Ski-Doo Bulletin: Vibration Damping Clutch Technology

mountainhorse · Mar 22, 2017

Things to ponder and some speculation.

Lots of good points on an brand-new, interesting/complex system... which , as an engineer, leads me to SPECULATE.

Npickle12 said:
They obviously still have a clutch heat issue. Most likely related to a calibration, airflow and alignment.

And/Or... It could be related to harmonics, variance in belt mfg, tolerance-stacking, the possibility of the 850 cranks having a super slight variance in phase when assembled, the 850 primary having variance in a production evironment... with a system that, would seem, not able to handle this variance because it needs to be so precise to start with, etc etc ... Lots in play here.

One thing that I have heard is that even the G4-850's that are not blowing belts... the clutches are still running really hot... but not as hot as the others that are going through belts like tic-tacs.

caper11 said:
Humm vibration from the 50 extra cc? Any xp/xm BB I rode was smoother than the 800.

It's not the extra 50cc like on a BB 800... it's the long 80mm stroke. Making the stroke bigger means making the crank throws bigger....which means that you need to remove the damping-reducing mass of a physically larger crank in order to maintain throttle response (the 'snappy-ness that makes this sled fun to drive). Take away the mass... take away the damping... and you are left with a need to minimize the resultant vibration transferred to the chassis that will make your hands and feet numb and fatigue metal and fasteners over the long run.

Summit74 said:
Think they use the 600RS pdrive vs the 850. If I remember correct there was a difference.

The 600, with it's small stroke would have no need for this intentional, but precise, factory 'wobble' built into the primary pDrive Clutch on the 850 engines.

I also find it strange that Ski Doo did not include this in their official service manuals (from what I'm told by people with the manual).... and this did not make it the press release of the innovative design elements of the sled when released for press last season OR this season. With belts blowing violently... it is common to check for bent sheaves like the video posted in the other thread.

Also... with a significant number of sleds that are blowing belts, some violently while under full load... this has to be hard on the engine and could also possibly knock the crank out of phase since it it is still pressed together at the center section.... making things worse for this brand-new vibration reduction system.

This new system is certainly putting certain demands on belts that never existed prior to this.

NorthMNSledder · Mar 22, 2017

From the Ski-Doo Facebook page just now:

We had hoped to keep this under wraps until we had the patent hanging in the engineering building, but we now want to reveal an innovative element of the pDrive clutch design. To minimize vibration from the additional 50cc, 10 horsepower and 30% faster throttle response from the Rotax 850 E-TEC engine, Ski-Doo engineers created an asymmetrical fixed sheave with a runout of .6mm (.024 in.) – essentially turning the clutch into a counterbalancer. The .6mm/.024 in. runout is right in the sweetspot for optimal vibration reduction and belt longevity, and adds no weight. This patent pending design also is why the pDrive requires the precise D-shaped crankshaft indexing . #ItsWhatsNext

Mort2112 · Mar 22, 2017

NorthMNSledder said:
From the Ski-Doo Facebook page just now:

We had hoped to keep this under wraps until we had the patent hanging in the engineering building, but we now want to reveal an innovative element of the pDrive clutch design. To minimize vibration from the additional 50cc, 10 horsepower and 30% faster throttle response from the Rotax 850 E-TEC engine, Ski-Doo engineers created an asymmetrical fixed sheave with a runout of .6mm (.024 in.) – essentially turning the clutch into a counterbalancer. The .6mm/.024 in. runout is right in the sweetspot for optimal vibration reduction and belt longevity, and adds no weight. This patent pending design also is why the pDrive requires the precise D-shaped crankshaft indexing .

That they are responding in this manner is very significant because
1) The internet is a loaded gun...information gets out and everyone takes it as gospel right, wrong, or indifferent and the balancing video is taking a feature and painting it as a problem (whether it is or not is a different topic and since I'm not an engineer I can't say), and

2) They are worried that their bottom line is going to be affected so they are releasing pre-patent details to "calm the nerves" of everyone involved.

I can say, as I work for a large manufacturer, that intellectual property and the protection of it is the life blood of the company and them choosing to take this route is very, very significant. Not the least of which is tacit recognition that they are indeed listening and are aware they have a problem.

