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Cracked exhaust hanger

bruceh

Well Known Member
I was doing an oil change today, and as usual, I give the entire engine a really good look over. I found one of the exhaust hangers had cracked.

IMG_7804-M.jpg


The hanger is made from thinwall stainless steel 3/8" tubing. I know I can source this stuff locally, but making the end flattened looks like it might require some special skills/tools. I don't want to just beat it flat with a hammer. My vise is probably not sufficient to pinch this, and I don't have a hydraulic press.

Any tips, or should I just call Vetterman Exhaust and get a replacement?

Would you replace all hangers, or just the one that is cracked?
 
I have 3 unused new ones. If you pay the postage via paypal and a bit extra for the paypal fee, I will send them to you.
Dave
 
I'm there at 800 hrs. Why did it fail? Was it connected to the engine or the somewhere else?
 
As to why the hangers break, having just installed a new 4 pipe Vetterman exhaust I note the accompanying hand drawn installation instruction shows the hangers attached to the engine mount tubes with the flexible rubber section allowing for engine movement. I did not attach mine to the engine mount, instead I went to a sump bolt on each side still with the rubber tube coupler. It seems to me that an exhaust hanger fixed to the engine mount will always break even with lubricated slip joints and rubber coupling. My system seems well supported and I can't see any problems with it other than to ensure the tail pipes have sufficient clearance to allow for the engine movement. What do others do and think about the Vetterman mounting instructions?
Thanks,
Russell
 
Positive support

Bruce - hangers per plans seemed too ?slippery?. I used 1/16? steel straps 1/2? wide made from ACS stock for end supports. Then bought 1/4? exhaust hanging material from the auto parts store and made straps about 1? wide, to desired length. Use 1/4? holes thru the tire straps and the steel mounts. No issues in 440+ hours. EZ to check and see if they are worn or failing. Flexible yet solid attachment points.
 
Here are the tubing swaging dies I made from aluminum angle to make a swage that isn't prone to stress cracks:

tubing_swager-2.jpg


Put them in the vice and squeeze the tubing:

tubing_swager-1.jpg


3/8" steel (not the soft, easily bent stuff) brake line purchased from the aviation aisle at the local auto parts emporium makes great exhaust hangars. I carry a pre-swaged and drilled piece in my flight kit for away-from-home replacement.
 
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Bruce - hangers per plans seemed too ?slippery?. I used 1/16? steel straps 1/2? wide made from ACS stock for end supports. Then bought 1/4? exhaust hanging material from the auto parts store and made straps about 1? wide, to desired length. Use 1/4? holes thru the tire straps and the steel mounts. No issues in 440+ hours. EZ to check and see if they are worn or failing. Flexible yet solid attachment points.

I flared my tubes slightly. no slip in 800 hrs.
 
Here are the tubing swaging dies I made from aluminum angle to make a swage that isn't prone to stress cracks:

tubing_swager-2.jpg


Put them in the vice and squeeze the tubing:

tubing_swager-1.jpg


3/8" steel (not the soft, easily bent stuff) brake line purchased from the aviation aisle at the local auto parts emporium makes great exhaust hangars. I carry a pre-swaged and drilled piece in my flight kit for away-from-home replacement.

that's better than a sharp corner
 
I'm there at 800 hrs. Why did it fail? Was it connected to the engine or the somewhere else?

It is installed according to plans up to the tabs on the oil sump, but the plans also state not to bend the end of the tubing tabs. There is really no way not to bend them if you want them to fit around the engine mount.

The broken one is the one in the middle of the photo here:
IMG_3018-M.jpg

You can see that without a slight bend on the tab, it won't line up with the other tube coming down from the sump.

The broken one is the lower one on the far side in this photo.
IMG_3039-M.jpg


I'm not shocked that it broke, since I know of many other cases from reading these forums about this issue with bending the tabs and then allowing them to crack. 750 hours isn't bad! Just a reminder to others to always check them. In my preflight, I didn't notice any extra looseness in the exhaust pipes with a wiggle test.

