I tried to check my plate for smoking rivets today, but the shop head is against the flywheel and I can't see a thing.  The round heads all seem fine.  Couldn't detect any that seem loose or smoking or anything.  Will just have to keep an eye on it.   David Leonard

 

Dave; there is a way to check.

 

I went for further checks on mine today – had to make the decision whether or not to fly it to Jean, NV, on Saturday for the CONTACT! Alternative Engine Fly-in.  (First I went flying for about an hour just to make sure I wasn’t going to be deprived of my enjoyment before I had to fix itJ)  I went to look for loose rivets, or to see is I could detect any relative movement between the spline adapter flange and the aluminum plate.

 

No way to get at the heads of the rivets without disassembly, and everything ‘looked’ fine on the front side of the flange. So I pressed my fingertips onto the plate, overlapping them onto the beveled edge of the flange; then pulled a prop blade back and forth with the other hand. I could detect that there was relative movement; however miniscule, as in maybe a few thousandths max, but it was there. I could not detect it visually, but I could feel it.  So after some considerable deliberation, I decided that this should be fixed before more flying. 

 

I suspect if I done the same thing many flight hours ago it would have been similar, so a few more hours wouldn’t really matter, but I had to consider that aluminum rivets will work-harden, and become brittle, and then at some point possibly subject to breaking, especially if there is any operating regime where there could be torsional vibration with force reversal.  No way of knowing when that point would be reached.

 

So I think you should give it the ‘sensitive fingers’ check, and feel for relative movement. Not that you necessarily have to replace the rivets right away, but if you are quite certain there is any relative movement it is definitely a cause for concern, and should be checked again after a few hours and see if you can detect a difference.

 

I’m planning on replacing the rivets with AN173-6A bolts, with MS21042-3 metal lock nuts over AN960-10L washers. Maybe Mark can tell us if the thin washers are enough to sure the threads don’t bottom out. About 4 or 5 of these bolts would be as strong as 20 aluminum rivets, but I guess all 20 would be good to distribute the stress in the aluminum plate.

 

Al G