I watched Al run his Poo 800 with a Polar and no spring in the primary as well....
TRA settups...attn clutch guru's
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I watched Al run his Poo 800 with a Polar and no spring in the primary as well....
What Bandit says.
So why does the TRA use a spring big enough to be used to hold up a corner a gravel truck? It's the weirdest thing to doo!
But back at the dawn of history, when clutching ideas were just being born, someone thought that a spring should be used to balance the weights that pinch the belt, AND doo some of the secondary clutch job as well. The bigger the spring the more exact the clutch sheave width could be controlled by the weights. Input a certain RPM and the sheaves move to a predetermined position, and it doesn't matter whether the belt is slipping or being crushed as power transfer is a byproduct of the internal balances as tuned at that time.
The graph line of the spring force in the TRA had to be accomodated by messing with the secondary clutch natural function. The result was a need to compromise the helix angles. A flattened helix finish was installed as the TRA was doing some of the secondary function already which was to easy up on the belt grip at the top of the sheaves at full power due to the emourmus spring pressure in the TRA.
The TRA design around springs was your typical evolutionary dead end that is found in flatlands and attached with a successful engine family only. The Rotax engine family performs much better without the parasitic TRA to rob performance, but the TRA is attached at birth.
At the end of the day the TRA fossil became a virtually imossible clutch to tune except for a very narrow performance power/load band. The competing forces in the clutch are used to balance the clutch forces, and transfering power became a side effect, if the balance isn't thrown off.
The rubber mounting of the Bouncing Betty just added to the scrub heat produced by the TRA primary.
A P-85 and a TRA commonly use springs very similar in force. So it's not just a TRA that uses a spring to aid in tuning.
I have found that using MORE weight, whether in a TRA or a P-85, in conjunction with a bit more spring (nothing excessive) will make things more consistant and better hold track speed under heavy load situation (climbing) than a setup that uses lighter spring and lighter weight. This has been consistant on different sleds and different brands and styles of clutches, including the old cat hex clutch which is functionally identical to a Polar. I recall changing ramps, springs and weight in those back in the '70's.
I'm a bit confused on this statement...."as the TRA was doing some of the secondary function already which was to easy up on the belt grip at the top of the sheaves at full power due to the emourmus spring pressure in the TRA".
Actually this was because of the geometry of the arms.....they just can't squeeze as hard at higher shift ratios....this was compensated when they went to the variable sheaves, the shallower sheave angle allows easier shift out on top end while the steeper angle down low helps hold the belt when there is a smaller contact patch.
The TRA does nothing as far as backshift, that is all the job of the secondary....as long as the TRA (or ANY primary) is spinning, it is creating force against the movable sheave. With a proper spring, this force can be better regulated and "dampened" to not be overly sensitive which would make for more RPM fluctuation.
Dang.....I need snow!
I have found that using MORE weight, whether in a TRA or a P-85, in conjunction with a bit more spring (nothing excessive) will make things more consistant and better hold track speed under heavy load situation (climbing) than a setup that uses lighter spring and lighter weight. This has been consistant on different sleds and different brands and styles of clutches, including the old cat hex clutch which is functionally identical to a Polar. I recall changing ramps, springs and weight in those back in the '70's.
I'm a bit confused on this statement...."as the TRA was doing some of the secondary function already which was to easy up on the belt grip at the top of the sheaves at full power due to the emourmus spring pressure in the TRA".
Actually this was because of the geometry of the arms.....they just can't squeeze as hard at higher shift ratios....this was compensated when they went to the variable sheaves, the shallower sheave angle allows easier shift out on top end while the steeper angle down low helps hold the belt when there is a smaller contact patch.
The TRA does nothing as far as backshift, that is all the job of the secondary....as long as the TRA (or ANY primary) is spinning, it is creating force against the movable sheave. With a proper spring, this force can be better regulated and "dampened" to not be overly sensitive which would make for more RPM fluctuation.
Dang.....I need snow!
Tollen 77 . good questions . figured the question i possed was one to scratch a few minds .
primary pressure needed to drive the 56 lb track i was playing with when i was tryiung to answer my own question.
