Im giessing here...Everyone does know that when click your TRA clickers Up or Down that it changes the engine rpm and ramp shift character.
OT
Ramps in the TRA, how they work and how they effect performance.
- Thread starter tollen77
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Im giessing here...Everyone does know that when click your TRA clickers Up or Down that it changes the engine rpm and ramp shift character.
OT
T
tollen77
Member
Just did a little calculation regarding centri***al force of a 33 gram TRA arm spinning at 8,200 RPM. I did the calculation for both a 441 and a 413 ramp. I'm assuming the 441 ramp holds the arm at a distance of 100mm from the centerline and and the 413 holds the arm 98.5mm away. (I realize that this is not the exact measurement. If someone knows the correct measurement or wants to take a measurement from their sled, please do and I'll post the revised calculation.)
Spinning at 8,200 RPM a 33 gram arm exerts a centri***al force of 2,430.87 N or approx 247.79 kg while pushing on a 441 ramp. That same 33 gram arm spinning at 8,200 RPM exerts a centri***al force of 2,394.41 N or approx 244.08 kg while pushing on a 413. This is the force applied by just one arm (not all three) and does not account for force vectors. The flatter ramp would transfer more of the force to closing and less to stressing the outside of the clutch.
In order for the same arm to exert the same centri***al force against the 413ramp (not counting for force vectors) you would need to add an additional 0.5gram for a total of 33.5 grams.
Once Joe gets his site up and runnning we should be able to calcualte these forces as easy as pie. Can't wait to see the new site Joe! Thanks again.
Note: For some reason the site thinks I'm swearing. I guess cen-tri-fu-gal is a bad word!!!
Note: I've made some changes to the figures as clearly I made a calculating error.
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I can tell you that from knowing and corresponding with an engineer from Dayco, he reported to me that an 800 cc sled that works with low elevation calibration on stock snowmobile - there can be up to 1100 lbs of force distributed between the 3 little rollers. There is up to 1100 lbs force put on the side of the belt through the push of the primary sheaves.
those 3 little rollers go through hell...
those 3 little rollers go through hell...
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tollen77
Member
I can tell you that from knowing and corresponding with an engineer from Dayco, he reported to me that an 800 cc sled that works with low elevation calibration on stock snowmobile - there can be up to 1100 lbs of force distributed between the 3 little rollers. There is up to 1100 lbs force put on the side of the belt through the push of the primary sheaves.
those 3 little rollers go through hell...
Joe, do you have the distance from the centreline to the tip of a 441 ramp? of the 413? Of any other ramp for that matter? Give me that and I'll calculate the exact force for a 33 gram arm.
Want a different arm weight? No prob.
I've dummed the equation down a little for everyone.
Force = mass * radius * 736,627.3929 (measured in Newtons)
Force = mass * radius * 165,543.878 (measured in lbs.)
For the 33 gram arm with a max radius of 0.1m the force exerted per arm is 546.29 lbs. 546.29 lbs x 3 = 1,638.88 lbs force over three arms. I think we can safely assume that the radius is too large in the equation. I'll measure my clutch when I get home tonight.
Plus, I make no guarantees I didn't put a decimal place in the wrong spot.... I haven't used these formulas since university.
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The rollers go through hell as do the springs...Kinda like tires on a race car. Add the extra load of deep deep snow under vthe track and you have your answer as to why the TRA gets hot in deep snow conditions.
OT
OT
OK, throwing a scenario for you DJ
You pin it from a stop on the trail and sled goes to target RPM, but RPMs fall off as speed increases.
Now in POW, WOT does not reach target.
Now, Im thinking the finish angle of the ramp is to low.
Would changing the helix accomplish the same thing? Lower helix angle, would backshift, Or HOLD the primary in lower gear longer??? Or does it not work that way?
The above is how my sled was performing and I just changed to a ramp with a flatter finish angle. Im thinking went the rong way?
You pin it from a stop on the trail and sled goes to target RPM, but RPMs fall off as speed increases.
Now in POW, WOT does not reach target.
Now, Im thinking the finish angle of the ramp is to low.
