torsion vs compression and helix angles

[justinator]

Hey Guys, I understand the difference between what torsion and compression is when talking about secondary springs, I was wondering if someone could explain how each effects the characteristics of the secondary clutch. The dalton lists specs for both their springs and factory yamaha springs and while some springs have similiar torsion values they have very different compression ratings. Wondering if each rating is of equal importance and how these numbers effect the clutch as in rate of shift, cruise rpms ,belt pinch etc
Also what is the general rule of thumb for finish helix angles such as 2 degrees shallower on finish equals 100rpm or 200rpm gain??? Thank You in advance

 

[ClutchMaster]

Hey Guys, I understand the difference between what torsion and compression is when talking about secondary springs, I was wondering if someone could explain how each effects the characteristics of the secondary clutch. The dalton lists specs for both their springs and factory yamaha springs and while some springs have similiar torsion values they have very different compression ratings. Wondering if each rating is of equal importance and how these numbers effect the clutch as in rate of shift, cruise rpms ,belt pinch etc
Also what is the general rule of thumb for finish helix angles such as 2 degrees shallower on finish equals 100rpm or 200rpm gain??? Thank You in advance

Torsion and compression both do basically the same thing, they provide some side pressure to the belt so it grips the sheave. In terms of clamping force on the belt they provide around 5~40 percent of the force that actually clamps the belt depending on setup and where in the shift your measuring it. 5~40 percent is assuming your under full power, at lighter loads the spring has a higher percentage of the clamp force. In the beginning of the shift almost all of your clamping force is provided by the helix, at full shift out the helix becomes less of a factor and the fully compressed/wound spring provides more side force.
Your secondary needs a spring to initially provide force. This closes the clutch back up and also maintains constant contact with the rollers or buttons on too the helix. Under hard acceleration the helix does most of the work pinching the belt, shallower angles pinch harder than steep angles. Twisting the spring more or using a spring with higher compression do really the same thing.
Let’s say you have a setup that works well off the line but slips the belt at full shift. You can use a stiffer secondary spring that has more rate of torsion and initially wrap it less, or a spring with higher compression and similar torsion and wrap it the same.
Secondary springs are generally for fine tuning the shift. I always try to use as little spring pressure as possible, when the helix angles are right you don’t need a lot of spring to make things work. I should talk, I’m using way to heavy secondary spring currently but there’s hope, I finally ordered a custom helix so will see how that works out!

PS. There’s no set in stone rpm for helix angle changes, it all depends on about a million things! Don’t change helix angles to gain or lose rpm, only change helix angles for more or less belt pinch. Figure out where the belt is too loose or tight and adjust angles accordingly. Rpm changes should be changed using the flyweights and primary spring.
Oh yea as OA would say....TEST Test test!

Mr.Knapp has a very ingenious way of testing the combination of twist and compression combined with helix angle, it’s revolutionary!

 

[justinator]

Torsion and compression both do basically the same thing, they provide some side pressure to the belt so it grips the sheave. In terms of clamping force on the belt they provide around 5~40 percent of the force that actually clamps the belt depending on setup and where in the shift your measuring it. 5~40 percent is assuming your under full power, at lighter loads the spring has a higher percentage of the clamp force. In the beginning of the shift almost all of your clamping force is provided by the helix, at full shift out the helix becomes less of a factor and the fully compressed/wound spring provides more side force.
Your secondary needs a spring to initially provide force. This closes the clutch back up and also maintains constant contact with the rollers or buttons on too the helix. Under hard acceleration the helix does most of the work pinching the belt, shallower angles pinch harder than steep angles. Twisting the spring more or using a spring with higher compression do really the same thing.
Let’s say you have a setup that works well off the line but slips the belt at full shift. You can use a stiffer secondary spring that has more rate of torsion and initially wrap it less, or a spring with higher compression and similar torsion and wrap it the same.
Secondary springs are generally for fine tuning the shift. I always try to use as little spring pressure as possible, when the helix angles are right you don’t need a lot of spring to make things work. I should talk, I’m using way to heavy secondary spring currently but there’s hope, I finally ordered a custom helix so will see how that works out!

PS. There’s no set in stone rpm for helix angle changes, it all depends on about a million things! Don’t change helix angles to gain or lose rpm, only change helix angles for more or less belt pinch. Figure out where the belt is too loose or tight and adjust angles accordingly. Rpm changes should be changed using the flyweights and primary spring.
Oh yea as OA would say....TEST Test test!

