Being a total cheapskate, and enjoying
the challenge of making something out of nothing, I built
my own turntable following an article that appeared in an
old MR (sorry, don't have the date). The basic element is
the pivot point, which this guy ingeniously built around
a headphone jack. Carefully centring and levelling the
male end on the turntable, he used a fast setting epoxy
to permanently moor the table to the plug, he then
installed the female end into the floor of the turntable
pit. (I was able to find a head phone jack that is
designed to install at 90 degrees to the cord, which has
a large, very stable mounting surface that has screw
mounts. No epoxy! (That was the guy's idea in MR). It's
been a long time since I built it, but it looks like I
use hot glue to stabilize the plug installation on the
bridge. It also has a lower profile than I remembered,
which would allow for a slimmer profile for the bridge.)
The wiring terminals on the male jack went to the bridge
track, and the female leads went to a DPDT, then on to
the power supply. The DPDT allows for a simple means of
reversing the bridge to match the stall polarity in the
round house.
On mine, I used a relatively thick (.040
I think) evergreen stock for the bridge, reinforced on
the inside with 3/16" x 1/8" Evergreen framing,
detailed the plate joints with strip styrene, added a
"planked" bridge deck with Evergreen scribed
car siding, built a simple overhead structure out of
strip and an operators shack on one end, and I had my
turntable bridge.
For the pit, I got two embroidery hoops
at Ben Franklin (6" diameter for my small turntable)
used the middle, seamless piece for the circular wall,
and a square piece of plywood for the floor. I laminated
a piece of evergreen smooth sheet stock to the plywood,
the using a good styrene cement, bonded the circular
track to the floor. You need to get your hoops first,
since the diameter of your bridge will be set by the hoop.
The circular track was the tricky part.
Using a dremel, I carefully cut a section of Atlas flex
track down the middle. I saved the side with the
permanent rail, where the ties are more or less bonded to
the rail. I flexed this in one direction a few times to
get the "curve" established. I then scribed my
base, marking the floor along the base of the embroidery
hoop. Using my Plastruct glue, I bonded the ties just
inside the mark, forming my circular running track. where
the two ends come together, I nipped it, slipped on a
rail joiner, and soldered it for a smooth curve, just as
one would do laying track.
On the bottom of the bridge, I attached
short lengths (1/8 to 1/4") of plastic tube stock,
small enough that a standard axle from an Atlas metal
wheelset would fit snugly, but still roll freely. I
modified four wheelsets by pulling one wheel off,
reversing it, and pressing it back on the axle with the
flange facing the same way as the other wheel. This gives
you a single tread width, but two flanges, which allow
the bridge to track evenly through the slight
irregularities in the pit track circle. The axles are set
loosely into the tubes to allow them to glide in and out
as the table turns.
After painting and detailing the bridge
and the pit, simply insert the male plug under the bridge
into the female jack on the floor, and press the two
together. You'll have to make sure your four wheel
assemblies are riding the rail, but once you do, you are
good to go.
This is strictly a manual turntable
design, although a little ingenuity from a modeller with a
bigger junk box than I have could probably engineer some
sort of drive into it. I was always to lazy and cheap to
worry about automatic indexing, but someone could
probably figure that out too.
The best part about it is the basically
wireless connection between the bridge and the power
supply. A 1/4" Radio Shack headphone jack is plenty
sturdy, and can spin 360 degrees infinitely. As long as
the DPDT aligns the polarity between the bridge and the
stall or lead track, the design works great for me and my
little 4 stall roundhouse.
The best part is I have a solid, easy
to build, easy to operate turntable for about $15 worth
of stuff. The only drawback is the headphone jack in the
bridge requires a bit of headroom, so my bridge is a
little taller, and the pit is a little deeper than might
satisfy a rivet counter. This could easily be overcome on
a longer bridge by tapering the side plates up from the
centre to the ends. The overall depth of the pit on mine
is about 3/4". The embroidery hoops are 3/8",
so a taper out to a single hoop depth would look good.
The centre female mount could also be easily recessed
into the pit floor, allowing the male end to project
below the visible plane of the pit floor.
Lee Weldon
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