33 grs was min . and i used a spring i ground down so as to only just hold the face off the belt.15lbs
thing i learned most was that i needed to build different shaped arms .
it got me playing with were and how much weight in the arm had effect on squeeze and were in the movement of the arm the added weight was most effective.
what one has to be careful of when starting to pull on the motor is not to pull on it to soon . what happens is the motor struggles to ever get going .
to late and the detonation in cyl can occur . unloaded motor scenario.
the secondery in the most part is the brain.
the primary isnt hard to genorate enough squeeze but does have a lot of room for improvement
consider the length of the belt traction patch on the primary when it is working in the very bottom of the primary . up to when it moves to being an inch and a half off the bottom it now has enough of a length of belt to properly grab the belt and stop spinning .
many years on the track dyno showed this and it didntr matter what brand . basic physics , not much rubber in contact till the belt has enough of a traction patch developed with the sheave to grab .
gearing down, only lessened the load , never cured the issue
only fix i could ever get decent results with was the adding of weight to the base of the arm . close to 20 grs . didnt effect the back shift as it wasnt far enough up the shive.ended up with adding weight in the middle and with a tip weight greatly reduced [ alum pin hollow ] 1 or 2 mm roller
this seemed to even out the clutch loading a tremendous amount.
all that playing on the primary i left the helix angle at 44 and the spring stock in the secondery.
is the reverse way to tune the transmission but is effective .
shallow helix angles require heavy primary weight
more agressive helix angle less primary weight
springs in either typically stock range.
lots of ways to do it .
mostly understanding what your sled is not doing .thats were the infared heat sensor gun is handy , there cheap and tell you were the heat is and what happens when you make a change . least you get to see weather it is primary or secondery that you need to be addressing.
primary pressure needed to drive the 56 lb track i was playing with when i was tryiung to answer my own question.
33 grs was min . and i used a spring i ground down so as to only just hold the face off the belt.15lbs
thing i learned most was that i needed to build different shaped arms .
it got me playing with were and how much weight in the arm had effect on squeeze and were in the movement of the arm the added weight was most effective.
what one has to be careful of when starting to pull on the motor is not to pull on it to soon . what happens is the motor struggles to ever get going .
to late and the detonation in cyl can occur . unloaded motor scenario.
the secondery in the most part is the brain.
the primary isnt hard to genorate enough squeeze but does have a lot of room for improvement
consider the length of the belt traction patch on the primary when it is working in the very bottom of the primary . up to when it moves to being an inch and a half off the bottom it now has enough of a length of belt to properly grab the belt and stop spinning .
many years on the track dyno showed this and it didntr matter what brand . basic physics , not much rubber in contact till the belt has enough of a traction patch developed with the sheave to grab .
gearing down, only lessened the load , never cured the issue
only fix i could ever get decent results with was the adding of weight to the base of the arm . close to 20 grs . didnt effect the back shift as it wasnt far enough up the shive.ended up with adding weight in the middle and with a tip weight greatly reduced [ alum pin hollow ] 1 or 2 mm roller
this seemed to even out the clutch loading a tremendous amount.
all that playing on the primary i left the helix angle at 44 and the spring stock in the secondery.
is the reverse way to tune the transmission but is effective .
shallow helix angles require heavy primary weight
more agressive helix angle less primary weight
springs in either typically stock range.
lots of ways to do it .
mostly understanding what your sled is not doing .thats were the infared heat sensor gun is handy , there cheap and tell you were the heat is and what happens when you make a change . least you get to see weather it is primary or secondery that you need to be addressing.
A P-85 and a TRA commonly use springs very similar in force. So it's not just a TRA that uses a spring to aid in tuning.
I have found that using MORE weight, whether in a TRA or a P-85, in conjunction with a bit more spring (nothing excessive) will make things more consistant and better hold track speed under heavy load situation (climbing) than a setup that uses lighter spring and lighter weight. This has been consistant on different sleds and different brands and styles of clutches, including the old cat hex clutch which is functionally identical to a Polar. I recall changing ramps, springs and weight in those back in the '70's.
I'm a bit confused on this statement...."as the TRA was doing some of the secondary function already which was to easy up on the belt grip at the top of the sheaves at full power due to the emourmus spring pressure in the TRA".
Actually this was because of the geometry of the arms.....they just can't squeeze as hard at higher shift ratios....this was compensated when they went to the variable sheaves, the shallower sheave angle allows easier shift out on top end while the steeper angle down low helps hold the belt when there is a smaller contact patch.
The TRA does nothing as far as backshift, that is all the job of the secondary....as long as the TRA (or ANY primary) is spinning, it is creating force against the movable sheave. With a proper spring, this force can be better regulated and "dampened" to not be overly sensitive which would make for more RPM fluctuation.
Dang.....I need snow!
You don't seem to have much experience with other clutches. Or did you not notice that when you add a bigger spring to the standard clutch (cat/Poo/Yam) that the engagement becomes so high that the sled engagement become really irritating, jerky and unuseable in tight trails. The harsh engagement digs a hole everytime and people get sick of getting you unstuck and driving over the track crap. You never knew that?
Adding a heavier flyweight to the standard clutch does not change the engagement, plus the motor doesn't have the horsepower to deliver what those heavy weights are pulling. So I call bull****.
There is no way the spring in the P-85 and the TRA are even close. Unless you are comparing the spring in the TRA out of the Elan to the 800 Polaris? Needs some fiquires on that call, otherwise I can't give no slack on that one either.
