Thoughts about using a button clutch and shift speed.

schu · Dec 9, 2008

I was just reading in the polaris forum about a guy comparing his old edge with his new dragon and asking why the edge performed better. More than once someone posted that button clutches work better. This got me thinking as this isn't the first time I've heard this. A buddy built an edge poo with a psi engine and also mentioned to me that the button clutch worked better.

I suspect the reason people say this is because the sled is a little slower to shift out which keeps it in a lower gear a little longer. Which aligns with my own experience. A few years ago I had a roller conversion for my 670X and I could never make it get out of the hole like the goodwin buttons on a 47* helix.

Now I'm running a cat with a bit of HP and have the same problem. The clutch shifts to fast and it seems like I'm in 2nd gear when the engine is still building rpm. The cat engine doesn't have exhaust valves (more weight and complexity, and it already has plenty on the bottom end) so that may contribute to the problem but it doesn't make any less HP than the 670X which has a bit more power for the first 20 feet.

I've tried a number of helix setups to resolve this but it seems that using shallower helix angles always cause my midrange to suffer and can even cause the belt to slip in the primary.

This leads me to believe that I'm going about this the wrong way and that I should spend more time in the primary when setting up how it should shift and leave the secondary just to the backshift and keeping the belt from slipping.

I ordered 2 new primary springs with higher initial load which should cause the sled to shift slower and at a higher RPM out of the hole which make fix the problem, but it might also cause my engagement to be too high and cause problems there.

So the question is, who else has noticed problems with the sled shifting too soon using roller clutches and what have you done to resolve it?

longhairfreak · Dec 9, 2008

A stiffer spring in your primary will slow the upshift. Try that its cheaper. You dont want a button clutch they are not as efficient.

sled_guy · Dec 9, 2008

The primary clutch is not going to affect the upshift/downshift of the secondary, the system doesn't work that way. The secondary will still shift up quick and pull you off the revs.

You can try a couple of things. A stiffer secondary spring will hold the secondary in low gear longer. The other thing you can do is try a multi-angle helix, hit it hard on the initial angle and then to a shallow angle to let the revs build without shifting out too quick.

sled_guy

schu · Dec 9, 2008

sled_guy said:
The primary clutch is not going to affect the upshift/downshift of the secondary, the system doesn't work that way. The secondary will still shift up quick and pull you off the revs.

That doesn't make sense, the source of the upshift is the primary, without it the secondary won't upshift at all. Just like using a higher or lower finish rate on the primary spring changes shift rate and top end rpms, wouldn't changing the starting rate on the spring do the same thing on the bottom end?

sled_guy said:
You can try a couple of things. A stiffer secondary spring will hold the secondary in low gear longer. The other thing you can do is try a multi-angle helix, hit it hard on the initial angle and then to a shallow angle to let the revs build without shifting out too quick.

More secondary pretension spring should work too, however that is not the same as a secondary spring with more rate as that will effect the top end not the bottom assuming the same initial pretention.

The problem with the helix is that the initial angle is too much. Right now I have a 58/46 in it which gives me great midrange but that first few feet aren't right because the secondary gives up too much belt to the primary before we get to target rpm. If I go to a 55/53 it's not nearly as strong in the midrange because the engine can pull the 58* shiftout just fine, it's just that I need it to wait until I have 1000-2000 more rpm before shifting.

I ordered a 120/300, 140/300, and 160/300 primary spring to experiment. I think that 160/300 with a little tighter secondary may work as long as it doesn't screw up my engagement.

While I'm on the subject anyone care to tackle the difference between a steep helix angle and lots of spring pretension and a shallow helix and less spring pretension?

schu

2zeros · Dec 9, 2008

Here ya go................

