Making plastic parts

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

Peter Dohm wrote:



I was about to suggest thermoforming from either Lexan or Plexiglas,

since I

thought that was how the lenses on Bonanzas and the like were made. So,

now

you made me curious--how much surrounding airspace was available iside

the

ones you made?

Peter




Almost 1/2 inch above the 12 watt (1 amp) bulb.

Remember that there are thermoforming plastics and thermoSETTING plastics.

That might make all the difference in the world here...

Richard


I'll try to get another look. What I had seem may have had more clearance,
or some source of ventilation; but I don't remember.

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