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The readings may be low because the tip of the guage was placed where i have the arrows written because i have my secondary back in. Maybe at the outtermost.point it will be .024 like brp says. I will check that later
I just realized that you are showing only the notch for the D. I was reading notch above the line for the balancing notch, and below the line I was reading center for the D lol

Can you also find the position of the balancing notch on the outer edge and double check the position of the D ?
 

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Wobble Up and down would make more sense than side to side
Wobble up and down at the sheave could also combat this, but it seems like a more complicated way, since both inner and outer sheaves would have to be machined 'off', and the tolerance between the 2 would be another factor subject to quality control.

FWIW:
There are 2 main sources of the vibration this is intended to combat.

1) On a 2 stroke, 180 degree crank, the piston moving down from top dead center (TDC) accelerates faster than the one moving up from bottom dead center. This difference in acceleration side to side causes one vibration source, and gets larger with larger engine displacement.
2) The firing of the cylinder with piston moving down from TDC causes further cylinder, crank, piston, and rod acceleration differences in the 2 cylinders, and is another, related vibration source.

Both of these 2 main sources result in both vertical vibration (up and down) plus a rocking vibration. The rocking vibration can be imagined by viewing the engine from front or rear of the sled. The engine will rock clockwise, then counterclockwise. This rocking cycle occurs once per crank rotation.

Since the sheave and belt vibration caused by this design is once per engine rotation, only the rocking vibration is combatted by this.

The vertical (up and down) vibrations from these sources occur twice per rotation. So the runout on the sheave plus belt movement cannot combat the vertical part of these vibrations.
 

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Discussion Starter · #85 ·
Wobble up and down at the sheave could also combat this, but it seems like a more complicated way, since both inner and outer sheaves would have to be machined 'off', and the tolerance between the 2 would be another factor subject to quality control.

FWIW:
There are 2 main sources of the vibration this is intended to combat.

1) On a 2 stroke, 180 degree crank, the piston moving down from top dead center (TDC) accelerates faster than the one moving up from bottom dead center. This difference in acceleration side to side causes one vibration source, and gets larger with larger engine displacement.
2) The firing of the cylinder with piston moving down from TDC causes further cylinder, crank, piston, and rod acceleration differences in the 2 cylinders, and is another, related vibration source.

Both of these 2 main sources result in both vertical vibration (up and down) plus a rocking vibration. The rocking vibration can be imagined by viewing the engine from front or rear of the sled. The engine will rock clockwise, then counterclockwise. This rocking cycle occurs once per crank rotation.

Since the sheave and belt vibration caused by this design is once per engine rotation, only the rocking vibration is combatted by this.

The vertical (up and down) vibrations from these sources occur twice per rotation. So the runout on the sheave plus belt movement cannot combat the vertical part of these vibrations.
The engine these clutches are on is a 3 cylinder 4 stroke engine. It shares nothing with the 850 or 2 stroke so its a real wonder why this wobble is on the 900 3 cyl 4 stroke
 

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That is not even close to what I would expect on an 850, and the runout is low. The plot thickens lol
Hey Daag,
First let me thank you for sending the BRP published info on this. Very instructive.

FWIW: Factor #1 listed above is a big factor in the rocking vibration of a large displacement twin, much bigger than most appreciate. (The mass of the pistons gets bigger and their distance from engine centerline increases.)

The peak of that occurs far from TDC. (At an angle I'd guess is in the 50 degree range . But I don't recall seeing exact numbers ...)
 

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The engine these clutches are on is a 3 cylinder 4 stroke engine. It shares nothing with the 850 or 2 stroke so its a real wonder why this wobble is on the 900 3 cyl 4 stroke
Check. Been following this with interest. A 3 cylinder, 4 stroke would have similar vibration sources, but the rocking vibration discussed would be expected to be less than a large twin's vibration, due to lower piston masses and the phasing of the outer cylinders being far from 180 degrees.

So yeah, what you found is not making sense. But engineering can humble you in a hurry lol
 

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120 is bad for vibrations/harmonics
 
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· Banshee Builder
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That is not even close to what I would expect on an 850, and the runout is low. The plot thickens lol
oh boy charles this thread has me digging through our many pages of back and forth convo about the 850 pdrive. deja vu 😂

The engine these clutches are on is a 3 cylinder 4 stroke engine. It shares nothing with the 850 or 2 stroke so its a real wonder why this wobble is on the 900 3 cyl 4 stroke
hope this does not seem like im hi jacking you thread, but the pics below defeinitely show everyone how spot on you are about the subject lol

this will not be news to many but good info on "wobble" design and its intentions lol
Automotive tire Wheel Automotive lighting Rim Font

Light Product Automotive tire Wheel Font

Wheel Automotive tire Alloy wheel Font Tread

Organism Font Parallel Art Circle
 

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Discussion Starter · #92 ·
Great info!

