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Steel into aluminum

Plummit

Plummit

Well Known Member
I was able to check the breakout force tonight and it was good so I didn't have to adjust. I was a little dismayed that the wheel pant cap screws seem to be galling the aluminum fork a bit and I was surprised that they were threaded into tapped holes in the fork. I feel that this is a weak spot and I imagine that at some point the holes will have to be drilled and tapped to the next size larger cap screw. Anyone else experience this?

~Marc
 
Plummit said:
I was able to check the breakout force tonight and it was good so I didn't have to adjust. I was a little dismayed that the wheel pant cap screws seem to be galling the aluminum fork a bit and I was surprised that they were threaded into tapped holes in the fork. I feel that this is a weak spot and I imagine that at some point the holes will have to be drilled and tapped to the next size larger cap screw. Anyone else experience this?

~Marc
Click to expand...

Stainless is quite a bit harder than aluminum and can easily deform the threads, especially with repeated mate/demates. I would consider installing an insert, like a helicoil, to protect the aluminum. Damaged helicoils are easier to replace than having to drill and tap to the next size.
 
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I put a little Anti seize on the threads and re-installed the existing cap screws. I know that I don't have 100% threads as there was some aluminum that came out with the bolts.

The reason I considered going to the next larger size is because the cap screws are also where you hook a tow bar/ tug, so it could possibly be beneficial. There could be some heavier shear loads on the bolts when pushing back into the hangar. I'm not as worried about the bolts as the aluminum they are threaded into.... Helicoils sound like they might be an answer, but I wanted to see if anyone else had this problem.

~Marc
 
These are easy to cross thread when starting. Check the start of the threads in the aluminum and carefully countersink with a large drill by hand if they are damaged there. If you have or can get a tap, run it thru the holes and then clean it out.

Clean the bolts and, as suggested, use Beolube which is made for aluminum. Getting the bolts and holes in the bracket aligned can be difficult.

When pushing or pulling the airplane the bolts are shear loaded. If you lost 95% of the threads there would be no issue except they might vibrate out. A Helicoil would solve all the problems.
 
Thanks everyone for the suggestions. I'll helicoil the holes and maybe even install longer bolts for more secure tug operation. To be continued....

regards

~Marc
 
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