Running without a torque tube center bearing ?

[Gary in La.]

A tubular driveshaft will whip if it is fairly long. The Hughes 500 (369) helicopter had a large diameter aluminum driveshaft for the tail rotor drive but at midpoint there was a damper encircling it to minimize whip.

[rotorwrench]

Originally Posted by Gary in La.

A tubular driveshaft will whip if it is fairly long. The Hughes 500 (369) helicopter had a large diameter aluminum driveshaft for the tail rotor drive but at midpoint there was a damper encircling it to minimize whip.

All of the Hughes light helicopters use the specially formed aluminum type drive shaft. These tubular shafts were designed to be able to flex a bit plus be light weight. The tail booms on the 500 and 300 aircraft flex too with strong tail rotor inputs. They shimmy a bit and can whip under extreme torque pressures so a damper was necessary for these types. Bell's shafts were supported so they didn't need dampers. Robinson uses long small diameter steel shafts but they put a damper in there due to the long length and small diameter. It also protects the couplings on both ends on shafts that have dampers.

The tubular shafts for the early Fords up to 1938 or so were either short enough or well shaped & large enough plus being fabricated from steel, that they didn't need a damper to calm the shimmy that naturally happens with long solid shafts or smaller diameter shafts. Dampers also help protect the U-joints on the shafts that use them.