Make sure you play with the spring adjuster (white ring)....it makes a big difference in low-end response. They tend to back out by themselves so try adjusting it a bit tighter if it has backed out against the cover plate.
What does a helix do exactly?
- Thread starter m7ascent
- Start date
Make sure you play with the spring adjuster (white ring)....it makes a big difference in low-end response. They tend to back out by themselves so try adjusting it a bit tighter if it has backed out against the cover plate.
Vern, I ride 5000-8000 so I'm right in there with ya. I also feel the orange holds me back a bit but I haven't found anything better option. I love the backshift over the stock white, but it finishes to high for my liking. I wish someone made a secondary spring that started at 175 or so like the orange, but finished closer to that of the white at 260. My two cents. I just don't know then about the helix thing bud, something like a progressive 38/36 or a 40/36 that was short on the steep side might work??? Maybe I'll try one of those for giggles.
Isn't going to the 10.4 doing the same as gearing down? Just lowers the gear ratio? Is there any other benifit to going to the 10.4 sheaves?
Winter brew, I have played with the spring adjuster, but as we all know as you crank that thing in your increasing the start and the finish of the spring...just multiplies the problem of losing it on the top with the orange spring. Thanks so much for the idea though.
Anyone running fuel reducers/regulators or timing keys whitnessing a increase in bottom end power on a M7?
Let's take this a little more theoretical.
Helixes can be thought of as the screw that squeezes the secondary belt sheeves together. Sure, the springs do that too, but it was discovered long ago the if one uses the engine torque to help provide belt squeeze, a very stiff spring is no longer required. Back in the old days, there was just the spring and it was very stiff to get enough side force when the clutch was closed. As the clutch opened excessive belt tensions resulted. In the day, the winner of the race was often the fastest belt changer, not the fastest sled....But I digress...
Lets start with the PRIMARY at engagement. The pully is very small and therefore torque is very high and belt tension is very high. As the belt pulls on the moveable sheeve of the secondary clutch it twists it forward and screws the clutch closed resisting up shift. This is like pushing a car up a very steep incline it takes alot of lateral force to push the car up the ramp. This is ok since we have alot of torque and high belt tension. Now as the PRIMARY shifts out the pully is larger and although engine torque is the same the belt is out farther from the crank centerline and belt tension drops. Now we can't push the car up the steeper ramp....we need shallower ramp to push the car up. That is the reason for a multi-angle helix....falling belt tension during shift out.
How does a secondary back shift. This is very interesting. We clutch for peak horsepower. not torque. In reality as the engine is pulled off of the peak horsepower rpm, torque actually rises and so does belt tension. This rotates the moveable secondary sheeve and the the clutch screws together overcoming the belt tension and push the belt out of the secondary. That is why we have helixes and also why the closer the peak HP rpm and the peak torque rpm are to each other, the harder it is to clutch.
Helixes can be thought of as the screw that squeezes the secondary belt sheeves together. Sure, the springs do that too, but it was discovered long ago the if one uses the engine torque to help provide belt squeeze, a very stiff spring is no longer required. Back in the old days, there was just the spring and it was very stiff to get enough side force when the clutch was closed. As the clutch opened excessive belt tensions resulted. In the day, the winner of the race was often the fastest belt changer, not the fastest sled....But I digress...
Lets start with the PRIMARY at engagement. The pully is very small and therefore torque is very high and belt tension is very high. As the belt pulls on the moveable sheeve of the secondary clutch it twists it forward and screws the clutch closed resisting up shift. This is like pushing a car up a very steep incline it takes alot of lateral force to push the car up the ramp. This is ok since we have alot of torque and high belt tension. Now as the PRIMARY shifts out the pully is larger and although engine torque is the same the belt is out farther from the crank centerline and belt tension drops. Now we can't push the car up the steeper ramp....we need shallower ramp to push the car up. That is the reason for a multi-angle helix....falling belt tension during shift out.
How does a secondary back shift. This is very interesting. We clutch for peak horsepower. not torque. In reality as the engine is pulled off of the peak horsepower rpm, torque actually rises and so does belt tension. This rotates the moveable secondary sheeve and the the clutch screws together overcoming the belt tension and push the belt out of the secondary. That is why we have helixes and also why the closer the peak HP rpm and the peak torque rpm are to each other, the harder it is to clutch.
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Wow. I just learned a lot in a few minutes.
I am however curious.... as to why snowmobiles use this type of drive system?
Motorcycles have 6 gears, and you can use each gear ALL the way through the motor's RPM to redline. It's not one consistant power, it's variable depending on which gear you're in.
I'm curious as to why sleds dont have "user shift-able" transmissions. Wouldn't it be even more reliable? Bang through gears like you can on a dirtbike, or a streetbike, and have a much wider range of track speed that way?
Just curious...... it's my ignorance coming out here....
