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2019 new vents and clutching

DanoXRS

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I have my sleds in storage far away. BUT if memory serves me correctly the secondary clutch is bolted in a fixed position on the shaft?

On Polaris you simply remove the spacers/washers "centering" clutch. The clutch would float compensating for belt deflection.

I think the SKIDOO shaft has little or no tolerance to let it float?

There is a discussion on here someone cut the spline on the shaft allowing float.

I misunderstood...I thought there was a reason that it could not be floated.
I have a floating clutch on my '17. Google the "Doo Doctor". He sells the kit. As does Ski-Doo...P/N 860200832.

Dano. :face-icon-small-coo
 

donbrown

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I misunderstood...I thought there was a reason that it could not be floated.
I have a floating clutch on my '17. Google the "Doo Doctor". He sells the kit. As does Ski-Doo...P/N 860200832.

Dano. :face-icon-small-coo

This should solve much of the belt heat up from misalignment … but Doo says this is for pre GEN 4 chassis?
 

Big10inch

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But that is the real issue.
BRP has determined that their customers want a Mechanically Quiet sled. Nice exhaust note, but don't want to hear the clutches shifting back and forth.





Well.... That would explain why I am not interested in being one of their customers then.


Sacrificing performance for sound control on a mtn sled is folly. How many mtn riders swap exhaust cans for more sound and less weight? 50%? 75%? I don't know ANY that haven't made that change. I bet 100% of those same customers would take more clutch noise in exchange for not blowing belts too.


So much for "market research". LOL
 

christopher

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Well.... That would explain why I am not interested in being one of their customers then.

Sacrificing performance for sound control on a mtn sled is folly. How many mtn riders swap exhaust cans for more sound and less weight? 50%? 75%? I don't know ANY that haven't made that change. I bet 100% of those same customers would take more clutch noise in exchange for not blowing belts too.

So much for "market research". LOL


But don't forget the little fact that the vast overwhelming majority of BRP riders are NOT blowing belts.


Only a small minority of riders have experienced this problem, but have been VERY vocal about it as it is impacted them in a big way. But by and by they ARE the minority when it comes to total sales volume of the Gen 4 sleds..


I have had 4 Gen 4 Summits now, and I have still NOT replaced a single belt on any of them in the last 2 years. I have 6 spare belts hanging in my garage and I absolutely pound my sled every week all winter long.
 

ZRP Engineering

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With the design of the cover and clutch sheave fins the air is flowed out the foot well and drawn in the vent. So maybe force more air in through the vent and keep the foot well clear of snow, if that is possible

My bet is the fan would actually restrict air flow at higher RPM, but would likely help in the midrange.
 

donbrown

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My bet is the fan would actually restrict air flow at higher RPM, but would likely help in the midrange.

Guess it depends on the mass flow rate.

With the money for some maybe a variable pitch fan allowing the blades to open if the measured natural flow rate exceeds the fans capacity !!!! :eyebrows:
 

Wheel House Motorsports

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You know you ride a ski-doo when this is the kinda stuff your dreaming up. Hahaha. Maybe, just maybe, some alignment, a little float and some logical calibration and they would be onto something... Nah
 

1Mike900

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The whole problem seems to be the efficiency of the drive system, I would bet it takes way more force to turn the track with 6 toothed drivers than with 7 tooth? Especially with grabbing more snow on a 16" wide as opposed to a 15" track! I am sure AC looked at this when going to the 3.5 pitch and said whenever you increase pitch resistance goes up? So make the track softer and have large radii to decrease drag. But then again shrouding clutch's that tight is a very bad idea! It is time to go back to the basics and make it work! I bet if one used a fish scale and pulled the track over the Doo would take way more force than the AC/Polaris tracks? Just a thought, Mike
 
D
May 24, 2012
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Why can't we float the secondary?

Dano. :face-icon-small-coo


Sure you can, but it won't correct a misalignment that can only be done by shimming the pto and mag engine mounts.

