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Proto48 Article: The art of scratch building is alive and well in Colorado by Tom Mix |
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Drivers in "O" scale are almost impossible to find. And when a set is found it must be machined to Proto 48 standards. This means new tires and the wheel casting must be thinned to be more prototype. Or, build your own.
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These two photos show the wheel rims with attached counter weights
and the aluminum jig for holding everything together for heating
with a torch.
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The next two images show a sheet of 0.040" brass for the spokes. I filed and rounded the full edge of the brass sheet, marked it off, then used a slitting saw to cut strips. Another small piece of .32 brass sheet had a cut out pattern to match the length and taper of each spoke.
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This photo shows a close up of the aluminum soldering jig with
some spokes in place and more cut to length ready to insert in the
slots. Note that some of the spokes must be cut to progressively
shorter lengths on the bottom of the crank hub and to the counter
weights. After spokes are filed to length and fitted in the slots,
the jig is positioned in a vice and a torch is used to heat up the
complete aluminum jig. Then solder is touched to each spoke where
it touches the rim, counter weight, and hub. Just enough solder
to give a little filet to give the appearance of a prototype wheel
casting.
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The next two images show a section of a brass bar holding jig in
the lathe that is used for both trimming the insides of the steel
tires to fit the wheel, and as you can see, to bore the center axle
hole to the proper size, and most importantly, to true the tire
with the axle hole. This is one of the critical points in assembling
the drivers. I used 6MM axle stock. The fit must be enough to need
pressure to push the wheel onto the axle…but only a little!
I learned a long time ago that trying to make a real tight fit usually
caused the axle hole to distort and the wheel to go on crooked.
I use LocTite and it works! (LocTite is also used to attach the
steel tires to the wheels. The insulated wheels use .10 x .100 strips
of styrene). You have to move right along or it will begin to cure
before you have the wheel set ready to assemble in the quartering
tool. I press a driver, one each axle, then after some cure time
for the LocTite, get the second driver ready to go on. Using pins
in the cranks, positioning the 90 degrees required, then using a
vice with the quartering tool, press on the second wheel on the
axle.
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The completed set for the Mountain engine. The steel tires on this
set are from Pat Mitchell. All the other tires on my engines were
machined on my Emco lathe from stainless steel.
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A close up showing that filet of solder to make it look like a casting.
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