I also noted when I had the cowlings off that both exhaust hangar Adel clamps had broken at the engine mount. I had one clamp break a few flights ago, and now there were two more. The problem is that the exhaust moves with the engine, but the engine mount is fixed. My exhaust system is an early RV-8 system, with very short rubber pieces that attempt to allow some movement between the exhaust pipes and the engine mount. There is only about 3 inches between the bolt on the Adel clamp and the bolt at the exhaust system. The metal tubes that the rubber hoese pieces are clamped too take up about two of those three inches, so there is only about one inche of rubber tube that can flex. Not enough.

Apparently this design has had a high failure rate, and the currently shipping exhaust systems have long supports that attach to the bolts at the back of the oil sump. I studied that as a possible mod, but I’ve got a heat muff that is in the way.

I looked at one of the Mooney’s in the same hangar. The back end of its exhaust system is supported from the firewall area, hanging from springs.

I went to a local hardware store that had a large selection of springs, and picked up a couple to experiment with. I stretched the springs to make some space between the coils, and I squeezed the loops at the end to reduce the diameter, and twisted the springs to get 90 degrees between the loops on each end. The spring as I bought it is on the left, and the modified one on the right.

We’ll see how this experiment works out.