One of the old steam rollers at the museum where
I spend a bit of time as a volunteer,is up for
restoration.
We have removed the wheels and gear train covers
to find that the final drive gears are badly worn.
The pinion has 14 teeth and the bull gear has 72..
The bull gear is about 1160 mm diameter on the
pitch circle. As we haven't removed the shafts
yet, I don't have exact centre to centre
distances. Looks like a straight forward exercise
in gear cutting, except for one problem. The gears
appear to be epicycloid in profile. The bull gear
, we (I) intend to draw in a cad program and send
a DXF file to a contractor with a CNC plasma
cutter.The pinion will have to be milled I think..
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.

Regards

Tom Miller

Tom Miller wrote:

One of the old steam rollers at the museum where
I spend a bit of time as a volunteer,is up for
restoration.
We have removed the wheels and gear train covers
to find that the final drive gears are badly worn.
The pinion has 14 teeth and the bull gear has 72..
The bull gear is about 1160 mm diameter on the
pitch circle. As we haven't removed the shafts
yet, I don't have exact centre to centre
distances. Looks like a straight forward exercise
in gear cutting, except for one problem. The gears
appear to be epicycloid in profile. The bull gear
, we (I) intend to draw in a cad program and send
a DXF file to a contractor with a CNC plasma
cutter.The pinion will have to be milled I think..
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.

Regards

Tom Miller

Seeing as you are replacing both gears, why not update
the profile?

Tom

"Tom" wrote in message
...
Tom Miller wrote:

One of the old steam rollers at the museum
where
I spend a bit of time as a volunteer,is up for
restoration.
We have removed the wheels and gear train
covers
to find that the final drive gears are badly
worn.
The pinion has 14 teeth and the bull gear has
72..
The bull gear is about 1160 mm diameter on the
pitch circle. As we haven't removed the shafts
yet, I don't have exact centre to centre
distances. Looks like a straight forward
exercise
in gear cutting, except for one problem. The
gears
appear to be epicycloid in profile. The bull
gear
, we (I) intend to draw in a cad program and
send
a DXF file to a contractor with a CNC plasma
cutter.The pinion will have to be milled I
think..
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.

Regards

Tom Miller

Seeing as you are replacing both gears, why not
update
the profile?

Tom

The conservators(sp?) have decreed that we must
stay as close as possible of original
specifications. I agree it would be a lot easier
but THEY have spoken! I suppose there is some
merit in it as it was the last stem roller built
in Australia.

Tom Miller

Tom Miller wrote:

"Tom" wrote in message
...
Tom Miller wrote:

One of the old steam rollers at the museum
where
I spend a bit of time as a volunteer,is up for
restoration.
We have removed the wheels and gear train
covers
to find that the final drive gears are badly
worn.
The pinion has 14 teeth and the bull gear has
72..
The bull gear is about 1160 mm diameter on the
pitch circle. As we haven't removed the shafts
yet, I don't have exact centre to centre
distances. Looks like a straight forward
exercise
in gear cutting, except for one problem. The
gears
appear to be epicycloid in profile. The bull
gear
, we (I) intend to draw in a cad program and
send
a DXF file to a contractor with a CNC plasma
cutter.The pinion will have to be milled I
think..
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.

Regards

Tom Miller

Seeing as you are replacing both gears, why not
update
the profile?

Tom

The conservators(sp?) have decreed that we must
stay as close as possible of original
specifications. I agree it would be a lot easier
but THEY have spoken! I suppose there is some
merit in it as it was the last stem roller built
in Australia.

Tom Miller

How old is this machine? late 20s or 30s?

Tom

"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.

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.

--
Ed Huntress

On Thu, 9 Feb 2006 19:58:41 +1100, "Tom Miller"
wrote:

One of the old steam rollers at the museum where
I spend a bit of time as a volunteer,is up for
restoration.
We have removed the wheels and gear train covers
to find that the final drive gears are badly worn.
The pinion has 14 teeth and the bull gear has 72..
The bull gear is about 1160 mm diameter on the
pitch circle. As we haven't removed the shafts
yet, I don't have exact centre to centre
distances. Looks like a straight forward exercise
in gear cutting, except for one problem. The gears
appear to be epicycloid in profile. The bull gear
, we (I) intend to draw in a cad program and send
a DXF file to a contractor with a CNC plasma
cutter.The pinion will have to be milled I think..
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.

Regards

Tom Miller
==========================
Good place to start is "Gears & Gear Cutting" (Workshop Practice
Series) (Paperback) by Ivan Law ISBN 0852429118. He discusses
both cycloid and involute tooth form and suggests ways to produce
a "one-off" gear. see
http://www.amazon.com/gp/product/085...lance&n=283155

I note that several Australian suppliers stock this book.

Good luck on identifying the profile. Do you have a shaper
available, or will this be a lathe/mill-flycut job? Let us know
how things progress.

