Technical Clutching/Gearing Help Needed!!!

[craigvansickle]

I am using stock 08 specs from my IQ service manual for the 600,700,800 rmk 155. All specs for 0-2000' The manual shows the all the sleds bellow have the same 56/42-.36 driven helix, the same 140/330 drive clutch spring, the same 3211115 belt, and the same 8250 operating rpm. The only thing that varies from sled to sled in regards to clutching is the drive clutch weights, driven clutch springs and the gearing.

600cfi rmk 155
125hp
Drive Clutch
Weights: 10-64
Spring: 140/330
Driven Clutch
Spring: 160/240
Helix: 56/42-.36
Gearing
19/41

700cfi rmk 155
140hp
Drive Clutch
Weights: 10-66
Spring: 140/330
Driven Clutch
Spring: 155/222
Helix: 56/42-.36
Gearing
20/41

800cfi dragon rmk 155
154hp
Drive Clutch
Weights: 10-68
Spring: 140/330
Driven Clutch
Spring: 160/240
Helix: 56/42-.36
Gearing
20/41

When you step from the 600 to 700 there is a 12%, 15hp gain. They 700 gains one tooth on top on the gearing. It also gets a softer secondary spring. It gets 2 more grams on the prim clutch weights. If I understand things correctly all of the changes above load the 700 engine with a little more track rpm at engine operating rpm than the 600 = better climbing. Not to mention the better engine response, but or now I am only talking about when all three engines are at there shared operating rpm of 8250

When you step from the 700 to 800 there is a 10%, 14hp gain. The gearing is unchanged. The 800 has the stiffer 160/240 secondary spring (same as 600) It receives another 2 grams of prim clutch weight. From what I understand the stiffer secondary spring would pull the belt more towards the driven clutch - reducing track speed. The added two grams in the weights would pull the belt more towards the drive clutch adding track speed.

Do I have things right so far?

 

[AKSNOWRIDER]

I am using stock 08 specs from my IQ service manual for the 600,700,800 rmk 155. All specs for 0-2000' The manual shows the all the sleds bellow have the same 56/42-.36 driven helix, the same 140/330 drive clutch spring, the same 3211115 belt, and the same 8250 operating rpm. The only thing that varies from sled to sled in regards to clutching is the drive clutch weights, driven clutch springs and the gearing.

600cfi rmk 155
125hp
Drive Clutch
Weights: 10-64
Spring: 140/330
Driven Clutch
Spring: 160/240
Helix: 56/42-.36
Gearing
19/41

700cfi rmk 155
140hp
Drive Clutch
Weights: 10-66
Spring: 140/330
Driven Clutch
Spring: 155/222
Helix: 56/42-.36
Gearing
20/41

800cfi dragon rmk 155
154hp
Drive Clutch
Weights: 10-68
Spring: 140/330
Driven Clutch
Spring: 160/240
Helix: 56/42-.36
Gearing
20/41

When you step from the 600 to 700 there is a 12%, 15hp gain. They 700 gains one tooth on top on the gearing. It also gets a softer secondary spring. It gets 2 more grams on the prim clutch weights. If I understand things correctly all of the changes above load the 700 engine with a little more track rpm at engine operating rpm than the 600 = better climbing. Not to mention the better engine response, but or now I am only talking about when all three engines are at there shared operating rpm of 8250

When you step from the 700 to 800 there is a 10%, 14hp gain. The gearing is unchanged. The 800 has the stiffer 160/240 secondary spring (same as 600) It receives another 2 grams of prim clutch weight. From what I understand the stiffer secondary spring would pull the belt more towards the driven clutch - reducing track speed. The added two grams in the weights would pull the belt more towards the drive clutch adding track speed.

Do I have things right so far?

yep..right so far craig..what are you trying to figure out? on mine all stock motor with stock track I run 19/42 gears,62/42/.46 helix, stock black/purple sec spring(160/240), slp green/pink primary spring(160/340) and 68 gram mtx weights with 3 extra grams in each weight turning 8300 rpm on my 08 D-8 163.... at 0-2000 ft. when I add the slp single setup I pickup rpm's to 8500 rpm at the same elevations (I have to add a gram to get back to 8400-8450 where it runs the best....)

