2012 rmk clutch broke....why?

[ejf50]

So I noticed I had a broken spring in my primary. We to pull the clutch off to check it over and change the spring. Started to tighten clutch puller and thought it was taking a little more than usual to get it to break loose. Finally the big 'pop' came and this is what I was left with.... Broken clutch.....

After inspecting the crack it was broken for a while. As there was some rust inside the crack. So did this crack because of the spring breaking last season?Just wondering if it could have been prevented.?



Sent from my iPad using Tapatalk H

 

[tinkerjohnson]

Clutch

This is a common problem, no real reason why, some just break. wouldn't hurt to check the runout on your crank

 

[Drewd]

I've read numerous reports of the spring breaking and many suggestions to replace it each season.

 

[ejf50]

 

[Buster Douglas]

I'm gonna see about three every seasons with out a doubt no real explination but it happens

 

[sledhead84404]

Mine e broke at wot .before it broke it was pulling cords out of belts and busting springs

 

[boondocker97]

I can think of a few reasons for this happening:

1. Clutch and crank taper are not matched up close enough from the factory.
2. Over-tightening of the clutch bolt.
3. Steel thickness in the clutch is not sufficient for the stresses induced from tightening it onto the crank taper.
4. Random defect in the material.
5. Clutch got loose and under load the clutch got slightly ****-eyed.

Judging by how many of these I have heard of breaking on here, I doubt it is #4. There would be more damage to clutches and the crank if it was #5. That leaves #1,2, and 3, which IMO are very closely related to each other. If the crank taper is steeper than the clutch taper then it makes it easy for the clutch to slide on too far. This ups the stress in the clutch bore, and since the tapers are not making contact all the way along, and concentrates it on the section that is making contact. Combine this with the smaller 31mm (I think?) taper size and the clutch bolt has to be torqued to a higher value to keep everything from slipping. Comparatively, the clutch bolt torque spec on a 33mm Cat motor is around 55lbs, and I remember my buddy tightening his 800 pro to like 90 or 95.

 

[Rick!]

I can think of a few reasons for this happening:



1. Clutch and crank taper are not matched up close enough from the factory.

2. Over-tightening of the clutch bolt.

3. Steel thickness in the clutch is not sufficient for the stresses induced from tightening it onto the crank taper.

4. Random defect in the material.

5. Clutch got loose and under load the clutch got slightly ****-eyed.



Judging by how many of these I have heard of breaking on here, I doubt it is #4. There would be more damage to clutches and the crank if it was #5. That leaves #1,2, and 3, which IMO are very closely related to each other. If the crank taper is steeper than the clutch taper then it makes it easy for the clutch to slide on too far. This ups the stress in the clutch bore, and since the tapers are not making contact all the way along, and concentrates it on the section that is making contact. Combine this with the smaller 31mm (I think?) taper size and the clutch bolt has to be torqued to a higher value to keep everything from slipping. Comparatively, the clutch bolt torque spec on a 33mm Cat motor is around 55lbs, and I remember my buddy tightening his 800 pro to like 90 or 95.

1. If the clutch doesn't slip, is the taper accurate enough?
2. How does the clutch bolt torque affect clutch stress again? I bet it actually reduces clutch shaft stress. Also, the high zoot necked down polaris bolt has more stretch to accommodate thermal effects.
3. If a larger diameter crank is used, where is the room made to make things fit? The clutch shaft OD needs to stay the same to keep the clutch starting ratio low so does it actually get thinner?

Cat clutches are not the bomb and I bet folks can post up pics of both flavors broken in the bottom of the fender.

 

[richracer1]

I remember my buddy tightening his 800 pro to like 90 or 95.

That's 10-15ft/lbs over the required torque spec.

 

[simnil]

Can for some reason not see the pic.

I'm guessing your clutch have split in two as a lot of other's have. Has happened to the two last Polaris sleds I had. (hoping my -15 RMK wont do it)

If I have the timeline correct this problem/failure started to happen about the same time as TEAM Industries started to manufacture the clutch for Polaris. MY -07 or -08-ish. (First of my sleds to have this failure was the -08 D7, in its first season, and I have not heard of any happening before that)