It is going to require a long a post to detail why the TRA doesn't stay the hell out of the secondary function. It may be simplier to explain that the secondary has more defined function behind a standard clutch. The secondary really is a spring/helix balanced torque device, and when the primary, as in the TRA, is also a spring balance system, then the graph of torque transfers get really complicated as the TRA spring rate balance intrudes on the spring rates in the secondary. The result is that weird compromise in a flattened helix secondary. Typically you would see an increasing helix angle to increase the clutch shear forces and stabalize the up shift to keep RPM under high load. So why does the TRA need help by flattening the helix? The springs are the problem again, it's not about RPM but helping a couple clutches that are completely knotted up with spring loads. Terrible way to waste a secondary that is supposed to be a torque device.
I don't thik you should be appologizing for the TRA by saying "..Actually this was because of the geometry of the arms....." Why do you want to accept crap like that? BRP doesn't care and aren't appologizing to you, so why appologize for them?
If the TRA is good enough for you, great. I hope you aren't offended if the rest of us know BRP could doo better, but won't.
TurboAl, You found the TRA had less belt squeeze down low and more up top? By Belt slip?? I was allways under the assumption that the TRA looses squeeze as the belt rides up. Thats why performance drops off the faster and higher the belt rides in the primary?
I may not be in the same power class, with my lowly 670, but am I the only one getting a headache??? LOL Twin pipes and higher port timing has sure made my 670 more peaky and narrow powerband. It sure emphasizes the TRA weakness. Couple years ago, when I first read YamaDooPolCat was talking about the "bouncing betty", I thought he was on crack or something, thought the TRA was the best thing since sliced bread. But now, I got the exact same thing happening with my Old School ride. But alas, I cant afford to buck up and through a new clutch on it and start over in tuning. So, I'll continue spending $300+/year chasing it down.
I may not be in the same power class, with my lowly 670, but am I the only one getting a headache??? LOL Twin pipes and higher port timing has sure made my 670 more peaky and narrow powerband. It sure emphasizes the TRA weakness. Couple years ago, when I first read YamaDooPolCat was talking about the "bouncing betty", I thought he was on crack or something, thought the TRA was the best thing since sliced bread. But now, I got the exact same thing happening with my Old School ride. But alas, I cant afford to buck up and through a new clutch on it and start over in tuning. So, I'll continue spending $300+/year chasing it down.
There is no way the spring in the P-85 and the TRA are even close. Unless you are comparing the spring in the TRA out of the Elan to the 800 Polaris? Needs some fiquires on that call said:
There is no way the spring in the P-85 and the TRA are even close. Unless you are comparing the spring in the TRA out of the Elan to the 800 Polaris? Needs some fiquires on that call said:
Yes....I think I'll save my typing finger trying to explain things to some people....some will refuse to try and learn new things or listen to those that CAN make a clutch work.
JFYI though YDPC....I am running a 185 engagement spring on a P-85 right now and it comes in at 3700 with 72g weights....so the weight DOES make a different on engagement RPM. Don't believe me, take the weights out and see what happens
T
tollen77
Member
Thanks for the info TurboAl and all.
Al, what did you find was req'd for ramps to achieve proper shift. Ramps are the area of clutching I understand the least so feel free to get into why you feel a certian ramp works better than others.
Last question: What the he!! do the numbers on the ramps refer to? I've searched high and low to find this out and can't find anything. I assume the numbers are something more than just a part number.
Thanks
Al, what did you find was req'd for ramps to achieve proper shift. Ramps are the area of clutching I understand the least so feel free to get into why you feel a certian ramp works better than others.
Last question: What the he!! do the numbers on the ramps refer to? I've searched high and low to find this out and can't find anything. I assume the numbers are something more than just a part number.
Thanks
Yes....I think I'll save my typing finger trying to explain things to some people....some will refuse to try and learn new things or listen to those that CAN make a clutch work.
JFYI though YDPC....I am running a 185 engagement spring on a P-85 right now and it comes in at 3700 with 72g weights....so the weight DOES make a different on engagement RPM. Don't believe me, take the weights out and see what happens
I don't see any spring that stiff listed in my book for the P-85. The hardest spring is the Silver/Gold at 168/300, but just about useless for regular riding. The most popular is the Blue at 110/280. The stock TRA starts at 160/230, but spring kits for our ridning area all use 230/390 or 230/410. Hardly comparable, so don't kid a kidder. The TRA uses a spring nearly double the compression of what a comparable Polaris would use in the mountains. The Polaris spring is also smaller in diameter.
Since we don't believe each other, how about a tech quote, "When the sleaves engage the belt, the flyweight force is just overcoming the pretension of the pressure spring. The clutching phase begins when the flyweight force overcomes the pretension, and lasts until the flyweights have generated enough side force to transfer the engine torque without slipping the belt." Belt engagement is set by the spring.
