coriolis effect

[ftbl74]

I am learning about coriolis effect and they mention center of mass alot in the books I read. But I can't find any information on what the center of mass is. So if anyone could help me to understand that I would be grateful. Thanks, Michael

[DakarNick]

Here you go: http://en.wikipedia.org/wiki/Center_of_mass

 

Basicially, it is the where the mass of the blade would act if all the mass was concentrated there. If the blades are rotating in single plane, each blade has it's center of mass at a certain point. With increased coning angle the center is more inward (closer to the hub in the horizontal plane) than with less of an angle. It is very similar and acts the same way as the center of gravity.

Edited November 12, 2008 by DakarNick

[Eric Hunt]

Get a ruler or straight stick, and balance it horizontally on your finger. Clearly, there is mass all along the ruler, but it acts as if it is in one place, directly above your finger. That is your centre of mass.

 

For the Coriolis effect, as the back blade cones up, the effective horizontal distance of its centre of mass moves closer to the axis. With conservation of angular momentum, the blade wants to turn faster (think of your spinning ice skater pulling her arms in) and the front blade, which has gone from being a bit coned up to being closer to the horizontal, wants to slow down.

 

This induces some big forces in the rotor head, fixed either by making it very strong, or by allowing lead and lag.