Ski-Doo Bulletin: Vibration Damping Clutch Technology

powdermuncher · Mar 21, 2017

Seems like a novel Idea ,but I cannot figure out how a belt that loosens and tightens every halve revolution as well as go up and down in the clutch sheave is supposed to have less friction and slip (= heat) than a belt that runs at a constant pull and engagement without the changes every half revolution. I understand the balancing part, but that comes with a mechanical cost and Heat in my mind. How about the beating on the PTO bearing and the rest of the clutch parts?

Just a few thoughts and questions to throw into the pot.

tchriste · Mar 21, 2017

if this is such a great innovation why was it not announced during the introduction of the new G4 850 sled? I then need to ask if the 3mm spacer in the engine motor mount would cause issues with engine movement and clutch alignment? For the life of me I don't understand why Skidoo didn't announce this earlier, the clutch/belt issues have been apparent since the beginning of the riding season.

Rotax_Kid · Mar 21, 2017

Npickle12 said:
I don't think you understand how this design works. As the engine moves towards and away from the secondary based on the firing order and natural imbalance of the engine, the clutch run out is properly aligned such that it neutralizes the effect of the engine movement. The premise here is that the belt tension remains more constant. There should be no fluctuation in RPM with this design. It's a cool idea.

They obviously still have a clutch heat issue. Most likely related to a calibration, airflow and alignment.

In theory it should counteract the vibration and stay neutral...you are correct. The way they have it written in the cartoons above almost contradicts this (and then itself later) unless we are missing some info somewhere in the middle?

caper11 · Mar 21, 2017

Npickle12 said:
I don't think you understand how this design works. As the engine moves towards and away from the secondary based on the firing order and natural imbalance of the engine, the clutch run out is properly aligned such that it neutralizes the effect of the engine movement. The premise here is that the belt tension remains more constant. There should be no fluctuation in RPM with this design. It's a cool idea.

They obviously still have a clutch heat issue. Most likely related to a calibration, airflow and alignment.

Yes your right, but the idea makes no sence for the application.

Torque and load make the most movement in the engine and sec tower tower braces and torque stops are generally used for this. Trying to counteract the harmonics/vibration caused by engine cyl firing in a vertical plane, by inducing a runout in a sheave the axial plane?? humm sketchy at best and overthought IMO.
So there is a new fixed sheave for 2018 with added mass. I find that interesting.

There are numerous belt failures this season and every 850 I rode this year it seemed to fall on its face on top end, but it pulled hard on the bottom to mid. Seeing that the runout is at its greatest at max dia may be the cause of the hot belt temps and belt failures along with the lack of top end.

lewey · Mar 21, 2017

seems odd that you would use runout causing the belt to go side to side to counteract the two clutches centre to centre distances changing. this would create stresses on the belt. machine your primary off centre from crank and balance it to compensate offset. seems a little like bs anyway. i think it would be pretty hard to predict vibration/movement across varying rpms up to 8000 with diff loads and throttle. you'd think if their engineering was that in depth they would have sold it more.

gopherchoker · Mar 21, 2017

Vibration is cheap. Belts are expensive :face-icon-small-dis

Sheetmetalfab · Mar 21, 2017

tchriste said:
if this is such a great innovation why was it not announced during the introduction of the new G4 850 sled? I then need to ask if the 3mm spacer in the engine motor mount would cause issues with engine movement and clutch alignment? For the life of me I don't understand why Skidoo didn't announce this earlier, the clutch/belt issues have been apparent since the beginning of the riding season.

Maybe they just dreamed it up.

Color me skeptical......

RGM · Mar 21, 2017

Oh Christopher you are as naive as everyone says. LOL

post your full email or a link

Ski-doo#1 · Mar 21, 2017

fredw said:
So what is that saying for doo for the guys that took the wobble out of it and fixed the hot clutch problem they had in the past.. Maybe back to the drawing board doo, your design is flawed

they f&&&ed up and you shouldn't believe everything on the internet. Also know who the Polaris trolls are that spread material.

Ski-doo#1 · Mar 21, 2017

Good to know Chris, thanks for sharing. I guess we can eliminate one issue many thought they had. Now our only reasons for people blowing belts are too much heat. Hopefully measures taken in 18 rid of the heat. And for '17 if you're still blowing belts and you have your rpms down to 8000 we still have to find the problem.

SidewaysInto3rd · Mar 21, 2017

Ski-doo#1 said:
And for '17 if you're still blowing belts and you have your rpms down to 8000 we still have to find the problem.

Who is WE .. and can you please hurry it up ?

Ski-doo#1 · Mar 21, 2017

SidewaysInto3rd said:
Who is WE .. and can you please hurry it up ?

Do you own a '17 850? If so I'd be referring to you and others who own a '17 850 and are having belt troubles. I assumed people with problems were trying to figure out what was going wrong with sleds alike?

For now it seems all we have come up with is making sure your rpms are down to 8000. Since "clutch wobble" is there for a reason from the factory this no longer stands as an issue.

OMG 3 sleds got brought into our shop and all 3 had the same wobble hahahaha anyone ever think that maybe it was like that from the factory? Even the XMs were offset a bit to compensate for the twisting of the motor. I will never get over this one. :face-icon-small-con

May I ask you what you have done if you are one with issues?

nickbeann · Mar 22, 2017

Will be interesting to see if the new 18 finned fixed sleave has this wobble built in or if the fins now are the counter weight
For a cvt system this wobble is nuts.
Thanks for the extremely hot clutches on my 850, doo, like f me ,,,,,oh forget that you already did!

