"DoN. Nichols" wrote in
message
rvers.com...
According to Ed Huntress
:
"Tom Miller" wrote in
message
...

Anybody have any thoughts on if there are any
standards for epicycloid gears? They were
supplanted by involute profiles many years
ago on
just about everything but clocks. I've found
a few
web sites by Googleing , but any help will be
appreciated.

'Can't help you with standards, but there is
one thing to watch for with
cycloidal gear forms: the between-axes distance
of the meshing gears is part
of the equation. In other words, unlike
involutes, which give you a little
slack in this department, conjugate action of
cycloidal gears depends on
getting the between-centers distance of the
shafts dead right. If you re-cut
or refine epicycloidal gears, thus changing
their effective diameter, you
effectively change the required between-centers
distance. It's tricky.

I think that it was spelled out in either _A
Catechism of
Steam_, or _Modern Machine Shop Practice_ --
both of which are available
in scanned PDF format on the web.

O.K. Here is where to get _Modern Machine Shop
Practice_,
written by Rose, and published back in 1887-1888
("Modern" is obviously
relative. :-). The first three chapters are the
ones dealing with gears,
and each chapter is downloaded separately. They
are about 150-160K per
chapter, at least for the first three.

http://digital.lib.msu.edu/collectio...fm?TitleID=274

I'm looking through it now (on the computer, so
it is very slow
turning pages), and so far, the first chapter is
defining terms and
concepts, including how to apply gearing to
accomplish various speed
ratios.

I would recommend printing out the chapters, so
you can study
them at your own rate for page turning, instead
of being slowed down by
the PDF rendering speed of your computer.

O.K. On page 8, we start getting into the
description of the
cycloid gears.

And the description continues for quite a few
pages, including
information on how to generate the shapes.

There are even details here on how to generate
asymmetrical gear
teeth, for greater strength running in one
direction compared to the
other.

BTW The original dimensions of the gear were
given in mm, but I suspect
that the original was designed and constructed
using inches
instead, unless Australia converted to metric
before I thought
that they did.

Good luck. You might have to dig into the heavy
gear literature. There is a
gear society around that publishes a sort-of
magazine. Check with their
editors.

The old _Modern Machine Shop Practice_ may be
just what he
needs, as it was written before the involute
tooth form came into use.

Good Luck,
DoN.
--
Email: | Voice (all
times): (703) 938-4564
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http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is
dividing by zero ---

Thanks for all the details Don. I'll download it
tomorrow and check it out over the weekend. I too
was tempted to resort to devious methods with
regard to the gears. Even worse, we spent all day
today trying to get the brake shaft out of the
miserable thing. A sixty year accumulation of rust
is nearly as solid as a weld. We finally got it
off this afternoon.. In my previous incarnations I
would have just had one of my fitters cut it off
and press the rusty remains of the shaft out to
send to the scrap merchant. We spent all day and
half a bottle of oxygen getting it off. We will
have to replace the shaft anyway,but that's what
they want, so that's what they get.

We still have a lot of work to do before we have
to cut the gears but our target is to have it
runable by the 12 Jun as there is a rally we would
like to display it at.

regards

Tom Miller