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RV14 Exhaust hanger

Tom Martin

Well Known Member
I am noticing a bit of vibration in the tunnel and side skins of the RV14. The aircraft is also a bit louder in the cockpit then I am used to.
When I installed the aft exhaust pipe hanger I wondered why such a solid metal arrangement had been used.
In the following picture you can see the stock hanger on the right side and the "rubber" isolator that I fabricated on the left. I made the hanger from automotive exhaust pipe hanger material. Both sides now have the modified hangars and I will test fly it tomorrow. I have never seen, on any equipment, such a rigid exhaust pipe hanger as was supplied by Vans' for the RV14. The new set up securely holds the pipe and I can not help but think it will help with both vibration and sound. I will report back

Finally something on the RV14 that looks like it was made by a homebuilder;-)


2lxt2eb.jpg
 
Really good looking riveting. On the rubber hanger strap I would use one on each side exhaust systems don't like to be rigid.
 
I think u will be happy. I used the same rubber material for my RV7A rather than the slippery tube and hose fittings per plans. More solid retention but the same or better flex. Has worked fine for my first 30 hours of phase 1.
 
I did the same thing with the exhaust on my Diesel Sportsman. The rubber ended up getting brittle and melting. So i cut 3/4" x 2" strips from a silicone turbo hose, and they have worked flawlessly for over 400 hours. They have remained soft and flexible; still look like the day i installed them.

FWIW....

Kurt Goodfellow
RV9 / WAM diesel 570 hours
Sportsman / CD155 Diesel 440 hours
 
1st flight with new isolators on exhaust got rid of almost all tunnel vibrations. Sound is subjective but seemed a lot quieter at all rpms.
So far I am impressed with the difference. The stock isolators are not at all similar to Dan's cable mounts. I can see how his to work as they allow the pipe to move. More flight tests yet today but it this looks like a step in the right direction.
 
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The stock exhaust installation uses links that act very similar to links in a chain and do allow for a lot of movement if they are installed per the plans (the bolts are not meant to be torqued up fully which would crush the nylon bearing inserts and prevent movement).

The prototypes haven't experienced a lot of vibration transfer from the exhaust.
Perhaps they were installed incorrectly or a dynamic prop balance is in order.

Noise level is subjective without using an actual sound meter. The noise level has been measured in the prototypes and was found to be on par with the other 2 seat RV's with similar engine size. This was done during the exhaust development while comparing the benefits of a muffler vs performance penalty.

On any of the four cyl RV's, when compared to an RV-10 (or Rocket) that uses a 6 cyl engine, the 6 cyl seems quieter because the exhaust note is toned down somewhat but the actual db level in the cockpit is not much different.

BTW, in your photo it looks like the aft part of your Y pipe is not centered. Either you never got it aligned properly or the slip joint on the left side has moved.
 
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Scott
Yes you are correct the pipe has move a bit off centre, I will correct
that. Every aircraft is different. The supplied hangers were installed as per plans and the bolts not too tight. Sound is subjective but I am hearing Garmin altitude alerts today that I have not heard for the first 15 hours. Vibrations are noticeably less with none in the tunnel area and now only slight on forward side skins. It has gone from a noisy aircraft to one smooth and quiet. Again every aircraft is different but my out of pocket cost are $5 and one hour of labour. Hard to argue about someone else trying it and reporting back
 
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Tom,
Not related to noise, but I too was having issues with my exhaust hangers, which I discussed with Vans. In response Vans published a short new video, found under the "Service Info and Revisions for the RV14" menu. Also there is a new exhaust installation step 8 in Section 48-02, both dated 9/12/17.

Congratulations on your beautiful aircraft!

Greg Novotny:D
RV-14a N14ZP
Tacoma Narrows Airport
Gig Harbor, WA
 
Thanks Greg. I checked out the plans and saw the video and I am not really sure what they are trying to demonstrate in the 3 sec shot? Perhaps my system did not download the sound file?
I will keep monitoring the current rubber isolators, 4.7 hours today and they show no signs of heat damage or any other issues.



Tom,
Not related to noise, but I too was having issues with my exhaust hangers, which I discussed with Vans. In response Vans published a short new video, found under the "Service Info and Revisions for the RV14" menu. Also there is a new exhaust installation step 8 in Section 48-02, both dated 9/12/17.

Congratulations on your beautiful aircraft!

Greg Novotny:D
RV-14a N14ZP
Tacoma Narrows Airport
Gig Harbor, WA
 
Rainy day here today so I pulled the cowling to see why the exhaust pipe was off centre. There is one attachment to the engine block and the clamp that goes with that hanger is supposed to secure the left side of the "Y" pipe and the left exhaust together The plans point this out and note a notch in the end of the pipe that should allow the outer pipe to be compressed to squeeze the inner pipe.
This keeps the main exhaust pipe entered in the tunnel.
As it turns out the clamp that I received would not compress the pipe enough to secure the two pipes together. I see no danger of the pipe actually coming loose but it definitely allowed the tail pipe to shift to the left as Scott noted in my first picture.
I was able to secure the pipe properly by inserting a shim half way around the pipe between the pipe and the clamp. This allow the clamp to tighten down properly on the pipe.
I do not expect this change to make any difference on sound or vibration.
 
I have 25 hours on the 14 now, 10 with the "new" exhaust hangers. If your system is working ok, leave it alone. If you are getting any vibrations in the tunnel or side skins then consider what I did.
Go to your local automotive supply house and purchase one of these exhaust hangers
akecya.jpg


You can see where I cut the piece out of one side and I am using the old part as a template to drill the 3/16" holes. After the holes are drilled I cut the piece using a band saw. A belt sander made quick work of the edges. Then I slit the piece using the band saw again; just enough to capture both ends of the attach points.

2qwfmmw.jpg


The original hangers used plastic bushings in each end and I installed these in the metal brackets on each end before sliding the rubber piece into place. It nicely captures those bushings and then longer bolts are installed with washers on both sides. Tighten the bolts just enough that they are not loose, then install cotter pins. I elected to put the nuts on top but I do not believe it matters which way they go with this installation. The cotter pins are
 
"... I checked out the plans and saw the video and I am not really sure what they are trying to demonstrate in the 3 sec shot? Perhaps my system did not download the sound file?..."


Tom, I think they're demonstrating the new Step 8:

Step 8: Check that the
tailpipe and hanger
brackets rotate
freely on their
bushing
attachments
 
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