The reason to float the secondary is to get the very best X alignment throughout the full shift. You can just as easily shim the secondary to get near the same results with the advantage that it will never get stuck on on the splines with the worst alignment.

Of course there are hidden advantages to the shaft itself of the floating secondary. The obvious one is making the removal/installation soo much easier. The least known reason is to have a stronger shaft. I don't know about the floating secondary that BRP sells, but the one from Doodoctor is thicker and will better resist the vibrations. The shaft on the G4 850 takes quite a beating, and I image a new beefier shaft will eventually become What's next :face-icon-small-sho
 
D
May 24, 2012
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The whole problem seems to be the efficiency of the drive system, I would bet it takes way more force to turn the track with 6 toothed drivers than with 7 tooth? Especially with grabbing more snow on a 16" wide as opposed to a 15" track! I am sure AC looked at this when going to the 3.5 pitch and said whenever you increase pitch resistance goes up? So make the track softer and have large radii to decrease drag. But then again shrouding clutch's that tight is a very bad idea! It is time to go back to the basics and make it work! I bet if one used a fish scale and pulled the track over the Doo would take way more force than the AC/Polaris tracks? Just a thought, Mike


Look for track dyno numbers. That's how you can measure the efficiency. When the measured Hp to the track is under 40% you know there is a major problem with the Hp of the engine making it to the track.

There is no need to worry about the enclosed clutches. The G4 850 is pushing the sled industry in the right direction with the first high flow ventilation system seen on sleds. We saw this happen with ATVs and SxS, so this was a long timing coming. In other words sleds are years behind the times.

The idea that we had to remove foam or cut the belt guard for better venting was craziness. The foam should not be a problem with enough air flow to keep the belt cool. With an air intake filter it should be even less of a problem.

I cannot wait until the day we hear from sledders that all they needed to drop belt temps was to adjust the alignment and clutching. Perhaps then we can see a focus on better intake and exhaust strategies from those who play in deep sugar :face-icon-small-ton
 
S
Mar 6, 2008
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If any significant percentage of the engine output was "eaten up" by the clutch system we would not just have belt problems we would quite quickly have two puddles of melted aluminium too!

The single largest, by a vaaaaaaaast margin, energy eater in the system is the track, not the clutch system.

Doing a simple calculation, 140hp is ROUGHLY 100kW, that is almost TEN TIMES the energy needed to heat a house in the winter. As I said, any significant fraction of that power would melt the clutches.
Connect a dyno to the secondary shaft and run the sled without a track and the power loss in the system is no longer anywhere close to 40-50-60%, more like 5%-ish, if even that.

I´m not saying that there is no problem(s) with the clutching, it obviously is, I´m just tired of people imagining that a properly functioning clutch system still looses half the input power before sending it on to the track, It doesn't!

I for one hope that BRP has come up with some good fixes for MY19 as I'm going from Polaris to Lynx. My old -15RMK has almost 3000km on the last belt, stock 800 with Fire N'Ice engine supports. So I'm not used to changing belt every single trip and I hope I don't have to get used to it either!
 
D
May 24, 2012
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If any significant percentage of the engine output was "eaten up" by the clutch system we would not just have belt problems we would quite quickly have two puddles of melted aluminium too!

The single largest, by a vaaaaaaaast margin, energy eater in the system is the track, not the clutch system.

Doing a simple calculation, 140hp is ROUGHLY 100kW, that is almost TEN TIMES the energy needed to heat a house in the winter. As I said, any significant fraction of that power would melt the clutches.
Connect a dyno to the secondary shaft and run the sled without a track and the power loss in the system is no longer anywhere close to 40-50-60%, more like 5%-ish, if even that.

I´m not saying that there is no problem(s) with the clutching, it obviously is, I´m just tired of people imagining that a properly functioning clutch system still looses half the input power before sending it on to the track, It doesn't!

I for one hope that BRP has come up with some good fixes for MY19 as I'm going from Polaris to Lynx. My old -15RMK has almost 3000km on the last belt, stock 800 with Fire N'Ice engine supports. So I'm not used to changing belt every single trip and I hope I don't have to get used to it either!


