What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Safety wire baffles

frankh

frankh

Well Known Member
Afternoon all,

I test ran my engine the other day and noted that my plastic tube that goes over the safety wire that holds the baffles tight to the cylinders and heads had melted.

I know the engine hardly got up to temp so I must have used the wrong stuff (I used PFA tube).

What is the correct material for this tube?? Nylon maybe?

Thanks

Frank
 
Hopefully it's the same material as the plastic brake lines, as that's what I used. I'm not sure what material it is though (nylon, etc.).
 
Anyone just leaving the tube out? I'm pretty sure my inboard wires aren't going to hit anything...

The outboard ones definitely were going to interfere though, so I put some #6 stainless rod between those, bent to avoid the oil return lines.
 
Dave is right

Use the same (hard white plastic?) line used for the break lines. The idea here is to not have chaffing from the wire to the cylinders.
I don't like the idea of stainless rod. When the engine is running there is alot of viberation going on. Things can move quite a bit under the cowl.

Kent
 
Outboard wires

The outboard ones definitely were going to interfere though, so I put some #6 stainless rod between those, bent to avoid the oil return lines.
Click to expand...

Hallo Paul, do you have more details on this, or pictures? I'm quite worried about the safety wires damaging the oil lines.
Does anybody else have solutions for this?

Thanx,
 
My baffle instructions said to house the wire inside "brake line tubing". The drawing showed the wire emanating from a nondescript tube of some sort. I guess I just considered this to be AL tubing and not the plastic stuff. I chamfered the edges and smoothed them out. Anyway, if I'm wrong, at least they work and did not melt.

Roberta
 
Rene Bubberman said:
Hallo Paul, do you have more details on this, or pictures? I'm quite worried about the safety wires damaging the oil lines.
Does anybody else have solutions for this?

Thanx,
Click to expand...

Here's a picture of the uninstalled rods (prior to trimming to proper length) -- as you can see they are bent downward to avoid the oil return lines. I should warn everyone that I haven't yet flown with these, so copy me at your own risk...however a number of people in the archives did report using this sort of approach with success. I'd like to hear if anyone has actually had problems with this strategy.

I'm waiting to get some #6 all-metal stop nuts before installing permanently, but everything looks good when I hold it in place by hand. They have a good 1/4" clearance on the oil return lines and there is nothing else in the vicinity that they might rub against.

20060820_IMG_3607.JPG


I guess it's *possible* that the rods could rotate upward and come to hit the oil lines. I wonder if there is something they could be safetied to -- to keep them in the downward-bent position. Perhaps I should install the brake tubing over these as well... :|
 
Last edited:
robertahegy said:
You're supposed to be using AL tube, not plastic.

Roberta
Click to expand...

I received a length of PLASTIC (not sure what type) brake tube in the baffle kit. I'm not sure I'll be using it, but the intent of the manufacturer seems clear.

If the purpose of the tube is to prevent chafing on the aluminum oil returns, I don't see how aluminum tubing is going to help that...it might slow it down...
 
Regarding the bent threaded rod approach... What happens when they rotate and chafe through the oil return lines? Unless you have some way of guaranteeing that they won't rotate, I wouldn't use that approach. "Success" to some people means 50 hours without an issue. YMMV.

"Brake line tubing" refers to a high density plastic type material tubing that acts as anti-chafe.

Van's plans indicate a method that has stood the test of time.
 
dan said:
Regarding the bent threaded rod approach... What happens when they rotate and chafe through the oil return lines? Unless you have some way of guaranteeing that they won't rotate, I wouldn't use that approach. "Success" to some people means 50 hours without an issue. YMMV.

"Brake line tubing" refers to a high density plastic type material tubing that acts as anti-chafe.

Van's plans indicate a method that has stood the test of time.
Click to expand...

Yeah, it's a reasonable concern. I'm looking for a way to safety it.

The reason I went this direction was that the path of the safety wire directly intersected the oil return lines, at least for the inboard baffle runs. It seemed risky to pull a tight length of steel wire up against a soft aluminum line -- plastic cover or not.

Another alternative I considered was to add some tabs on the baffles to lower the location of the safety wire. Finding no mention of this in the "literature", I have moved toward an approach that at least a few people have tried before...

Paul
 
Use the Inter-Cylinder Baffle

Guys.... one way of doing it...

The inner baffle wraps can be secured to the factory inter-cylinder baffle part.

This picture shows it on a Grumman Tiger.

http://www.aucountry.com/Team_Folder/Projects/Baffles/B23.jpg

The outer baffles on my Tiger are held to the same inter-cylinder baffle part with small springs (factory Maintenance Manual). Other mechanics use twisted safety wire, with a kink for tightness. Pic here for same source.

http://www.aucountry.com/Team_Folder/Projects/Baffles/B24.jpg

The routing is direct if you attach to the inter-cylinder baffle, and does not get near the oil return line.

Some other baffle info. in the top level pages here...

http://www.aucountry.com/Team_Folder/Projects/Baffles/Baffles.html

gil in Tucson
 
Thanks for the tip, Gil. Now that I've finally been to the hangar, it looks like that might work.

I may be able to drill the inter-cylinder baffles without removing them, but it looks tricky...does anyone know if there is an easy way to remove them? Looks like there is some sealant on them at the bottom as well.
 
Follow-up: I was able to drill the intercylinder baffles "in assembly" with a long #40 bit, and safety-wired them to the main baffles without too much trouble. Took care to drill so as to not hit the cylinder, with careful hole placement and drill stop.

I only used this technique on the outboard pair of wire runs, since only those had an interference problem. I did still use the brake line covering since there was some danger of rubbing on the cylinders.

One downside of this approach is that you have to do 6 or 8 wire runs instead of just 4...it's pretty tedious work due to the various obstructions and the tough .041 wire they call for. Took me <mumble> hours... :|

Another downside is that removing and replacing the intercylinder baffles becomes a much more time-consuming task. Hopefully you don't need to do it. I still need to fish some junk out from down there...

Paul
 
Paul Eastham said:
One downside of this approach is that you have to do 6 or 8 wire runs instead of just 4...it's pretty tedious work due to the various obstructions and the tough .041 wire they call for. Took me <mumble> hours... :|

Another downside is that removing and replacing the intercylinder baffles becomes a much more time-consuming task. Hopefully you don't need to do it. I still need to fish some junk out from down there...

Paul
Click to expand...

Paul.. on the Tiger (and other production planes) the outers are held in with springs, one at each cylinder. I found some nice 1/4 diam., 040 wire coil springs about 1.25 inches long that did the job.
Installing the springs is also "fiddly" but probably easier than 0.041 safety wire..... :)
Both should do the job though...

gil in Tucson
 
You must log in or register to reply here.
Back
Top