And no, I don't own an 850. I'm simply pointing out that for a manufacturer this is a really big step to release patent-able information before the patent is obtained.

winter brew · Mar 22, 2017

Thinking out loud here...geek stuff. :face-icon-small-blu
So the intention is to counteract the engine reciprocal movement by offsetting the inner sheave run-out, giving more consistent belt tension. cool.
To accomplish this, I would assume they calculated a specific amount of engine movement and came up with the amount of sheave run-out required. (.024")
This assumes a consistent amount of engine movement. What happens under a high load condition (full throttle, big track lugs, heavy snow, long pull) where the increase in belt tension pulls the engine "tighter" to the motor mounts and secondary clutch? Under those conditions is there less reciprocal engine movement than there is at lower load conditions as it appears when running on a stand or track dyno?? If that description makes any sense. :face-icon-small-con
Or, when the motor mounts are pulled (by belt tension) to their max allowable movement, is engine movement then lessened and the unequal sheaves are simply "scrubbing" the belt and making MORE heat in certain conditions?...especially at higher ratios where the run-out is greater?
It seems lessening engine movement and having "true" clutches would be more consistent over a wider range until they can also ensure that the amount of engine movement will be consistent regardless of belt loads. Maybe they addressed this as well, but haven't told us?

mountainhorse · Mar 22, 2017

Questions to ask?

This innovative tech may be great once dialed in... but for the meantime.....

What does a standby/experimental fixed sheave cost?
What does the machining cost?
How much do a few belts cost?
How much 'fun-time' is burned up with a sled that goes down in the field and used up spare belts?
What wear and tear does a belt, that has violently blown, cause on crank/clutch/sled?
What does a sled cost that hit a tree after loosing control from no fwd momentum when you loose a belt? (Warranty does not cover this

)

So.... with this in mind... How much is the 850-G4 Actually vibrating after the sheave has been cut... and is it acceptable in terms of cost and vibration felt?

Most importantly... are the belts generating less heat after the cut has been done and the clutch runs true to axis. ??

In the end... the short term solution for the 2017 850-G4 sleds that ARE belt eaters for specific owners... MAY be to have the clutch machined true... and live with some vibration :face-icon-small-con

.

mountainhorse · Mar 22, 2017

WB... I think that harmonics and other variables 'in use' very well could play a larger role than may be able to be dealt with in a production environment as you allude to.

.

.

MrSledhead · Mar 22, 2017

I feel your pain.

Hello everyone, not here to bash anyone, just to tell you i feel for you. Yes I'm a Cat guy, but some of you on here may remember the 2012 banner year for us, we had a 2012 M8 that ate belts in less than 50 miles no matter what we did. We tried every fix we found here on the forum to no avail. It didnt help that we had a dealer that lied to us either, the dealer is the one that will help the most when they can( i used to be a dealer many years ago, I know)but calling the factory and putting in claims got us the most although it didnt fix the sled.

Needless to say we tried other sleds and were very happy but after a few years we came back( a 2015 and a 2016 and looking at the 2018) and these have been great.

It can be very frustrating and nerve racking and for the people out there trolling its the last thing anyone needs when trying to fix you 15k pos. Just wanted to let everyone having issues know that I feel for you and hope they fix this issue soon, ours took three years.

I also want to tell you that we ride with a couple of 850s and they are not currently having issues and they go very well, well enough my son is considering one for next year.

I wish everyone good luck and hope this gets resolved soon.:face-icon-small-coo

christopher · Mar 22, 2017

winter brew said:
Thinking out loud here...geek stuff. :face-icon-small-blu
So the intention is to counteract the engine reciprocal movement by offsetting the inner sheave run-out, giving more consistent belt tension. cool.
To accomplish this, I would assume they calculated a specific amount of engine movement and came up with the amount of sheave run-out required. (.024")

This assumes a consistent amount of engine movement.

What happens under a high load condition (full throttle, big track lugs, heavy snow, long pull) where the increase in belt tension pulls the engine "tighter" to the motor mounts and secondary clutch?

Under those conditions is there less reciprocal engine movement than there is at lower load conditions as it appears when running on a stand or track dyno?? If that description makes any sense. :face-icon-small-con

Or, when the motor mounts are pulled (by belt tension) to their max allowable movement, is engine movement then lessened and the unequal sheaves are simply "scrubbing" the belt and making MORE heat in certain conditions?...especially at higher ratios where the run-out is greater?

