Snowmobile World banner

1 - 6 of 6 Posts

·
Registered
Joined
·
154 Posts
Discussion Starter #1
I have been reading the AAEN clutch tuning book and am a little confused. He says that there are really 3 properties to a spring. Engagement load, full shift load and rate. I understand the first 2 and that is the way any manufacturer lists them. You never see the rate of the spring listed (except in his book). From what I understand the rate plays a role in the shift curve also. Is it not as important and that is why you don't see it listed? Is there a relation between the full shift load and the rate? Is there a way to figure out the rate based on the other two properties? Any insight to this would be appreciated. Thanks.
 

·
Registered
Joined
·
113 Posts
The spring rate is distance/time it takes from full extension to full compression. I believe the higher the rate the harder it is to compress fully.
 

·
Registered
Joined
·
154 Posts
Discussion Starter #3
Here is what I found out:

If you take the difference of the engagement load and f.s. load and divide that by the clutch travel you get the shift rate.Most springs give their engagement load @ 2.5'' and full shift @1.25'' for Polaris sleds.Polaris gives their full shift load @1.19'' which is into overdrive.1.25'' is for a 1:1 shift ratio.So if if your spring is a 150-300 divide the difference(150) by 1.25 and you get your shift rate.The lower the shift rate the quicker your primary will shift.Higher rates wil shift slower and give the engine a revvier feel.

///////////////////////////
I tried it for many different springs and that formula works. I was wondering because I have an AAEN purple (150/320) and replaced it with an EPI (185/320) and it doesn't seem to accelerate as hard. The higher the rate the harder the acceleration. According to the formulas I went from a spring with a reate of 136 to a spring with a rate of (320-185)/1.25 = 108. In theory this sounds right. Thanks.
 

·
Registered
Joined
·
1,026 Posts
the "Rate" of a spring is basically how many pounds it takes to compress it one inch, you need a special spring load tool which measures this, if you have Olav Aaen's book it describes this fairly clearly, just trying to help
 

·
Registered
Joined
·
1,026 Posts
Sorry that sounded snippy, it was not, if you have the same book as me the spring tool is on page 26
 

·
Registered
Joined
·
316 Posts
Mj, Your right about the higher engagement spring not accelerationg as hard as your old one. On some sleds, the clutches are not shifting quick enough and not loading the motor. Your lower engagement spring loads the motor a little quicker and gives you harder acceleration. I have used this techniques extensively with my Mach Zs and had others find it much quicker too. In trail conditions this allows the Mach Z to accelerate much quicker than it normally would. But, the reverse is also true. If you are running on ice with ice picks, this would only make you go slower as you have so much traction you really need the motor to rev quickly to peak power. It all depends on how you want to ride your sled. That is the beauty of setting up a sled for your personal tastes. It's fun! The worst is a trail driven sled clutched for drag racing. It just doesn't work well in the trails.
 
1 - 6 of 6 Posts
Top