GlennRMK · Dec 9, 2008

For what its worth

I put a 900 HTG XCR triple in my EDGE RMK

I tried TEAM secondary with a few different springs

And Cat roller with at least 5 different helixes and 3 different springs

Couldn't not make the sled run using a variety of different weights and primary spring

Threw on the old button with a straight 36 and orange spring(stiffest one Polaris had) i think and worked perfectly. Not quite as good of a backshift but much better trackspeed and perfect RPM and held it.

That being said the Cat roller worked great on my 700 twin with twin pipes.

sled_guy · Dec 9, 2008

The source of the upshift is the secondary. The secondary is the transmission, it's the "gear" part. As the secondary goes up the ramp it is like shifting your car. If you have too steep of an angle, or not enough spring tension to hold it back then it's like short shifting your manual transmission into a higher gear, lugs the motor and on a 2stroke once it's off the pipe you never get it back.

Also your numbers are backwards. The 58/46 is a 58 initial angle and 46 final angle. If you went to a 55/53 then I would expect the thing to be worse because now you have quite a bit more final angle and it's being pulled off the pipe by the intial angle and never catching up in the final angle.

If a 58/46 gives you good midrange and topend pull then try something like a 54/46 or the likes.

Are we talking button clutch or TEAM, I'm not clear on which you are using now.

If TEAM, then the final number on the helix matters too. Either .46 or .36 or the likes. Same is true for a button helix. You can get a 58/46 long or short helix which means the 58 is longer or shorter in the overall helix travel.

Rate affects the secondary as well. The TEAM and a button spring work differently because with the TEAM there is no torsional force from the spring (ok, some, but not like on a button). With a button, the initial compression only affects belt slip, the torsional rate is what controls upshift. That's why moving the spring 1 or 2 or 3 holes tighter can help with RPM.

Ok, now I've thrown about 5 topics out there and have probably even confused myself.

sled_guy

AKSNOWRIDER · Dec 10, 2008

try going stiffer on initial on the secondary spring with the same final pressure..it should make it up shift slower, backshift faster and shouldnt affect topend.....

schu · Dec 10, 2008

sled_guy said:
The source of the upshift is the secondary. The secondary is the transmission, it's the "gear" part. As the secondary goes up the ramp it is like shifting your car. If you have too steep of an angle, or not enough spring tension to hold it back then it's like short shifting your manual transmission into a higher gear, lugs the motor and on a 2stroke once it's off the pipe you never get it back.

I disagree. The source of the upshift is the primary since without it pulling on the belt the secondary wouldn't shift at all. I agree that the helix plays a major role in how quickly the primary can overcome the secondary and can change the upshifting characteristics, it is only reacting to what the primary is doing.

sled_guy said:
Also your numbers are backwards. The 58/46 is a 58 initial angle and 46 final angle. If you went to a 55/53 then I would expect the thing to be worse because now you have quite a bit more final angle and it's being pulled off the pipe by the intial angle and never catching up in the final angle.

When I run the 55/53 I use a little more spring tension in the secondary which causes the clutch to shift slower initially because of both of the higher spring pretension and because of the lower angle, while on the high end it's roughly similar because the higher spring rate keeps the rpms in check even though there is more finish angle.

I'm not confused about the initial and finish angles, I know I want a steep initial angle because that rapid shift out makes the sled pull hard as long as the engine can do it and mine can. The problem is that it doesn't start pulling hard until I'm 20-30 feet out of the hole because it starts shifting to soon. In other words the shift rate (how fast it shifts) is just fine, rather the shift rpm (at what rpm it starts to shift) is a little too low.

I'm just looking for that pop off the bottom that you get when your clutching isn't soft on the bottom.

sled_guy said:
If a 58/46 gives you good midrange and topend pull then try something like a 54/46 or the likes.

I could try a 54/46 and that may work, but I suspect that it will cause a lazy midrange depending on where the helix transitions from 54 to 46. What would really fly is if I had something like a 50/58/46 where the 50 was only the first 10% if that.