Would changing the helix accomplish the same thing? Lower helix angle, would backshift, Or HOLD the primary in lower gear longer??? Or does it not work that way?
The above is how my sled was performing and I just changed to a ramp with a flatter finish angle. Im thinking went the rong way?
You pin it from a stop on the trail and sled goes to target RPM, but RPMs fall off as speed increases.
- For whatever secondary details you have installed, that calibration would have too much pinweight (weight determines rpms)
The combination of the calibration of the two parts cannot resist the push from the primary and the rpms drift lower.
You pin it from a stop in POW, WOT does not reach target.
- For whatever secondary details you have installed, that calibration would have too much pinweight (weight determines rpms)
The combination of the calibration of the two parts cannot resist the push from the primary and the rpms are low from the get go.
Now, I'm thinking the finish angle of the ramp is to low.
I assume you speak of the TRA ramp in the primary.
IF low rpms then the tra ramp final angle would need more of a curve on it to resist the push of the tra lever, the engine would have to build rpms to continue to push the primary clutch closed.
also...
-Spring force can determine rpms in either clutch. More spring force = higher rpms.
-Helix angle can determine shift rpms under w.o.t. Less helix angle = higher shift rpms.
- Combination of i)primary spring final force not high enough. ii)secondary spring start or final force not high enough. iii)helix angle is too large.
The combination of the calibration of the 3 parts cannot resist the push from the primary and the rpms are low - or the rpms drift lower.
Would changing the helix accomplish the same thing?
- what "thing" are you talking about?
Lower helix angle, would backshift, Or HOLD the primary in lower gear longer??? Or does it not work that way?
-Helix angle can determine shift rpms under w.o.t. Less helix angle = higher shift rpms.
-Lower angle "stalls the upshift" from the primary, you would see higher rpms.
The above is how my sled was performing and I just changed to a ramp with a flatter finish angle. I'm thinking went the wrong way?
-Do you mean the ramp in the primary clutch?
cya
Joey
- For whatever secondary details you have installed, that calibration would have too much pinweight (weight determines rpms)
The combination of the calibration of the two parts cannot resist the push from the primary and the rpms drift lower.
You pin it from a stop in POW, WOT does not reach target.
- For whatever secondary details you have installed, that calibration would have too much pinweight (weight determines rpms)
The combination of the calibration of the two parts cannot resist the push from the primary and the rpms are low from the get go.
Now, I'm thinking the finish angle of the ramp is to low.
I assume you speak of the TRA ramp in the primary.
IF low rpms then the tra ramp final angle would need more of a curve on it to resist the push of the tra lever, the engine would have to build rpms to continue to push the primary clutch closed.
also...
-Spring force can determine rpms in either clutch. More spring force = higher rpms.
-Helix angle can determine shift rpms under w.o.t. Less helix angle = higher shift rpms.
- Combination of i)primary spring final force not high enough. ii)secondary spring start or final force not high enough. iii)helix angle is too large.
The combination of the calibration of the 3 parts cannot resist the push from the primary and the rpms are low - or the rpms drift lower.
Would changing the helix accomplish the same thing?
- what "thing" are you talking about?
Lower helix angle, would backshift, Or HOLD the primary in lower gear longer??? Or does it not work that way?
-Helix angle can determine shift rpms under w.o.t. Less helix angle = higher shift rpms.
-Lower angle "stalls the upshift" from the primary, you would see higher rpms.
The above is how my sled was performing and I just changed to a ramp with a flatter finish angle. I'm thinking went the wrong way?
-Do you mean the ramp in the primary clutch?
cya
Joey
If less helix angle = higher shift RPM
and
More TRA ramp angle means higher RPM
Is that kind of the same thing?
Im saying, if my combo needs more TRA Ramp angle, but I don't have that, another ramp that is. Can increasing preload, or a lower helix angle accomplish the same or close to same effect? Or is changing the helix a bandaid fix for the problem?
Reason is, Im trying to dial a combo in that has no known precedence. I dont even know where to start clutching for my sled. Maybe im trying to skip a step, more so, I think Im trying to save a few hundred $$$ in ramps, helix's springs, etc. You yourself know they aint cheap.
and
More TRA ramp angle means higher RPM
Is that kind of the same thing?
