Annoying Exhaust Problem

[Kyle Boatright]

I have the standard Vetterman exhaust with the hangar system he provided back in ~1999-2000. The system has two downrods that hang from the engine mount using adel clamps and a crossbar that goes between the two pipes. There are small pieces of aluminum angle that provide a locating point for the vertical and horizontal attach points. Both the horizontal and vertical hangars/spacers use welding hose for shock absorption.

Anyway, the issue is that every 5-10 hours, the exhaust pipes rise up and contact the firewall flange. I don't know if the cause is exhaust pulses, the slipstream, or whatever, but I'm tired of having to reach under the belly of the airplane and push/pull on the exhaust pipes to re-center them vertically in the air outlet.

I've tried adjusting the geometry of the exhaust hangars, but the problem always comes back.

Has anyone else experienced this? Suggestions? Solutions? Is there a revised exhaust hangar system that has proved trouble free? FYI, I seem to break something in the exhaust hangar system every couple hundred hours, and wouldn't mind installing a hangar system that's a bit more robust.

[Walt]

My Vetterman exhaust has been trouble free other than replacing the hose (reinforced fuel line) about every 2 years. My hangers are from 2 sump bolts and then the single cross brace between the L/R pipes.

I can always tell when the rubber starts to get hard and slip, the pipe starts to sag down and I start losing the clearance between the pipes and the cowl.

[jsharkey]

The newer mount attaches to the rear sump flange of the engine using two of the existing 1/4-20 bolts that screw into the crank case. It means that you don't have relative engine motion issues - but I recently lost both of the bolts at around 60 hrs. I also noted that the vertical hose "shock absorber" on one side has become "soft" - as if the material has degraded leaving the braided core to extend.

Jim Sharkey
RV-6

[rvbuilder2002]

Walt and Jim are right.

Hanging from the engine mount does not work.

[hgerhardt]

Definitely change the mounts to hang from the sump bolts instead of the engine mount.

But other than that, my -6 Vetterman setup has also tends to push up the RH tailpipe until it contacts the fus. I had to insert a piece of steel tubing inside the rubber hose to keep the hose from collapsing. I cut the intermediate tube exactly the length of the space between the upper and lower support tubes so that it would butt between the support tubes. That solved the problem.

[Bob Axsom]

I hang the exhaust support from the engine mount and have no trouble with it. The metal support parts used with the clamps and the tubing are stainless steel tubing. I had a problem with the initial tubes in that they were flattened hard at the ends and they cracked and broke at the crease at the transition from the flat to the tube. I bought new ss tubing from Aircraft Spruce and flattened it with a hammer in a way what "softened" the transition and none of them have broken since. I also cut off the turn-down tips for speed so maybe that is a factor in the lack of mount deterioration. 6 years and ~600 hours WOT except for landing leaned for power, Cruise RPM 2450, Race RPM 2720 (haven't figured out to get higher yet), LASAR ignition.

Bob Axsom

[Kyle Boatright]

Can someone with the sump mounted exhaust hangars post a picture? It sounds like something that would be easy to fabricate.

Thanks,

[Clouddancer]

I would be very interested to see a picture of such a sump mounted exhaust hanger as well!

Thanks,

[johnfurey]

I used to have problems with the pipes slipping down but several years ago I ran twisted safety wire from the top bolt to the bottom bolt along side of the tubing and never had another problem.

[Doug]

http://bypass.dyndns-free.com/MyRV6/engine/IMG_5841.JPG

This method has been tried and tested on numerous local RVs, the arrangement was pioneered by Simon Pike (probably up to about his 10th RV now).

The support is steel angle approx .125 X .75 x .75.

Doug Gray