My colleagues in the Midland Mills Group (mostly interested in corn mills)
regularly say that wooden teeth were preferred, even with metal machinery,
because they were easily replaced. Mishandling the mill could easily strip
several teeth, so that it was desirable to have something that could easily
break and be replaced, thus preventing worse damage.
What is your 1723 reference? I had heard of the change to driving several
stonenuts off the same great spur wheel, but I had seen a source pinning the
change down.
Peter King
49, Stourbridge Road,
Hagley,
Stourbridge
West Midlands
DY9 0QS
01562-720368
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-----Original Message-----
From: Arch-Metals Group [mailto:[log in to unmask]]On Behalf Of
Lyle E. Browning
Sent: 30 October 2008 16:00
To: [log in to unmask]
Subject: Hybrid gears
Spur gearing is generally recognized as being invented in 1723
allowing the 1 wheel to 1 device problem that had plagued mills from
the get-go to disappear. There was a transitional hybrid period where
the wheels were metal and the teeth were wood. Then it all moved to
totally metal gearing.
Was the transition from wooden lantern/pinion gearing to hybrid metal/
wood to all metal a result of incremental steps from the familiar to
the new a result of the then presumed inherent brittleness of cast
iron or was it a stepwise progression based on the known and workable
system? The problem was in if one bought a cast wheel with teeth and a
tooth broke, you had to replace the entire wheel, so better to have
wooden teeth that if one broke, then the tooth could be replaced. This
was standard on wooden gear systems.
Wooden transmissions used lantern/pinion systems. A secondary thought
was that the move to metal started by using metal for the wheels as it
was cheaper and more durable. Wood was used for the teeth because they
had to mesh with the wooden lantern. Is this a reasonable supposition?
In my surveys of gristmills, I see examples of hybrid wheels under the
stone floor as they were replaced by all metal bevel gears, but which
were kept for various reasons.
At some point in the 19th century, the hybrids stopped and the all
metal gears took over, at least here in VA and elsewhere in the US
that I have managed to find info concerning. When do all metal bevel
gears start?
Were there advances in iron casting that would allow for all metal
wheels with teeth and bevel gears to replace the hybrids?
In short, can metallurgical advances be shown to parallel the
transition from wood to hybrid to metal? Or are we looking at a
conservative step-wise progression for which cast metals already
existed that would work that the millers and other power applications
were slow to adopt?
Any thoughts gratefully received.
Lyle Browning
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