Im saying, if my combo needs more TRA Ramp angle, but I don't have that, another ramp that is. Can increasing preload, or a lower helix angle accomplish the same or close to same effect? Or is changing the helix a bandaid fix for the problem?
Reason is, Im trying to dial a combo in that has no known precedence. I dont even know where to start clutching for my sled. Maybe im trying to skip a step, more so, I think Im trying to save a few hundred $$$ in ramps, helix's springs, etc. You yourself know they aint cheap.
D
Dock
Member
I don't mean to be totally off topic here, But what causes clutch heat???
Everyone i hear from says allignment? It just seems to me that heat is would be caused by Slipping, if you don't have enough weight in your primary can it slip around the belt? example might be my 07 fried belts. if i increased my primay weight, causeing less RPM but more force on the belt, and decreased my helix angle to compensate for the lost RPM, might this stop the belt from slipping in the primary and causing heat.?? can you have to much force on the belt say a large wight in the primay and a really shallow helix?
Everyone i hear from says allignment? It just seems to me that heat is would be caused by Slipping, if you don't have enough weight in your primary can it slip around the belt? example might be my 07 fried belts. if i increased my primay weight, causeing less RPM but more force on the belt, and decreased my helix angle to compensate for the lost RPM, might this stop the belt from slipping in the primary and causing heat.?? can you have to much force on the belt say a large wight in the primay and a really shallow helix?
I think one thing that produces clutch heat is that when the belt is low in the primary it it enters the sheaves a bit higher up and as the sheaves pinch the belt it also is being forced lower in the sheaves. At 1-1 (belt at same height in primary and secondary) this doesn't happen.
As for the rollers with 250KG force on each of them no wonder they where out. Does anyone make them out of harder material?
BRP should be paying you for all this work. Good job.
But how do you post a full picture on this site? I go to the Additional Options, Manage Attachments, Browse and select a picture Upload and Submit Reply. Then what comes out is a thumbnail ... WTF!
Ya, in theory.
In the real world the belt squirts up to the top of the primary and that's the end of that. Or are you holding the belt down in the primary somehow? Did you bolt the secondary sleaves together or something?
my mind hurts from computing this info....DAAAAAAAAAMMMMMMMMNNNNNNNN!!!!!!!
Thats alot of info...
I would think about changing my set-up if i hadnt gone through it a coupe dozen times..
Thanks DJ...all day, every day...8200 rpm.....
I really cant say enough good things about DJ. He REALLY knows his CHIT!!!!!!
I promise...you work with Joe, you will be glad in the long run....
I really love the backshift on my 800r Joe, You are the MAN>>>>PERIOD!!!!!!
Thats alot of info...
I would think about changing my set-up if i hadnt gone through it a coupe dozen times..
Thanks DJ...all day, every day...8200 rpm.....
I really cant say enough good things about DJ. He REALLY knows his CHIT!!!!!!
I promise...you work with Joe, you will be glad in the long run....
I really love the backshift on my 800r Joe, You are the MAN>>>>PERIOD!!!!!!
BTW...going on 2 seasons with the same belt...
am I serious...YES!!!!
am I serious...YES!!!!
T
tollen77
Member
I agree with everything you said Dock.... but you have to know where the extra heat is coming from too. If the heat is coming from the primary, what you said is exactly the right thing to do. If the heat is coming from the secondary (ie: belt slipping in the secondary) you need a stronger secondary spring, less primary belt squeeze, or a combination of the two. Personally I lean towards more secondary spring since reducing squeeze in the primary simply causes that to slip a little along with the secondary.... then both clutches are hot - not exactly ideal.
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tollen77
Member
Hey man, i agree that's complately theory.... but it gives you a starting point for when you get on the hill. I mean, the calculation I did there is pretty rudimentry. It doesn't really give you any useful information as it is. But using it, you can calculate the approx. difference in clamping force when going from one ramp to another.
Once you know that, you can then figure out how much weight to add or subtract to get you approx the same clamping forces, if that's what you're after. If you want more belt squeeze, add more weight ---- less force you need less weight. But, instead of just taking a guess, if you use that little formula you should be within 0.5 g... this means a lot less time adjusting clickers and a lot more time riding.
