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What does a helix do exactly?

M
Feb 21, 2009
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So I got asked about helixes today and I think I kinda understand the concept, but it would be nice to know for sure. I guess I want to know what changes as you change degrees. Also how do progressive helixes work? Thanks for all your info!
 

Frostbite

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I guess I'll take a poke at it and try to keep it simple.

It sounds like you understand the helix resides within the secondary or driven clutch? The helix is the mechanical device that actually separates the sheaves of the secondary via rub blocks or rollers.

The helix angle basically determines how quickly the secondary opens and closes. A straight cut helix (let's say 36 degrees) opens and closes the sheaves at a constant rate.

A progressive helix typically has the larger number (steeper angle) first (but sometimes it's reversed) say a 44/36 helix. The steeper the angle the more load you put on your engine. You can load your engine via the primary clutch AND the secondary clutch. So, the advantage of a progressive helix is the steeper angle loads your engine very quickly and allows your sled to accelerate more quickly while it's still in the meat of its powerband.

The "progressive" means you may start at 44 degrees but, your helix angle is gradually decreasing down to 36 degrees in this case so you can still have a good backshift. Some helixes aren't progressive and have more or less a "step" between your 44 and 36 degree angles. They aren't used as widely, especially for the mountains where you end up stuck on the step between the two angles at the most inopportune time. Straight cut helixes are often prefered by mountain riders due to their consistant shift rate.

The "backshift" I speak of is best illustrated by the thinking of climbing a hill. You are going pretty good up a mountain and there's a snow covered log across the hill diagonally so you have to slow down. The backshift is showcased right after you slow down and want to hammer the throttle again. You wanted your helix and secondary spring combination to shift you back to a lower gear quickly so the sled accelerates quickly again without a bog.

High initial angle helixes with lower finish angles are great for drag racing where your motor is loaded quickly but, the helix drops to a lower angle after your sled reaches the limits of its low end grunt and allows it shift out for higher top speeds. They also CAN work in the mountains but, the machining of the inital angle may be abbreviated to ensure you are on the straight cut portion of the helix for the vast majority of your up and down adventures.

I hope this helps.

Good Luck

Frostbite
 

Idcatman1

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Nov 26, 2007
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Helix

One bit of info left out is that the helix governs the amount the driven clutch spring tightens as the sheaves open. Everything else said was great.
 
M
Nov 23, 2008
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Thank you frostbite, That was an awesome way to explain that. I messed with my clucthing last winter and asked all kinds of questions. Never did fully understand but now i do. I still had back shift problems even after shift assist and screwed in the plastic adjuster one half inch. 06 m7, stock springs for 6-9000 ft. Maybe need m8 orange spring? Oh running 36 helix.
 
M
Feb 21, 2009
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Awesome write-up Frostbite, thanks for all the info. Just to confirm I am understanding all of this correctly, take a 36 helix for example, that helix works well for us mountain guys because it doesn't load the engine quickly and thus it's a better transfer of torque and traction to the ground...where as a higher degree helix would load the motor faster and thus transfer all that horsepower quickly and trench?

Also, M7 I would recommend running the orange spring with your setup, I'm at the same altitude as you and am running the orange with shift assist and Black Diamond Rollers and the performance is noticibly better than stock. Although I never tried the stock white spring with shift assist but I know the orange spring set up backshifts way better than stock did even screwed in.
 

Frostbite

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M7ascent, your question " Just to confirm I am understanding all of this correctly, take a 36 helix for example, that helix works well for us mountain guys because it doesn't load the engine quickly and thus it's a better transfer of torque and traction to the ground...where as a higher degree helix would load the motor faster and thus transfer all that horsepower quickly and trench"?

The answer is yes.

A lower angle helix will not load the motor as hard as a steep angle helix thus, not as much power is being transfered to the ground. Lower angle helixes are again, great for the mountains for the very reason you expressed.

Take the Shockwave adjustable helix for instance. In lower elevations (in the parking lot) where you have more power because there is more atmosphere, you would have the adjustment ring all the way out which INCREASES the helix angle because your sled can pull that steep helix angle at lower elevations.

As you climb the air thins out, and as it does so, you lose horse power to the tune of 3% every 1,000 feet of elevation. As your sled gets less powerful your sled that was pulling 8,200 RPM at the parking lot now only pulls 7,800 with your 54 degree helix. So, you turn in the adjustment ring and walla, your helix angle goes from 54 to all the way to 36 (depending on how many revolutions you make to the ring) and you lose roughly 4 degreess of helix angle and gain roughly 200 RPM per turn of the ring. So, you are able to keep your sled right in the thick of its powerband even at altitude. This just showcases how lowering your helix finish angle is a great way to bring your shift RPM into tolerance.

Here's a link to what I was tasking about.

http://www.shockwaveperformance.com/

Now, a question for you. What does "Although I never tried the stock white spring with shift assist but I know the orange spring set up backshifts way better than stock did even screwed in".