Mr.Knapp has a very ingenious way of testing the combination of twist and compression combined with helix angle, it’s revolutionary!

Thank You, I have some experience with clutch tuning but mostly on polaris with team secondarys so all spring ratings are compression only. so discussing the dalton black/orange vs the black/tan........ They have very slighty different compression ratings except the black tan has a stiffer finish by about 5kg, the one difference is the torsion value is 8.5kg on black orange at 70degrees and 12 kg on black tan at 70 degrees. Switching nothing else in a clutch setup but these 2 springs , are you saying the black tan would provide similiar results as black/orange but requires less wrap to achieve the same results? For example the black tan has a 10kg torsion value at 50degrees and it increses by 1kg per 10 degrees of wrap, so wrapped at 30-40degrees it should act similiar to the black orange at 70degrees if Im understanding you correctly? I am aware that the primary should be in charge of controlling rpm, was just curious what a guy could expect to happen to his rpms with a helix swap and nothing else but I get what your saying.....many variables involved! Thanks again

 

[KnappAttack]

To test torsion secondary springs and actually see what the belt is seeing, put a bathroom scale on the drill press, set it up so it is upside down on top of a spacer the shaft can go thru, I use and old Cat reverse cam helix, cycle it and record the pressures, just be sure your bathroom scale goes up to around 400 lbs or so. Record the low speed setting as you just push down on and twist the movable, then push all the way down to where the shaft is at full travel without coil or hub binding it and record that pressure.

You will be amazed at what you find. Springs you thought were heavier could be lighter, and visa versa. Don't go by the Yamaha spring chart on Dalton's site, although its a great chart, it does not tell the full and whole story when you factor in the twist added to the equation. The Cat torsion springs also work in the Yamaha secondary. There is SOOOO Much more to it that the Dalton spring chart shows, and you won't know until you start testing them yourself on the scale. Also, springs are all measure different and have tolerances up and down, no two are the same even if they are the same spring. They will sack and lighten over use.

 

[fourload]

Thank You, I have some experience with clutch tuning but mostly on polaris with team secondarys so all spring ratings are compression only. so discussing the dalton black/orange vs the black/tan........ They have very slighty different compression ratings except the black tan has a stiffer finish by about 5kg, the one difference is the torsion value is 8.5kg on black orange at 70degrees and 12 kg on black tan at 70 degrees. Switching nothing else in a clutch setup but these 2 springs , are you saying the black tan would provide similiar results as black/orange but requires less wrap to achieve the same results? For example the black tan has a 10kg torsion value at 50degrees and it increses by 1kg per 10 degrees of wrap, so wrapped at 30-40degrees it should act similiar to the black orange at 70degrees if Im understanding you correctly? I am aware that the primary should be in charge of controlling rpm, was just curious what a guy could expect to happen to his rpms with a helix swap and nothing else but I get what your saying.....many variables involved! Thanks again

Lots of variables in rpms indeed. I went from a straight stock 35 to a 35/39 dalton and my rpms dropped right around 200 rpms at higher speeds where it was into the 39 angle. Nothing else was changed. In my case it was about 100rpm per 2degree change. They say the dalton angles measure the same as stock.

 

[ClutchMaster]

Lots of variables in rpms indeed. I went from a straight stock 35 to a 35/39 dalton and my rpms dropped right around 200 rpms at higher speeds where it was into the 39 angle. Nothing else was changed. In my case it was about 100rpm per 2degree change. They say the dalton angles measure the same as stock.

Good example^^^^
Helix angle change tends to have more of an effect at the start angle than the finish angle. Changing the start angle 4 degrees higher would more than likely cause a drop in your rpm’s double that if not more, considering everything else stays the same.

 

[justinator]

Lots of variables in rpms indeed. I went from a straight stock 35 to a 35/39 dalton and my rpms dropped right around 200 rpms at higher speeds where it was into the 39 angle. Nothing else was changed. In my case it was about 100rpm per 2degree change. They say the dalton angles measure the same as stock.

Good info! How do you like the helix vs the 35 on your sled, aside from the small rpm loss?

 

[fourload]

Good info! How do you like the helix vs the 35 on your sled, aside from the small rpm loss?

I like it. Very smooth with a little more upshift while trail riding. Backshift is good. The higher finish angle keeps the Powertrail tune rpms in check with the stock weights and the xs belt.