Mountain Clutch Kit question

[rmk2112]

I have talked to 2 different highly respected sled shops and gotten 2 different answers regarding Polaris clutch kits.

• Both offer "mountain clutch" set ups.
• Both include new helix and secondary.
• Both include the next weights up from what would be used in my riding elevation

Only 1 of them mills the sheave faces for a different finishing angle.

My question is:

Does milling the sheaves add that much more performance and how does it add to performance, if any.....and is it worth the extra cost?

 

[RockyMtn.Kris]

I have talked to 2 different highly respected sled shops and gotten 2 different answers regarding Polaris clutch kits.

• Both offer "mountain clutch" set ups.
• Both include new helix and secondary.
• Both include the next weights up from what would be used in my riding elevation

Only 1 of them mills the sheave faces for a different finishing angle.

My question is:

Does milling the sheaves add that much more performance and how does it add to performance, if any.....and is it worth the extra cost?

Ok I might be a little old school, but I see no value in changing sheave angle unless its to run a cheaper belt like the AC 046

 

[AKSNOWRIDER]

on the pro, Polaris set the inner sheeve angle different then the belt angle, carls machines the angle to match the belt..yes it does help with temp(grip) how much? that's debatable..

 

[skibreeze]

I had the machining the clutch sheave conversation the other day. The belt is just going to wear to match the new angle, so any performance gain will be short lived.

 

[rmk2112]

I had the machining the clutch sheave conversation the other day. The belt is just going to wear to match the new angle, so any performance gain will be short lived.

Doesn't that defeat the purpose?
As the belt wears to match the angle, you're creating a belt and clutches worst enemy....heat.
Seems like sheaves at the same belt angle would eliminate excess and unwanted heat.

 

[rmscustom]

Sent mine out to have them machined and balanced. It will about pay for itself if it saves a belt this year.

 

[Sickbuild]

Hmm

Ski breeze, I see that you say the belt will wear and end up matching the angle.
However the primary and sencondary don't have the same angles. So it wouldn't just wear into place(say on the primary) because the secondary will want to make it wear another angle? Maybe I'm wrong but that what I read on the e- net so it's got to be true.

 

[Carls Cycle]

CLUTCH CUT AND BALANCE

Our shop does quite a few a year, with a one or two day turn around and it runs $175.

 

[rmscustom]

Our shop does quite a few a year, with a one or two day turn around and it runs $175.

Do you do just the primary or the secondary also? Explanation of the benefits from doing this would be helpful to.
Thanks

 

[DLynn]

I have yet to see a good response to "why modify the sheave angles" on a primary clutch. We balance many clutch's every year and we do correct sheave wear on most every used clutch we service. Right back to the angle for the application. If you look at a belt chart you will see the angle does change on some models. It seems to me that you could buy a belt with a different angle if that is your intent.
We put more attention of Belt to Sheave clearance than the sheave angle. I am not saying anything about the process however I would like to see some real data on the subject before I try to out think the Polaris engineers. We charge 95.00 for a complete Disassembly and Inspection, Cleaning, Belt to Sheave adjustment and Balancing. We also do secondary clutch's.
With all do respect to Carl's Cycle they have always been a great resource and my comments are not intended to reflect poorly on them in any way. I just need to see the science before I get all excited.

 

[rmscustom]

DLynn,
When you correct sheave wear do you notice any inconsistencies in the stock sheave angles?
Does the stock sheave angles match the belt?
I noticed my clutch and belt appeared to be at different angles. Maybe that's on purpose?

 

[DLynn]

DLynn,
When you correct sheave wear do you notice any inconsistencies in the stock sheave angles?
Does the stock sheave angles match the belt?
I noticed my clutch and belt appeared to be at different angles. Maybe that's on purpose?

Mostly the belt wears a spot right were it sits at idle. The rest of the sheave angle remains consistent because the belt spends very little time in the same place when off idle. In a perfect world the belt would match the angle perfectly. However it's very hard to measure the angle under load. If you are running for example an 080 Polaris belt on a PRO you would see a angle difference. The standard 115 Polaris belt is 1.46" wide and has a 26 deg angle were the 080 is 1.438" wide and has a belt angle of 28 deg.

 

[LoudHandle]

I have heard and confirmed on a few of my clutches that there is a disparity between the angle of the fixed sheave and the movable sheave. That is where truing the sheave angles is most beneficial. As it is typically the movable sheave that pulls cords, correcting this angle decreases this problem and allows the clutch to grip the belt better, decreases the slippage, and the heat generated from this slippage.

The Polaris clutches, I've put a straight edge to are a straight cut not a multi angle cut like some of the cat clutches.

I believe Balancing, Truing the sheave Angle, as well as setting the proper sheave to belt clearances are key to optimum performance.

 

[winter brew]

One thought I have had on this is the belt squeeze is always/only on the forward half of the primary. There is some play between the 2 sheaves with bushings and flex. Is the angle disparity intentional to make for a closer match when in actual operation? Does this angle change from static to load? I don't see how it can not change a little depending on bushing clearances.
If this theory has any merit, the angle between sheaves on the forward half will be less under load than when measured static.

 

[DLynn]

Lets drop back the clutching Bible. My comment the other day about "lets see the science" was a bit out there. So I referred back to the old standby. Olav Aaen's.
Go read page 12 - 14 it goes into the Drive Ratio and Efficiency of the primary and secondary clutch's. These is a lot going on during the idle to full throttle run up. The sheave angles have been adjusted over the years and in some cases they run the secondary clutch with different angles than the primary. The basics have not really changed from 1951 when Eliason "Kitchener Series" K-10 came out with a belt drive that was under constant pressure. How do we turn a belt at maximum efficiency and make something move forward with the ability to upshift and downshift while the load is changing continuously? Hummm I think I see the problem.