Carving a cork butt plug- warbird related

[Forgotten Field]

This thread has nothing to do with HGU CSU.

Okay, here's the question. I'm asking about techniques for carving cork to make fuel selector switch replacements. What do you do, and how do you do it? Do you use fuel lube in the re-assembly process. What alternative materials do you use?

[Jack Cook]

Carving a cork butt plug

I was getting concerned for a moment

[b29flteng]

I haven't carved a valve but I did carve a float for a fuel gauge. I did that by using a high speed grinder with a sanding disc. I imagine you can chuck it up in a lathe and carve it that way. Find the finest grained cork to use. I would also use the gas resistant grease made by Parker Lube. I've used that lube in fuel valves also and it works great.

[Forgotten Field]

Thanks- I have a few obsolete fuel sender units that have big enough cork floats to be useable material for the selector valve. I thought about doing it on a CNC lathe, but I don't have the room on my computer for the program. Next computer will be big enough for that software. Did you do any polishing on the exterior of the float?

[bdk]

Some of these were made from laminates of cork (maybe 1/8" thick or so?). Not sure how (or if) they were bonded together.

You might consider freezing the cork with dry ice on your lathe and cutting with a conventional machine tool. Probably have to refreeze a number of times depending on how much you have to cut. Rubber can be successfully machined this way. Might work on cork too.

Should work assembled dry. I wouldn't want lube to clog my fuel filter. Every time you turn the selector lube would get scraped off the cone and into the fuel line.

[Wheels up]

Most of the smaller ones (E2?) are very readily converted to a slug of teflon or nylon....can be lathed very well. The housing is then counterbored to accept a viton lip seal and that's the last time you'll ever have to mess with it!
If insistant on cork you might be better served grinding or sanding the cork. Afterall, it is a wood. This can be aided and improved by freezing the cork to make it hard enough to acutally cut and not compress. Sand a bit, freeze, repeat. Longer work sessions may be obtained by freezing in liquid N. For final sizing, you can turn a similar cup as the valve body and line it with A wt. sand paper and then basically lap the cork in to the accurate geometry.
I believe the original had a black/grey appearance didn't it? This is graphite. It was impregnated with a graphite based lubicant. A popular process in dry bearing applications, particularly steel mills where the heat nullifies the use of liquid lubricants.
The teflon/nylon deal has been done by several people and concerns. Including Banaire (scroll down to 9th item).....

[51fixer]

Be careful!
Several T-6 crashes have been attributed to the cork in the fuel selector IIRC.
I have seen them loose on the mount ring they are glued to.
Rich

[Forgotten Field]

I have heard that the teflon ones still leak. Is that true?

[b29flteng]

Did you do any polishing on the exterior of the float?

No, but I did coat it with 3M EC776 fuel tank coating. I glued two peices of cork together with fuel tank sealant PR890-A2 or B2, to make a large enough piece to carve. Freezing it in dry ice or liquid nitrogen sounds like a good idea.

[gilt]

A bit of leaking is much preferred to flaking and clogging.

[Wheels up]

I have heard that the teflon ones still leak. Is that true?

Yes, they will ...drip....at about a drip per minute. Something I would much rather deal with than crumbling cork. There are solutions to that as well but it is all based on a poor foundation to begin with.
There's a reason they are obsolete.

[Forgotten Field]

Thanks for the responses. No need to do so at this time, but I'm planning on doing some experimenting with a (bad) spare fuel valve I have.

[bdk]

Yes, they will ...drip....at about a drip per minute.

Based upon that result, will the FAA issue a field approval?

[planeoldsteve]

You may try one of this type http://www.andair.co.uk/system/index.html

I dont know about an S.T.C.

Steve

[Wheels up]

Yes, they will ...drip....at about a drip per minute.

Based upon that result, will the FAA issue a field approval?

C'mon bdk.....you know how that goes. Jim O'Brian knows that one! Shop your FSDO till it does get a blk 3 signoff!!