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The flap drive tube is supported by the flap mount blocks which are bolted to the airplane with AN3-21 bolts. Can anyone recommend a torque value for these bolts. The tube is level & true etc but it seems that if I go past 20 on the T wrench it gets stiff..rotatable but stiff. The blocks are made from Delrin and I'm wondering if this stuff compresses. Tube is cleaned and lubed. I even put small alum foil shims between the blocks.
Any thoughts/recommendations would be appreciated.

peter

SNB0021
Wings, Tail, Control Surfaces, Tailcone done...getting ready to make something else twice.

pfhoeycfi wrote:The flap drive tube is supported by the flap mount blocks which are bolted to the airplane with AN3-21 bolts. Can anyone recommend a torque value for these bolts. The tube is level & true etc but it seems that if I go past 20 on the T wrench it gets stiff..rotatable but stiff. The blocks are made from Delrin and I'm wondering if this stuff compresses. Tube is cleaned and lubed. I even put small alum foil shims between the blocks.
Any thoughts/recommendations would be appreciated.

peter

SNB0021
Wings, Tail, Control Surfaces, Tailcone done...getting ready to make something else twice.

Hi Peter, this doesn't answer your question but I'm wondering, did you remove the powder coat from the tube where it passes through the blocks? You may have meant this when you said it was "cleaned and lubed" but just want to be sure. The powder coat can cause gumming/binding.

That said, as long as the block halves are pressed together such that they wont be wobbly or leave a gap for the tube to work into, the nuts just need to be tight enough for the nylock to be fully engaged and secure the blocks. The bolts aren't subject to rotation and shouldn't be going anywhere. If I were to choose one of the bolts to be tighter than the other (for ease of movement), the forward bolt on each block is where aerodynamic pressure is going to be most forcefully applied so I'd want to be sure the block is tightest on the forward side.

Another option would be to just sand out the holes in the blocks to make them a little bit bigger, I think I did this several times before I was happy with the fit.

Yes I had taken the coating off will a torch. I'll try your suggestions. I wasn't sure about sanding the delrin block given how smooth it is to begin with. I was prob overtightening...
Thank you,
Peter