Sunday, September 27, 2009

Exhausting

You're supposed to put the exhaust system on the engine before doing any serious firewall forward work, so I bought the Vetterman system for the RV-7A project. It fits like a glove but it's been a pain in the neck to install anyway, almost exclusively because of me.

After the system is bolted on the engine, and the ball joint attached, you have to add brackets from the oil sump, since the moving and vibrating engine is going to shake the heck out of the pipes. So two rods in a hose are used to brace the pipes vertically, and then a similar arrangement ties the two pipes together. Simple, right?



My problem is I can't tell exactly how the pipe should be located -- that is, how far outboard of the nose gear weldment. I know it should be 3/4" below the firewall -- no problem there -- but side to side, I can't tell the perfect spot.

Vetterman's instructions say the horizontal brace should go behind the fork that goes to the nose wheel. No way. It interferes -- or nearly so -- with the castle nut on the engine mount and -- even if I moved it, it seems too likely the horizontal brace would occasionally hit the engine mount. That's a bad thing.

Now, I realize some builders attach it to the engine mount with a clamp but I think so highly of Tony Bingelis that I'm not going to do that. His advice was quite clear on the subject, even with the idea of the "floating hangar."

You can see on the picture above how I've placed the right tail pipe (I haven't done anything with the left side yet). Is that too far inboard? Too far outboard? Who knows?

Here's a look at the vertical hangar:



Here's the view from above. You can see the flat part of the bracket, which will hold the horizontal piece. It's angled a bit down now, so I'll have to bend the tab on the hangar. I'll probably also have to put a spacer under it because I don't want it to hit that nose gear fork.



And here's the view from the side. You can see the 3/4" clearance from the firewall and you can also see -- I hope -- why you really can't go behind the nose gear fork with the horizontal hangar.



I want to install the second side, but I couldn't find the tab that connects the hangar to the bolt on the oil sump. And that's typically for me, these days. Even though I think I know where I put things, I don't. I swear, I spent half my time looking for things these days. Finally, I gave up and asked Larry Vetterman to send another. I'll probably lose that one two.

I am having difficulty with another area of this installation. I can't get a socket onto inside bolts on cylinders 3 and four.



Close, but no cigar. So I can't tighten -- let alone torque -- the pipes on those cylinders. I'm going to look to see if there's a short socket with some sort of ball-adapter that may allow me to get in there.

Others have reported they've put these system on in under an hour. I started mine three weeks ago.

Figures

6 comments:

  1. Bob,

    Putting on the lower cowling should help you answer a lot of your questions. Mine didn't go on in one hour, but don't recall it being too difficult either.

    Good luck.

    trg

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  2. If you have one swivel point at the engine and one distance (3/4" from the firewall) there should be no room for choosing - the pipe can 'travel' on an arc and no more than two places on this arc will be exactly 3/4" from the firewall right?

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  3. I don't really follow that Tomasz. The ball joint allows the pipe to travel laterally. So there can be multiple locations where it's 3/4" from the firewall.

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  4. The hanger on my 6A ended up further forward than your pictures show. Basically as I recall it runs straight down from the rearmost oil sump bolt, the tab being on the upper nut side of the oil sump bolt.

    Hans

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  5. One other thing: A very experience builder taught me to not worry about the exact placement of the "tailpipes". He was right. If you think about it the vibration is amplified that far from the engine, so the placement will change as everything vibrates and shifts the first twenty hours or so. The pipes with bounce around, hit things and then find their place on their own. This is exactly how it worked out on my machine.

    Hans

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  6. It can't go straight down on the Vetterman exhaust, at least for my set-up. Larry provides an angled "tab" that connects to the bolt on the oil sump (it's actually made by Van's) So the hangar follows the angle dictated by the tab, which looks to be about 45 degrees.

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