Here are some other ideas. I have supreme tool weights in with the heavy inserts on the base the of the weight, kinda like heavy hitters. I wonder if I could use a primary spring with more finish rate to keep the top end the same but move the heavy inserts to the middle which would cause the weight to shift out slightly slower on the bottom.

Another approach would be to take off .010" off the of the top of the weight where it touches the roller and have a very slight flat spot right after engagement.

The point is that I don't want to completely change how it shifts, I just want another 1000 rpm before it starts shifting and I think I need to be in the primary to do this.

sled_guy said:
Are we talking button clutch or TEAM, I'm not clear on which you are using now.

It's the old cat roller clutch.

sled_guy said:
Ok, now I've thrown about 5 topics out there and have probably even confused myself.

sled_guy

I hear ya, I'm more or less thinking out loud and trying to sort this out. If I can make the roller setup work and post my testing and results then it will probably help a lot of people that have gone back to the button clutches since they are just slightly more lazy to shift.

schu

freak58trio · Dec 10, 2008

If i'm thinking right the primary is like a torque {stall}} converter the weights being heavier slow the initial clutch engagement along with the spring rate . And the opposite with lighter weights . With that being said the helix and spring in the secondary are like a "shift kit " in the tranny so the secondary would upshift and down shift not the primary. maybe i'm wrong it just sounds right .:light:

schu · Dec 10, 2008

You can't compare it like that because it doesn't work.

More weight = more centri***al force = more upshift.

The heaver the weights are the quicker it will shift, the problem is that you don't want your system to short shift your engine by having to much weight There are a few more variables as these weights are working against a spring so the rate and preload of the spring will change how fast it will shift and what the final sheave force will be at target rpm. Also the shape of the weight will change how much of the centri***al force is converted to shift force on the sheaves.

The secondary reacts to all of this. It yields belt to the primary depending on a few factors. The helix more or less controls how fast it will yield the belt and how fast it will take back up the belt if it senses load on the track (backshift). The secondary also has a spring it works against which can affect the rate of upshift or backshift.

That is basic clutch theory, the debate here is how change the shift rpm the most effective way without changing the other shift characteristics which are pretty good.

According to theory above this can be accomplished by the following:

1. More primary spring preload.
2. More secondary spring preload
3. Shallow initial helix angle.
4. Less primary weight at the base or a flatter shape at engagement.

The question is which works the best. I ordered 3 primary springs to play with and I'll be looking to pickup another set of weights I can grind down a little. I've already played with the helix and find that changing the angles completely changes the shift curve which I don't want, I just want 1000 rpm more before I start shifting.

Anyway, hope that helps.

go high fast · Dec 10, 2008

button vs. roller will have little to do with shift speed if they are both tuned properly for your riding conditions. A clean and properly tuned button clutch with a good belt sacrifices little as compared to the roller clutches.

The only purpose of the secondary to to provide enough "grip" or sideforce on the belt. Belt slippage is from too little grip and causes excessive heat and leads to short belt life. Too much grip is wasted HP and inefficient. Once you have the grip thing figured out then you turn your attention to shift speed through the primary.

The correct shift speed is that which maintains steady RPM at max HP throughout the entire shift.

Shift speed is a function of primary weight and primary sprng "rate".

Oh, by the way.......if you're shifting out too soon I would first try a helix that has a smaller start angle or try one with a straight angle. For instance lets say you have a skidoo 800 and went with a Team roller and started with a 48/42. My first move would be to try a straight 42. The reason I would start here is because its a 10 minute adjustment. Basically you have added more "grip" or sideforce and so it would shift out as quickly. Your may also find cooler clutches and longer belt life.

Most important thing you could do is get the clutch tuning book from Aaen and study it like a mad man.

Comp 670 · Dec 10, 2008

Put a cutler button cover on the cat roller clutch.

It slows the whole deal down and makes it do exactly what you are saying you want.With the rollers the clutch is too sensitive and it just blows open (shifts to soon)when you apply alot of power to it.

