Good, good, good...Good vibration

Seems I keep chasing the vibration dawgs. Today, after a thorough pre flight I took off and immediately noticed a little, oh so subtle vibration. Felt like something loose again with my exhaust system.

I check the hangars pretty close as they are a four into 4 so lots of hangar pieces. After I landed and before I took anything apart I asked my neighbor, RV7a builder/flyer to take a gander at my exhaust pipes and get his opinion.

He thought as I did that they were secure. So I took the cowling off and was very happy to find this...




I don't have any spare DG11's but Roger with the RV7a had a spare rubber insert piece.

Talk about an easy fix.
I think I need a more secure exhaust hangar system in general though. This is my second time recently that I've had hangar issues.

Also I have 3/4 OD tubing where the adel clamp attaches. I look up in the catalog and it shows a DG12 and yet this DG11 I am using seems right.

Look at that, hangar paraphernalia everywhere.

I know there are varying opinions on this, but my experience is that with the exhaust tied to the engine at one end, and the engine mount at the other - something is going to flex every time the engine moves in the mount - and it does that a lot! Try hanging the supports off of oil pan bolts so that the entire exhaust moves with the engine and isn't in a tug of war between the engine and the mount.

Yep, like Paul said. Mine are all doing the dingle-dangle off of the engine sump bolts. Still going strong with 1300+hrs. Although, now I'm certainly jinxed.

When the Vetterman kit came with my RV 7A it came with a hand drawing that showed the hangers coming off the oil pan as Paul suggested. I suspect that this was an update to an older method of attachments that kept creating issues for some folks.

Oil pan

Hmm, thanks guys. I bet if I call Vetterman they might send me that drawing.
I looked around the oil pan today and couldn't really see a good way to hang.

Hello, Vetterman......

tomorrow I'll call them.

exhaust hangers

He'll probably even sell you new hanger hardware.

Hangers

http://i59.tinypic.com/20zpvz9.jpg[/IMG][/IMG]Hanging the exhaust off the oil pan/engine is the preferable method so it all moves in unison. But on my RV8, i can't get a straight shot between the pan bolts and the exhaust on the left side of my crossover exhaust. So, I used the excess crankcase vent hose to hang the exhaust from the engine mount. It gives a flexible mount that allows the relative motion but stiff enough to hold it securely in place. Punched holes in both ends and through bolted the hose to the exhaust clamps from Vetterman. At the engine mount, i used two adel clamps to hold a 3/4 x 3/4 inch angle on each side and through bolted the tubing to the angle. I used Vettermans method to spread the two pipes, flattened stainless tube at each end with rubber tubing clamped between. 210 hours no problem. Several certificated aircraft use similar method except with tire wall rubber as the hanger.

HI everyone, We receive a lot of calls from people convinced that they need to hang the exhaust from the sump bolts so that the engine and exhaust can move together.
The reason that we hang most of the exhausts from the sump, is because then we have a one size fits all hanging kit for MOST of the rv's, (rv-6-7-8-9) with the standard crossover. However, all of the rv-3's and 4's are hung from the engine mount, and all of the 7's and 8's that are using the 4 pipe. There are probably between 1-2000 rv's with the exhaust hung this way. Also, the rv-10's mufflers are hung from the engine mount, but that's another story.
Usually, when people have trouble with the hanging kit, it is because the "smashed tubes" have some oil residue on them. They also need to be "scuffed" with some 60-80 grit sandpaper. Every time that I have installed a different test exhaust on my plane, I have to use a vise grip to break the smashed tube out of the rubber hose, because they will bond together with the heat/cool cycles of the engine. Also, it has been my experience, that the wdg clamps are rock solid as long as the tube that they are mounted on is clean.
If anyone has questions, or needs a mounting kit sketch, feel free to call. Clint Busenitz/ Vetterman Exhaust (605) 891-1290

Check the mount tube!

Vetterman

I called Clint, drawings coming shortly. Amazing this internet.
Thanks fella's.

Clint B said:

Also, the rv-10's mufflers are hung from the engine mount, but that's another story.

Click to expand...

True, but the RV-10 hangs from the anchor point via a flexible cable that decouples the engine/exhaust movement from the fixed anchor point.

I'm not sure what the current hanger recommendation is on the other systems that tie to the engine mount, but my experience over many years using this supporting scheme (I think Larry originally got the idea from me when he visited Vans in the late 90's and and saw what we were doing on the prototype RV-8, and he incorporated it into the exhaust kit... your welcome Larry ) I have never (nor seen anyone else) gotten any long term service from the tube style supports with them anchored to the engine mount.
If all the systems successfully doing so are hanging from a flexible cable like the RV-10, then I can see that that night work.

Pictures

First time posting a picture, but this is how I have my exhaust hung as described in No. 7 above[/IMG][/IMG]

Exhaust mounting

Mine are mounted from the sump, hose connectors are braided hydraulic hose, droppers from sump are milld steel felt bar, no hose clip, wrap around steel clamps on exhausts, 900 hrs have never touched them.

If the exhaust it connected to the engine mount at some point you will have an issue. Don't forget the mouse milk! It Works...

acroflyrgirl said:

Seems I keep chasing the vibration dawgs. Today, after a thorough pre flight I took off and immediately noticed a little, oh so subtle vibration. Felt like something loose again with my exhaust system.

I check the hangars pretty close as they are a four into 4 so lots of hangar pieces. After I landed and before I took anything apart I asked my neighbor, RV7a builder/flyer to take a gander at my exhaust pipes and get his opinion.

He thought as I did that they were secure. So I took the cowling off and was very happy to find this...

I don't have any spare DG11's but Roger with the RV7a had a spare rubber insert piece.

Talk about an easy fix.
I think I need a more secure exhaust hangar system in general though. This is my second time recently that I've had hangar issues.
]

Click to expand...

Flygirl,

I seem to recall that the four pipes of my vetterman exhaust are hung just like yours with one exception. The flexible link from the pipes to the engine mount go to a piece of aluminum angle attached in the center. The two ends of the angle each have an adele clamp fastened to the engine mount. That might solve your vibration wear problem as it distributes the load.

Don