what does the rate and total force have for an affect on clutching?

brianbailey440

brianbailey440

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trying to better understand what rate, and force actually do when changing primary springs.i know that going to a heavier spring will increase rpm,and lower will decrease rpm.what i need to know is does a higher rate mean a slower shift?does a higher total force also mean a slower shift?example,i try a ywy primary spring with a 2.5 rate/128 total force.it works good, but my rpm is low on top,so i go to a ggg with a 2.75 rate/131 total force.i gain back some rpm, but it shifts totally different.the ywy gets me to 105 on the dreamometer, but the ggg gets me to 100, and the belt starts to slip on the top end.the ywy pulls better at the top, and the ggg pulls better at the bottom.the secondary is a green spring.why does the ggg work better on the bottom than the ywy, and vise versa?
 

yup, read that,just wish i could spend some time with the pros, and get more insight on how to couple primary and secondary springs as a pair.im sure that at some point of higher primary spring pressures, that you will need to use a higher #secondary spring to match.just dont have enough time testing to fully understand it.i wish that there was a chart that would sort all this stuff out.it would make it much easier for people to understand.
 
you already answered your own question, the stiffer the primary spring the more rpm and the slower the shift is, it also requires more weight to overcome the spring. The reason your sled would run better down low with a stiffer spring is your running it in lower gear ratio(shift ratio) in the cvt system, like winding out a stick shift car and not skipping gears.
 
i was hoping you would chime in,i really appreciate your advise so i have a question for you.now that im getting much closer to being dialed in with the weights and spring in the primary, im going to start working on the secondary.im thinking that i need to try a higher torsion, and compression rate in the secondary.it looses pull after about 700 ft. with the 51/43 helix.knowing that the primary is allmost perfect with rpm, but the secondary is probably shifting too soon to keep pulling till i run out of gear, im gonna try a silver spring in the secondary.i know it will make it shift slower, and keep the power where it should be, but my question for you is , is there a rule of thumb about what primary spring matches a secondary spring, or is it just something that needs to be tested out in the field?i have a thirst for information,and i have a pretty good idea how clutching works now, but im no expert by any means yet,lol.im thinking that i wanna pull as hard as the engine can pull till i run out of gear, then a slight over rev on top right?
 
mrviper700 said:
you already answered your own question, the stiffer the primary spring the more rpm and the slower the shift is, it also requires more weight to overcome the spring. The reason your sled would run better down low with a stiffer spring is your running it in lower gear ratio(shift ratio) in the cvt system, like winding out a stick shift car and not skipping gears.
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well now you put it that way,im starting to get it.
 
The big thing I learned during my clutching experience is that the factory Yamaha setting are pretty good and a green secondary spring works for 99% of the applications. I ran a silver secondary spring for a season because a seasoned mountain builder said it was the way to go. I had no upshift and would rev out past 1/2 throttle but I didn't know enough about clutching to understand what was causing it. The second thing I learned is that grinding rivets sucks. I tried running a softer engagement spring to lower rpm but a softer engagement even with the same rate will result in a slightly lower total force so then it's time to play with rivets.

In the end I ended up goin with heelclickers. They were spot on the first time. Engagement was a little high but the bushings are a little sticky on the pivots at first and I haven't put enough miles on them to break them in yet.

The AAEN clutch tuning book really is the bible of you want to understand all this stuff. The first read you will probably have more questions than answers. By the 3rd read it will all make sense. The fundementals always hold true though. The primary controls engine rpm and the secondary controls back shift. End of story that's the way it is. I tried convincing myself that one thing would effect something differently but it just doesn't.

All clutching is different too. The TRA I think is great because it allows small adjustments in the primary on the sled. Polaris preaches adjusting peak rpm with the secondary assuming the primary has the correct weights. He we say don't adjust rpm with the secondary. If you need to change rpm's work the primary. There are exceptions to that rule, especially in the mountains. If the sled is set up and dialed in with the secondary at 70 and you have a deep day with soft snow a helix change to 60 will up shift sooner and keep revs down. Likewise in wet heavy snow a quick change to 80 will prolong upshift and keep you from bogging down with the heavy snow load. A 12mm ratcheting box wrench is great to keep in your tool kit then you can make helix changes trail side.
 
im looking at aaens book right now.chapter 3, page 13,it says the main rule of clutching is, if you want to change engine speed,work on the primary.if you want to improve {efficiency} or backshifting, work on the secondary.efficiency being the key word.the secondary controls the shift by sensing torque.you need to have the correct secondary spring pressure to be 100% efficient.too little spring pressure, and the belt will slip,too much, and the clutches will fight each other.this is what im working on next.
 
I also learned that for a mountain sled an rx-1 helix is a waste of time. It's progressiv vs dual angle and you never really know where it is in the angle range. For me the stock 43 degree straight helix worked great.
 
Backwoods M Max said:
I also learned that for a mountain sled an rx-1 helix is a waste of time. It's progressiv vs dual angle and you never really know where it is in the angle range. For me the stock 43 degree straight helix worked great.
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Ya know , I was talkin to Snowdad on a different thread last week. He also said that a 43 worked the best for his mountain set-up.
 
buried my face in aaens clutch tuning handbook again,focusing on the primary spring.preload is the engagement,rate is what keeps the shift curve straight,buy choosing the correct rate spring, you can achieve a straight shift.total force is how much force it takes to fully compress the spring.i also studied chapter 9,gearing can make a huge difference on clutch efficiency.i have tried gearing down before, and all the sled would do off the line is spin.geared from 22-39 to 23-40, and the sled pulled harder.geared up to 23-39, and the sled pulled much harder.reason being is you are gaining traction, and making the clutches run in a more efficient ratio.gonna gear up again to 24-39 and see what it does.im willing to bet that the sled will be quiker, and faster because the clutches will be in an even better ratio for efficiency.i dont have the silver secondary spring yet, so im going to try and wrap the secondary, and see what it does.a good dose of chapter 4 is on the plate for my next choice of reading, then ill be done, and roosting everyone,lol
 
A couple of bucks said:
Ya know , I was talkin to Snowdad on a different thread last week. He also said that a 43 worked the best for his mountain set-up.
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I had a 45 that I tried too and it just held too long before back shifting. The 43 really has been where it's at. I know people who run a 51/43 dual angle, but the 51 is only for the first 3/4" maybe of the ramp so you get track speed quick when coming from a dead stop in deep snow but for the major bulk of the shift ratio range your in 43 anyways.
 
A couple of bucks said:
Ya know , I was talkin to Snowdad on a different thread last week. He also said that a 43 worked the best for his mountain set-up.
Click to expand...

I had a 45 that I tried too and it just held too long before back shifting. The 43 really has been where it's at. I know people who run a 51/43 dual angle, but the 51 is only for the first 3/4" maybe of the ramp so you get track speed quick when coming from a dead stop in deep snow but for the major bulk of the shift ratio range your in 43 anyways.
 
i talked to gary at micro belmont today.he made helixes for yamaha and hauck.i told him what my sled was doing, and he said i should go to a 52-44 or a 52-45.he told me that my sled will shift better with a higher angle to accomplish what im doing, 1000 ft runs.i trust in what he has to say, he has more experience than most when it comes to helix angles.im gonna use his knowledge,and put it to the test on my sled.updates to come!!!
 
got the helix yesterday,my buddy found some snow and im going to test it out today.gonna find out if i can beat his f-7 in a 1000 ft. drag race.wish me luck!!!
 
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