SCAT tube and heat muff direction questions

ArVeeNiner · #1 03-13-2010, 07:52 PM

I have the Robbins Wings cabin heat muff that Vetterman supplied with my exhaust. Coupla questions:

-Which end is the "in" and which is the "out"? One end has some sort of screen/baffle in it, the other doesn't. I thought mine was marked but now that I'm ready to hook it up, I see no marks.

-Is there a recomended way to install it on the exhaust? Do you want the inlet higher than the outlet on the pipe or vice versa?

-I bought the 2" SCAT tube from ACS and it's a bear to put on! ACS also sells an 2 1/4" tube. I there a way to actually intall the 2" tube to the carb and heat muffs or should I just order the 2 1/4" version?

Thanks

Lionclaw · #2 03-13-2010, 08:16 PM

It looks like the side of mine marked "INLET" is the side without the screen. I'm using the 2" stuff. Sometimes I have to twist it a bit while putting it on. If the cut wire at the end is causing problems you may have to use a pair of pliers to bend the end of the wire out a bit.

rvmills · #3 03-13-2010, 10:46 PM

Kelly,

Here's one technique for making it easier to put the ends of the scat tubes onto the flanges. I just did some scat replacing and rerouting, and the multple RV builder next door showed it to me (and hopefully one of the VAF vets will confirm whether it's in keeping with best practices).

Carefully pull out a turn or two of the wire inside the scat, and clip it with dikes. That will give you about 3/4" of tube with no wire that will fit more easily over the flange. If your scat has string on the outside, you can also pull about the same amount off of the outside, and snip it off. Should give you a nice surface to fit over the flange and under the hose clamp.

One method...and is subject to the thumbs-up from the gurus!

Cheers,
Bob

Ironflight · #4 03-14-2010, 07:07 AM

That's pretty much how I do it - but when I clip off the wire, I bend about 3/8" of the remaining end at a 90 degree angle, laying it along the tube surface, so I don't have a sharp "pokey" end trying to stab a hole in the tube.

Was taught this decades ago by an A&P, and have been doing it ever since....

Paul

Ron Lee · #5 03-14-2010, 08:13 AM

Sounds like 2 and 1/4" tubing would be better. Any reasons why not?

Captain Avgas · #6 03-14-2010, 10:48 PM

Quote:

Originally Posted by ArVeeNiner

I have the Robbins Wings cabin heat muff that Vetterman supplied with my exhaust. Coupla questions:

-Which end is the "in" and which is the "out"? One end has some sort of screen/baffle in it, the other doesn't. I thought mine was marked but now that I'm ready to hook it up, I see no marks.

I asked Larry Vetterman this same question a couple of months back. He said that it doesn't matter which way the air enters or leaves the muff......it will still be slowed down by the screen.

ArVeeNiner · #7 03-15-2010, 08:05 AM

Thanks guys. I got it all finalized yesterday. Once you pull some of the wire out and cut the string, it goes on like butta!

alpinelakespilot2000 · #8 04-21-2010, 12:49 PM

Bob-Not sure if I read this correctly... Are you suggesting that the hose clamp only go over the tube but not the wire? I would think best practices would suggest clamping the wire as well since it is the wire that provides some of the tube's strength.

Also, I found that trimming the tubing flush with the first wire helped get it on to the flanges. Having extra tubing made it harder for me. Just another experience.

Quote:

Originally Posted by rvmills

Kelly,

Here's one technique for making it easier to put the ends of the scat tubes onto the flanges. I just did some scat replacing and rerouting, and the multple RV builder next door showed it to me (and hopefully one of the VAF vets will confirm whether it's in keeping with best practices).

Carefully pull out a turn or two of the wire inside the scat, and clip it with dikes. That will give you about 3/4" of tube with no wire that will fit more easily over the flange. If your scat has string on the outside, you can also pull about the same amount off of the outside, and snip it off. Should give you a nice surface to fit over the flange and under the hose clamp.

One method...and is subject to the thumbs-up from the gurus!

Cheers,
Bob

jetjok · #9 04-21-2010, 01:45 PM

Quote:

Originally Posted by Ironflight

That's pretty much how I do it - but when I clip off the wire, I bend about 3/8" of the remaining end at a 90 degree angle, laying it along the tube surface, so I don't have a sharp "pokey" end trying to stab a hole in the tube.

Was taught this decades ago by an A&P, and have been doing it ever since....

Paul

What Paul said....But when you are done, push the wire back inside so that the "spring' tension of the wire is riding on the spiraled wire inside. Otherwise the crimped end will wear through the hose is short order.

AlexPeterson · #10 04-21-2010, 06:00 PM

The heater will heat better if the air goes in the opposite direction from the exhaust gases. I see almost none set up this way, but unless there is a very good reason not to, try to set them up this way.

For those curious as to why, the goal is to maximize the temperature difference between the exhaust gases inside and air outside of the pipe at all points. The temperature difference at each point along the pipe is what determines the amount of heat transferred.