Making plastic parts

"cavelamb himself" wrote in message
...
Peter Dohm wrote:
"cavelamb himself" wrote in message
...

Peter Dohm wrote:

Actually, I did have a car a while back with one of those rear window

brake

lights that eventually failed. For no obvious reason, the replacement

bulb

(of the same physical size and generic part number) quickly burned

through

the top of the plastic casing--despite having a peice of foil (which
was
original equipment) directly above the bulb. That was also in the 1amp
range at 12-14 volts; but I believe that the clearance was closer to a
quarter inch.

A strobe should generate much less heat, especially localized heat,
than

an

incandescent bulb; but this is a good problem to keep in mind for nav
lights. Of course, LEDs have become an affordable and reliable

alternative

that also eliminate much of the heating problem--especially if the

current

source is remotely located.

Peter



Peter,

I just happened to have the plug and one of the "experiments" on hand.

Guess I need to revise the clearance question to LESS than 1/2 inch.

This one, I believe, is polycarbinate (DUE TO THE LACK OF BUBBLES IN THE
PLASTIC).

The lexan attempts were made with .065 scrap from my windshield.
Every one of those bubbled like crazy in the baking phase.

Lexan is hydroscopic and retains considerable water.
This stuff "boils" out while heating unless "baked" out at below 212
for several hours. It was kinda pretty with the colored light on inside
it. But not exactly the sleek smooth aircraft parts I had in mind...

Pic at:
http://www.home.earthlink.net/~cavel...sc.htm#wingtip

More clearance, thicker plastic, maybe they use some kind of special
stuff - I really dunno there.

Just that thin stuff with a fairly hot bulb simply didn't work...

YMMV

Richard


I am not really sure why, but I was thinking of the type of lens that
ends
up being an entire corner of a wing, so that it has a lot of volume and
a
lot of area. Now that I have thought about it, 12 to 14 watts is a
*lot* of
heat for this size lens.

I am not sure what material is used in the currently offered commercial
assemblies, but it may very well be glass. (As you might guess, I also
don't know what material to use as a mold for glass--much less how to
form
the resulting mold.)

Peter




Well, I think we know it has been done before.
I know I've seen those corner style covers.

But the details?

Might be I was just too close and too thin for the amount of heat.

Continue researching this, Peter.

Like my Ex was fond of saying..."Three weeks in the lab will save you
4 days in the library every time".

Richard

It really is always Hell, when anyone's Ex was right...

Peter