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  #11  
Old 07-22-2013, 10:17 AM
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Kevin Horton Kevin Horton is offline
 
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Originally Posted by Russ McCutcheon View Post
Lee, the fellow that built my RV-4 said he could not keep the exhaust on tell he got a decent prop=less vibration, I bet you have a good prop already though, has it been dynamically balanced?
No, the prop has never been dynamically balanced. I found a guy who does it in ON (or rather he found me, after reading my tale of woe), and I plan to get that done soon after OSH.


Quote:
Next idea, once when flying formation with a local RV driver, taking a look at his belly revealed his exhaust stacks vibrating in a circle about twice the size of the pipe, told him about it and had him raise and also lower his RPM, 50 RPM either side would result in rock steady pipes. You could try running at a different RPM.
Hmm. Sounds like I need to organize a formation flight. I bet I can talk Glenn C. into that with his RV-7A.

I also got an email from Larry Vetterman. He suggested I might want to try a different configuration exhaust system to see if that helps. I've got a crossover system now, but a four into one, or a four pipe system are also possibilities. I wonder how many of these types are in service, and what their service history is.

Thanks for the ideas.
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  #12  
Old 07-22-2013, 10:30 AM
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FORANE FORANE is online now
 
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I had the same problem with circumferential cracking at the flange. I had it welded once and it reoccurred. The next time I brought it to a drag race engine builder who manufactures custom 1500+ hp before nitrous drag motors. He looked at it and said the pipe should have been a little thicker for the first inch or 2 from the flange. He took 2 stainless tabs and welded them onto the pipe from the flange to the side of the pipe just wide enough to allow passage of the socket needed to remove the flange bolt. I have not had a reoccurrence.
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  #13  
Old 07-22-2013, 11:39 AM
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Kevin Horton Kevin Horton is offline
 
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Originally Posted by FORANE View Post
I had the same problem with circumferential cracking at the flange. I had it welded once and it reoccurred. The next time I brought it to a drag race engine builder who manufactures custom 1500+ hp before nitrous drag motors. He looked at it and said the pipe should have been a little thicker for the first inch or 2 from the flange. He took 2 stainless tabs and welded them onto the pipe from the flange to the side of the pipe just wide enough to allow passage of the socket needed to remove the flange bolt. I have not had a reoccurrence.
I'm having a hard time figuring out what the drag race engine guy did. Any chance of a picture of what the modified exhaust looks like?
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  #14  
Old 07-22-2013, 11:56 AM
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Quote:
Originally Posted by Kevin Horton View Post
I'm having a hard time figuring out what the drag race engine guy did. Any chance of a picture of what the modified exhaust looks like?
Probably something like this:



Just a pic I found with a quick google search, but my vetterman exhaust has those reinforcements welded on to two of the tubes. It seems like the ones where the tube bends closer to the flange has the reinforcements.
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  #15  
Old 07-22-2013, 01:02 PM
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FORANE FORANE is online now
 
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Quote:
Originally Posted by Kevin Horton View Post
I'm having a hard time figuring out what the drag race engine guy did. Any chance of a picture of what the modified exhaust looks like?
Quote:
Originally Posted by tmbg View Post
Probably something like this:



Just a pic I found with a quick google search, but my vetterman exhaust has those reinforcements welded on to two of the tubes. It seems like the ones where the tube bends closer to the flange has the reinforcements.
That looks like a good option also but not what my engine builder friend did. I do not have any pics available and it would require cowl removal to get a pic but I painted in Ian's pic to show where tabs were welded on mine.


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Last edited by FORANE : 07-22-2013 at 02:48 PM.
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  #16  
Old 07-22-2013, 01:05 PM
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Hi Kevin, Perhaps you could try mounting a gopro or equivalent camera on the belly to see what it looks like from there.
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