| Author | Message | ||
     Purpony |
I was wondering what the purpose of the belt tensioner on the XB is for and why the older Tubers dont have one? Is there an advantage? | ||
| Jramsey |
Tubers have axle adjusters. (Message edited by J.ramsey on July 10, 2008) | ||
| Echoseven |
Hey man this may answer your question better, click on the vid in the lower left corner, also this page has all of Buells "trilogy of technology" basically all of his design principals. Enjoy! http://www.buell.com/en_us/buell_way/buell_on_buel l/radicalprinciples.asp | ||
| Badlionsfan |
Evolution my friend. Less driveline lag and maintenance free. | ||
| Rah7777777 |
I just got one of the free spirits belt tensioners from trojan and in theory (and in my head) this is how they should have come from the factory! The factory piece doesnt move so tension is always at different weights. with the trojan tensioner it seems as if it will have a more constant pressure. no matter if your going over bumps or jumping a ramp or just cruising down the highway) Which I would think would help the belt have less stress and last longer. Havent installed it yet, but it sure looks kick ass!! | ||
| Djkaplan |
"The factory piece doesnt move so tension is always at different weights." Perhaps because of manufacturing tolerances, what you say may be somewhat correct, but the system was designed to provide constant tension in the belt throughout the rear suspension's range of motion. "with the trojan tensioner it seems as if it will have a more constant pressure. no matter if your going over bumps or jumping a ramp or just cruising down the highway" There will be no tension at all in the upper portion of the belt when you use compression braking. If anything, it'll be pretty loose. Not saying anything one way or the other as far as a tensioner goes, but you should have your facts straight. | ||
| Rah7777777 |
Hey i'm no rocket scientist, but thats how it appears to me...... you may be right about the engine braking, but i "think" it would still have the same if not more then the stock tensioner during engine braking for the upper portion of the belt. i'd have to get exact dimensions to figure everything out and i'm not about to go through all that trouble but it appears to me, the tension would never be less then the stock piece at any moment during riding. always equal to or greater..... but no rocket science degree under my belt :-) | ||
| Damnut |
but the system was designed to provide constant tension in the belt throughout the rear suspension's range of motion. How does it provide constant pressure in the suspension's range of motion if it doesn't move?? The FS tensioner moves with the belt and suspension travel thus it provides constant and even pressure on the belt throughout the suspension's range of motion. Since the stock one is fixed it will apply more tension/pressure on the belt at certain points of the suspension range. There will be no tension at all in the upper portion of the belt when you use compression braking. If anything, it'll be pretty loose. There isn't anything there to provide tension on the upper portion of the belt even with the stock setup. That makes no sense. I don't want to start an argument over this but you should know the facts before telling other to. | ||
| Deks69 |
I concur with Damnut. It's fixed, so how can it possible keep constant tension? Move the belt up and down while off the bike, then get on and move the belt up and down. See were the stock tensioner is now coming into play? | ||
| Lanretsr |
I think what he is trying to say is that under acceration or load the belt is pulled toward the trans pulley, tension on the top of the belt, thus creating slack on the bottom which the factory tensioner then takes up. When you are using the engine to slow the bike or compression breaking the tension in the belt is on the bottem since the motor is slowing the rear wheel instead of pulling it through the belt. If you had a spring tensioner it would want to overpower the tensioner to pull the belt straight and then creat slack on the top. I hope you guys can understand what I'm trying to say | ||
| Nik |
The wheelbase changes throughout the rear suspensions range of motion; its longer when compressed, when the tensioner exerts less force, and shorter when extended when the tensioner exerts more force. The net result is constant tension even with a fixed tensioner. | ||
| Ducxl |
I remember all of the hype about the many complex calculations about exactly WHERE to locate the tensioner. THe theory being as the swingarm pivots,the tension should remain neutral.THus eliminating the NEED for axle adjusters. I posted fact! | ||
| Treadmarks |
