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In lugnet.trains, Ray Sanders writes:
> In lugnet.trains, Mike Walsh writes:
> >
> > "Rick Clark" <jrclark@nospam.aol.com> wrote in message
> > news:3A513A94.87EF98B0@nospam.aol.com...
>
> <snippage>
> > > These are the little mysteries that puzzle me...
> > >
> > > Rick C
> >
> >
> > Along this same line, the train windows currently being produced in the
> > soccer bus sets and in the train windows packs are not compatible with the
> > snap in doors that were used on 4564 (on the engine) or 1831 (used on the
> > containers). The holes in the top and bottom of the frame are not there.
> >
> > Odd ...
> >
> > Mike - mike_walsh@mindspring.com
>
> (taking a shot into the dark)
> Might it have something to do with simplifying the mold process for
> that part. By elminating those 'thru the rail' slots, they now have/had
> a more simple molding operation. Same might be true of those train windows.
> Anyone know more about how this is actually done ?
I know a little. In considering how to mold a part you have to consider
every concave surface carefully. Many things with concave surfaces can
nevertheless be made with non dynamic two part molds if you choose the mold
separation line carefully enough.
The train rails with thru the rail slots are not producable with two part
molds. You need more parts, or you need dynamic (a part of the mold
retracts) molds. The ones without are makable that way, as are the vast
majority of bricks.
The train (and other) windows with holes for hinge pins need dynamic molds
(having the pins retract in an otherwise simple two part mold is easier than
multiparts just for pin holes)
ObCred: I worked a summer in an aluminum foundry where we made sandcast and
tooling steel molded parts, including some with dynamic parts for pinholes,
etc... if you've ever rode a DC9 you may have seen some of our work in the
seat tray arms.
> BTW, the cad folks might want to designate these two as 3228 and 3228b
> (just to keep everyone straight). I'd hate to list these on BrickBay,
> sell em, then have someone yell about not being able to use them for
> train track.
Good point, I've copied this post to lugnet.cad.dat.parts and set FUT there.
> Ray
> l#124
++Lar
l#<who cares?>
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