Use the calculation, and it gives you a good approximation of what weight and ramp combo will work on the hill. It's not the answer to everything... you still need seat time. But it will get you closer
.
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I have had guys come back to me saying "look what i've done with all the stuff I read from you"
These guys have plowed through everything I've typed that they could read or was available and in point form have cut/paste what is important in the topics.
Example of what I have done on this page...I just copied what I mentioned previously
-Spring force can determine rpms in either clutch. More spring force = higher rpms.
-Helix angle can determine shift rpms under w.o.t, Less helix angle = higher shift rpms.
-Lower helix angle "stalls the upshift" from the primary, you would see higher rpms.
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@Dock I don't mean to be totally off topic here, But what causes clutch heat???
I have read papers by drive belt mfg's and automotive mfgs. Have findings from my own testing and calibrating. In my clutch book I site the quotes from such companies that write on the topic of "high system temps"
- The #1 cause of system high temperature is "RPM FLUCTUATION"
An engine has "rated rpms" An engine has "torque point rpms"
IF you run a system at less than rated rpms, THEN temperatures will increase. (The clutches stop upshifting - mph ceases to increase)
IF you run a system at more than rated rpms, THEN temperatures will increase. (The clutches stop upshifting - mph increases ONLY by virtue of increased engine rpm)
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@C-Bolt He REALLY knows his CHIT!!!!!!
C-B, I only know the principles that's it. I don't know setups I can only recite a principle of the parts, just like what is bullet form above. ....and you can too, everyone can.
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These principles are difficult to disprove although I know of one individual who will try hard to do so.
-Spring force can determine rpms in either clutch. More spring force = higher rpms.
-Helix angle can determine shift rpms under w.o.t, Less helix angle = higher shift rpms.
-Lower helix angle "stalls the upshift" from the primary, you would see higher rpms.
-IF you run a system at less than rated rpms, THEN temperatures will increase. (The clutches stop upshifting - mph ceases)
-IF you run a system at more than rated rpms, THEN temperatures will increase. (The clutches stop upshifting - mph increases ONLY by virtue of increased engine rpm)
These are details I live by, they are principles derived from the laws of how the parts work.
When you run the system, your sled and observe the tach, make your notes....you see something that is not right, you have a question "Why" ain't it right?
You go back to the principles and identify one of them to help you make a decision on what part to change with the capacity you have at that moment.
These guys have plowed through everything I've typed that they could read or was available and in point form have cut/paste what is important in the topics.
Example of what I have done on this page...I just copied what I mentioned previously
-Spring force can determine rpms in either clutch. More spring force = higher rpms.
-Helix angle can determine shift rpms under w.o.t, Less helix angle = higher shift rpms.
-Lower helix angle "stalls the upshift" from the primary, you would see higher rpms.
----------------------
@Dock I don't mean to be totally off topic here, But what causes clutch heat???
I have read papers by drive belt mfg's and automotive mfgs. Have findings from my own testing and calibrating. In my clutch book I site the quotes from such companies that write on the topic of "high system temps"
- The #1 cause of system high temperature is "RPM FLUCTUATION"
An engine has "rated rpms" An engine has "torque point rpms"
IF you run a system at less than rated rpms, THEN temperatures will increase. (The clutches stop upshifting - mph ceases to increase)
IF you run a system at more than rated rpms, THEN temperatures will increase. (The clutches stop upshifting - mph increases ONLY by virtue of increased engine rpm)
----------------------
@C-Bolt He REALLY knows his CHIT!!!!!!
C-B, I only know the principles that's it. I don't know setups I can only recite a principle of the parts, just like what is bullet form above. ....and you can too, everyone can.
----------------------
These principles are difficult to disprove although I know of one individual who will try hard to do so.
-Spring force can determine rpms in either clutch. More spring force = higher rpms.
-Helix angle can determine shift rpms under w.o.t, Less helix angle = higher shift rpms.
-Lower helix angle "stalls the upshift" from the primary, you would see higher rpms.
