 Spherical Recesses in the Instrument Unit
At NARAM-50 Peter Alway and I discussed several of the details that we did not
do on our respective SA-5 models (Peter's model is in 1:69 scale).
On both our models, the four spherical recesses of the Saturn I's Instrument Unit
were approximated without their distinctive spherical shape.
Shortly after NARAM I began brainstorming some ways I could simulate
this detail. I decided on a one piece casting that will fit
through a hole in the body tube wall. After my third attempt to create
the master pattern, I took some photos of the part (see photos to the right). For a comparison with the real thing, go here.
The part will need to be primed and sanded smooth before pouring the
rubber for the mold. The final casting will be much shallower
than the pattern, perhaps no more than 1/4" total height.
The basics of the master pattern:
The body is a two-layer wrap of cardstock (close in size to a BT-20).
The internal tube is for reinforcement only. The spherical disk
is .02" styrene heat-formed over a 1.75" wood doll head, then cut to
the proper diameter with a circle cutter, using the back of the blade
to score the cut. The spherical disk is inserted snugly into a
hole in a flat scrap of .02" styrene, then CA'd from the back.
The disk/scrap combo was then glued on top of an additional .02"
styrene layer for reinforcement (with a small hole cut in the middle
for glue access), then cut down to the final diameter for proper fit within
the cardstock tube. The internal brown tube is for
reinforcment, but with a nice square cut at the end it also aided in
positioning the styrene unit before final gluing.
The plan is to have an hole cut-out in a 2.6" dia plywood or fiberglass
tube (same size as BT-80). The outer lip of the detail should sit flush
with the outer layer of tube and will need some sort of filler at the
joint. The plastic strips on the master pattern form 'stops' that will
help position the part (and since they're narrow, they should be easy to
adjust on the final castings). Four of the longitudinal lines are
scored and will show "valleys" in the casting that help orient the
part visually before gluing.
For a more typical 1:70 scale model, a 1.5" dia wood sphere or doll
head would work. Bear in mind that I'm using diameters larger
than Peter's drawing
shows due to some Instrument Unit data and a (low-res) photo I have
come across. If anyone
wants more information on this, feel free to send an email. I may
eventually post that here.
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