I have used this button cover on alot of cat clutches with many different engine combos and it allways seemed to help with opening up the tuneing window.

schu · Dec 11, 2008

That part sounds very interesting and I know it would work for the upshift, but does it hurt the backshift a bunch. If it was a bit cheaper I would just order one to try it, but that is pretty pricey.

schu

Norway · Dec 26, 2008

I'll throw in some ,02.

First, the button clutches do work well for lots of people. Could be like sugested that they slow things down a bit, gets thing right instead of jumping back and forth.

Theory is that the rollers SHOULD be steady, just react faster than buttons.
Again, I have not done scientific testing but some VERY good tuners on here has said they could never get the roller to work...

Now, on the function of the secondary:

My own way of explaining the function of the helix is to call it an equalizer, a balancer. It will balance the power availiable from the engine vs. the resistance to turn the track, load.

The helix and spring then becomes the calibration of this balance, to suit the engine/track combo. The gearing will be the performance level demanded of the machine (174" track geared for 150mph will be to high a level etc.).

Going to try this myself pretty soon tho, Cat roller vs. buittons. Have Poo button and TEAM to so will be interesting to try.

RS

DRD · Dec 26, 2008

AA/AT said:
Put a cutler button cover on the cat roller clutch.

It slows the whole deal down and makes it do exactly what you are saying you want.With the rollers the clutch is too sensitive and it just blows open (shifts to soon)when you apply alot of power to it.

I have used this button cover on alot of cat clutches with many different engine combos and it allways seemed to help with opening up the tuneing window.

My buddy had a worked over T-Cat and he found the same thing. The button clutch was more consistent and worked in a wider variety of snow conditions.

sfrp · Dec 30, 2008

sled_guy said:
The primary clutch is not going to affect the upshift/downshift of the secondary, the system doesn't work that way. The secondary will still shift up quick and pull you off the revs.

You can try a couple of things. A stiffer secondary spring will hold the secondary in low gear longer. The other thing you can do is try a multi-angle helix, hit it hard on the initial angle and then to a shallow angle to let the revs build without shifting out too quick.

sled_guy

The clutch weights do all the upshifting in a CVT, the springs and helix control the upshift by resisting the shift force of the weights.
A/C tapered tip weights shift very hard initially [can overshift] because most of the weight mass comes into play at lower track speeds requiring a straight cut helix [ 53 deg and red/white AC work good in low geared mountain sleds].
A heavy tip weight will not shift up as much initially as a comparable tapered weight [will make up for it at higher track speeds] but you could probably get away with a using a progressive helix [57/50 AC with red/white 4th hole works well] and have the added bonus of more traction and less trenching when starting off because of the 57 deg start angle.
The roller cover gives much better back shift then a button cover and is more sensitive and reacts faster to changes in load.
These are just some observations from many years studying clutching.

spring snow hero · Dec 31, 2008

the primary is RPM sensing. the secondary is load sensing. the primary is always tring to upshft, the secodary tells it how fast based on load. the helix angle dictates the rate of shift, the spring has some affect on the rate of shift and moreso the pinch of the belt. the roller is faster reacting and sometimes to a fault. a properly tuned roller is going to be more efficient then a button......but not much.

get your primary rpms nailed and keep feeding it helix till it shifts like you want. keep adding spring till it stopps slipping.

that is my take on it.

longhairfreak · Dec 31, 2008

longhairfreak said:
A stiffer spring in your primary will slow the upshift. Try that its cheaper. You dont want a button clutch they are not as efficient.

Trust me this works I just tried it and it solved my problem.

Anylizer · Dec 31, 2008

.02 rollers are more efficient. thay also overshift. because they re-act so quick to a slight change... they have a tendency to hunt around for the proper shift point. they accelerate great and backshift awesome..... they just hunt too much for my likes. CPC button cap will sove the prob. Gauranteed. A.

Thoughts about using a button clutch and shift speed.

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