| Author | Message | ||
     M1combat |
No permission... Describe it or save and e-mail them? Address is Don dot Hann at co dot yavapai dot az dot us. | ||
| Jandj_davis |
Nevermind. I was imagining things. You have e-mail. -- Original Post -- Here are a few videos from Motorcycle.com that show what a difference a belt makes in regards to suspension reaction to acceleration. Look at the way the Buell moves in the exact opposite direction when the throttle is applied with respect to the other two bikes, a Brutale and a Tuono. If anyone has an explanation for this, please let me know, because it baffles me. http://www.motorcycle.com/mo/mccompare/04_Streetfighters/photos/XB-12S_Dyno.mpg http://www.motorcycle.com/mo/mccompare/04_Streetfighters/photos/Tuono_Dyno.mpg http://www.motorcycle.com/mo/mccompare/04_Streetfighters/photos/Brutale_Dyno.mpg (Message edited by jandj_davis on September 14, 2005) | ||
| M1combat |
In your e-mail though... You mentioned that you were pretty sure that the rear of the bike squats down on acceleration... I think if you were to watch another buell (w/o it's tire strapped down anyway) you would find that the entire bike lifts. Damn that Brutale sounds good... Thanks for the videos. | ||
| M1combat |
I think it feels like the rear squats because the front comes up too, sometimes (especially in first and second  ) more than the rear. | ||
| Lovematt |
I can confirm the bike lifts under acceleration...I have the Woodcraft rearsets and the left side heel guard is removed as I like it better that way. As a result my heel touches the swingarm and my foot definitely slides up when on the gas and then back down upon letoff... | ||
| Henrik |
Anti squat depends on the angle of the swingarm in relation to the belt/chain pull. Most bike are set up for anti squat. However, if the rear of the bike is tied down during a dyno pull, or if a sizeable dyno tech sits on the bike during the run, you could change swingarm angle in relation to the belt, to alter anti squat to pro squat. It's all about the angle of the dangle Henrik | ||
| Jandj_davis |
So has anyone looked into this from a physics standpoint? Acceleration would cause the weight to want to shift to the rear, squatting the rear suspension. However, somehow the forces applied to the swingarm via the belt/chain cause the rear to lift. This means there is a significant downword force on the swingarm. If anyone has an explanation for this downword force, I would love to hear it. Diagrams would be awesome too. Thanks. Don't worry about going over my head either. Another thought, regarding Moto Guzzis and BWMs in particular, can you set up a shaft drive to be anti-squat? Wow, I love thinking about motorcycles. | ||
| Imonabuss |
What are you seeing in the video that I'm not? All three bikes have antisquat and lift the bike under acceleration. In no way does the Buell do the opposite. The Buell seems a little firmer in how it accomplishes this is all. Also, note how the chain flops around on the others. The Buells definitely have anti squat, and well done. It helps traction and keeps the bike from running wide in the corner. Another important thing is how whether and how a chassis maintains having anti squat as the suspension compresses. Some bikes have anti-squat at normal ride height, but when the suspension is compressed (like in hard cornering), the antisquat isn't there when you need it most! | ||
| M1combat |
If there was no damper or other method of stopping the rotation of the swingarm, The wheel would push itself up under the bike...  The relationship between the swingarm angle and the rake is a VERY important relationship. Any time the forks or swingarm move, the wheelbase of the bike changes. If the swingarm is very close to perpendicular to the forks, the wheelbase changes less. Stability  . This also gives you anti squat (which is good on a short bike), this also helps the rear of the bike to lower when the rear brakes are applied (this way the fact that we have 21 degrees of rake and a short wheelbase is somewhat mitigated... Smart fellers those Buell engineers... There's more to it of course . The engine IMO has a lot to do with the stability. I don't think the XB would be as stable with a rotax engine... | ||
| Jandj_davis |
My earlier post said "Nevermind." What it should have said is that after a second look, all three bikes do the same thing, but I still didn't understand why the rear lifted under acceleration. M1's diagram helped alot. Thanks. I still love thinking about motorcycles. | ||
| Reepicheep |
Joshua... Here is an overly simplified view... picture an XB with the swingarm pointing nearly straight down, and you accelerate. The belt can only pull, never push, so you are pulling hard on the top edge of the sprocket to turn it. But that same upper edge of the sprocket is still lined up such that if you pulled it in, the swingarm tries to rotate even further under the bike, so the bike is "lifting" or showing anti-squat characteristics. If the you started with the swingarm pointing straight up, you would get the opposite effect, and the bike would squat. So when you design the swingarm, you just need to make sure that a line going through the top of the front pully and the top of the rear pulley would pass below the axis of the swingarm pivot, and you have some level of anti-squat behavior. The real rub would be tuning and maintaining that behavior under all circumstances. | ||
| Reepicheep |
M1 types faster then I do |