 

[craigvansickle]

So lets say you had an otherwise stock sled and the only thing you changed was the gearing from 20:41 to 19:42. How does that change the track speed at engine operating rpm in the exact same conditions? It seems to me that it would REDUCE track speed. Unless the secondary senses less torque from the track due to the reduced gearing - applies less belt pressure - allowing the drive clutch to pull the belt more towards the drive clutch - INCREASING track speed. So what do you gain? You gear down and the clutches sense the load change and gear back up? The only thing I can figure is that gearing down allows the clutches to operate in a more efficient range - thus gaining a little more track speed.

 

[AKSNOWRIDER]

So lets say you had an otherwise stock sled and the only thing you changed was the gearing from 20:41 to 19:42. How does that change the track speed at engine operating rpm in the exact same conditions? It seems to me that it would REDUCE track speed. Unless the secondary senses less torque from the track due to the reduced gearing - applies less belt pressure - allowing the drive clutch to pull the belt more towards the drive clutch - INCREASING track speed. So what do you gain? You gear down and the clutches sense the load change and gear back up? The only thing I can figure is that gearing down allows the clutches to operate in a more efficient range - thus gaining a little more track speed.

if you change the gearing very much..you will most likely need to change the clutching as well..but you are right..the steeper gears allow the clutches to turn easier...and shift out farther..in deep snow factory gearing is normally a little high and the clutches cant normally reach a 1 to 1 shiftout(where clutches work best as far as heat and wear), gearing them down allows the clutches to go 1 to 1..kind of like with your 4 by 4 truck..go smack it in low range and feel how much more snappier it is and how much easier it moves a load vrs. high range..

 

[sasky]

Craig,
What type of riding conditions are you trying to set up for?

 

[craigvansickle]

Craig,
What type of riding conditions are you trying to set up for?

At this point I am absorbing all the info I can on clutching. I really prefer riding in deep snow, so that is most what I am interested in. Olav Aaen's Clutch Tuning Handbook has been a good read.

 

[craigvansickle]

if you change the gearing very much..you will most likely need to change the clutching as well..but you are right..the steeper gears allow the clutches to turn easier...and shift out farther..in deep snow factory gearing is normally a little high and the clutches cant normally reach a 1 to 1 shiftout(where clutches work best as far as heat and wear), gearing them down allows the clutches to go 1 to 1..kind of like with your 4 by 4 truck..go smack it in low range and feel how much more snappier it is and how much easier it moves a load vrs. high range..

The torque sensing Continuously Variable Transmission adds another element to understanding how gearing effects real world performance thats for sure. It really is a remarkable piece of ingenuity. Thanks for all the good input. It is great to be able to read and ask questions on here. Definitely the best forum of any subject I have been a member of. So many knowledgeable people willing to help out.

 

[Trenchmaster]

I can't say that I'm knowledgeable, but I do know that any sled I have owned liked to be geared down for the riding I do. The best set up was to go one or two teeth down on top with one or two teeth up on the bottom. This way I could use the stock chain with the new gears, this is like going from a .373 rear end to .411's in your car or truck.

 

[MORSNO]

I'm watching this thread closely also. I just regeared my 07 D7 last week to 19/42. Now I'm interested to see how this will affect the clutch. I'm under the impression that the lower gears will be similar to the comment above (going from 3:73 to 4:11 rearend gears in a truck) and also reducing heat in the clutches.

 

[craigvansickle]

"Most drivers (referring to the driven clutch) are designed to have about 30% more side force than necessary to make up for variables in friction due to belt wear, sheave surface, belt speeds, temperature, etc." - Olav Aaen

I would think from that statement that a well set up and tuned pair of clutches could get away with less belt pressure???

I find it interesting that the 125hp 600 and the 154hp 800 have the exact same secondary setup. You would think that the 600 would require less belt pressure? At any given static track rpm they would have the same pressure (600 vs 800) The capability of the 800 to spin the track faster would in turn apply more belt p (through the torque feedback ramp (helix)) - but only at track speeds higher than the 600 could attain - or if the 800 produced a large surge of power that the 600 wasn't capable of.

I know a stiffer secondary spring applies more belt pressure - pulling the belt more towards the driven clutch - and in effect gearing the sled down? On the 600 you would think that you could run a softer spring in both clutches, lighter weights, reducing the belt pressure but keeping the two clutches balanced for proper function? Even if you could reduce the pressure by only 10% it seems like that would be signifigant in regards to power being lost to friction - causing heat?

 

[sled_guy]

First off, don't think that because the 600 and 800 have the same secondary setup that that is the best... it may have more to do with costs/supplies/etc than actual performance.

