Originally Posted by
Speed of Sound
Has anyone actually calculated the torque required to move the stabiliser under maximum aerodynamic load? As the friction forces to be overcome on the threads of the screw-jack will increase exponentially as it moves towards maximum load, adding an electric servo as a solution may need to be done in conjunction with a redesign of the screw-jack mechanism to cope with this additional force.
Its not really the friction forces per se that are the problem- The jack screw uses a recirculating ball bearing ' nut' on the jakcrew which is then attached to the stabilizer. The the actual design- installation must take care to use a nut- screw thread combination to prevent being back driven ( eq ' nut' rotates even when jack screw does not ROTATE. ) . Cant post links - but look up ball screw calculator for example. Boeing has used the ball screw arrangement for decades- probably since the 707 for such actuation..
Last edited by Grebe; 28th Sep 2019 at 02:48.
Reason: changed jackscrew move to ROTATE for clarity