While it certainly is a good idea to relieve enough stress in your life to ensure that you stay healthy and keep your medical, that is not what I am going to write about!
No, I am talking about preload and residual stress in the assembly of our aircraft. this thought came to me tonight while I was re-installing my wheel pants. When I put in the two screws that hold the rear half of th pant to the bracket, it was wonderful how the bolt that holds the outboard side fell perfectly into the hole in the axle nut. I didn't have to do any bending, twisting, or forcing of the pant to get it to line up. In contrast, I remember how awful it used to be putting the wheel pants on my factory-made Grumman - lots of pulling to get things lined up. And guess what? There was a whole lot of wear on those Grumman pants!
Avoiding assembly preload is a great way to avoid having your airplane's parts wear against each other. Fasteners (screws, bolts, etc) should HOLD things in position, not force them together, or into alignment. he resulting wear from having a piece held out of it's natural shape by a fastener can lead to cracks, enlarged holes, and warped bits and pieces - it is more easily seen in fiberglass parts, as fairings deform, but is also a big cause of wear and cracking in metal parts.
You can avoid preload by carefully aligning things during construction. Any time you have to force parts together, then quickly slip in a bolt to hold them you have set up a preload condition. Stop, go back, and make the parts fit together naturally. It may take more time in the building, but believe me, it will save tons of time and stress (YOUR stress this time) in the field when you are flying - and have to stop flying to make a difficult repair down the road.
Paul
No, I am talking about preload and residual stress in the assembly of our aircraft. this thought came to me tonight while I was re-installing my wheel pants. When I put in the two screws that hold the rear half of th pant to the bracket, it was wonderful how the bolt that holds the outboard side fell perfectly into the hole in the axle nut. I didn't have to do any bending, twisting, or forcing of the pant to get it to line up. In contrast, I remember how awful it used to be putting the wheel pants on my factory-made Grumman - lots of pulling to get things lined up. And guess what? There was a whole lot of wear on those Grumman pants!
Avoiding assembly preload is a great way to avoid having your airplane's parts wear against each other. Fasteners (screws, bolts, etc) should HOLD things in position, not force them together, or into alignment. he resulting wear from having a piece held out of it's natural shape by a fastener can lead to cracks, enlarged holes, and warped bits and pieces - it is more easily seen in fiberglass parts, as fairings deform, but is also a big cause of wear and cracking in metal parts.
You can avoid preload by carefully aligning things during construction. Any time you have to force parts together, then quickly slip in a bolt to hold them you have set up a preload condition. Stop, go back, and make the parts fit together naturally. It may take more time in the building, but believe me, it will save tons of time and stress (YOUR stress this time) in the field when you are flying - and have to stop flying to make a difficult repair down the road.
Paul
