Re: Kit production technical question


Andy Carlson
 

Please note that by the nature of the process, Vacuum forming is essentially laying a thin sheet over a positive pattern. There is the problem, for the detail has to "punch through" this thin sheet to erupt on the far-side, meaning all detail is rounded off and quite softened. I feel that there are few things in freight car construction that lend themselves to Vacuum Forming, which probably explains why there are ZERO on the HO marketplace.
Andy Carlson

On Wednesday, June 12, 2002, at 08:35 AM, benjaminfrank_hom wrote:

Ray Breyer wrote, in part:

... why have I never heard of any using vacuum-formed styrene? I
seem to remember dozens and dozens of model aircraft, tanks, and
automobiles produced for other modeling markets using this medium,
and I've run across the occasional DPM kit with parts vacuum formed.


Ray, no experience in building railroad cars, but some in building
WWII aircraft. To answer some of your points:

"Yes, vacuum formed styrene is thin, but it wouldn't be a problem to
laminate sides to a thicker styrene box. And thinner part cross-
sections could actually be a benefit in some circumstances."

Vacuum formed styrene is thin. The problem for a railroad car is
that it's not thin enough to pick up fine details or cross sections
(rivets, for example) common to a model railroad car without running
into durability problems - scale modelers don't have to run freight
cars on a layout as many of us do. If you check out a vacuum-formed
aircraft kit, you'll see that the wings and fuselage of a typical
aircraft look pretty good, but the vacuum-formed detail parts leave a
lot to be desired. In fact, most scale modelers throw the detail
parts away and substitute injection molded or resin parts.


"And the relative ease of using plastic cement may lure some
hobbyists (with ACC-phobia) into trying these kits. Production would
also be easier, as making a vacuum-formed kit would be the work of
seconds (offsetting machine costs?)"

Production costs are lower, and that's why you see a dizzying array
of obscure prototypes among the vacu-formed kits on the other side of
the hobby shop. However, don't fool yourself into thinking that
these kits are any easier than a resin kit! Vacu-forms often require
a significant amount of do-it yourself engineering on the modeler's
part:

1. Parts have to be cut and sanded from the sheet. You have to be
careful during the sanding process (more so than for a resin freight
car kit) to ensure you get a good joint between parts (for an
aircraft kit, wing and fuselages are molded in halves). Expect to
use filler no matter how well you do.

2. For the most part, location or keying tabs do not exist, and
structural reinforcements are required to keep thing from falling
apart during handling, especially for larger kits. No problem for
those of us used to putting together resin kits, but a significant
one for the hobby mainstream who are buying fewer and fewer kits.

3. As mentioned before, detail parts leave a lot to be desired and
need to be replaced with an injection molded or resin part (yeah, I
know, we do that with brake parts already.)

Of course, I'll be happy to be proven wrong if someone can come up
with an acceptable vacu-formed freight car kit!


Ben Hom



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