Clutching theory

[ruffryder]

I have to correct you here - the bold should read shift ratio , as the weight in each position of the flyweight effects a certain part of the shift curve, and should still be tuned to run at shift rpms.

correct, thanks for the clarification. Yes, that statement should not say rpms but force at shiftout.

I have edited my post.

 

[winter brew]

Sheave angle...both primary and secondary will have a huge impact on setup. For example, the Hyperlite sec had a fairly steep sheave angle.....makes for less belt squeeze compared to most sec's if using the same spring/helix angle. Made for a quick upshift and less backshift signal...good drag race clutch.
I think just about every primary and sec is running a different angle so it's one more thing to think about when tuning.....and the TRA primary has a variable/progressive angle.

 

[shortstop20]

What angle do the sheaves start and end at on the TRA winter brew? The TRA has a steeper sheave angle than the P85 if I remember right?

 

[winter brew]

I believe it's still 24-28.....but memory is bad.

 

[thefullmonte]

OK so now that everyone has X's and Y's confusing them I need to review my college physics books one of these days

care to add more specific info as to the effects of a flatter or more curved profile as well as a heal/toe weight bias in actual application. ie the meat and potatoes of the above explanation, heal weight does this, toe weight does that kind of a thing.

I'll take a little stab at this. Please note there are many ways to get to the same end with clutching. As well your riding style comes into play. This is what I have found to work for me lately. However, it seems I'm always tuning and learning. Remember....baby steps. Oh, and I especially want to thank AKsnowrider and Winter Brew for helping me out over the years.
I assume you are referring to something like the Heavy Hitter weights from Thunder Products or the MTX from SLP. The heavier weight in the pivot area will allow more belt squeeze at lower RPM. This has been said. What does this do really? It allows you to use the full gear ratio provided by your sheave faces. Standard (Polaris type)weights slip quite a bit at low rpm and actually require more rpm to positively engage the belt. So what most people do is go to a very steep initial angle on their secondary. Why? So the primary can shift through the secondary very quickly. This allows the clutch to move to a higher gear where it is less likely to slip and you are now into a ratio and rpm the clutch weight can perform at more efficiently. With a heavy pivot weight you have positive force on the belt so it can engage and pull smoothly at lower rpm as well pull less angle of helix. This gives you a nice low crawling gear without trenching.
Adjustable weights tend to also have a center hole and tip hole. As also stated earlier the tip hole will have the greatest effect on overall rpm. Now here comes a BUT. For most mountain applications we tend to like a very aggressive up shift. So if the heavier pivot weight already has things moving. Lets just add some to the center to control our up shift characteristics. Please note that I'm not taking into account weight angle. Now if you need more top speed you tend to move more weight to the tip. If you are running a few RPM shy you can take weight out of the tip.
I was on the phone with Lon from Thunder products today (Heavy Hitters) He gave me a bit of a, OK a huge refresher course . Now something I've always known, but sorta forgot is that the secondary isn't a clutch at all. It is a torque converter. It senses torque being applied to it from the primary during acceleration and from the track during deceleration. That may help a bit for some of you.
I hope I got all that right

 

[XC700116]

Sounds about right and yeah the Heavy hitters or a MTX style weight is probably the angle most would be looking at for adding or removing weight from a certain area. I personally will be working with a set of lightning weights and primarily removing weight from the heal due to the turbo application. I may also pick up a couple sets of 10 series weights and grinding on them to play with the profile a little.

and yes technically the secondary is a torque converter and not a clutch but clutch is easier to type

Lets keep this thread going, the more info the better and like has been stated there's more than 1 way to skin a cat.

 

[Funoutfitters.com]

If you guys have questions on clutching, feel free to use our website, and you can talk to cat master techs free of charge!!


Josh Zieske

 

[XC700116]

We are trying to build an informative thread for people to use as an educational tool and get the info out there to those that want to learn it.

Thanks for the offer and the info for those that are looking for a direct answer on a specific problem especially as it pertains to Arctic Cat sleds this is a great tool, but I don't think we would want to tie up your application and your technition by giving the quiz show to him for hours on end either.

If you could please have one of your guys come in and participate in the discussion from time to time, always looking for different viewpoints and info on different applications. I would ultimately love to get a Cat, Doo, Polaris, and Yamaha specialist in here to contribute to the thread.

 

[XC700116]

Oh and I'm not trying to lay claim to the thread just trying to help it along and keep it going.

 

[devilrmk]

This is exactly what I was hoping for in this thread. Keep it up guys.