So my take is that my 252 clutch is exactly what the picture describes- the line notch is the high spot of 20 or .020 in my pic and is 60 degrees from the D notch in crank.
So, should this be on a 900 triple with different firing order? The article all relates this for the 850 only and based off synchronization with its fring order.
Need a engineer to explain this one to us please
 

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Always good to hear from you Mike! PM is ttt for easier find ;)

nm9stheham, I sense a riddle with the peak movement @ ~50° ATDC lol In return I'll send you are twister. The engine movement is not only up and down, but also rotational. Now I need to find a cool video of this lol

Just a fun mind teaser. When the piston fires that side of the engine moves down. Since for every force there is an equal opposing force, what makes the engine go down and not up? Or why don't they both move and cancel each other out?
 

· Descending doooowwwwnnnnn
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Great info!

So my take is that my 252 clutch is exactly what the picture describes- the line notch is the high spot of 20 or .020 in my pic and is 60 degrees from the D notch in crank.
So, should this be on a 900 triple with different firing order? The article all relates this for the 850 only and based off synchronization with its fring order.
Need a engineer to explain this one to us please
I don't need an engineer to explain anything about it to me. Clearly doo designed the wobble for the 850 twin with the 252 part number. Now the 900 Turbo has a 210 part number so it is a different part it may have a different wobble it may not have a wobble it is the part that is called to be on the machine. So the 252 is not meant for the 900 otherwise it would be that way in the fiche.
 

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Great info!

So my take is that my 252 clutch is exactly what the picture describes- the line notch is the high spot of 20 or .020 in my pic and is 60 degrees from the D notch in crank.

So, should this be on a 900 triple with different firing order? The article all relates this for the 850 only and based off synchronization with its firing order.

Need a engineer to explain this one to us please
I have enjoyed comparing notes with your 850 pDrive. Note that I have not discussed its use on a triple 4S Mach Z. For me it is not computing. After reading your first post I knew it was a phenomenal find. Have you thought of contacting BRP directly to share your findings?
 

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I don't need an engineer to explain anything about it to me. Clearly doo designed the wobble for the 850 twin with the 252 part number. Now the 900 Turbo has a 210 part number so it is a different part it may have a different wobble it may not have a wobble it is the part that is called to be on the machine. So the 252 is not meant for the 900 otherwise it would be that way in the fiche.
Exactly, a 3 cylinder 4 stroke doesn't need any kind of a wobble.
 

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Discussion Starter · #97 ·
I have enjoyed comparing notes with your 850 pDrive. Note that I have not discussed its use on a triple 4S Mach Z. For me it is not computing. After reading your first post I knew it was a phenomenal find. Have you thought of contacting BRP directly to share your findings?
Ya that might be a option. I am going to see what my dealer comes back with first. I also want to go check a few of my buddies 900t and see what they have on them.
 
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· Descending doooowwwwnnnnn
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According to the fiche for my model none of the primary have the correct number, spider,sliding shiv,fixed shiv.
Fixed shiv is the 252(850 etec wobbler) fiche says 210
Spider is a 417 224 629( fiche says 870) Cant find the 629 anywhere on fiche?
Slider is 417 224 190(fiche says 767)
Now not worried about the slider, but the spider was supposed to be stronger due to the 900r but numbers dont match with fiche. Man there are so many different numbers for the pdrive its stupid. No wonder some are getting wrong parts.
 

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Discussion Starter · #100 ·
According to the fiche for my model none of the primary have the correct number, spider,sliding shiv,fixed shiv.
Fixed shiv is the 252(850 etec wobbler) fiche says 210
Spider is a 417 224 629( fiche says 870) Cant find the 629 anywhere on fiche?
Slider is 417 224 190(fiche says 767)
Now not worried about the slider, but the spider was supposed to be stronger due to the 900r but numbers dont match with fiche. Man there are so many different numbers for the pdrive its stupid. No wonder some are getting wrong parts.
What a mess this is turning out to be. I compared the spider of the mach z to my 2018 600rs pdrive spider and the mach is beefier.
So its looking like the stamped numbers are not being used by brp and they are assigning there own numbers to these parts? What a nightmare it will be to identify parts in the future if there is no change up number trail for these stamped parts...
Hope my dealer gets back with something but not holding my breath
Just want to know if brp thinks the 900t/r should have the wobble fixed primary of the 850
 
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