fiebichpvFebruary 4, 2021, 10:34pm
Strut-to-wing attach update
Several months ago I posted photos of the replacement strut update I made on my AirBike. In that post, Scott Peterman noticed an installation arrangement that would cause a bending moment on the bolt holding the assembly to the wing. The strut centerline was not in line with the spar brackets but was offset. Taking his observation and concern seriously, I redesigned that installation.
Replacing the block that formed the "universal joint" with rod end bearings brought the strut centerline in line with the spar brackets. Due to differences in the rod end bearing size and the bolt holding the assembly to the wing, some additional hardware was needed.
The rod end bearing's I.D. was and An-5 while the bolt holding the assembly to the wing was an AN-4. Also, the rod end bearing's thickness was less than the aluminum block initially used. To fill the remaining space, on my lathe, I machined a spacer from aluminum rod stock having a spherical radius on one end, and after facing the other end, a chamfered edge. A 3/8" hole was then drilled through its center. I did not drill out the strut bracket to 3/8" and replace the AN-4 bolt with an AN-5 bolt because that would have resulted in insufficient edge margin on the bracket.
A bushing made from 3/8" O.D. and 1/4" I.D. steel tubing was cut to a length equal to the combined length of the rod end bearing's width and the aluminum spacer.
During assembly, the AN-4 bolt and flat washer is inserted into one strut bracket, through the bushing, spacer and rod end bearing, then if needed, additional washers then through the other strut bracket. Then the protruding bolt could be secured with another flat washer and a Nylock nut.
Notice that the first photo below shows the attachment in the position Scott observed to cause the bending moment. Other photos are of the update from that condition. Notice in the last two photos that the diagonal brace wire has not been taughtened, once is has been, it clears the strut.
Update on the AirBike has been made.
Thanks for your sharp eyes Scott.
Paul Fiebich
a.ka. AirBike Ace
Several months ago I posted photos of the replacement strut update I made on my AirBike. In that post, Scott Peterman noticed an installation arrangement that would cause a bending moment on the bolt holding the assembly to the wing. The strut centerline was not in line with the spar brackets but was offset. Taking his observation and concern seriously, I redesigned that installation.
Replacing the block that formed the "universal joint" with rod end bearings brought the strut centerline in line with the spar brackets. Due to differences in the rod end bearing size and the bolt holding the assembly to the wing, some additional hardware was needed.
The rod end bearing's I.D. was and An-5 while the bolt holding the assembly to the wing was an AN-4. Also, the rod end bearing's thickness was less than the aluminum block initially used. To fill the remaining space, on my lathe, I machined a spacer from aluminum rod stock having a spherical radius on one end, and after facing the other end, a chamfered edge. A 3/8" hole was then drilled through its center. I did not drill out the strut bracket to 3/8" and replace the AN-4 bolt with an AN-5 bolt because that would have resulted in insufficient edge margin on the bracket.
A bushing made from 3/8" O.D. and 1/4" I.D. steel tubing was cut to a length equal to the combined length of the rod end bearing's width and the aluminum spacer.
During assembly, the AN-4 bolt and flat washer is inserted into one strut bracket, through the bushing, spacer and rod end bearing, then if needed, additional washers then through the other strut bracket. Then the protruding bolt could be secured with another flat washer and a Nylock nut.
Notice that the first photo below shows the attachment in the position Scott observed to cause the bending moment. Other photos are of the update from that condition. Notice in the last two photos that the diagonal brace wire has not been taughtened, once is has been, it clears the strut.
Update on the AirBike has been made.
Thanks for your sharp eyes Scott.
Paul Fiebich
a.ka. AirBike Ace
