Ski Doo Tech Info [Archive] - Page 2 - Snowmobile World : Your #1 Snowmobile Forum

Dynamo^Joe

06-03-2004, 11:06 PM

KRAGAR]...Joe; what do you think attribute to more belt squeeze on your helixes?
JOE]...More belt squeeze than what helix or who's helix. It's slight difficult to answer from your question.
I'll say from most of the talk you see on any of the sled forums and common helixes mentioned, my helixes progress to a low angle that tuners are not too much familiar with.

KRAGAR]...Is it the low finish angle or is it that the secondary actually twists more to get to full shift giving more tension.
JOE]...If you have a torsion spring in the secondary then you have both the "increasing pretension" and "Angle progressing lower" that adds more belt clamp.
More spring force > more clamp.
Lower helix angle > increased resistance to the sheaves opening > more clamp.

With the compression spring secondary the spring rate is constant so to neglect the helix in the problem the only way to add additional clamp force by the sheaves is to install a spring with a higher final compressed force.
Add in the helix angle now, as the helix angle gets lower the length of the button/roller path becomes longer. So now your button/roller path gets longer the angle gets lower, the sideforce against the belt increases as the shift increases.

KRAGAR]...[i]Have you compared the final shift force on a secondary with the same spring and your cam and say a straight 50 which has about 1/4 inch less travel?
JOE]...I have not tested with my helix. I have tested a straight 50 against a str.34, prog 50/36, 46...and a few other helixes.
I don't know if you can look at this page or not. The information needs to be tuned and I have notes for it that are slight easier to understand.
http://www.picturetrail.com/gallery/view?&...id=17807801#top (http://www.picturetrail.com/gallery/view?&members=1&p=3&uid=486172&gid=1520953&&imgid=17807801#top)

KRAGAR]...Going testing this weekend on the asphalt again and have added more weight again using your helix. Actually hope to make the sled puke down the track and then take out some weight to find were I can go with this.
JOE]...Hah...Good luck doing that. lol Lay clicker down and break the engines back. Regardless of holeshot, in fact you can neglect it just for testing purposes, load the engine just to see how it pulls with the lower clicker and/or more flyweight.
Heh...check the backshift. he he

Dynamo^Joe

02-09-2007, 09:41 AM

@ski-b]...Clutching is a very personal preference........As long as a person is happy with there set up just ride it and have fun, that is what it is all about having fun.

Joe]...Yes, Regardless of this clutch or that clutch or an old p.o.s. to the flavor of the week - If the tuner knows basic principle of clutching they have the power of a flow chart to make a decision for the next direction on getting to calibration that they like.
...in the end, the sled tells you what is wrong.
You use principles to guide you what to change.

I will say something about me...I have learned to filter out the crap and know what the parts do. I've learned what the parts do by learning the principle of it.
This is a part, it works this way and it has a specific function.
This is another part, it works this way and has a specific function..
This is another part, it works this way and has a specific function...

Principle
*Clicker number influences the "response" of the system.

Need quicker responce = Raise clicker #.
Need engine to push harder = Lower clicker #
Any higher clicker than #1 = quicker rpms. [TRA lever pushes less hard]Any lower clicker #6 = engine pulls harder. [TRA lever pushes harder]

Clicker 1 tra lever pushes hardest ~ Clicker 6 tra lever pushes least hard.
If...this problem.
Then...it comes from the calibration of this part
Consider...The function of the part. What the sled told you.
Change...the part shape to change the calibration.
Test...[/b]

My engine runs 8000 rpms.
I don't want to change the flyweight.
I am in clicker 3.
I make a run up a hill at w.o.t. and get correct rpms. As I get higher track speed while accelerating, the load changes. I go thru a dip then over a hump and land and lose 400 rpms while i maintain w.o.t. The engine rpm hangs 7600 unless I can turn the sled away to let the rpms recover.
The engine is sluggish to respond to my throttle cycle.
***I don't want to change the flyweight***
What can I do with a clicker change?

*If...Rpms drop when the load changes. Rpms are difficult to recover.
Consider - For the present flyweight and clicker number the TRA lever is pushing too hard and low rpms are revealed.
I don't want to change the flyweight.
I can change the clicker.

*Then...Knowing principle [Any higher clicker than #1 = quicker rpms. [TRA lever pushes less hard]]
I change from clicker 3 to clicker 4.
Test...

Consider...The function of the part. What the sled told you.
Change...the part shape to change the calibration.[/b]

@RonS]...Snowmobile clutches are more efficient at low/mid shift points-not as efficient at high ones.
Joe]...I don't believe in black art. I believe everything can be measured. A clutch setup that works to suit your personal requirements is a "Measured Success"

That statement can be proved right and it can be resolved with a clutch being extremely efficient at high ratios. If you have the internal details to offer low temperatures at high ratios, then the clutch is efficient at high ratios. "Power in" is not being lost to heat.

Heat in a great setup is a curious problem...
I have taken the clutches from identical 600's and switched them sled to sled and the hot clutches seem to follow each other with little calibration change.
There are setups that upshift and backshift with low hp engines that still produce a large amount of heat.
There are high hp 200+ setups where under w.o.t. acceleration produce cool temperatures.
I suspect that the surface of the sheave may be a culprit/factor. I have asked an engineer to help me learn what kind of information I can get from Relative roughness experiments.

================================================== ================================================== ==========================

Regarding a spring;
Question - What is the "final force" of A spring?
Answer - The amount of force whan the clutch is fully shifted (the sliding half can't travel any further)
Regardless of primary or secondary - Given a 70/140 or 85/115 spring then would be the xxx/140 final force or a xxx/115 final force at full shift o.d.

