Overview
When flight testing the Tucano, the effort to operate the rudder was a little heavier than the rest of the other circuits.
Luigi Ferrando contacted me by email regarding this comment and stated that he had installed ball bearings into the pulleys of his Tucano and was happy with the improvement.' Roller bearings generally provide 1/10 or better less friction than a plain lubricated bearing. Another advantage is that they have tighter internal tolerances at the running faces reducing any potential excessive clearances in service.
 |
| Cables will be tensioned to 50 lbs with an estimated drag of 0.15 lbs 100 lbs used in error for calculation but loads proportional to tension load used |
Installation
It was decided that the simplest way to add bearings was to install 16 mm OD x 12 High x 6 mm ID needle roller bearings making the machining easier and reducing the amount of material to be removed.
The pulleys were removed from the aircraft, and then the factory lubricated dry bushes. With the pulleys in the chuck, these were bored to 16.7/16.8 mm OD to create a force fit with the needle roller bearing outer.
Note: Nylon will expand quickly under any pressure, so an undersize hole was employed. The selected bore could be a little tighter but its a balance between to much internal pressure in the nylon and grip.
With the holes prepared, the outer was inserted in the press with high strength Loctite applied to the outer surface of the bearing to ensure a tight bond.
Comment
The last job in rudder circuit - hope to tension cables soon and then lockwire before installing the wings.
Lots of small jobs underway to finish so not a lot of blogs - follow the weekly grind on Facebook - Gary Spencer-Salt
No comments:
Post a Comment