-IF you run a system at less than rated rpms, THEN temperatures will increase. (The clutches stop upshifting - mph ceases)
-IF you run a system at more than rated rpms, THEN temperatures will increase. (The clutches stop upshifting - mph increases ONLY by virtue of increased engine rpm)
These are details I live by, they are principles derived from the laws of how the parts work.
When you run the system, your sled and observe the tach, make your notes....you see something that is not right, you have a question "Why" ain't it right?
You go back to the principles and identify one of them to help you make a decision on what part to change with the capacity you have at that moment.
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T
tollen77
Member
Thanks for all the input Joe. This info is a big help for someone trying to learn more about clutching (that'd be me!)
One of the principles you mentioned was:
-IF you run a system at less than rated rpms, THEN temperatures will increase. (The clutches stop upshifting - mph ceases)
-IF you run a system at more than rated rpms, THEN temperatures will increase. (The clutches stop upshifting - mph increases ONLY by virtue of increased engine rpm)
Can you explain why this is? Why would th ebelt get warmer while running less than rated RPMs??? Having trouble getting my brain wraped around that one.
.
These principles are difficult to disprove although I know of one individual who will try hard to do so.
Me, me! (hand waving in the air)
Nah, the principles are accurately stated, and one thing about the TRA, it does make you think!
I doo find it interesting that people can read the principles and then don't know why they are correct.
Take the "Spring force can determine rpms in either clutch. More spring force = higher rpms." statement. Anyone think about why this works in isolation? It works because all the bigger spring does is suck up a portion of the force that the flyweight is generating. The engine hp gets a chance to escape in the form of higher RPM, because the HP hasn't changed (non mountain sled). To take it to the extreme you could have a spring from the front end of a Buick car in the TRA, and if you can add enough weight to the arms that clutch will move, but why would you want to doo that? Now you need a different ramp profile to match the spring rate of the Buick spring.
This is all fine on a lake, but change the weight of the sled or the HP curve and the tuning starts all over again.
Heat is another great friend of the TRA. The TRA loves to make heat. So anytime the tuning of the clutch is off a little the engine HP will escape in the form of heat, and poof! No more belt. All clutches produce heat. The difference is they do not overheat as quickly or as severely as the TRA. I'm thinking it was the rubber wiggle mount of the TRA outer hub that lets the TRA scrub the belt to make it so hot so quick. If the belt was loose enough to slip, then the secondary would be broken or stuck.
I don't see where there is a tuning solution for the TRA on a sled where the weight changes and the HP constantly changes through out the day. Can't be done.
The principles are correct, just the TRA is no good.
@tollen 77
When you break down into principle form, then it does not matter what brand oem or aftermarket clutch you speak of.
The hat you wear right now, says "snowmobile" specifically "skidoo".
I am going to take my snowmobile hat off and put on my "Automotive" hat.
.....I am not thinking snowmobile, I am thinking "Car" one of my fave cars is a 350 hp "Nissan Murano"
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Example (The clutches stop upshifting - mph ceases)
The question is designed to achieve a yes or no answer - any other answer is non-responsive.
Regarding Primary clutch - IF the clutches stop upshifting, THEN does the belt continue to move across the sheave face on the primary? yes or no?
Regarding Secondary clutch - IF the clutches stop upshifting, THEN does the belt continue to move across the sheave face on the secondary? yes or no?
When you break down into principle form, then it does not matter what brand oem or aftermarket clutch you speak of.
The hat you wear right now, says "snowmobile" specifically "skidoo".
I am going to take my snowmobile hat off and put on my "Automotive" hat.
.....I am not thinking snowmobile, I am thinking "Car" one of my fave cars is a 350 hp "Nissan Murano"
---------------------------------------------------------------
Example (The clutches stop upshifting - mph ceases)
The question is designed to achieve a yes or no answer - any other answer is non-responsive.
Regarding Primary clutch - IF the clutches stop upshifting, THEN does the belt continue to move across the sheave face on the primary? yes or no?
Regarding Secondary clutch - IF the clutches stop upshifting, THEN does the belt continue to move across the sheave face on the secondary? yes or no?
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