Ramps in the TRA, how they work and how they effect performance.

[YamaDoo PolCat]

There is no mechanical connection with the "cushion" to the governor cup.
There is a plate that is fastened to the governor cup.

The cushion is laminated with glue to the plate on the governor cup.
This is called a "Cushion Drive". The splined shaft connects to the female portion of the governor cup. This cushion is held on the aluminum cup by virtue of friction - the rubber is laminated onto the disc, the disc is held on by force of the torque of the clutch bolt.

When the clutch is spinning the rollers push out against the ramps, the ramps are connected to the governor cup. Under full throttle the clutch is like a solid piece of aluminum even though power transmit through the rubber cushion.

The cushion is under torque and flex so little almost not measurable. The little bit that the clutch is flexible reduces the "natural frequency" that the crankshaft rings at and prevents crankshaft failure due to cracking, also prevents failure of the ignition stator due to stator natural frequency. The design of the clutch is very deep that it is built with an inherent quality it will reduce if not eliminate engine component failure due to vibration.

All right. But just a couple of questions, please!

Is the rubber connector puck softer when it is hot, and what does the heat do to the rubber stiffness? Is there kevlar in the rubber donut? Why can't the rubber drive belt dampen out vibration just as well? Why is it that only Rotax cranks need a rubber puck and not the other million engines out there that are of the same size? Who knows what the TRA engineer back in the early 80's were thinking, maybe the rubber donut was to save the TRA splines like the old rubber driveshafts in old cars. Wasn't cushion drive shafts in cars all the craze about the same time the TRA came out? May be that's where the idea came from? The idea was was abandoned anyhow, so the only one left today is the TRA.

Point is I'm sceptical that there is any value in the rubber donut in todays small engine. I know big car engines have harmonic balance wheels, but no one else is using anything like it in their drives. And the sun will rise tommorow, if the donut is retired.

 

[dirtball08]

Hey Dynamo Joe, Looking forward to the website. The info I've seen so far has helped me alot ,thanks.

 

[banditpowdercoat]

I agree on the cushion drive. I dont think its really needed. Im still running a 1st version TRA, Non cushion drive on my 670. No issues here. Im acctually suprised that cushion holds up as well as it does to power. Be then, I aint seen one on a Turbo APEX LMAO

 

[DaveB]

I agree on the cushion drive. I dont think its really needed. Im still running a 1st version TRA, Non cushion drive on my 670. No issues here. Im acctually suprised that cushion holds up as well as it does to power. Be then, I aint seen one on a Turbo APEX LMAO

I think it may depend on what year 670. I know the 617's had a fluid filled dampner behind the starter cup.....and I think some early 670's had that as well. I stuck a 617 balancer with a shorty cup on my 94 (?) 670 that came out of a Mach. I ran a Comet on it for several years with no crank issues.

 

[Dynamo^Joe]

Ditto to the throttle winng,wingg, wingg...with every wingg the TRA arm/rollers works harder as it shifts on any ramp.

By the way the TRA is a vey simple clutch to operate and shouldn't be discouraged by the scienctific discovery being displayed.

OT

Can you elaborate on how to operate the TRA primary?

 

[banditpowdercoat]

Can you elaborate on how to operate the TRA primary?

Well, Like any vehicle, constantly blipping the throttle is not the most effective way to operate. And I mean quick blips, like 1 second on/off/on/off

I know some people that ride like that. Its annoying as heck. Must go through a throttle cable a season LOL

 

[Interceptor]

Can you elaborate on how to operate the TRA primary?

Dont feel lost DJOE - the "winng winng" sound is one that most people have not heard so dont be suprised - it mostly comes while track stand tuning while you are listening for the TRA ramps to move

 

[Original Tetonice]

Can you elaborate on how to operate the TRA primary?

