Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

This post refers to duplicating a railroad shell, and a comparison
between casting the part and photo-etching brass. I have been
lurking on both etching and casting forums, and I have been debating
using either method for my project.

I plan to create a body shell to replace an existing body shell.
Just picture 2 sides, front/back and roof (no floor needed).

If I were to cast the part in resin, I would have to create a master,
and pound out each rivit. This would be very time consuming, and I
could possible ruin the master if I mistakenly create a rivit
incorrectly or in the wrong place. I would then have to create a two
part mold then cast my duplicates. This also seems to be expensive,
as 1 LB of Alumilite mold in $25, 28 OZ of resin is $28, clay is $2.
Total about $55.00 to get started. But I can cast the entire shell
in one part, no assembly (just cleaning up flash).

If I were to photo-etch in brass, I would use a cad program to layout
a design of rivits, window openings, etc. Then make a copy onto
transparency. Then use the transparency to expose a sheet of brass
costed with resist. Then let acid eat away at the brass, hoping that
the rivit details are left standing above the surface. Then I would
have to piece together the shell (the brass sheet is flat - walls,
sides and roof are done seperately) into it's final form. Cost of
etching: Brass sheet (4x10) $1.60, acid $4.00, developer $0.95, photo
resist $??. Seems much cheaper to create (if I could find someone
selling a spray photo-resist), just more time to assemble. No need
to pound in rivits, just design them using a computer (rivit lines
perfectly straignt, etc). Downside - consistancy of etching varies
for beginners. Also, you have to assemble the shell, and the
chemicals can be bad for you/environment.

Any thoughts from those who have experience in both methods?

GregC
Antioch, CA