However you seem to have been able to get past the design characteristics of the Polaris clutch somehow. It is possible you installed smaller rollers or reground the cam, but why bother? You just compromised the rest of the shift charteristics of the Polaris clutch for nothing.
All you are dooing is increasing the internal stress on the clutch. And the weights don't start to work until they get on the ramp, which is after the clutch has engaged, which is set by how stiff the spring is. What motor and elevation are you riding to swing 72 grams?
T
tollen77
Member
The spring I'm referring to is on a turbo 800 Polaris. Clutch is stock configuration.
I'm not going to argue with anyone, I know what has worked for myself and many others.
I'm not going to argue with anyone, I know what has worked for myself and many others.
Alot of guys put to much into engagment. We Don't Ride At Engagment Do We ?......The name of the game is sqweezing the belt in the mid & peak of the power band. Stiffer spring(s) will offer a more aggressive engagment and better belt sqweeze and less slippage in the mid & peak where we ride.
Giving up a little throttle comfort at engagment results in better track speed at peak rpm. Another area to watch is how you use the throttle....The TRA responds best to consistant throttle and not the IN/OUT of the throttle like many riders do.
Consistant thottle give the best sqweeze on the belt...Every time your IN/OUT of the throttle the TRA has to react to what your thumb is doing.
OT
Giving up a little throttle comfort at engagment results in better track speed at peak rpm. Another area to watch is how you use the throttle....The TRA responds best to consistant throttle and not the IN/OUT of the throttle like many riders do.
Consistant thottle give the best sqweeze on the belt...Every time your IN/OUT of the throttle the TRA has to react to what your thumb is doing.
OT
T
tollen77
Member
OT, you've got me a little confused. If the spring in the primary is effectively holding the moveable sheave and arms back from pinching the belt, how does a stiffer spring help with belt pinch?
I'm with you that having a spring that requires more force to compress it initially will make engagement harsher (a 160/320 will be more aggressive at take-off than a 130/320). The engine will have to be higher in the power curve before the arms will have enough force to overcome the spring leading to a more aggressive start.
But how does this generate more force than a similar sled with a lighter spring assuming they are both sleds are spinning at the same RPM?
Sled #1 160/320 at 6,500 RPM should generate the same amount or maybe even slightly less pinch than Sled #2 with a 130/320 at 6,500 RPM. Sled #2 will have less spring to overcome (say approx 290 lbs vs approx 300 lbs of spring force at 6,500 RPM)
At WOT (8,150 RPM) both sleds should create the same amount of belt pinch since both springs have the same finish (320 lbs) but all through the rest of the RPM range sled #1 has more spring to overcome.
Thoughts???
First things 1st the spring preload and its side force is what sqweezes the belt. The question is how well it works in conjunction with the torque sensing secondary at WOT where the helix/spring than takes over.... Primary 160/320 or 130/320 at 6500 rpm isn't much of a comparison..How's about a 130/320 vs 200/320 or 200/350 climbing wot in deep snow where sqweezing the belt is very critical and belt slippage often occures due springs with not enough preload ability .
One way to mitigate the harsh engagment of a spring with a high pre-load would be to have a look at you ramps.....A taller ramp at the engagment point of the ramp = higher engagment. Ramps like 419,427 and 435 at the engagement point are notched and not as tall which help in decreasing the harsh engagment when running heavy primary springs.. A lot of racers will custom taylor there ramps just to address the harsh engagment.
OT
Yes your right about me thinking backwards about the up/down thing in the secondary and thanks for your explanation. I guess if the secondary spring lets the belt slip the down early in the secondary than the motor rpms would drop off fast due to the load? Is this what everyone is experiencing?
T
tollen77
Member
"First things 1st the spring preload and its side force is what sqweezes the belt."
In the secondary! Not in the primary. The only thing that squeezes the belt in the primary is the arms pushing on the ramps!
T
tollen77
Member
More than anything T-A, if the secondary spring doesn't provide enough clamping force the primary will pull the belt down into the secondary too fast (which does reduce the effective ratio as you are saying). But rather than making the engine lug and bog more than likely the belt will simply slip in the secondary and not transfer any force to the track. This will cause increased heat in the secondary (friction) and reduced track speed... just like Al had found in earlier tests.
Hope that helps!
S
shortstop20
Well-known member
I don't know what sheet you're looking at but you're wrong.
What Throttle Junkie said about Polaris springs is correct. I have seen a 120/340, 140/310 and 140/320 all with my own eyes and I can guarantee ya they make more in that area. Most popular is the blue? I've never heard of anyone running that spring. The "almond" springs are very popular, far more popular than any of the other springs people are running(as far as Polaris springs). There are alot of stiff springs out there made by Team and other companies too.
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