Principle:
Spring force resists the push of the TRA Lever.
TRA lever push = (Current flyweight - spring force)
[/b]My engine runs 8000 rpms.
I don't want to change the flyweight.
I am in clicker 3.
Primary - 100/290
I make a run up a hill at w.o.t. and get correct rpms. As I get higher track speed while accelerating, the load changes. I go thru a dip then over a hump and land and lose 400 rpms while i maintain w.o.t. The engine rpm hangs 7600 unless I can turn the sled away to let the rpms recover.
The engine is sluggish to respond to my throttle cycle.
***I don't want to change the flyweight***
***I don't want to change the clicker***

*If...Rpms drop when the load changes. Rpms are difficult to recover.
Consider - For the present flyweight and clicker number the TRA lever is pushing too hard and low rpms are revealed.
I don't want to change the flyweight.
I don't want to change the clicker
I CAN change the final force of the primary spring.

*Then...Knowing principle [TRA lever push = (Current flyweight - spring force)

IF...TRA lever pushing too hard = (Current flyweight - xxx/290)
THEN...TRA lever will push less hard = (Current flyweight - xxx/320)
(Lever pushes less hard because you added spring force)(Spring force resists the push of the TRA Lever.)

The TRA lever is pushing too hard with the 100/290 so I can go to a 100/320

Test...

Consider...The function of the part. What the sled told you.
Change...the part shape to change the calibration.[/b]

================================================== ================================================== ==========================

Rpms are determined by the combination of the 3 components. Clicker, spring force, TRA Lever flyweight.
If you have an rpm problem as in the previous examples then this is the final part you can change the shape of to alter the calibration "where" you had the problem.
.
.
.

Regarding Flyweight

*Flyweight determines rpms*
*Need less rpms; Increase flyweight mass, The TRA lever pushes harder.
*Need more rpms; Reduce flyweight mass, The TRA lever pushes less hard.
[/b]My engine runs 8000 rpms.
I don't want to change the flyweight.
I am in clicker 3.
Primary - 100/290
Flyweight - 13 grams.
I make a run up a hill at w.o.t. and get correct rpms. As I get higher track speed while accelerating, the load changes. I go thru a dip then over a hump and land and lose 400 rpms while i maintain w.o.t. The engine rpm hangs 7600 unless I can turn the sled away to let the rpms recover.
The engine is sluggish to respond to my throttle cycle.
***I don't want to change the clicker***
***I don't want to change the spring force***

*If...Rpms drop when the load changes. Rpms are difficult to recover.
Consider - For the present flyweight and clicker number the TRA lever is pushing too hard and low rpms are revealed.
I don't want to change the clicker
I don't want to change the primary spring.
I CAN change the flyweight.

*Then...Knowing principle; Flyweight determines rpms.

IF...TRA lever pushing too hard with 13 grams.
THEN...TRA lever will push less hard with 12 grams.

The TRA lever is pushing too hard with the 13 gram flyweight so I know the Lever will pull less hard with any flyweight less than 13 grams.

Test...

Consider...The function of the part. What the sled told you.
Change...the part shape to change the calibration.[/b]
================================================== ================================================== ==========================

Calibrating with a secondary spring.

Regarding a spring;
Question - What is the "final force" of A spring?
Answer - The amount of force when the clutch is fully shifted (the sliding half can't travel any further)
Regardless of primary or secondary - Given a 70/140 or 85/115 spring then would be the xxx/140 final force or a xxx/115 final force at full shift o.d.

Principle:
Spring force resists the push of the TRA Lever.
TRA lever push = (Current flyweight - spring force)
[/b]My engine runs 8000 rpms.
I don't want to change the flyweight.
I am in clicker 3.
Primary - 100/290
Flyweight - 13 grams.

Secondary
225/300 RER spring

I make a run up a hill at w.o.t. and get correct rpms. As I get higher track speed while accelerating, the load changes. I go thru a dip then over a hump and land and lose 400 rpms while I maintain w.o.t. The engine rpm hangs 7600 unless I can turn the sled away to let the rpms recover.
The engine is sluggish to respond to my throttle cycle.
***I don't want to change the clicker***
***I don't want to change the Primary Spring force***
***I don't want to change the flyweight***

*If...Rpms drop when the load changes. Rpms are difficult to recover.
Consider - For the present flyweight and clicker number the TRA lever is pushing too hard and low rpms are revealed.
I don't want to change the clicker
I don't want to change the primary spring force.
I don't want to change the flyweight.
I don't want to change the helix.

I CAN change the final force of the secondary spring.

*Then...Knowing principle [TRA lever push = (Current flyweight - spring force)

IF...TRA lever pushing too hard = (Current flyweight - xxx/300)
I look around in the aftermarket and find several secondary spring options. It just so happens that a company has a 200/335. 35 lbs more final force than my present secondary spring.

THEN...TRA lever will push less hard = (Current flyweight - xxx/335)
(Lever pushes less hard because you added secondary spring force)(Secondary spring force resists the push of the primary clutch (TRA Lever.))

The TRA lever is pushing too hard with the 225/300 so I can go to a 220/335.
Will the loss of 5 lbs at the start going from 225/xxx to 220/xxx be an issue? I doubt it.

Test...

Consider...The function of the part. What the sled told you.
Change...the part shape to change the calibration.[/b]

Your new data should reflect a change after a run.

Run #1
clicker 3.
Primary - 100/290
Flyweight - 13 grams.

Secondary
225/300 RER spring
Loss of 400 rpms at a point of load change and difficult engine rpm recovery.

Run #2
clicker 3.
Primary - 100/290
Flyweight - 13 grams.

Secondary
225/335 RER spring
Loss of maybe 400 rpms at the point of load change yet engine rpm recovered while I kept the throttle pressed to the bar.