What does the "screwed in" part mean?

Does this mean there's a way to tighten the secondary spring?
 
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M
Feb 21, 2009
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Yeah, on '05 M's only I think, maybe '06's also? But yes, on '05 m's the helix was threaded on the end and there was a plastic bushing that the secondary spring rode against. You can take a tool and stick it through the end cap and screw that bushing in thus tightening or increasing your spring rate. For example, alot of guys screwed that bushing in with the stock white spring to about a half an inch from the cover, thus increasing the white springs spring rate to something similar to that of the cat orange spring. I wanna say I have seen conversion kits for the new m's that convert to this adjustable style helix/end cap, but I can't think of where off hand.
 

Frostbite

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Wow, if that's the case. I want to buy one for my 09 M8. I'd love to be able to adjust my secondary spring rate.

If you or anyone can think of who sells the adjustment setup, please let us know.

Thank you

Frosty
 
C
Nov 27, 2007
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One other thing, don't think it was mentioned.

- The drive clutch shifts based on RPM

- The driven clutch shifts based on torque applied by the system (in the this case the system is the drivetrain of the snowmobile). The Helix controls the shift pattern.
 
F
Dec 5, 2001
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I like to think of the secondary as a torque sensing device. When there is extra torque from the engine, enough to turn the track in the conditions, plus some, then the secondary will allow the sheeves to move apart, reducing drive ratio. It seems like the engine torque causes the sheeve to "climb" up the helix ramp against the spring. When there is not enough torque, the track (via the driveshaft) will pull the sheeve back down the helix, forcing the belt back out of the secondary to a higher drive ratio.

That may not be technically correct, but it helps me visualize the forces and actions.

Yes, M7, the orange spring should work better for you than the white at any preload setting. As you add preload to the white, it does start to backshift better, but the extra spring force limits total upshift (by adding preload, you increase the spring pressure at the start of the shift, but also at the end, by the same amount).

Frosty, it may be worth playing with if you change altitude a lot, but I found with a good secondary spring, it is not that necessary. I do need to remember that trick, though, next time I need a little more at the high end of my normal altitude range.

John
 

iluv2fly

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Dec 3, 2007
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At the end of last season I switched out to a progressive helix on my 09 M8. I bought a SLP 44/36 and really like it, I ride 6-10K. The 44 degree angle is very short so it jumps off the line real hard and shifts into the 36 degree part real quick for excellent backshift. I liked it much better than the straight 36 but mine also has a slp pipe and porting.
 
M
Feb 21, 2009
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Here's another question, I ride an '05 M7 and it lacks a little in power on the bottom end, sled starts to shine in midrange and top end as most of you M7 guys know I'm sure. If I went from a straight 36 helix to something like a 40/36, wouldn't that almost overload the motor on the bottom end thus making the bottom end power transfer even worse? Maybe even creating a bog? I guess I'm just trying to figure out if a 40 degree cut on bottom would transfer what little power I have on the bottom end better or overload the system and bog out? Cuz if I could go to like a 40/36 and get this sled to pull harder off the line instead of having to wait paciently for the power to come on in the midrange, I would be ordering a helix today.
 

Vern

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Here's another question, I ride an '05 M7 and it lacks a little in power on the bottom end, sled starts to shine in midrange and top end as most of you M7 guys know I'm sure. If I went from a straight 36 helix to something like a 40/36, wouldn't that almost overload the motor on the bottom end thus making the bottom end power transfer even worse? Maybe even creating a bog? I guess I'm just trying to figure out if a 40 degree cut on bottom would transfer what little power I have on the bottom end better or overload the system and bog out? Cuz if I could go to like a 40/36 and get this sled to pull harder off the line instead of having to wait paciently for the power to come on in the midrange, I would be ordering a helix today.

what elevation do you ride in? if a lower elevation you may be able to pull the 40/36 with no problems and it will give you a better feel out of the hole. i ride from 6-9000ft and one year i tried a 42/36 progressive helix in my m7 and it felt good out of the hole but it was very inconsistent on the topend. on one hill it would pull good rpms, then the next hill it would be low then the next it would be different again. i believe the issue was at my elevaton it didnt have enough power to pull it through the transition into the 36 angle of the helix thus it never really shifted right and felt like it had to big of helix. if the 40/36 is not progressive but just a dual angle then it might work better but i've never tried one.

there are other ways to get the bottom end power out of a m7, like an rkt head and either regear or throw the 10.4" clutch on are some big steps. maybe make sure the fuel pressures right and a little fine tuning of the clutches, springs, weights(even with the stock 36) can help to. personally i'm not a fan of the m8 orange spring, it backshifts better than the stock but i believe its at the cost of upshift and it holds the sled back. my sled with rkt head and geared down a couple sizes with some clutch work feels night and day different on the bottom end than my brothers and buddys stock m7s. theres may pull on me a bit in the top but my bottom end is way better.
 
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