100 three foot baseboard heaters could certainly power a house. Would need to double the fuse box and then some to handle the load. Cogs to generator and mag side engine mount screw adjustment as the governor :light: lol

Track is indeed the greatest power consumer. Exactly how much the CVT consumes in the drivetrain I don't think really matters. But if you can get a belt driven CVT on a G4 850 to run with less than 5% losses then you can quit your day job and start making piles of money selling your secret ;)

In my opinion the best way to tackle these things on a dyno is to avoid trying to find an accurate percentage loss, and use the whatever number is measured as a baseline to measure any gain or losses. That way it doesn't matter if the dyno reads high or low.

Monitoring the belt temperature is a lot cheaper and all we really need to know.
 
S
Mar 6, 2008
510
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Northern Sweden
So no loss in hp in the chain or belt drive?.
I'll take the one with 75% efficiency when that becomes available

A single stage chain gear in oil bath has somewhere around 98-99% efficiency.
Belt drive has more friction so it should be a tad lower.

5% out of the 100kW in my example is 5kW. Im using maximum 15kW to heat my house AND my detached shop in the coldest winter days, -35 to -40 centigrade. So even a third of that is a lot of energy.

I have no absolute figures but I am skeptical that the clutching system would work as well as it does if it continuously had to get rid of several kilowatts of energy. It should be mentioned though that not many riders uses a power output above 140 hp continuously or even for more than a few seconds at a time.
 
D
May 24, 2012
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A single stage chain gear in oil bath has somewhere around 98-99% efficiency.
Belt drive has more friction so it should be a tad lower.

5% out of the 100kW in my example is 5kW. Im using maximum 15kW to heat my house AND my detached shop in the coldest winter days, -35 to -40 centigrade. So even a third of that is a lot of energy.

I have no absolute figures but I am skeptical that the clutching system would work as well as it does if it continuously had to get rid of several kilowatts of energy. It should be mentioned though that not many riders uses a power output above 140 hp continuously or even for more than a few seconds at a time.


You made a good point, it is seldom a continuous maximum power output. On a lake at wot there will be maximum ventilation with temps easily reaching the 200F+ range. Mountain riders are seeing over 300F, but their belts don't last long. The Belt Eaters are reporting 100-200 km (60-125 miles) before the belt blows.


There is an incredible amount of heat coming out of those clutches if not aligned or tuned right. If you need to see for yourself you could try to blocking the venting on your clutches to see :face-icon-small-ton just kidding, please don't do this.



Dobeck shared a video on YouTube showing the belt and clutch heat using FLIR Thermal Imaging on an RZR 1000 dyno pull that you might find interesting. Click the link below.



https://www.youtube.com/watch?v=WkU4Xaya0Ks
 
S
Mar 6, 2008
510
346
63
Northern Sweden
.........


There is an incredible amount of heat coming out of those clutches if not aligned or tuned right. If you need to see for yourself you could try to blocking the venting on your clutches to see :face-icon-small-ton just kidding, please don't do this.
........

Of course there is a lot of heat being created, even by a good clutching system. It's the "the clutches are soaking up 70% of the engine power"-myth I'm tired of hearing =)

Even if the clutches only transforms 5-10% of the engine power into heat that is a lot of energy, more than adequate to cause a lot of problems.

What I don't understand is why the old art of making solid, dependable, adjustable and durable engine mounts was forgotten? The old "clamp the engine mount between two rubber disks and run a big bolt with a spacer through it all"-style mounts went out of fashion? I know, there are more parts in that type of mounting system but it has the great advantage that regardless which way the engine wants to move it has to compress rubber, i.e no rubber parts are ever stretched which is a good thing!!
 

kanedog

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What is causing the heat in the 1st place?
Find what's causing the heat and work on the component that is generating the heat.
So far, 3 components have been changed(primary got fins, secondary got fins, tiny gear change) but the heat is still there. Why? What has been missed?


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