I am however curious.... as to why snowmobiles use this type of drive system?
Motorcycles have 6 gears, and you can use each gear ALL the way through the motor's RPM to redline. It's not one consistant power, it's variable depending on which gear you're in.
I'm curious as to why sleds dont have "user shift-able" transmissions. Wouldn't it be even more reliable? Bang through gears like you can on a dirtbike, or a streetbike, and have a much wider range of track speed that way?
Just curious...... it's my ignorance coming out here....
N
Nubulin
Well-known member
I have thought about this too over the years.
My reasons:
1) Transmissions have a lot of parts to fail and warrenty. Too much $$
2) They are a lot more expensive than the snowmobile CVT.
3) They would be heavy to take the HP of the average snowmobile.
4) They are a hold over from the days of 10HP single cylinder sleds and nothing else was needed. They just have evolved and work quite well for thier intended purpose.
5) They eat belts which is a big $$ maker.
Have you seen the horsepower some sport bike transmissions take though!?
As long as there's either a wet or dry clutch (ie just like on a dirtbike / streetbike) to take the "shock" outta the system, a 6-speed tranny wouldn't be very heavy at all. Plus, they're super reliable.
last year towards the end of the season i switched to a speedworx blck/orng sec spring with the rates of, if i remember correctly, 140-270. it feels like it upshifts much quicker than the m8 orng spring but it may still be a bit stiff on the finish rate. i have also wondered what a spring with a stiffer start rate and softer finish rate would do to, but i've spent enough money and time tinkering on my sled so i'll probably run what i got for now. however Team sells alot of springs i wouldn't mind tryin though with stiffer start rates and softer finish rates if i had money to blow. they got one close to what you was mentioning, the black/yellow at rates of 180/260, that is if there rates are measured at around the same hights as cat springs. check out the team selection you might find one worth tryin and i believe the team conversions are not to spendy for the DD clutch.
yes the 10.4 does gear the sled down a bit but it also is supposed to help with belt grip as the longer belt does not get pulled down into the secondary as far thus giving it more contact area on the secondary sheaves at all positions.
as for the manual trans comments aside from the chance of more crap to go wrong and more weight i think a problem would be in having to worry about having to shift in general. generally mountain riding you tend to be all over the sled depending on how aggressive you ride so it could be a hassle trying to make sure you are in a position to shift and also being able to shift at proper times when the sled is starting to pull down rpms if you dont hit the gear just right you could lose momentum. also knowing when you got the power to pull the next gear without risking it powering out. i see being stuck alot more tryin to shift a manual trans. thats just my opinon though, and i always preffered a manual trans on most vehicles but i dont think a sled is a good application.
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I think this may be what was happening to me this weekend. The sled is new to me and I'm just starting to learn about it.
It was only after coming to a stop, but when I would try to get her moving again she would just make a grinding sound. When I open the hood the secondary looked like it was half engaged. I would lift the track, get her spinning again and the spring would then fully separate the sheaves.
Any thoughts on how to fix this? I'm thinking I can adjust the positioning (right now it in the center hole and runs a Green sping) but maybe I need a new spring or get rid of the step type helix?
Found my problem to be improper adjustment. I had adjusted one hole to the right of center which appeared not to spring the helix back to resting position. I have since adjusted 2 holes to the left of center and now the helix resets without issue.
F
Flange
Well-known member
Sleds don't roll very well. There is a lot of resistance due to the track and the snow. Wheels roll, tracks don't. In order to shift a transmission with gears, the load must be removed momentarily in order to shift gears. It would be difficult to maintain momentum given the reasons I already mentioned. Yes, there are gear transmissions that can shift in milliseconds but they cost a fortune and are relatively heavy.
What would be wrong with one consistant power...as long as its maximum power? Actually, the perfect transmission would allow you to hit maximum RPM (and thus max power) and stay there all the way through the transmissions' shift ratios. An even better transmission would automatically change gear as the load changed, with the engine staying at peak power. Go one step further and have an infinite number of gears available so you are always delivery this maximum power in the most efficient way. This, my friend, is what the continuously variable transmission...or CVT does.
On the other hand, a gear transmission forces you to let off the power, shift, then let the RPM build again to peak power, at which time you repeat this in order to get to a taller gear. Unfortunately, each time you shift, you momentarily lose power. Years ago the Williams F1 team put a CVT in one of there F1 cars and immediately proceeded to break the track record. The driver was able to keep the car at max power between each corner, never having to lift in order to change gears. The CVT was immediately band by the FIA. Even in today's F1 cars, although the gear changes take place within milliseconds and the driver doesn't even have to take his foot off the gas, they are still forced to spend time off of their peak power curve. These transmissions are built extremely light, at considerable cost, but I hazard to guess that if they allowed a team to use a CVT, the CVT car would win.
http://www.youtube.com/watch?v=x3UpBKXMRto
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