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- Feb 2, 2016
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Hey guys,
as I moved on with the build of my Ultimate I came across the part of the 10-200 plans where the pushrods have to be bent. Both the elevator and aileron pushrods shall be bend to allow clearance to either the bottom ribs or the torque tube of the stick itself. Bending pushrods is something that absolutely scares me.
Since the loads on the aileron are relatively low I don't bother with the bend Pushrods here, but I'm scared of the pushrod from stick to first idle on the elevator. JAR23 demands 300 N force on the stick in aileron direction and 745 N in elevator direction. Taking the leverage into account (4:1) this equals ~3000 N on the pushrods of the elevator. I just did a simple test (in direction of the tube of course) with my own bodyweight (~100 kg) on the bend pushrod - it was deformed about 1 mm after the test - so I'm pretty sure that it will buckle with the higher load. (We don't talk about tailslides or torque rolls with a hard knock over which might result in even higher loads...)
The tube is 5/8*.035 which is prone for buckling, especially if it's bend. My intention now is to increase the size to .049 or even .058. I'll do a FEM calculation on it on monday but still I'd like to hear your experience on bend pushrods. I know that the aileron pushrods on the Pitts S1 are bend, too - but not the elevator pushrods. Please let me know what you think about it, in an airplane that is going to be pushed to every limit.
Second thought I have is about tailslides. I heard that there are some mods that should be done if you want to do tailslides. Are there additional elevator stops or something? In my oppinion it would be good to have suchs stops that hit after the stops on the stick. This way one would also have the damping of the pushrods itself and would - in case of a really hard knock overs - hit the stop before the drive system gets damaged.
Thank you guys for the help. See also the attached pictures.
as I moved on with the build of my Ultimate I came across the part of the 10-200 plans where the pushrods have to be bent. Both the elevator and aileron pushrods shall be bend to allow clearance to either the bottom ribs or the torque tube of the stick itself. Bending pushrods is something that absolutely scares me.
Since the loads on the aileron are relatively low I don't bother with the bend Pushrods here, but I'm scared of the pushrod from stick to first idle on the elevator. JAR23 demands 300 N force on the stick in aileron direction and 745 N in elevator direction. Taking the leverage into account (4:1) this equals ~3000 N on the pushrods of the elevator. I just did a simple test (in direction of the tube of course) with my own bodyweight (~100 kg) on the bend pushrod - it was deformed about 1 mm after the test - so I'm pretty sure that it will buckle with the higher load. (We don't talk about tailslides or torque rolls with a hard knock over which might result in even higher loads...)
The tube is 5/8*.035 which is prone for buckling, especially if it's bend. My intention now is to increase the size to .049 or even .058. I'll do a FEM calculation on it on monday but still I'd like to hear your experience on bend pushrods. I know that the aileron pushrods on the Pitts S1 are bend, too - but not the elevator pushrods. Please let me know what you think about it, in an airplane that is going to be pushed to every limit.
Second thought I have is about tailslides. I heard that there are some mods that should be done if you want to do tailslides. Are there additional elevator stops or something? In my oppinion it would be good to have suchs stops that hit after the stops on the stick. This way one would also have the damping of the pushrods itself and would - in case of a really hard knock overs - hit the stop before the drive system gets damaged.
Thank you guys for the help. See also the attached pictures.
