Exhaust hanger critique

Wanted to see if the more experienced than me on here thinks I did this somewhat right. It's a Vetterman trombone exhaust. Upper support connected to oil sump bolt. I tried for at least 1/2 inch of clearance around anything. I'm not sure how much this will move on start up so is 1/2" enough? There are some temporary bolts holding things together so don't critique me on using the wrong hardware . Thanks!!

Exhaust

I have never had much luck with adel clamps for anything with potential for a lot of movement. There are similar clamps available which are used on steel tubing with no cushion. They clamp really tight and usually will not hurt epoxy paint. Umco JJ-12 is one example. That would be for 3/4 tube. They are very hard to find.

Thanks for sharing. I think it looks fine... I will critique (for which you pay nothing and it is worth every penny of that) there is no support in the vertical direction, up down.... The strap going forward to the engine... yeah its all connected to engine so they all move together. Not sure it is doing much in supporting, but will dampen the pipe vibration. It looks good to me... Nice workmanship.

So strap side to side is on engine mount, which is typical. Engine shakes like a wet dog when starting and shutting down. However the rubber hose will slide off if pulled or buckle if pushed on. Don't think it hurts. However I would love to see an experiment where the total deflection is measured. Most of the engine is deflection is rotation around crank and nose of engine going down with "G" force.

Pipe support for vibration on airplanes is a weird deal. On one hand you may be hurting more than helping by restricting pipe moving with engine to a fixed engine mount. The pipe of course is supported by the flange at the exhaust port and the two bolts. Pipes are cantilevered off engine HANGING down. So the vertical support would help and be tolerant to engine rotating around the crank... This is my theory and sticking to it. However if the goal is dampen vibrations your setup looks fine.

gmcjetpilot said:

. However the rubber hose will slide off if pulled or buckle if pushed on. Don't think it hurts. However I would love to see an experiment where the total deflection is measured.

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I was concerned about this on my 6. I sanded the SS tubes and cleaned them and the ID of the rubber tube with laquer thinner to get rid of release agents. I wanted to adjust one of them at 50 hours. The rubber had fused to the SS tube (likely due to the clean surfaces and the elevated heat seen) and I had to pry it off with a decent amount of force. It was apparent that the tube was not moving inside the hose. I was happy that it worked. In my case the vertical support is truly vertical and mounted to the engine mount. It uses a bar with two adel clamps that also are not moving after 600 hours. This works because the cross over exhaust has ball joints to allow flexing. It actually helps to keep the joint supple and not sieze up. Though I use the mouse milk pretty often on them.

I had seen this type of fusing with rubber radiator/heater hoses in the past.

Larry

Although you say the rubber hose is not sliding off the tubing, I'd use a brake double flaring tool to make a bulge on the end of the tube so the hose definitely won't slide off.

Start the double flare, but don't complete it to get the bulge.

It?s an iterative process

Completely agree with the before mentioned vertical support. Need something or you have potential for exhaust to bump up against lower flange of firewall and lower skin.

I tend to like very short hose lengths in short supports. Less hose the more deflection control you get. The shorter the overall support lengths the better the load path since none of these, no matter the orientation, are carrying true column load.

I found I get the Adel clamps that are clamped to the engine mounts tend to slide when the supports intersect the tube at angles less than 45 degrees. Always slides out, never slides in. My solution has been, if I can’t change the support to better angle, is use another Adel clamp right next to it to get protection against it sliding.

Over the 900+ hours I have, I would guess I have replaced clamps maybe 50 times and rearrange the support configuration maybe 6-8 times. YMMV. I have finally gotten something a little more permanent to work over all these iteration. You will find the exhaust hangers will be a check item every time the cowl comes off. I actually check every preflight by getting under airplane and wiggling the pipe to check if degrees of freedom of pipe has changed.

One last tip. I hate Adel clamps. I used to scar them right at the bend from the fastener hole to the loop getting them closed using pliers. That scar causes them to crack fairly quickly with all the vibration they see. I bought the Adel plies from Spruce and use the stainless Adel clamps now and no longer get the Adel breaks I used to get.

Thank you for the suggestions! I went by the instructions from Vettermans. As far as the vertical support some have mentioned I thought that was what the supports going to the oil sump were for. I have seen some examples where the pipes are fixed to the engine mount by the opening in the lower cowl. Is this what you are talking about?

Mount to the sump bolts...

An RV-7 guy in my hangar row was replacing his exhaust hangars. I asked why, he said they broke... I asked why... he said they break every year, I asked why and he didn't have an answer...

The reason why they break is that they were attach to the engine mount that doesn't move with the engine. A year's worth of flexing breaks them over and over again.

Mine have been mounted to the sump for 1450 hrs with no issues.

bigginsking said:

An RV-7 guy in my hangar row was replacing his exhaust hangars. I asked why, he said they broke... I asked why... he said they break every year, I asked why and he didn't have an answer...

The reason why they break is that they were attach to the engine mount that doesn't move with the engine. A year's worth of flexing breaks them over and over again.

Mine have been mounted to the sump for 1450 hrs with no issues.

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A couple build sites I follow have one support going to the sump then another support between the 2 pipes. No connection at all to the engine mount. Figured I'd try it this way and if it breaks I'll try it that way.

As Bigginsking said. One support from sump to each tube and then one in between them to tie them together. The tubes need to move with the engine. Mine have never loosened or broken.

Are these parts from Vetterman?

Yes they are. I had to bend the tabs to line up with the supports coming off the sump. Seen it done that way in others build sites too.

DanH said:

Are these parts from Vetterman?

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dwranda said:

Yes they are. I had to bend the tabs to line up with the supports coming off the sump. Seen it done that way in others build sites too.

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Pretty much guarantied to break, in my opinion. Particularly with one leg tied to the engine mount.
In how much time? Hard to say. 50 hrs? 200 hrs? there are so many other factors that have an influence on the longevity of highly vibration stressed parts like this (such as smoothness of the engine, etc. that is one of the reasons there is a wide range of experiences for this type of thing).

Brockster said:

As Bigginsking said. One support from sump to each tube and then one in between them to tie them together. The tubes need to move with the engine. Mine have never loosened or broken.

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Do you have any pics of the way you tied the 2 exhaust pipes together? The supports sent by Vetterman aren't long enough to go between the pipes.

rvbuilder2002 said:

Pretty much guarantied to break, in my opinion.

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Mine too. Those things are wrong as a soup sandwich.

DanH said:

Mine too. Those things are wrong as a soup sandwich.

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What would you recommend as a replacement?

Conceivably, you could improve their chance of survival by simply flipping them 180 and sliding them down the tubes, so the tabs point forward toward the sump hangers, without bends.

Flotation test the bent ones, then order new ones.

A really good solution would probably require welding and/or machining.