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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.

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  • Guest

    Hi Kevin,Peter here in CA (SZP) RV6 IO360 B1B Inverted system 4 pipe exhaust, RV8 rudder .020 tail skins.
    I have had some trials with Exhaust Hangars you may find of use. My pipes are attached to the sump via steel tubes (Vetterman supplied) with hose acting as a vibration damper between the tubes. Vetterman supplied the small 4130 brackets to attach to the sump to bolt the tube to. I found that I had to bead the tubes as the hose slipped down over time (witness marks) tube beading is hard on steel tube BTW. This is the solution that has worked for the last 160 hours. Others had failed, the #1 Cyl pipe once got loose and gave me a vibration like a very out of balance prop, necissiting imed landing. From my acrobatic days, pitts planes have caught on fire due to loose pipes. It is better for the pipes to move with the engine if possible (the 4 pipe system does not have ball joints on all pipes) My next door hangar mate is set up the same way on his 8. Better not to have to design mechanisms to take out so much slack. As I do lots of aerobatics my engine moves more than the usual acro pilot (so far I have done loops, slow rolls, hammerheads, pull pull humptys, pull push too, Cuban and reverse cubans, sawtooths, square and rounds loops 2 turn spins both directions, inv flight and turns. If I ever get any good in this plane I plan on flying sportsman.
    I hope this helps, better not to have to think about pipes.
    PS we cut our pipes so they do not stick out below the cowling

  • Thanks for the comments Pete. I'll attack this area again once it warms up. It is miserable working in the hangar in the winter.

    Kevin Horton