SidewaysInto3rd · Mar 22, 2017

Ski-doo#1 said:
Do you own a '17 850? If so I'd be referring to you and others who own a '17 850 and are having belt troubles. I assumed people with problems were trying to figure out what was going wrong with sleds alike?

For now it seems all we have come up with is making sure your rpms are down to 8000. Since "clutch wobble" is there for a reason from the factory this no longer stands as an issue.

May I ask you what you have done if you are one with issues?

First and foremost, I've gone to my dealer and asked for a resolution. I've called BRP, started a case and asked them to help my dealer with a resolution. This is the ONLY thing an owner of a brand new machine should do. end of story.

but what the hell, I like to tinker ... ive gotten my RPMs down to 7900 (I've found clickers and pin weights to be useless), increased belt grip on both clutches, brought my temps down (not by using vents or fans), geared down, maintain the crap out of my clutches, and have dramatically increased my belt life .. yet it still blows ! 12 belts later... it still blows !

A considerable amount of my free time goes into thinking about this stuff .. and it shouldn't.. I should be pouring gas and oil in and go for rides.

So mr skidoo-#1 please tell me .. what should I do next ? I'm all ears !

powdermuncher · Mar 22, 2017

All I want is a sled with clutching that runs within manufacturers specs that I can get a season out of a belt.
Is that to much to ask.

Daag44 · Mar 22, 2017

caper11 said:
Yes your right, but the idea makes no sence for the application.

Torque and load make the most movement in the engine and sec tower tower braces and torque stops are generally used for this. Trying to counteract the harmonics/vibration caused by engine cyl firing in a vertical plane, by inducing a runout in a sheave the axial plane?? humm sketchy at best and overthought IMO.
So there is a new fixed sheave for 2018 with added mass. I find that interesting.

There are numerous belt failures this season and every 850 I rode this year it seemed to fall on its face on top end, but it pulled hard on the bottom to mid. Seeing that the runout is at its greatest at max dia may be the cause of the hot belt temps and belt failures along with the lack of top end.

The Secondary tower brace and torque stop you speak of are to keep the two clutches in alignment, not to cancel vibrations.

The clutch sheave offset is to help keep the belt tension as even as possible which transfers less vibration from the engine movement to the secondary clutch and chassis. In other words instead of the belt being tugged back and forth, the clutch is machined to take the slack each time the engine grows close to the secondary clutch. Also note the Center to Center line between the two clutches is closer to the line of the piston movement.

I agree that the excess belt wear is likely done when the belt is nearing the max diameter, but there is more then likely a combination of factors including alignment, engine movement, how tight the belt is turning around the secondary, and the amount of snow blocking the left footwell belt heat exhaust area.

An Alignment Bar and Belt Temp Gauge would work much better to Pin-Point the problem and cost far less than multiple belt replacement.

Vern · Mar 22, 2017

So just because doo did the wobble on purpose that automatically rules it out as a cause to belt blowing?

I'm not saying it is the cause, I just think it's funny how so many people are like "oh, well if they did it on purpose that can't be the problem". It's still a new concept and very well could be a contributing factor, the whole thing just sounds hokey to me.

caper11 · Mar 22, 2017

Daag44 said:
The Secondary tower brace and torque stop you speak of are to keep the two clutches in alignment, not to cancel vibrations.

The clutch sheave offset is to help keep the belt tension as even as possible which transfers less vibration from the engine movement to the secondary clutch and chassis. In other words instead of the belt being tugged back and forth, the clutch is machined to take the slack each time the engine grows close to the secondary clutch. Also note the Center to Center line between the two clutches is closer to the line of the piston movement.

I agree that the excess belt wear is likely done when the belt is nearing the max diameter, but there is more then likely a combination of factors including alignment, engine movement, how tight the belt is turning around the secondary, and the amount of snow blocking the left footwell belt heat exhaust area.

An Alignment Bar and Belt Temp Gauge would work much better to Pin-Point the problem and cost far less than multiple belt replacement.

When the engine is under load the primary and sec pull together and the belt loosens.

Try it on a track stand, youll be surprised how much it moves.

If doo wanted to reduce vibration on the primary than mass shoukd be added or a dry shot harmonic balancer shoukd be used. Inducing runout in only 1sheave just reduces the clamping force.
As mentioned, it looks like the fixed sheave has added mass for 2018.

winter brew · Mar 22, 2017

While I get what they are trying to accomplish with this, and applaud the "outside the box" engineering, part of me thinks this is not the best route to go for belt, clutch and crank life. And based on the unexplained belt issues many people are having, it needs to be revisited by BRP. What they see in testing does not always translate into real world results.
Then there are those that are MUCH farther than .025" out of true like the one in the video...what about those? :face-icon-small-dis

salmonbum · Mar 22, 2017

https://www.youtube.com/watch?v=SuYffVx0l9M
2:50 it look sliek both sheaves on primary are a bit off
3:15 It looks like the out sheave is really off

Ski-Doo Bulletin: Vibration Damping Clutch Technology

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