What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Priming inside pushrods and torque tubes

SabreFlyr

Well Known Member
Sponsor
First off, the easy questions. One, how do you determine how much primer to mix for a given length and size of tube? Second, should the outside of 4130 tubing also be primed?

Also, I recently saw a video, I think on YouTube, showing a novel way to prime the insides of pushrods. This gentleman suspended the pushrod vertically from the ceiling with a rag stuffed a few inches down from the upper end and a string tied on the rag and extending out the bottom end. He then poured a quantity of his mixed primer into the top of the tube and then proceeded to slowly pull the rag down through the tube. He ended up with the inside fully and evenly primed with no runs. Now I’m getting ready to work on my aileron pushrods and would like look at that video again with the idea if using that technique. I suspect that I can figure it out well enough for myself but would like to review the video for any missed details. Of course I can’t find it. Did anyone see that video and remember where they saw it?
 
I didn't see the video...... But, I tried not to overthink this.

I used 2 part epoxy primer (Azko). Mixed up what I though would be enough by eyeballing it (doesn't take a lot, I had plenty of waste). Poured slowly down one end of the tube while rotating. Had a plastic bucket at the end to catch everything. Left it sitting up against the wall to drain out excess. Interior looks evenly coated.

Yes on priming 4130.
 
Primer

Check my blog. Neat trick for priming tubes. Cut fingers off Nitrile glove. Slip one over the end of the tube. Pour in primer. Slip one over the open end. Slosh. Remove.

Coverage calculator is also on my blog. Typically I got from 2-3 ft² per ounce. Calculate area of a cylinder using an online widget and go from there. 2"x48" tube is about an ounce of mixed paint.
 
As info, when I primed mine, I leaned you need to let them fully dry/set before you install the rod ends. I ruined all six on the aileron/elevator push tubes. The out gassing will freeze up the ball connector. I just couldn’t get them free enough to work the way I wanted. Not real expensive, but very inconvenient.YMMV Bob
 
Didn't prime, I used Chemetall Ardrox AV-8 anti corrosion preservative. Spray some in, let drain to bottom, invert and let it drain out. Leaves an anti corrosion film on the inside. I did this after I attached any ends to the pushrod or torque tube (including the elevator torque tube brackets).
 
Thanks, guys.

One of my concerns about sloshing the primer per (I think) Van's instructions is that it seems too easy to get less than full coverage.

Larry, I'll take a look at your blog. I've got it pulled up in another tab in my browser but looking at your fiberglass work.

AV-8? Never heard of it. I'll take a look.
 
Check my blog. Neat trick for priming tubes. Cut fingers off Nitrile glove. Slip one over the end of the tube. Pour in primer. Slip one over the open end. Slosh. Remove.

Coverage calculator is also on my blog. Typically I got from 2-3 ft² per ounce. Calculate area of a cylinder using an online widget and go from there. 2"x48" tube is about an ounce of mixed paint.
I did similar except I just used masking tape to seal the end of the tubes. Not ideal but I had lots of tape handy. Not sure on the amount of primer I mixed up but it was probably about half a dixie cup.
 
Back
Top