Your all right. But this is what I have observed. While changing the fan (rear shock off) you can move the suspension up and down very easy. Try it. With the swing arm down to its normal extended position, feel your belt tension. Now raise the swing arm whatever your bike shocks travel is, now feel the tension. There is a considerable difference. While it may not be great enough to cause problems on a shorter travel XB, on the uly it is quite a bit more. I welcome comments from those that have tried this.  The difference was enough when I tried this the first time at 8k miles, that I bought a FS adjustable tensioner. The second time I had the shock off the FS unit was installed and the difference was way less. Remember the preload on the FS unit is adjustable. Due to the common uly rear wheel bearing failures (due to excessive belt tension at max travel..I believe) I run my preload pretty light. It is possible to adjust the tension on the FS unit to equal the factory preload of the fixed tensioner if desired. I agree there is an accell decell difference on top, but a couple of turns of the preload adjuster and it will go away. | ||
| Spatten1 |
Ducxl is right. The geometry is worked out for the placement and OD of the pulley to be at the one point that keeps tension stable during suspension movement. In reality it is not exact, but close. I sat on a plane next to an engineer that works at the belt plant, I think in Indiana, that developed the system for Buell. He said Buell engineers were concerned that if the belt is loose it vibrates and slaps along the width, in the horizontal perpindicular plane, and causes more wear than the torque of the engine. With a non-adjustable system the owner can't let the belt get too loose. I'd still prefer an adjustable system due to manufacturing tolerances. Some people just get the wrong stack-up and keep breaking belts. Others run them for twice the service limit. | ||
| Spatten1 |
Treadmarks: That is certainly interesting. I've heard that the belts get overly tight when you jack up the rear end and the suspension is extended all the way, but never checked it myself. I'm not surprised that the Uly magnifies the issue. I had to run a chain for over a year while trying to figure out why my damn belt was too tight and got a lot of good feedback from badwebbers. This system is just one of those things engineers get very proud of, and keep around, even though the rest of the world is less convinced that it is the best way to go. Most owners have no trouble, so all in all, it is probably serving it's purpose. | ||
| Jlnance |
I concur with Damnut. It's fixed, so how can it possible keep constant tension? http://www.google.com/patents?vid=USPAT6866112 | ||
| Djkaplan |
Kinematics of motion is a science taught in all mechanical engineering programs. The mechanics of motion in the Buell idler arrangement are outwardly simple to understand, but execution of the concept is a fairly complex matter. Husqvarna had a similar arrangement that used teflon blocks instead of an idler in the late 70's. The main benefit of their much simpler system was the elimination of the chain tensioner (while keeping chain tension constant enough). It worked really well. | ||
| Djkaplan |
I don't care one way or the other if you replace your XB or 1125 idler with a tensioner, btw, but everyone should at least understand the reasoning behind why it's like the way it is. | ||
| Djkaplan |
"I don't want to start an argument over this but you should know the facts before telling other to." That's the only thing you've posted on this thread that I agree with. Abstract (from the patent) A motorcycle includes a frame, and an engine and transmission mounted to the frame. A swingarm is pivotably mounted to the frame, and a rear wheel is rotatably mounted to the swingarm. An output shaft of the transmission is coupled to the rear wheel to cause rotation of the rear wheel under power of the engine. A stationary tensioner is mounted to the frame such that as the rear wheel bounces up and down with respect to the frame, the tensioner maintains substantially constant tension and belt path length in the belt without requiring the tensioner to move in a translational or pivotal sense. edited for bitchiness content - djkaplan (Message edited by djkaplan on July 11, 2008) | ||
| Jlnance |
Dr Greg was going to run through the math in that patent, I don't know if he ever did. One thing I would like to know is if the belt length is (theoretically) constant over a range of swingarm motion, or if it is some complex function with a derivative of zero at the nominal operating point. | ||
| Dr_greg |
I'm working on it! The geometry is QUITE tricky, BTW. I'm using dimensions from the Uly. I'll report back, but don't hold your breath. FWIW, the principle is that changes in belt length are compensated by an equal change in belt wrap around the idler pulley. | ||
| Djkaplan |
"Any fool can criticize, condemn and complain and most fools do." - Benjamin Franklin Great quote, Dr_greg. | ||
| Dr_greg |
When (if) I finish my analysis of the belt tension variation it would be interesting to formulate the idler positioning (and size) as a constrained multivariable optimization problem and see if I get anything like their results. Or I just might do some riding instead... |
