Re: More thoughts on resin warping & shrinkage


CJ Riley
 

Be careful about generalizing on resin color. I was in the casting business for
many years and used several suppliers as I came up to speed. Alumilite is not
the only yellow (buff?) resin. And , as I am sure Tom and the other
professional casters know. there are hundreds, if not thousands of varieties of
resins in many colors. They are all formulated to have specific properties so
as to meet the needs of a range of customers. I didn't cast thin parts so I can
offer little to that discussion.

CJ Riley
--- Tom Madden <tgmadden@worldnet.att.net> wrote:

Pierre Oliver writes:
Which leads me to my question. The kits that are showing all this
warping, which resin was being used? The older yellow stuff? The
soft white, such has used by F&C? Or the grey resin like what
Sunshine and Westerfield use?
The "older yellow stuff" is Alumilite. I have no idea what resin F&C
uses but am sceptical that it's polycarbonate, as they claim. Al and
Martin use different resins, and I think Al even uses different
resins for his flat kits than for his one-piece bodies. Ted's caster
(his second) uses the same resin I do, but some of his kits were
contracted out for casting in Canada while his new caster was coming
up to speed. I'm pretty sure the Speedwitch NP 50' auto car was done
in Canada.

I'm suspecting that this issue may be more about the kind of resin
being used, along with improperly cured castings.
I don't have one of the Speedwitch NP auto cars but have heard there
were problems with the sides being too thin. That would be a pattern
problem, not a casting problem. While Ted was having those cars cast
in Canada I was doing a bunch of Georgia RR boxcars for him, a
private run of kits to be given to attendees at his first prototype
modelers seminar. I remember insisting on thicker sides on the one
piece body so resin would flow better in the mold, and so he could
incorporate a pocket in the body casting to receive and register the
floor casting. I have one of his K-106 CB&Q 40' boxcar kits, done by
his second caster, and the body is done that way. The NP auto car
was the first one-piece body house car Ted did. If that's one of the
problem kits that started this thread, I'd say Ted was a quick
learner and thickened the sides on subsequent models. Anyone have
his CN Fowler car or M-K-T boxcars at hand? Those followed the NP
car and it would be interesting to know if they have thicker sides.

Tom Madden




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