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Treadmarks
| | Posted on Friday, March 07, 2008 - 12:42 pm: | 
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How would ya like to have a go at those tensioners.
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Wademan
| | Posted on Friday, March 07, 2008 - 03:42 pm: |
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Treadmarks, I BELIEVE your arguement regarding the graphs and simply sliding to the left because of an increased belt length is making way to many assumptions to be correct.
The system of the belt, sprockets and idler pulley is simple to model being that it is all in a plane. Many constants had to be fixed to get the graphs shown in the buell pdf. (for example maybe they held constant the vertical distances between the idler pulley and the sprockets) Assuming that the XB 'X' suspension 'constants' and the old XB suspension 'constants' are the same... I think is going to far. (given the example above the vertical distances between the idler pulley and the sprockets are NOT the same between the two different suspension configurations) Because of this simply moving the the left on the graphs in that document is wrong and misleading.
The idler pulley may very well reduce the constant load on the belt making the bike roll better, shift smoother, etc...
But think about this...
The belt is likely capable of handeling very high loads, but maybe its NOT capable of handleing large percentage variations in that load (e.g. cyclic loading). By Buell providing a high constant tension in the belt the forces of suspension movement, acceleration, and other loads to the belt appear to the belt as smaller percentage increases in tension when compared to the constant tension applied. If a smaller constant tension is provided the loads from the above appear much larger percentage wise in comparison to the constant load.
Maybe due to belt design, instead of leading to a longer belt life this will lead to more premature belt failure.
You be the judge.
Ill just ride the stock setup and if a belt or bearing fails, replace it under warranty.
Good discussion by the way. |
Wademan
| | Posted on Friday, March 07, 2008 - 04:09 pm: |
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All motorcycles run some chain slack depending on the amount of travel in the suspension..(
And you need to run slack in a typical chain setup because the distance between the engine sprocket center and the wheel sprocket center changes as suspension moves because the swingarm pivot and the engine sprocket center dont share the same center line. This causes a change in the drive line length.
Buell basically figured out that by adding a third 'sprocket' (the idler pully) and getting the geometry just right you can create a drive path that will change in length depending on the suspension travel by very very little.
The one thing it does not account for is how when the rear suspension moves the rear sprocket is forced to rotate, causing the from sprocket to move. Bicycle riders actually notice this action because their feet are the front sprocket. One mountain bike company did some pretty cool stuff to get rid of this reaction...
http://www.gtbicycles.com/int/eng/id
You have to scroll down on the left to see the whole deal...
I wonder what effect this would have on a motorcycle... my guess is that motorcycles dont even feel this reaction so it is a null point. |
Treadmarks
| | Posted on Friday, March 07, 2008 - 06:12 pm: |
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I'm getting dizzy as a school girl on prom night. |
M_singer
| | Posted on Friday, March 07, 2008 - 07:23 pm: |
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Treadmarks, Do you know if the increase travel of the Uly over the previous XB's was archived by:
a) lowering the topped out swing arm position
b) raising the fully compressed swing arm position
c) a combination of the two?
Your theory seems to be dependent on the Uly having a lower topped out swing arm position which may be the case but I don't think that we have established that here. |
Treadmarks
| | Posted on Friday, March 07, 2008 - 08:10 pm: |
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Longer swingarm and shock, I do believe.
But what do I know? |
Nipsey
| | Posted on Friday, March 07, 2008 - 09:16 pm: |
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You know a good Catwoman.... |
M_singer
| | Posted on Friday, March 07, 2008 - 09:16 pm: |
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Don't the Uly, lighting long and supper TT share the same frame and swing arm? |
Reepicheep
| | Posted on Saturday, March 08, 2008 - 09:23 am: |
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The point I was hinting at was something Blake calculated out a LONG time ago... back in the tuber days. And something I experienced first hand.
Looking at the design of the belt and the path it takes, and knowing the "snap strength" it probably takes to break that belt, I think that even if you *tried* to set up a system that would bind the rear suspension by belt tension, you would be destroying wheel bearings / 5th gear drive assembly bearings / swingarm bearings (do we even have swingarm bearings?) in fairly short order.
I did exactly that on my M2. I adjusted my belt slack according to what I thought the service manual said. I rode for a while, it was fine. I rode on a group ride, and went through a slight dip in the road pretty quick, and I can still to this day still *clearly* remember the sensation of the belt binding the rear suspension as it approached full travel.
A few weeks later, I started to get the symptoms of destroyed needle bearings in the 5th gear drive assembly. Can't even begin to imagine the forces required to mess up that bearing...
That was at 12k miles or so. The destroyed needle bearings worked like plain bearings for another 5k miles or so until I figured it out, at which point they had destroyed the output shaft in the transmission, before creating shifting problems (well, shifting problems beyond the normal M2 operational envelope  ). Full transmission rebuild at about 19k, including replacing the bearings in the 5th gear drive assembly.
The original belt was still running strong at 29k miles when I sold the bike.
I dont understand all the physics, so that is just one anecdotal data point, for what thats worth. |
M_singer
| | Posted on Saturday, March 08, 2008 - 12:58 pm: |
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Reepicheep, I understand your point very clearly. What I am question is whether the Uly's belt at full suspension extension or compression is any tighter then the rest of the XB line.
Just b/c the Uly has more suspension travel does not necessarily mean that the belt tension is greater at some point then the other XB's.
If the Uly has the same topped out swing arm position as the TT and lightning long then it also has the same belt tension in the topped out position. I don't know if the added travel was accomplished at the upper end bottom end or combination.
Buell seems to be suggesting that the tension does not vary much though the rear wheel travel.
My bike is under warranty for 2 years. If I leave it stock and it breaks Buell will have to fix it. If I mod the bike and it breaks I'm likely going to be on my own. |
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