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Annoying Exhaust Problem

K

Kyle Boatright

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

Thanks,
 
Sump mounted exhaust hanger

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

Thanks,
 
Safety Wire

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.
 
I just went through this ordeal with my Vetterman exhaust. My setup is an o-320 crossover with mufflers. He recommends attaching to the sump with two tubes and two tubes to the mount. I think the trick is to only have 1/4 inch gap between the stainless tubes. He told me that was important. The tubes that are connected to the mount use adel clamps and the two at the sump have angle brackets that he supplies. Also the rubber hose is not fuel hose. It is transmission cooler line which he said is better. I bought a whole new set of stainless tubes, hose, clamps, and brackets for very little money form him last week. I haven't flown yet but everything feels nice and tight with no extra movement. One other thing he said was very important is to wipe the tubes down with acetone and pour a small amount down the hose pieces to get rid of any oils that might be on them. The heat from the exhaust will vulcanize the hose to the stainless tubes in short order and they will not move. I will post pictures tonight as I have the cowl back off dealing with a leaking carb issue.
 
When I built my RV7 I put a very small flare on the ends of the SS tubing going into the rubber tubing and never saw them move in over 200 hours. They were hung from the sump bolts.
 
Kyle Boatright said:
Can someone with the sump mounted exhaust hangars post a picture? It sounds like something that would be easy to fabricate.

Thanks,
Click to expand...


Kyle,
These pictures I found on a builder's website years ago and carbon copied it :)

View from the top


topview.jpg



Sides


side2.jpg



side1.jpg



Hangers view from the front


frontview.jpg



bottom.jpg



Below is hand drawing of the hanging system supplied by Larry Vetterman


plans.jpg


I hope you find it useful.
 
Not sure why Larry told me to do mine somewhat different unless it had to do with mufflers or maybe he changed the design later. The tubes coming from the sump are the same but I don't have the crossbar on mine. The second tubes go to the engine mount. One thing that could happen in the old design is both pipes could move left or right and maybe touch the lower cowl which was my problem.

EDIT: I just talked to Larry and he said there were 8-10 different installations depending on your set up. What is right for mine may not be the best for yours.
 
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Thanks alot to everyone, especially for the detailed pictures! I can figure out now, how the mount on the oil sump works. Hanging the exhaust to the oil sump does make a lot more sense to me, than to hang it on the engine mount. The exhaust will move with the engine this way, because there is no relative movement. This should induce less cracking problems. Of, course all depends on the location of the flexible points in the exhaust system as well.
 
Kyle, have a look at the first post here. The thread drifted into all sorts of reasons of why it won't work, etc., but a couple of us are trying the idea out (I've worked in product R&D for a few decades, so I'm quite used to the "help"...). I too had 1300 hours of maintenance pita's on the original system that I tired of. I've only got about 6 hours on the new brackets, and will report back in a few years. One planned modification next de-cowling will be to put another adel clamp on the vertical outboard motor mounts, and connect a strut to the bracket, to prevent any lateral movement of the system.
 
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