You are doing just fine XC

 

[www.team-ind.com]

To build on the theme of a secondary clutch being torque sensing, attached is a link to the spreadsheet that we posted on the Mod board that shows belt side pressure at WOT with either a TEAM TSS-04 clutch or a Tied Secondary clutch. With this you can see the big changes that a helix can make in side pressure and the relatively small changes a spring makes. Like previous posters have said, first tune with gram weight and helix angle and fine tune with springs.

BTW the other reason higher helix angles at the start of the shift curve work well is that there is a lot more belt in contact and thus less side force needed.
http://www.snowest.com/forum/showthread.php?t=172390

Mark Schiffner
TEAM Industries

 

[sunbather1969]

what he said funoutfitters

We are trying to build an informative thread for people to use as an educational tool and get the info out there to those that want to learn it.

Thanks for the offer and the info for those that are looking for a direct answer on a specific problem especially as it pertains to Arctic Cat sleds this is a great tool, but I don't think we would want to tie up your application and your technition by giving the quiz show to him for hours on end either.

If you could please have one of your guys come in and participate in the discussion from time to time, always looking for different viewpoints and info on different applications. I would ultimately love to get a Cat, Doo, Polaris, and Yamaha specialist in here to contribute to the thread.

thanks for the offer but give some input instead of output

 

[likkerpig]

Great thread! Here's something I'd like to know (and it's probably not a cut and dried answer, but I'll just put it out there...)

Say you have a motor spinning 8100 RPM and you want to raise or lower the RPM. How many RPMs per gram of weight can you shoot for when tuning clutch weights? For example, say if you wanted to drop 300 RPM, how many grams lighter/heavier would you need to go? 2g? 3g? Is there a constant "formula" where Xgrams = Xrpms?

(Also realizing you could maybe try and adjust that via primary spring with a stiffer finish rate...)

 

[shortstop20]

There's really no set formula. Just have to go try it. I've seen peak RPM stay the same with heavier weights.

 

[XC700116]

There's really no set formula. Just have to go try it. I've seen peak RPM stay the same with heavier weights.

This is really dependant on the spring your running and what kind of clutch your dealing with. "normally" and with a "normal" spring on a polaris P-85 I've seen an average of about 100 RPM to 2 grams of weight/arm. Now that is a very vague answer I know but it is very dependant on many other variables. but as a general rule of thumb it's pretty close on a setup that is "pretty close" to a good running setup, ie everything is pretty good except it overrevs just a touch.

 

[astro]

How fast do you like to hit your max RPMs when you go from idle to WOT? It's the starting helix angle that effects this right?

 

[XC700116]

How fast do you like to hit your max RPMs when you go from idle to WOT? It's the starting helix angle that effects this right?

That's kinda a question that is very application/riding style specific. Some people or circumstances require max hp immediately and some torque. Some will want to hit their Max RPM immediately while some will want it to climb to it after launch.

Drag racing you'd normally like to get to your peak torque RPM right out of the gate and then rev to peak hp as the shift progresses.

From what I've seen and what I prefer this is about what I shoot for on most any NA sled while trying to keep a good backshift/in and out of the throttle response.

Initial helix angle does effect this aspect as well as the other components of the system but that is one of my main areas of focus when going for the goal I just mentioned.

Most of the entire clutching formula is dependant on what your doing with the sled, and the running characteristics of the motor. NA 2 strokes you want to utilize the bottom end while on turbo applications you normally want to get the motor on boost ASAP so both require a different approach. This is where knowing where your motor makes hp and torque are abosoluetly critical.


Astro, your sled is a pretty special animal, I'd love to hear some of the things you've found to work while tuning that monster.

 

[astro]

Been having a few belt slippage issues but hopefully I will get them taken care of this year! Going through the whole sled right now- New T35r turbo to try this year. Should be done dialing the M10 in also. Running the new Motec knock module this year also.

Back to clutching, my motor makes lots of torque at low RPMs and lots of HP at the top. Been playing with the Paragon for a while. Got a new helix to try as soon as the snow hits, but ready to move to a different secondary if it doesn't solve the slippage issues. Maybe I'll try the Team Tied.

 

[XC700116]

I know a guy that had great luck with his paragon but I haven't messed with them at all and he's not running anywhere near the HP that you are. Best bet on that is to talk to Duane about it but he's not always easy to get ahold of.

Sounds like the Tied can provide you with some pretty serious belt pressure though so that might be the best route.

 

[winter brew]

How fast do you like to hit your max RPMs when you go from idle to WOT? It's the starting helix angle that effects this right?

IMO, from idle to WOT, RPM should go almost immediatly to PEAK....maybe 1/2 a second...??