Joe the clutch doesn't work to good if you not squeezin the throttle......The more you squeeze the throttle the more the TRA arms/rollers will shift to higher shift ratios. Back off the throttle the TRA arms/rollers drop back down the ramps to lower shift ratios. The throttle controls the amount off shift at any given time....The differance between deep snow riding and trail riding is the load from the deep snow. Going down the trail you have minimal snow load and resistance at the track.....The snow load/resistance really makes the secondary work very hard to maintain consistant belt pressure in order to maintain correct rpm/ trackspeed in deep snow....The same goes for te primary clutch in deep snow the primary clutch works much harder as well than going down the trail. Example of that is the amount of heat the TRA primary makes in deep snow vs trails......I think we can agree the trail riding is easier on the TRA than operating the TRA in deep snow..... By going wrinng, wrinng, wrinng to the throttle that is increasing the already overworked TRA primary in deep snow condition. Any time you back off the throttle of the TRA arm/rollers you begin to fall off the power curve of the ramp profile making the TRA in deep snow have to work even harder to maintain consistant belt pinch and rpm at higher shift ratios.

When your operating in deep snow would you rather be in low shift ratios or high shift ratios ?

OT

 

[YamaDoo PolCat]

Joe the clutch doesn't work to good if you not squeezin the throttle......The more you squeeze the throttle the more the TRA arms/rollers will shift to higher shift ratios. Back off the throttle the TRA arms/rollers drop back down the ramps to lower shift ratios. The throttle controls the amount off shift at any given time....The differance between deep snow riding and trail riding is the load from the deep snow. Going down the trail you have minimal snow load and resistance at the track.....The snow load/resistance really makes the secondary work very hard to maintain consistant belt pressure in order to maintain correct rpm/ trackspeed in deep snow....The same goes for te primary clutch in deep snow the primary clutch works much harder as well than going down the trail. Example of that is the amount of heat the TRA primary makes in deep snow vs trails......I think we can agree the trail riding is easier on the TRA than operating the TRA in deep snow..... By going wrinng, wrinng, wrinng to the throttle that is increasing the already overworked TRA primary in deep snow condition. Any time you back off the throttle of the TRA arm/rollers you begin to fall off the power curve of the ramp profile making the TRA in deep snow have to work even harder to maintain consistant belt pinch and rpm at higher shift ratios.

OT

WHoa!! OT you are going to make DJoe go grey(er)!

And so OT knew all along it was the da wingdingy trottle tingy and yoalla didn't tink ta tell us!! GRRRrr! Snap!

HeeHee!! Here's a picture of how OT gets his sled to go. Too funny!

 

[YamaDoo PolCat]

Da picture!!

 

[Dock]

belt heat

If a clutch stops "up shifting" I would tend to believe there is no motion.

Remember how early natives started fires?
If you rub a stick in one spot back and forth hard enough and long enough, in "one location" from the continuous use in one location "range", would the stick get hot enough to ignite? yes or no?
Would the stick ignite from excessive temperature? yes or no?

From what I understand when the clutch stops up shifting, motion of the belt ceases, it ceases to move across the sheave face.
While under full throttle(continuous energy input), the belt dwells in one location "range" on the sheave face.(no motion output)
If you continue to apply energy without motion increase - something is bound to happen, the energy is expelled somewhere - more than likely "heat"
Would continuous application of this calibration cause heat? yes or no?

The longer the belt dwells in one location, heat increases.

The more frequent the belt stops up shifting (rpm fluctuation) the more times the belt stalls in a "range" on the primary clutch, heat increases.

I quote only reputable sources, this information is not me
---The #1 cause of heat is rpm fluctuation.

Evidence of RPM fluctuation is excessive heat.

Here is the big question - What causes rpm fluctuation?

DJ. I see what you are saying here and understand what you mean when the belt has NO MOTION, however if the belt has NO MOTION then there would be no friction, now i understand that the belt is going around in the same spot on the clutch would tend to heat it up, however it brings me back to my thought on primay slipping, if the bealt sits in one spot on the primary but the primay doesn't have enough weight to pinch the belt enough to stop it from slipping, that would create a lot of heat real quick. Again takes me back to my thought on more weight in the primary and shallower helix to couteract the increased weight. Like i said just a though i'm only new to this clutching.

