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  #1  
Old 12-05-2021, 02:11 PM
00Dan 00Dan is offline
 
Join Date: Nov 2016
Location: Atlanta, GA
Posts: 273
Default Issues with exhaust, hangers, and engine mount interference.

BLUF: I need help identifying the band clamp used on my exhaust, and also finding a solution for interference between the end of one exhaust pipe and my engine mount.

I previously had an issue with one of my exhaust pipes contacting the the lower engine mount crossbar inside the gear leg. I caught it after it had worn a slight divot into the mount (although the exhaust pipe didn’t show any signs of chafing). To adjust I shimmed the engine to rotate the exhaust away from the mount and made sure all the hangers were secure.

The other day I discovered this pipe was loose and able to touch the mount again. On decowling I discovered the clamp around the pipe which connects to the hangers had broken. This leads to my questions.

First, I’m having trouble identifying the clamp to find a replacement. Perusing the ACS catalog and the aviation isle of the hardware store hasn’t yielded any equivalents. The picture shows this clamp, basically just a band clamp with a perpendicular tab for a screw. The clamp broke at one of the tabs.

Second, moving the pipe back into place where the existing hangers place it once again looks as if it may not have enough clearance with the engine mount. I’m not sure if my hangers are vans but they are solid tubes, one running between the two pipes and then a third that connects up to the accessory case. This is a pre-Vetterman crossover exhaust, for reference. My first impulse would be to shim the band that connects the pipe to the hangers to move the pipe down away from the mount, but I’m concerned about the longevity of such a solution, as moving it a sufficient distance is putting a load on the pipe. I’ve seen some people that may fastened the pipe to the mount with a hanger system, should I consider this or am I better off just shimming the pipe out of the way? My engine mounts have less than 100 hours on them and don’t appear to be sagging, and I don’t have room to shim the one corner again to further rotate the plane of the engine and exhaust away from the mount.
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Last edited by 00Dan : 12-05-2021 at 02:14 PM.
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  #2  
Old 12-06-2021, 06:31 AM
06ktrv6 06ktrv6 is offline
 
Join Date: Feb 2008
Location: Halifax,VA.
Posts: 27
Default

Thatís a clamp used on discharge hoses on irrigation water pumps, not intended to be used on exhaust pipes
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  #3  
Old 12-06-2021, 07:19 AM
PhatRV PhatRV is offline
 
Join Date: Mar 2018
Location: Buena Park, California
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Default

The exhaust hanger clamps in my RV8 firewall kit are thicker chromoly steel. The aft portion of the exhaust is attached to the rear of the engine by the bolts that hold the rear oil pan. The connecting rods are stainless steel tubes. There is an OP drawing that shows this connection.

Link to Vans Order page:

https://store.vansaircraft.com/2-exh...anger-kit.html
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Last edited by PhatRV : 12-06-2021 at 07:35 AM.
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  #4  
Old 12-06-2021, 08:38 AM
00Dan 00Dan is offline
 
Join Date: Nov 2016
Location: Atlanta, GA
Posts: 273
Default

Quote:
Originally Posted by 06ktrv6 View Post
Thatís a clamp used on discharge hoses on irrigation water pumps, not intended to be used on exhaust pipes
Quote:
Originally Posted by PhatRV View Post
The exhaust hanger clamps in my RV8 firewall kit are thicker chromoly steel. The aft portion of the exhaust is attached to the rear of the engine by the bolts that hold the rear oil pan. The connecting rods are stainless steel tubes. There is an OP drawing that shows this connection.

Link to Vans Order page:

https://store.vansaircraft.com/2-exh...anger-kit.html
I assumed it was a generic clamp; it sounds like Iíll need to seek out something more robust as a replacement.
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  #5  
Old 12-06-2021, 08:05 PM
gasman gasman is offline
 
Join Date: Mar 2007
Location: Sonoma County
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Don't fasten exhaust to engine mount or airframe. Fasten to the motor. It MUST move with the motor.
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  #6  
Old 12-08-2021, 01:06 PM
00Dan 00Dan is offline
 
Join Date: Nov 2016
Location: Atlanta, GA
Posts: 273
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I found a stainless T-bolt clamp that should prove heartier than the clamp that broke. The pipe is now held in place well but Iím still concerned over clearance with the bottom of the mount. The pictures attached show how little there is, and also show where the pipe chafed the mount when it was previously loose before I found it. The exhaust doesnít touch the mount when I grab it and test how much flexibility is in the hangers but it still looks really close. Any thoughts on how to open this up beyond attempting to shim the engine-mount interface further?
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  #7  
Old 12-08-2021, 02:07 PM
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cderk cderk is offline
 
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Location: Park Ridge, NJ
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Quote:
Originally Posted by gasman View Post
Don't fasten exhaust to engine mount or airframe. Fasten to the motor. It MUST move with the motor.
So youíre saying that Vanís instructions are wrong???
Mine is supported by attaching to the motor mount, which is accordance with the instructions.
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  #8  
Old 12-08-2021, 04:10 PM
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rv6n6r rv6n6r is offline
 
Join Date: May 2007
Location: Gearhart Oregon
Posts: 518
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Quote:
Originally Posted by cderk View Post
So you’re saying that Van’s instructions are wrong???
Mine is supported by attaching to the motor mount, which is accordance with the instructions.
At the risk of starting a primer-esque debate, I'll jump in here - yes there's a case to be made for attaching to the engine, since it isolates the vibration that's otherwise between the engine and mount that would theoretically lead to earlier failures.

The key word is "theoretically". I've tried both, and had much better luck with the traditional engine mount attach points. The reason being, when attaching to the engine (sump bolts) the angle is more acute and the hangars have to be longer, resulting in more breakages and also a tendency for the pipes to shift around. Attaching to the engine mount, the rubber hoses or whatever you use seem to be (for me anyway) adequate to keep the hangars from failing (or at least rarely). YMMV and I imagine there are other ways to attach than what I've used.
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Last edited by rv6n6r : 12-08-2021 at 08:49 PM.
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  #9  
Old 12-08-2021, 09:20 PM
OKAV8r OKAV8r is offline
 
Join Date: Feb 2007
Location: Seattle
Posts: 270
Default Depends

Quote:
Originally Posted by gasman View Post
Don't fasten exhaust to engine mount or airframe. Fasten to the motor. It MUST move with the motor.
This may not be true if the exhaust system has ball sockets employed, as the 4-pipe Vetterman system that I have. Attaching the exhaust pipes to the engine mount near the firewall works fine, and is an accepted method by Vetterman. Now, if your pipes are solid, no articulation, then, yes they need to be hard to the engine.
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  #10  
Old 12-09-2021, 07:04 AM
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olyolson olyolson is offline
 
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Location: St Louis, MO
Posts: 1,183
Default Exhaust mounts

This is the approved solution from Vetterman Exhaust on my RV-8:



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