Flash wrote:
"Orval Fairbairn" wrote in message
news_r_fairbairn-
If you wish to be more up-to-date, use red LEDs instead of the
grain-of-wheat bulbs. You CAN use clear plexiglass, with an inverted
bevel at the instrument holes. I would suggest painting both sides of
the plexiglass white, to contain the light, before the cutting/engraving
operations. The front face can be left whit or painted in your desired
color.

--



Orval is on the right track.

But for best results, use clear plexiglas, coat both sides of it white for
better internal light transmission. Then, coat both sides of it black, to
stop extraneous light. Bevel or reverse-bevel the edges,, depending on the
effect yu require/desire. Engrave through the top black /white layer into
clear plexi. You CAN use white plexi for this, but you will rquire so much
more light (numbers of lights, at many places) to achieve the illumination
and readability at night that you desire, as most white plexi absorbs a
great deal of the light - it just isn't as translucent as it seems,
especially being edge-lighted..

As for the "name-tag" material, the white inside in MOST oif that stuff is
opaque, and it is of such differing quality and material from various
manufacturers as to be a literal crap-shoot.

Flash



Maybe I have just had good luck with "name tag" material. As for
white plexiglass I never suggested opaque white although there are
varying degrees of translucence. Bear in mind any engraved plate used
for switches or similar don't have to be all that bright. It's all
relative to ambient lighting. An exception might be a panel that is
normally in shadow in daylight ops.

As for engraved plates there is one more idea. It's something I have
never tried myself. I have disassembled internally illuminated military
engine and pressure indicators. Many of them had 2 or more 328 sized
lamps. The one inch round gauges had 2 lamps and the 2 inch round
engine/fuel etc had 2 or 3. What they had in common was a disc thick
enough to accept the lamp, the proper number of holes equally spaced ina
circle and a centre hole for the pointer shaft. The instrument face was
constructed one of two ways; either the face was silk screened directly
onto the aforementioned disc or another, thinner disc.

The round indicator bodies are brass so if you want to see what I
mean see if you can find an inoperative one on which to perform an
autopsy. I used to get the 1 inch ones with burned out bulbs, but
working movements, just for the synchro inside.

Your suggestion for using clear plexiglass might work with silk
screened faces. I have never tried it since the plates I have made were
all one offs or so.

I have never used plexiglass instrument illumination so I have
nothing to say in the matter. A habit I picked up in the military is a
preference for internally illuminated indicators when possible. The
major drawback to that is the connectors for military instruments such
as clocks, g-meters and pitot-static instruments costs around $80.

I suggest anyone wanting to try anything along these lines should
obtain various plastics in various colours and thicknesses and haul off
and experiment.

Dan, U.S. Air Force, retired