I'm curious when some of you say "it likes to be geared down" what it likes about that? I am not a fan of gearing a sled down. Of course if you go to huge tracks and the likes then gearing has to change usually because of belt heat issues. But I played with gearing a lot over the years and almost always by gearing the sled down from stock gearing (RMK is my reference) I've seen decrease in track speed, decrease in ground speed and decrease in climbing ability. I have seen it help belt heat at times though.

sled_guy

 

[Ron]

First off, don't think that because the 600 and 800 have the same secondary setup that that is the best... it may have more to do with costs/supplies/etc than actual performance.

I'm curious when some of you say "it likes to be geared down" what it likes about that? I am not a fan of gearing a sled down. Of course if you go to huge tracks and the likes then gearing has to change usually because of belt heat issues. But I played with gearing a lot over the years and almost always by gearing the sled down from stock gearing (RMK is my reference) I've seen decrease in track speed, decrease in ground speed and decrease in climbing ability. I have seen it help belt heat at times though.

sled_guy

We are both going to get flack but I agree with you, at least in powder snow. It just seems logical that gearing down works better but without comparing like sleds "before and after" it's a seat of the pants comparo, not always reliable. Gearing down will help cover up bad clutching.
The primary clutch is most efficient in the center 50%. Loading the track is the other goal in loose snow. Try low gear & high R's in your truck on icy roads!

Edit: Craig, I think that's where we are with the Polaris Team clutch from last year, the lightest spring possible-condidering the reality of deep lug tracks, harder belt, backshift, etc. The Edge 8's pulled a 44 helix with a lighter spring but had shorter lugs and the 080 belt. The new Team Tied clutch will likely get us back where we need to be with lighter springs yet good backshift and maybe less heat, more power to the track. It's going to take some time and $ to get the new clutch figured out but it seems like a no brainer to me.

 

[Trenchmaster]

First off, don't think that because the 600 and 800 have the same secondary setup that that is the best... it may have more to do with costs/supplies/etc than actual performance.

I'm curious when some of you say "it likes to be geared down" what it likes about that? I am not a fan of gearing a sled down. Of course if you go to huge tracks and the likes then gearing has to change usually because of belt heat issues. But I played with gearing a lot over the years and almost always by gearing the sled down from stock gearing (RMK is my reference) I've seen decrease in track speed, decrease in ground speed and decrease in climbing ability. I have seen it help belt heat at times though.

sled_guy

I think you answered the gearing down question in the first comment of your post. The 155" and 163" track sleds came with the same gearing. Sled manufacturers build a sled for Joe average riding average terrain. I'm 6'3" 230# with my gear on, when I buy a sled I need to make it work for me. The clutches run cooler and the sled seems more responsive with lower gears. Maybe I should have said I like my sled geared down, the sled could care less. For sure you will lose top speed, can't say if climbing ability is worse or not, my sled allways seemed to work better after gearing it down.

 

[craigvansickle]

First off, don't think that because the 600 and 800 have the same secondary setup that that is the best... it may have more to do with costs/supplies/etc than actual performance.

Good point, I agree. That may be the case. I am trying to understand/discuss the topic and thought that the factory specs would be a good place to start. One could also argue that same point about factory gearing. I think it goes without saying that sleds are geared/setup with a broad range of factors. MPG, emissions, top speed, etc. I would guess a large percentage of RMKs never see the type of riding that would warrant fine tuning anything.

But I played with gearing a lot over the years and almost always by gearing the sled down from stock gearing (RMK is my reference) I've seen decrease in track speed, decrease in ground speed and decrease in climbing ability.

When you played with gearing did you adjust your clutching? If so, I am curious what you did.

There is thread after thread on gearing. Someone will ask what gears they should run in there particular sled and in the replies there will be quite a few that did because a buddy told them to. There will be a couple posts by guys that really know their stuff and have a lot of technical knowledge/personal experience. What I am very curious about is exactly how gearing a mountain sled up/down affects everything from how the clutches operate to how the sled performs/rides after the change.

Chapter 3 of Clutch Tuning Handbook states that the clutches are most efficient in the 2:1 - 1:1 range. From the graph it looks like 1.5:1 is peak efficiency. The Polaris IQ service manual Gear Ratio Speed Chart for the 8.373 CD chain case states that 19:41 gearing will get you 82 mph track speed with the engine rpm at 8250 clutches in 1:1. 19:42 gearing will get you 80 mph. 19:46 will get 73 mph. As best as I could tell I was seeing 36-40 mph track speed with my 600 155 in powder. Coming only from the standpoint of powder riding - it would make a lot theoretically to gear down. Now like AKSNOWRIDER stated any significant changes in gearing will require changes to the clutching. You would think one could gear down to 19:46 and adjust the clutching to regain possible lost track speed. Ron stated that the goal is also to load the track in powder and gave the analogy of high revs/low gear on icy roads. It seems to me that would be a back shifting/helix issue that would need to be addressed with significant changes in gearing.

