill holes in the outer circumference of the inner sheave and the ones like seen in this thread on the cover.

Are components individually balanced then assembled, individually balanced, assembled then final balanced or assembled then balanced. My guess would be the last. I would also guess the cover is getting carved up to correct imbalance in the much heavier movable sheave and spider.

The proper way would be individually balanced, so parts can be replaced.

Doo clutches are at least match marked, I dunno about polaris or cat.

 

[Caper11]

Unless it’s BRP ? They build a wobble into the clutch .

Clever way to combat resonance and harmonics, without adding mass.

 

[Krause09]

I’ve went over my 18 with a fine tooth comb and no sign of fatigue, but the sled vibrates violently at 3-5000rpm.
the pull cord handle just dances around and am trying to figure it out, thinking of adding more tension on the recoil spring I replaced it with a cobra last year. Could the Engine mount Possibly be the issue? 1200 miles

 

[Teth-Air]

I’ve went over my 18 with a fine tooth comb and no sign of fatigue, but the sled vibrates violently at 3-5000rpm.
the pull cord handle just dances around and am trying to figure it out, thinking of adding more tension on the recoil spring I replaced it with a cobra last year. Could the Engine mount Possibly be the issue? 1200 miles

Most light weight 2 strokes do have a rpm range in which they shake pretty bad. They would have to make the cranks pretty heavy to reduce it to where it is not noticeable. I bet if you checked another it would be similar.

 

[kanedog]

New info, just in!

Jaws pipes are using thicker gauge metal for the ctec2 pipes.

Speedwerx is now sending pipe banding, like all Slp pipes have, with their Ctec2 pipes. Speedwerx pipes now have serial numbers on them.

This doesn’t mean the pipes are junk though. The harmonics issue forces the companies to improve the pipe and workmanship quality which is good for everybody.

Why the changes? Motor vibes?

Feel the vibrations.

To prevent sled harmonics, the only solution I can come up with is a tungsten(2.5x steel weight) balancing ring and smaller one on the flywheel. Maybe tungsten bolts. The steel ring that’s stock isn’t stopping the vibes.

Maybe loading up both ends of the crank is the only way to avoid cracks. I will be a test dummy for this new strategy. I’m ok with the extra weight to save the expensive clutches and other stuff.

Adding crank weight to reduce harmonics and resonance opinions are welcome with open arms. Educumate me please. I have no experience with this.

 

[kanedog]

I’ve went over my 18 with a fine tooth comb and no sign of fatigue, but the sled vibrates violently at 3-5000rpm.
the pull cord handle just dances around and am trying to figure it out, thinking of adding more tension on the recoil spring I replaced it with a cobra last year. Could the Engine mount Possibly be the issue? 1200 miles

Ya know, I put a cobra pull cord handle on and it dances all over the place for me too. It drives me nuts. This is funny. We have Mexican jumping handles!

 

[Caper11]

Mass dampens resonant natural frequency of a component, and slows it from exciting.

Laws of physics usually mess a person up when trying to combat this problem.



http://blog.prosig.com/2014/04/10/how-do-we-design-or-modify-a-system-to-avoid-resonance/


Than you can get into torsional vibration from the cylinders firing and the crankshaft twisting.

Than there is belt frequencys to deal with.

Get them all playing a tune together and its fun to try to reduce.

 

[Caper11]

I’ve went over my 18 with a fine tooth comb and no sign of fatigue, but the sled vibrates violently at 3-5000rpm.
the pull cord handle just dances around and am trying to figure it out, thinking of adding more tension on the recoil spring I replaced it with a cobra last year. Could the Engine mount Possibly be the issue? 1200 miles

That is a good example of how critical speed works. Critical speed excites a natural frequency of a rotating object. As the speed of rotation approaches the objects natural frequency, the object begins to resonate, which increases the vibration.


I have never worked on a cat but is there match marks on the crank to index the clutch to the crank???

I did that on my 09 xp and it dramatically reduced the vibration of the sled. Funny how skidoo started doing it on the etec.

 

[TROLLCAT]

That is a good example of how critical speed works. Critical speed excites a natural frequency of a rotating object. As the speed of rotation approaches the objects natural frequency, the object begins to resonate, which increases the vibration.


I have never worked on a cat but is there match marks on the crank to index the clutch to the crank???

I did that on my 09 xp and it dramatically reduced the vibration of the sled. Funny how skidoo started doing it on the etec.

going to look for them marks on a doolaide you say (thnx)

 

[skegpro]

That is a good example of how critical speed works. Critical speed excites a natural frequency of a rotating object. As the speed of rotation approaches the objects natural frequency, the object begins to resonate, which increases the vibration.


I have never worked on a cat but is there match marks on the crank to index the clutch to the crank???

I did that on my 09 xp and it dramatically reduced the vibration of the sled. Funny how skidoo started doing it on the etec.

Service manual doesn't mention anything about indexing the clutch on the crank shaft.

But I was talking with the dealer about doing the 911 cover and he didn't seem to think it was a good idea as the stock cover is used to balance the whole clutch.

 

[tex78]

going to look for them marks on a doolaide you say (thnx)

That is a good example of how critical speed works. Critical speed excites a natural frequency of a rotating object. As the speed of rotation approaches the objects natural frequency, the object begins to resonate, which increases the vibration.


I have never worked on a cat but is there match marks on the crank to index the clutch to the crank???

I did that on my 09 xp and it dramatically reduced the vibration of the sled. Funny how skidoo started doing it on the etec.

I also indexed my 10 Xp and made a big difference

 

[Clode]

The fixed sheave on my team primary have balance holes in it. The spring cover has lots of balance drill spots. Gonna put a 911 on it.

 

[LMLCHEVY]

Service manual doesn't mention anything about indexing the clutch on the crank shaft.

But I was talking with the dealer about doing the 911 cover and he didn't seem to think it was a good idea as the stock cover is used to balance the whole clutch.

So can’t a guy put a 911 on and then send it away to get balanced?

 

[skegpro]

So can’t a guy put a 911 on and then send it away to get balanced?

I would say yes.
But where?

 

[Caper11]

Service manual doesn't mention anything about indexing the clutch on the crank shaft.

But I was talking with the dealer about doing the 911 cover and he didn't seem to think it was a good idea as the stock cover is used to balance the whole clutch.

So if thats the case, do you have to send the whole clutch out for balancing when the cover is replaced?

 

[skegpro]

So if thats the case, do you have to send the whole clutch out for balancing when the cover is replaced?

I would say yes

 

[LMLCHEVY]

I would say yes.
But where?

Indy Specialties? If they’re still around that is.

 

[TROLLCAT]

dynamic balancing

 

[Shitfly]

So finally got home to check the clutch on the new sled, found the part number has been scratched off and has a new one etched in by hand, also a sticker with the ‘new’ number stuck on it. In total 10 balance holes drilled into the cover and 3 on the outer edge of stationary side. Sled is a 2020, but the clutch is stamped it was made in 2018. Only reasons this caught my eye was this thread and the mention of the “changes” made with the clutches/ part numbers etc, who knows what the old part number was on this clutch...
Have not had a chance to ride it yet, honestly first time I’ve had a sled, especially a new one where I’m a bit hesitant on the quality of this part.. I’ll be continuing to watch this thread and keeping a good eye on my clutches.
My last sled ‘17 M8 had well over 3k km and zero issues with anything, clutches included. Cover had a total of 4 balance holes drilled into it.

 

[skegpro]

This leads me to believe that the bolts may be the only update.....