It seems lessening engine movement and having "true" clutches would be more consistent over a wider range until they can also ensure that the amount of engine movement will be consistent regardless of belt loads. Maybe they addressed this as well, but haven't told us?

Very interesting thought.
That MIGHT explain why we hear from primarily a small subset of 850 riders that are blowing belts over and over again..

Ski-doo#1 · Mar 22, 2017

Ski-doo#1 said:
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.

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.

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?

SidewaysInto3rd said:
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 !

So yes, I stated multiple times that we can eliminate this factory offset as an issue. You are right and I did later realize that this pre-manufactured offset could still be the cause of the problem for you and others. All except for the fact that this factory offset seems to be working just fine on other 850s and working well. So where I was right on the basis that this factory offset, which I still standby, is not the problem. The idea of counterbalancing the movements is not incorrect and has clearly shown to work on many sleds!

However, as has already been mentioned, maybe the tolerances are off on the manufacturing side of things. Off by just a little bit might just be the difference for you and others having issues.

To be more clear. I don't see the need for people to be bashing the idea of the counterbalancing act and saying it doesn't work. More so I just don't want people to get worked up about their clutch being out of alignment when it is supposed to be like that. Could it still be the problem?

1.) The idea works, so no

2.) The manufacturing only most time works, not all the time, so yes

I am afraid as this involves the whole system of parts, it is beyond a machine shop to fix it

If you are all ears and to other owners, I have a feeling Ski-doo is going to come up with something. Sure you don't want to go off my feelings, fine. Just know they have more tools than any other shop and more ears than any other shop to come up with a solution, so patience might just be key.

geo · Mar 22, 2017

"The .6mm/.024 in. runout is right in the sweetspot for optimal vibration reduction and belt longevity".

Well there goes 50 60 yrs of clutch theory down the tubes. Learn something new everyday eh. All those scammers telling us to machine the faces true over the years when we just needed to put them on the crank correctly.

Poor sliding half. Did any one ask it how it would feel as it's partner in squeeze leaves for vacation for half a revolution or the poor secondary that has to deal with a 24 thou alignment change every ENGINE revolution or the belt wondering which way to go this time, left or right.

Brew, you pointed out the difference in tension between loaded and cruising on the motor mounts and, just wondering cause I thought a 2 stroke twin makes 2 power pulses per revolution.
Does the Mag pulse not count? Do we have a twingle here? Isn't this kinda like playing tug of war with your dog as he shakes his head back and forth except the crank is shaking the engine in the motor mounts?

Sure do appreciate tried and true as you get older. If this is new world clutching I'm out.

winter brew · Mar 22, 2017

geo said:
"The .6mm/.024 in. runout is right in the sweetspot for optimal vibration reduction and belt longevity".
Well there goes 50 60 yrs of clutch theory down the tubes. Learn something new everyday eh. All those scammers telling us to machine the faces true over the years when we just needed to put them on the crank correctly.

Poor sliding half. Did any one ask it how it would feel as it's partner in squeeze leaves for vacation for half a revolution or the poor secondary that has to deal with a 24 thou alignment change every ENGINE revolution or the belt wondering which way to go this time, left or right.

Brew, you pointed out the difference in tension between loaded and cruising on the motor mounts and, just wondering cause I thought a 2 stroke twin makes 2 power pulses per revolution.
Does the Mag pulse not count? Do we have a twingle here? Isn't this kinda like playing tug of war with your dog as he shakes his head back and forth except the crank is shaking the engine in the motor mounts?

Sure do appreciate tried and true as you get older. If this is new world clutching I'm out.

I was thinking more along the lines of the tension between the two clutches...loaded vs unloaded, and its effect on the reciprocal movement that BRP is attempting to offset. I may be thinking all goofy here, but if any one factor in their equation changes during operation, instead of a harmonious, happy system that perfectly offsets, you have a 8,000rpm belt abrasion system. :face-icon-small-coo

Ski-doo#1 · Mar 22, 2017

"While the majority of 2017 850 E-TEC owners have had no issues, we always strive for no issues for all owners. So 2018 sleds will have:

Finned fixed pDrive sheave
Revised clutch calibrations
New belt
New gearing (Summit and Freeride)
Revised PTO and MAG engine mounts
Better cooling in CVT compartment

We are still looking into the issue for 2017 850 E-TEC owners."

