Balance and centrifugal force?

[GrantR]

If you have a 60 inch prop that takes 1.5 ounces added to one tip to make it balance, how does centrifugal force effect the prop?

Prop rpm is 2519 and the diameter is 30 inches. These numbers put into this (http://www.calctool.org/CALC/phys/newtonian/centrifugal) calculator give a centrifugal force of 556 pounds of force. So does that mean when the prop was out of balance the heavy blade was pulling 556 pounds more on the hub center than the light blade?

[hillberg]

556 inch pounds?

[L_Butler]

The force on the hub due to the 1.5 oz weight is 506 lbs when on a 60" diameter (30" radius) prop.

Now you see why balancing your car tires makes such a difference.

[RotoPlane]

Hmm….I would say that something is terribly wrong with that prop….like the light blade root is not all the way out to the end of the hub socket. 507 lb. would tear that engine from your aircraft!

[GrantR]

That’s only if the 1.5 ounces is added 30" out correct?

If one blade is 1.5 ounces heavier than the other wouldn't the extra weight pull against the hub center from the heavy blades center of mass since the overall mass is heavier and not just concentrated at the tip?

[RotoPlane]

That’s only if the 1.5 ounces is added 30" out correct?
Yes.

If one blade is 1.5 ounces heavier than the other wouldn't the extra weight pull against the hub center from the heavy blades center of mass since the overall mass is heavier and not just concentrated at the tip?
Yes.

For a smooth prop, both blades must have their CG at the same distance from the hub center....and they must weigh the same at that CG point.

[Jean Claude]

If you have a 60 inch prop that takes 1.5 ounces added to one tip to make it balance, how does centrifugal force effect the prop?

Prop rpm is 2519 and the diameter is 30 inches. These numbers put into this (http://www.calctool.org/CALC/phys/newtonian/centrifugal) calculator give a centrifugal force of 556 pounds of force. So does that mean when the prop was out of balance the heavy blade was pulling 556 pounds more on the hub center than the light blade?

This is true only if the engine is completely rigid. But this is not possible. While the effort depends on the rigidity of the support. If the hub is totally free, then there is no effort. Just a movement around the center of mass. If the propeller weighs 6 pounds, then the hub moves on Radius 1 / 4 "
Jean Claude