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MMD > Archives > January 2008 > 2008.01.03 > 04Prev  Next

Ampico Transmission Frame Replication
By Don Teach

I am happy so many people have wanted the Ampico A transmission frames.
There are two foundries left in my area doing brass castings.  These
foundries will work in my job between their big jobs as if they are
doing me a favor.

I have one of the foundries casting Wurlitzer gears.  I gave them
the patterns in October and they have yet to work me into the line.
The patterns I am using for the Wurlitzer gears are the original
patterns from Wurlitzer, loaned to me by the current owner.

I took the Ampico patterns in to them this morning.  They did not like
the way I had arranged them on the pattern board so I am redoing the
arrangement of them on the pattern board over the next couple of nights,
if it warms up in the shop.  It was 22 degrees F. here last night,
which is not normal.

It always sounds so simple but there are a lot of details to consider
when doing sand castings.  First and foremost is finding a foundry that
doesn't use sand that leaves your casting looking as were cast in pea
gravel.  The originals were cast using a pot metal or product known
today more commonly as zinc diecast, using very nice molds that left
the casting needing very little cleanup.  Today there are very few
foundries (I know of zero) that will go to the expense of making the
molds for such a small quantity.

If you decide to do brass castings then you need to make your patterns
3/16-inch to the foot larger than you need.  Brass shrinks 3/16-inch
per foot as it cools.  Cast iron will shrink 1/4 inch.  On small
castings this is not usually a problem when sand casting, as your
pattern will usually get shifted in the sand enough to make up the
difference.  The ones that have been done in the past couple of years
that were cast in brass were cast in green sand.  Those castings were
then cleaned and painted with a heavy coat of black enamel.

I have cut Wurlitzer gears in the past on a vertical milling machine
using an indexing head.  I believe they would have used a different
machine in the old days such as a gear hobbing machine.  I took some
gear castings to a local gear shop with a hobbing machine only to find
they wanted $350 to $400 per gear.

The cutting of gears on a vertical mill, one at a time, is time
consuming, with a learning curve few want to tackle.  Cutting bevel
gears is a whole different matter, with a steep learning curve.  I had
to cut one twenty years ago when I was in machine shop school.  It made
cutting spur gears look simple.

The bottom line is what sounds simple has a learning curve.

Don Teach - Shreveport Music Co.
Shreveport, Louisiana

(Message sent Thu 3 Jan 2008, 17:42:11 GMT, from time zone GMT-0600.)

Key Words in Subject:  Ampico, Frame, Replication, Transmission

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