Once again I am not trying to state the case either way. I really would like to understand the technical details and then to follow through with some real world experimentation.

 

[AKSNOWRIDER]

craig, I think you are on the right track to understanding this stuff...I am no expert..but I am very very good at analizing cause and effect from a lifetime of wrenching and racing....And I agree..I would rather run as high of a gear as I can make the sled pull....but on mine with the 163 and the agressive upshift/backshift of the clutching I felt it needed a lower gear...A good analogy that you see alot is guys throwing a slp single pipe on their dragon without touching the clutching or the intake venting..then coming on here and saying its junk..no improvement over stock....to get the most out of any mod..you must go thru and retest and try alot of things to dial the complete sled into the new mod..Ie add a pipe..change clutching..maybe gearing, maybe have to shorten limiter...all to compensate for adding a simple single pipe...thats where the top shops have the advantage..they have seen so many different setups over the years they have an easier time figuring out just what combo makes magic.....

 

[Going Up]

Great info guys. My brain hurts now trying to take all that in. there is some goos stuff here though.

 

[Bubba700]

Since i have been wondering this, how does the helix affect trenching/accelerating/ etc.

Also you say with a change in gearing we should be looking at looking at different helixs or spring combos any suggestions on where to start.

For example on 19/41 or 19/42 gear sets.

 

[AKSNOWRIDER]

Since i have been wondering this, how does the helix affect trenching/accelerating/ etc.

Also you say with a change in gearing we should be looking at looking at different helixs or spring combos any suggestions on where to start.

For example on 19/41 or 19/42 gear sets.

bubba, the helix angle controls how fast the sled upshifts/loads the motor(it also controls back shift as well)..thats why bone stock the sleds want to trench..they dont upshift quite fast enough in that first 15-18 mph of track speed...I went from a intial angle of 56* to 62*..all to load the motor more and help both acceleration and trenching...same deal with going steeper on the gearing..allows the motor to spin the track easier so if it is a big enough change you may need to change helix /weights/springs to redial in...(for peak performance)..everything is a balancing act..there is no perfect setup..its all in how you want your machine to respond to your thumb input......

 

[Bubba700]

So in lamemans terms, since the helix is shallow ( 52*) it keepthe driven clutch geared low too long causing it to spin or trench? Similar to say leaving a car in 1st and putting it to the floor, it will put too much power down and spin the tires and push you no where?
So by going to a stepper helix it makes you shift out ( higher gear so to speak) faster which helps you hook up and not trench/spin?
For instance on my sled 08 700, I have it geared at 19/42 stock springs it spins 8200 at 8k ft with the 10-58 in it. When i pin it from a stop it feels like it takes a bit for it to really hook up, like I am spinning then it finally grabs and pulls hard. Switching to a steeper helix may cure that a bit or going back to say 19/41 might take some of it out also?

 

[theultrarider]

So in lamemans terms, since the helix is shallow ( 52*) it keepthe driven clutch geared low too long causing it to spin or trench? Similar to say leaving a car in 1st and putting it to the floor, it will put too much power down and spin the tires and push you no where?
So by going to a stepper helix it makes you shift out ( higher gear so to speak) faster which helps you hook up and not trench/spin?
For instance on my sled 08 700, I have it geared at 19/42 stock springs it spins 8200 at 8k ft with the 10-58 in it. When i pin it from a stop it feels like it takes a bit for it to really hook up, like I am spinning then it finally grabs and pulls hard. Switching to a steeper helix may cure that a bit or going back to say 19/41 might take some of it out also?

Exactly. I too would stay with the lower gearing and try the helix. Then again, I am about 240 and can use the lower gearing to give the belt and clutches a break. We also tend to do alot more boondocking than full out highmarking or chute pulling. Therefore our belt temps stay better in check that way and still have more topend left than what your motor will pull on a steep pull. Like Mike said (aksnowrider) there is more than one way to end up with the same result more or less. The key is to match it to your style of riding and conditions. Don't be afraid to expieriment! You can always change it back if you don't like it. That is the best way to learn what really works and what does not. It takes alot of time to get it right, but it is so sweet when it is.