Bell 212 Main Rotor Head Construction

[ralphmalph]

Hey,
Could anyone point me in the right direction (or explain if possible?) to an explanation of the purpose of the weights on a 212 rotor head?. Have seen them on other types at different angles and have had a good look through websites with Sikorsky and Hafner references but no avail!

Cheers

[Ascend Charlie]

Are you talking about the weights on the end of the stabiliser bar at right angles to the blades?

The bar acts as a sort of gyroscope for stability. The control input goes from the pilot controls via mixing levers to the swashplate. Then up the control rods to the stab bar, where through a system of levers, about half of the input goes straight to the blades, and the rest of it goes in gradually- the rate of input depends on the springs in the stab reservoirs, which have to return to the middle from full displacement in less than 6 seconds.

Similarly, if the blades get moved by turbulence, the stab bar takes out half of the input and smoothly puts the rest in. Or so the theory goes.

When Bell got to the 206 series, they worked out that the stab bar could be disposed of.

[chuckolamofola]

If you are talking about the weights on the pillow blocks then those weights are used for static balance of the hub and yoke assembly prior to installing the m/r blades.

Regards,

Chuck

[ralphmalph]

Thanks guys,
Thats exactly what I was after.
Cheers