Keith's suggestion is intriguing, to use auto exhaust hanger material between steel straps. Got any photos?
 
your arrangement is good. the design for a flattened tube is poor but it's light weight and fits a rubber tube so it's worth trying to improve. what about a set of dies that transition from round to flat smoother. I don't know if it's worth much but I'll give it a try. if it works I may also be able to put a bend in there. there has to be an optimal design for this transition. I'll poke around.

round_to_flat_zpszadgpwon.png
 
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Mine Recently broke as well. Was a simple fix however I suspect it was due to the fact that I had not been lubricating the exhaust joints, which I was not aware of. I am now. This was an easy fix. Clamped the ends and then drilled a hole and reattached.

Jon

I was doing an oil change today, and as usual, I give the entire engine a really good look over. I found one of the exhaust hangers had cracked.

IMG_7804-M.jpg


The hanger is made from thinwall stainless steel 3/8" tubing. I know I can source this stuff locally, but making the end flattened looks like it might require some special skills/tools. I don't want to just beat it flat with a hammer. My vise is probably not sufficient to pinch this, and I don't have a hydraulic press.

Any tips, or should I just call Vetterman Exhaust and get a replacement?

Would you replace all hangers, or just the one that is cracked?
 
yeah, we want to get away from this stuff. there could be a market for a fitting welded to a tube to take the place of these smashed tubes. perhaps anti-splat could pick this up.
 
yeah, we want to get away from this stuff. there could be a market for a fitting welded to a tube to take the place of these smashed tubes. perhaps anti-splat could pick this up.

3/8" solid steel rod can be used instead of the flattened tubing, that's what I use for the hanger that goes between the tailpipes.
 
What I did..

I used 3/8 Stainless tubing which I threaded the inside of the ends and put in Heim bearings similar to the hinges on the flight controls. I then cross drilled a rivet through the shank to prevent any back out of the Heim bearing. A Stainless tab is installed on the sump and the exhaust hanger at the tip bent to the correct angle, then bolt the tube/rod end assembly in. It allows movement, but has no flattened ends to fail. If you are flattening a tube, the best crack prevention is a small piece of steel (1/16"-1/8" thick)looking like a popsicle stick inserted in the tube an inch or so then squeeze the tube over it. This prevents the sharp radius failure point of the flattened tube.
 
3/8" solid steel rod can be used instead of the flattened tubing, that's what I use for the hanger that goes between the tailpipes.

ditto on this method. replaced all my hollow tube supports with solid ones. flattening the end took some work but worth the effort. will never break. :cool:
IMG-0106.jpg
[/url][/IMG]
 
I used 3/8 Stainless tubing which I threaded the inside of the ends and put in Heim bearings similar to the hinges on the flight controls. I then cross drilled a rivet through the shank to prevent any back out of the Heim bearing. A Stainless tab is installed on the sump and the exhaust hanger at the tip bent to the correct angle, then bolt the tube/rod end assembly in. It allows movement, but has no flattened ends to fail. If you are flattening a tube, the best crack prevention is a small piece of steel (1/16"-1/8" thick)looking like a popsicle stick inserted in the tube an inch or so then squeeze the tube over it. This prevents the sharp radius failure point of the flattened tube.

a clever guy
 
What am I looking at, Dan?

Dan,
Help me understand what's in your image.

Is that steel cable you're using to suspend the exhaust?
How long have you used that assembly?
Reasonably easy to fabricate and install?
Benefits?
Cons?
 
I was doing an oil change today, and as usual, I give the entire engine a really good look over. I found one of the exhaust hangers had cracked.

I had lots of broken Adel clamps but never the flattened rod. No more broken clamps once I realized I was scarring them right at the edge of the bolt in the corner due to the way I was squeezing them to install. Also went to SS clamps from Aluminum.