-Ski-doo on Facebook

They have admitted to some owners having problems, if your belts aren't getting warrantied that sounds like your dealer not helping you out.

They are looking for a solution to the 2017 sleds so really patience remains key. I give props to Ski-doo as I always do, yes. They have not left any 2017 owners out to dry and you will most likely see a fix just judging by the sounds of their comments.

mountainhorse · Mar 22, 2017

Ski-doo#1... just curious

Do you work for BRP, affiliate (marketing/advertising/transport) or a BRP dealer?

.

silver_bullet · Mar 22, 2017

Belt Heat is Terrible!!!!

I have scattered 4 belt with in 475 miles. I am still on my 5th belt with 380 miles on it. I vented my clutch area and tore all of the foam out and cut the clutch cover bottom area off. I ride hard but stop and melt snow on my clutches just so I don't scatter another one. Its not easy to cut the cords out when a belt goes. I just ordered a floating secondary. I hope it works. Friends on poo's can't believe how hot my clutches get. I wish we had their clutching. 30 minutes max of hard riding and I stop. Its embarrassing to always be cooling my clutches down with snow and making stops for 2 850's in our group. With that said they run really good and are great to ride. I just wish it wasn't in the back of my mind while riding steep and deep in the tree's!!!! I hope there is a fix soon. With a 18 already snow checked it won't be easy to sell with out it!!!!!!!!!!!

SidewaysInto3rd · Mar 22, 2017

Ski-doo#1 said:
They have admitted to some owners having problems, if your belts aren't getting warrantied that sounds like your dealer not helping you out.

I've blown 12 belts... the first 11 got warrantied .. last one did not

BRP is no longer giving out replacement belts.

They have not fixed my belt issue, and they have stopped providing me with replacement belts. I paid out of pocket for the last one

what gives ? :juggle:

SidewaysInto3rd · Mar 22, 2017

silver_bullet said:
30 minutes max of hard riding and I stop.

Wow .. I wish I could ride for 30 minutes without stopping

Chadly · Mar 22, 2017

It sounds like people are exploding belts... The two I have ruined started making a massive noticeable vibration and a few cords were pulled and I stopped and changed them out. Do people not know what a vibration feels like and just hold her pinned until the sled won't go anymore?

Ski-doo#1 · Mar 22, 2017

mountainhorse said:
Ski-doo#1... just curious

Do you work for BRP, affiliate (marketing/advertising/transport) or a BRP dealer?

.

NO but hope to someday

Everything I say is mostly opinion based and gathered thoughts. I see lots of people rippin into Ski-doo quite often just cause it isn't what they ride and lots of other people read that stuff and I just don't see that as fair. But life isn't fair... although I strive to make it fair. A lot less people tear into companies like people tear into Ski-doo, I guess that is what being #1 for years and years gets you. However, I also see Ski-doo as a industry leader for innovative products by 10 strides. So I stand by them with reason.

Ski-doo#1 · Mar 22, 2017

SidewaysInto3rd said:
I've blown 12 belts... the first 11 got warrantied .. last one did not

BRP is no longer giving out replacement belts.

They have not fixed my belt issue, and they have stopped providing me with replacement belts. I paid out of pocket for the last one

what gives ? :juggle:

Your sled is the perfect case for Ski-doo to study and find the issue. Do you record your riding by any chance? Sounds like you ride quite often you must have something? Maybe you even have video proof of these blows? What do they give you for warranty claims/receipts on the belts? I'm just curious but would like to see them. They gave you over $2000 in belts I think that is amazing.

Old Scud-doo · Mar 23, 2017

Ski-doo#1 said:
Your sled is the perfect case for Ski-doo to study and find the issue. Do you record your riding by any chance? Sounds like you ride quite often you must have something? Maybe you even have video proof of these blows? What do they give you for warranty claims/receipts on the belts? I'm just curious but would like to see them. They gave you over $2000 in belts I think that is amazing.

Personally, they should come get his sled and use it a their test mule! Get it while there is snow and try to fix the ones that EAT belts like Dorito chips on Super Bowl day and then they be able to fix the one that don't go through them as badly. If they are so sure on their fixes for the 18's, drop them on this guys sled and let him try it. If it works, make him a deal on the changes.

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