Our technicians are the industry's clutching specialists, racing and riding with our products year round. They know snowmobile and ATV drivelines inside and out - clutches, chains, sprockets, helixes, u-joints and more. And they test and use all the major brands - Polaris, Arctic Cat, Ski-Doo, Yamaha, Kawasaki, Suzuki & Honda. So, when it comes to snowmobile & ATV performance, our techs have the answers.

We plan on regularly presenting technical tips for snowmobiles and ATV's. See the list on the left for our current Tech Tips archive list. Select any tip in the list to view it. Feel free to print these Tech Tips out to save for future use, or check back here regularly to view new tips as they are added.

Remember, these are strictly Tech Tips. Feel free to contact our technicians directly with any part-specific, or application-specific questions.  Call 218-829-6036 for assistance.

Tech Tip #11:  Progressive vs. Compound Radius Helixes

The main difference between a true progressive helix and a compound radius progressive helix is the way the ramp angles are cut on the helix. For example, a 50-36 true progressive helix has a 50 degree angle at the top of the ramp and a 36 degree angle at the bottom of the ramp and the angles between are divided equally between the top and the bottom. A 50-36 compound radius progressive helix will start at 50 degrees at the top of the ramp and stay in a straight 50 degree angle for an 1/8 to 3/4 of an inch down the ramp (depending on brand and style) and then progress very fast to the ending angle of 36 degrees. Each style has it own advantages and disadvantages.

There any many different combinations and sizes of progressive style helixes. The right one for you depends on where and how you plan to ride and what sled you are riding. Here are some basic characteristics of the different styles of helixes.

A true progressive helix will normally have a faster and more consistent backshift through the low end and mid-range. We would normally choose this style for all around trail riding. A compound radius progressive can give you a harder holeshot from a dead stop and may accelerate harder but it will not normally backshift as fast and be as responsive on and off the gas once you are moving. These helixes are good for drag racing or straight line acceleration.

Helix angles also effect the all around performance on both styles of helixes. For example; the steeper the angles, both the beginning and ending, the faster the clutch will up-shift and accelerate, but it will have a slower backshift and throttle response. Smaller angles create a slower up-shift and a faster backshift. Depending on your riding style, people that want a good all around set-up would use smaller helix angles then someone who just cares about racing across the lake or field.

Helix angles can be deceiving and confusing for the following reason. A 50-36 true progressive will accelerate harder the a 50-36 compound radius with a real short 50 degree angle (like a OEM Polaris helix) because the true progressive helix stays in a steeper angle longer through the mid range. This is why it is important to know how long a compound radius helix is in a certain angle.

As stated before, there are many different styles and uses for the different kinds of helixes depending on what performance and handling you are looking to achieve. If you need help choosing the correct helix for your application please call EPI.