Is it possible to have to much primary weight? would that create heat?

 

[shortstop20]

Yes it is possible to have too much primary weight. It would definitely create heat if it is making the primary shift out too fast and then the belt is slipping in the secondary.

 

[Original Tetonice]

Da picture!!

I least the kids got enough common sense not to bye into the hype of a Polar

 

[tollen77]

DJ. I see what you are saying here and understand what you mean when the belt has NO MOTION, however if the belt has NO MOTION then there would be no friction, now i understand that the belt is going around in the same spot on the clutch would tend to heat it up, however it brings me back to my thought on primay slipping, if the bealt sits in one spot on the primary but the primay doesn't have enough weight to pinch the belt enough to stop it from slipping, that would create a lot of heat real quick. Again takes me back to my thought on more weight in the primary and shallower helix to couteract the increased weight. Like i said just a though i'm only new to this clutching.

Is it possible to have to much primary weight? would that create heat?

As I understand it Dock, the friction in the system when the belt stops moving up or down in the clutch is due to the motion of the belt moving over the sheaves (think of the heat your tires generate as they roll down the highway. They`re not slipping, but they still generate heat.) and the clamping forces of the two sheaves on the belt (a heavy truck generates more tire heat than a light car, even if the tires aren`t slipping).

As for too much clutch weight, the additional weight would clamp that belt harder the same way the heavier truck pushes harder (due to gravity) on its tires than the light car. Too much squeeze will generate more heat, though it`s a clearly better alternative that the heat generated from the belt slipping in the clutch. At least this way most of the RPM generated by the engine is being transferred to the secondary.

The other problem with too much weight, which I`m sure you already knew, is that additional weight makes the engine work harder and so becomes less responsive. Nothing new there.

I still don`t understand what about RPM fluctuation causes heat though. I`ve been racking my brain trying to understand how it works. Please, if anyone has a little clearer explanation of how this works, please feel free to share.



.

 

[Original Tetonice]

DJ. I see what you are saying here and understand what you mean when the belt has NO MOTION, however if the belt has NO MOTION then there would be no friction, now i understand that the belt is going around in the same spot on the clutch would tend to heat it up, however it brings me back to my thought on primay slipping, if the bealt sits in one spot on the primary but the primay doesn't have enough weight to pinch the belt enough to stop it from slipping, that would create a lot of heat real quick. Again takes me back to my thought on more weight in the primary and shallower helix to couteract the increased weight. Like i said just a though i'm only new to this clutching.

Is it possible to have to much primary weight? would that create heat?

From 6500 rpm to 8150 rpm the belt does not move up or down in the sheave very much at that shift ratio. Other than the dwell patch between the sheaves is slightly wider. LOL... The notion that heat can be eliminated from the TRA is false promise in deep powder. Your best chance to reduce heat at the sheaves would be to add correct hood vents which work excellent at reducing belt heat.

To test where the heat between the sheaves dwell take a Black-ElMarko and draw a vertical lline on both primary sheaves. You will see quickly see where your belt dwells between the sheaves between 6500 rpm and 8150 rpm as the ink is gone.

Once your belt has become "heat soaked" your clutch performance goes down hill fast.

OT

 

[shortstop20]

As I understand it Dock, the friction in the system when the belt stops moving up or down in the clutch is due to the motion of the belt moving over the sheaves (think of the heat your tires generate as they roll down the highway. They`re not slipping, but they still generate heat.) and the clamping forces of the two sheaves on the belt (a heavy truck generates more tire heat than a light car, even if the tires aren`t slipping).
.

