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Where would I ask a math question?

Posted by davestexas (My Page) on
Sun, Dec 23, 12 at 11:55

H-D motorcycles have a bank-angle sensor that comes into play at a 45° angle. The engine shuts-Off automatically when the bike is at a 45° angle for 1-second.
The math problem concerns what angle would have to be achieved to get the lower muffler-shell in contact with the ground. I believe that angle would be at/close to sensor setting.
I'm thinking engineers have a math-formula for something like that.
There are riders claiming they are scraping their lower-muffler shell when making fast turns. I say BS. I don't believe a Harley tire can go that degree and have traction, much less than scraping a muffler-shell that is 9" off the ground when the bike is parked at vertical.
Is there a way for a math-challenged guy to make that angle calculation or the right place to ask? The MC forums are of no help with this....
Thanks for any replies

Merry Christmas!


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RE: Where would I ask a math question?

The ansewer to your question is: It depends. You can scrape parts when leaned over in a curve and that lean angle varies. You viewed your motorcycle when it was parked and you saw road clearance of 9 inches. You were not sitting on it, right? Have someone about your weight sit on the bike and hold it vertical and then measure the clearance. I'll bet it is less than without a rider.

Now, this is the clearance at one gravity with the bike vertical. Lean the bike over 45 deg and take a look. Is stuff getting nearer to the ground?

A big variable is increased acceleration while in a curve. When you've got the bike leaned over in a fast turn, you are pulling more than one gravity in the direction with respect with the bike. The faster the turn, the greater the acceleration. Now while heeled over in a turn, hit a bump or undulation and the suspension compresses farther. How far depends on the rider's weight, speed, sharpness of the curve, and severity of the bump. There is no one fixed answer. The answer depends on all these factors. The suspension spring stiffness is a factor also.

Another factor is the amount of tail pipe extension. If your mufflers pass below the rear axle and extend as far as the rear fender, the end of the pipe heads toward the ground faster than the seat does. The degree is increased as weight is moved toward the rear. The farther back you move, the more the rear suspension compresses. Dressy road bikes with long and low pipes are subject to this effect. You'll note that sport bikes and scramblers that are expected to be ridden agressively and on rough terrain have pipes that are high mounted, angled upward, or do not extend beyond the rear axle.

Scrapping the tail pipe is sometimes due to owner after market modifications.


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