I like fixnflyguy rod ends idea. May swap out flattened tubes for rod end versions next time cowl is off.
 
Dan,
Help me understand what's in your image.

Is that steel cable you're using to suspend the exhaust?
How long have you used that assembly?
Reasonably easy to fabricate and install?
Benefits?
Cons?

I'm not Dan but that's the same mount I received with the 4 into 1 exhaust I bought from Aerospace Welding. There's 2 SS blocks with horizontal holes welded to a plate that bolts to the fuselage. There are corresponding blocks welded to the clamp that goes around the exhaust pipe. You thread about 3 loops of SS cable on either side of the pipe to connect it to the fuselage blocks. Mine's not flying yet but it looks like the best mount I've seen.
 
ditto on this method. replaced all my hollow tube supports with solid ones. flattening the end took some work but worth the effort. will never break. :cool:
IMG-0106.jpg
[/url][/IMG]

Turbo -- I'm just wondering what the significance of the picture is here?
 
Adding to the chorus... When I was installing my exhaust system about 10 years ago I saw numerous posts describing broken Vetterman style flattened tube hangers.

Stainless is good for being stainless, but 300 series stuff isn't exactly strong and is relatively brittle and fatigue sensitive compared to other types of steel. Didn't want to have a field failure and/or carry spares.

I bought a piece of 4130 chrome moly tubing from the aviation department at McMaster-Carr and cloned the Vetterman-supplied tubes. I did make a fixture similar to Sam Buchanan's, to avoid a sharp crush, which was necessary since the 4130 was so dang hard that I had to heat it in order to be able to crush the ends. In hindsight, brake line tubing like Sam used is probably plenty strong.

What ever. 900 hours and counting, including the (upgraded to some sort of fancy blue) rubber tubing, mine is still fine. In the end I probably only had an hour into making the upgraded parts. Are there better ways? Almost certainly. But with minor refinements, the Vetterman design works pretty well.
 
I'm not Dan but that's the same mount I received with the 4 into 1 exhaust I bought from Aerospace Welding. There's 2 SS blocks with horizontal holes welded to a plate that bolts to the fuselage. There are corresponding blocks welded to the clamp that goes around the exhaust pipe. You thread about 3 loops of SS cable on either side of the pipe to connect it to the fuselage blocks. Mine's not flying yet but it looks like the best mount I've seen.

Right...nothing custom here, just a better idea from a different pipe vendor. I've posted it in the last thirty or so "My exhaust hanger broke" threads, but apparently folks love flattened tubes and hose clamps.
 
Right...nothing custom here, just a better idea from a different pipe vendor. I've posted it in the last thirty or so "My exhaust hanger broke" threads, but apparently folks love flattened tubes and hose clamps.

Count me among those that think it looks hokey. Etc. But in the end (and actually, it was the beginning since my RV-7 wasn't even flying yet) all the other solutions I was dreaming up seemed too difficult to implement, especially given the space constraints with a muffler-equipped crossover system on a vertical draft engine installed in a side by side RV. And since the slight permutation I came up with (I'm not a big fan of 300 series stainless, does it show?) keeps working, I keep dreaming up other things to over-complicate ;)
 
if you stay with the flattened tube you may consider 3/8 inconel 600 or 625 tubing. stronger, but not as much elongation capability when it's smashed. you may need to heat it progressive as it's smashed.
 
if you stay with the flattened tube you may consider 3/8 inconel 600 or 625 tubing. stronger, but not as much elongation capability when it's smashed. you may need to heat it progressive as it's smashed.

....or just use 3/8" steel brake line....readily available.....easy to swage....only takes a couple of minutes.....and last a long time...... ;)
 
Good results so far with stock Vans arrangement. One thing I did to reduce possibility of slippage was to make 4-5 slits with a Dremel cut-off wheel, perpendicular to length of tube. Gives the rubber something to bite into.
 
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