chassis stiffness on motorcycle 1

[m.piron]

It's a well known engineering rule that inside a component, the change of section must be gradual, to not create a stress-concentration zone.
But the same rule should be applied between components?
I'm thinking about the motorcycle fork and the motorcycle chassis: when braking, the fork and the chassis flex.
Thus, the longitudinal stiffness of the chassis should be the same of that of the fork, to distribute the stress between the fork and the chassis?

 

[SuperSalad]

Chassis and suspension components (stiffness only being one aspect of their design, albeit an important one) is a fairly complex science.

For performance, race teams and manufacturers have invested huge amounts of money into these designs and they are constantly trying to improve them.
MotoGP Chassis Wars

For reliability, I'm not sure if there are any real widespread problems. So I would think it is well understood in the industry.

I don't know if uniform stiffness would be desirable though.

Andrew H.

http://www.mototribology.com

 

[3DDave]

The force isn't distributed during braking, it is transmitted. That is, a force that is applied at the ground through friction as modulated by the leverage of the brakes on the wheel is carried throughout the motorcycle and to the rider. That force must be transmitted to the mass of the motorcycle and the rider to change the momentum of that mass.

By definition there is a discontinuity between the forks to allow them to rotated, at the axle to allow the tire to rotate, and so forth.

In some applications there is a concern for what is called elastic matching. In the case off a horizontal pulley shaft it is beneficial if the bearing supports rotate to match the bending deflection of the shaft as load is supplied to allow the bearings to remain aligned with the local slope of the shaft. In the case of the fork, it ideally acts as a cantilever and the ideal condition is very high stiffness to prevent oscillation.