I could see where if you had the belt in the same spot for minutes at a time it would create some excessive heat but I can't see there being any hardly measurable difference over a short time, say 10 seconds or so. I think what Joe is getting at is no matter how good your clutching is, there's going to be some amount of slip(although minimal) no matter where the belt is riding in the clutches. None of us are that good of tuners to ever get truely "perfect clutching". If you ride with the belt contacting the same areas of the sheave over time it will generate heat and slip, which generates more heat and slip. The belt slip and heat would sort of keep exponentially increasing, whereas if the belt keeps moving in the clutches you are giving that heat a chance to dissipate from that area of the clutch sheaves.

 

[Original Tetonice]

As I understand it Dock, the friction in the system when the belt stops moving up or down in the clutch is due to the motion of the belt moving over the sheaves (think of the heat your tires generate as they roll down the highway. They`re not slipping, but they still generate heat.) and the clamping forces of the two sheaves on the belt (a heavy truck generates more tire heat than a light car, even if the tires aren`t slipping).

As for too much clutch weight, the additional weight would clamp that belt harder the same way the heavier truck pushes harder (due to gravity) on its tires than the light car. Too much squeeze will generate more heat, though it`s a clearly better alternative that the heat generated from the belt slipping in the clutch. At least this way most of the RPM generated by the engine is being transferred to the secondary.

The other problem with too much weight, which I`m sure you already knew, is that additional weight makes the engine work harder and so becomes less responsive. Nothing new there.

I still don`t understand what about RPM fluctuation causes heat though. I`ve been racking my brain trying to understand how it works. Please, if anyone has a little clearer explanation of how this works, please feel free to share.



.

It's the other way around it's the heat making the rpm bounce around......

As for 2 much weight you need weight to run at the motors factory calibrations. If the 800R is calibrated to peak at 8150 rpm your going to need the weight to acheive those rpm's. Weight is not an option

The addition of adding or subtracting clutch weight in the TRA primary should only be used for acheiving and maintaining peak rpm as you tune your sled. If i want to grab the belt harder im not going to add or subtract weight in the primary nor do i advise anyone else to do so.

2 thing could occur either you have 2 much finish on the primary spring or your ramp profile is to steep. When useing a steep profile ramp you slow the shift becuase it's harder for the roller to go up the steep ramp into higher shift ratios thus causing added friction in the process. Or you could also have a combination of both.

The TRA need weight between the ramps, roller/arms X 3 = 300 grams approx. to operate add 16 grams of pinweight to each roller and your near 340 grams of weight plus or minus.

each ramp 63 grams
each roller/ arm 34 grams



OT

 

[DaveB]

I least the kids got enough common sense not to bye into the hype of a Polar

That's funny! But I actually think the child DOES have a Polar on that sled.....see, he's pushing it! Clutch is in 9 pieces in the belly pan. (Sorry YDPC....had too....hahahaha)

 

[Original Tetonice]

Funny Stuff DaveB.

OT

 

[tollen77]

I could see where if you had the belt in the same spot for minutes at a time it would create some excessive heat but I can't see there being any hardly measurable difference over a short time, say 10 seconds or so. I think what Joe is getting at is no matter how good your clutching is, there's going to be some amount of slip(although minimal) no matter where the belt is riding in the clutches. None of us are that good of tuners to ever get truely "perfect clutching". If you ride with the belt contacting the same areas of the sheave over time it will generate heat and slip, which generates more heat and slip. The belt slip and heat would sort of keep exponentially increasing, whereas if the belt keeps moving in the clutches you are giving that heat a chance to dissipate from that area of the clutch sheaves.

Yeah, I didn't mean to imply that the heat genereated from normal operation was a really meaningful amount... just that some heat is generated. What I meant really backs up what you're saying here: You're never going to achieve perfect clutching and you're never going to eliminate all the heat in the system. All you can do is get close.

As for heat being disapated by the belt moving up and down the clutch face, I'm pretty sure DaveB prooved me wrong there. Have a look at what he said a page or two back.



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