Uncle George

"Tom" wrote in message
...
Tom Miller wrote:

"Tom" wrote in message
...
Tom Miller wrote:

One of the old steam rollers at the museum
where
I spend a bit of time as a volunteer,is up
for
restoration.
We have removed the wheels and gear train
covers
to find that the final drive gears are badly
worn.
The pinion has 14 teeth and the bull gear
has
72..
The bull gear is about 1160 mm diameter on
the
pitch circle. As we haven't removed the
shafts
yet, I don't have exact centre to centre
distances. Looks like a straight forward
exercise
in gear cutting, except for one problem. The
gears
appear to be epicycloid in profile. The bull
gear
, we (I) intend to draw in a cad program and
send
a DXF file to a contractor with a CNC plasma
cutter.The pinion will have to be milled I
think..
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.

Regards

Tom Miller

Seeing as you are replacing both gears, why
not
update
the profile?

Tom

The conservators(sp?) have decreed that we
must
stay as close as possible of original
specifications. I agree it would be a lot
easier
but THEY have spoken! I suppose there is some
merit in it as it was the last stem roller
built
in Australia.

Tom Miller

How old is this machine? late 20s or 30s?

Tom


1939 is on the nameplate

Tom Miller

On Thu, 9 Feb 2006 19:58:41 +1100, "Tom Miller"
wrote:

One of the old steam rollers at the museum where
I spend a bit of time as a volunteer,is up for
restoration.
We have removed the wheels and gear train covers
to find that the final drive gears are badly worn.
The pinion has 14 teeth and the bull gear has 72..
The bull gear is about 1160 mm diameter on the
pitch circle. As we haven't removed the shafts
yet, I don't have exact centre to centre
distances. Looks like a straight forward exercise
in gear cutting, except for one problem. The gears
appear to be epicycloid in profile. The bull gear
, we (I) intend to draw in a cad program and send
a DXF file to a contractor with a CNC plasma
cutter.The pinion will have to be milled I think..
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.


tom, not that I understand it all, but:

http://www.du.edu/~jcalvert/tech/trochoid.htm

is, truly, interesting if one wants to know more about the epicycloid
gear forms.

Mike in BC

Tom,

Are your museum conservators technical types who KNOW the difference
between the two gear profiles, or are they political appointees
throwing their weight around?

If the latter case just make the appropriate drawings and tell the gear
cutting outfit verbally that alternative, better, cheaper, profiles are
acceptable. (The "cheaper" is to CYA)

Unless, of course, your museum has sooooo much money to throw around on
this that one could make a career out of this one job. (I'm available
as a consultant on this! )

Let us know what finally happens.

Regards,

Wolfgang

I think you should order a set of involute gears as a "stopgap" measure, so
that restoration can proceed, pending receipt of the proper cycloidal gears.
In the meantime, the steps in acquiring the "permanent" set won't have to be
pushed very hard, and perhaps will grow complete cold.

Leo Lichtman wrote:
I think you should order a set of involute gears as a "stopgap" measure, so
that restoration can proceed, pending receipt of the proper cycloidal gears.
In the meantime, the steps in acquiring the "permanent" set won't have to be
pushed very hard, and perhaps will grow complete cold.


That's a standard way to handle many such difficult restorations,
especially those that intend to operate the device. Fit new parts, being
careful (in so far as possible) to make all necessary modifications to
the NEW parts only, keeping the original parts unmodified, so the
'restoration' is completely reversible. Then keep the old parts for
those that need the historical information they represent, and run the
device using the new (and expendable) parts.

Dan Mitchell
============

They're not restoring this to use for road building, they're
restoring it for a museum. It should be as close to the
original as possible, or else why not just use photos and
paper mache models?

wrote:
Tom,

Are your museum conservators technical types who KNOW the difference
between the two gear profiles, or are they political appointees
throwing their weight around?

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
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

"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
(too) near Washington D.C. |
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

wrote in message
...
On Thu, 9 Feb 2006 19:58:41 +1100, "Tom Miller"
wrote:

One of the old steam rollers at the museum
where
I spend a bit of time as a volunteer,is up for
restoration.
We have removed the wheels and gear train covers
to find that the final drive gears are badly
worn.
The pinion has 14 teeth and the bull gear has
72..
The bull gear is about 1160 mm diameter on the
pitch circle. As we haven't removed the shafts
yet, I don't have exact centre to centre
distances. Looks like a straight forward
exercise
in gear cutting, except for one problem. The
gears
appear to be epicycloid in profile. The bull
gear
, we (I) intend to draw in a cad program and
send
a DXF file to a contractor with a CNC plasma
cutter.The pinion will have to be milled I
think..
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.


tom, not that I understand it all, but:

http://www.du.edu/~jcalvert/tech/trochoid.htm

is, truly, interesting if one wants to know more
about the epicycloid
gear forms.

Mike in BC
Thanks Mike All information helps.

By the way, is that BC as in British Columbia?
I spent my first 28 years in Alberta and
Saskatchewan,before I discovered that not everyone
in the world had to shovel snow off their
doorsteps every morning for six months of the
year..

They're not restoring this to use for road building, they're
restoring it for a museum. It should be as close to the
original as possible, or else why not just use photos and
paper mache models?

In thg original post it was stated that the wear was not
discovered until the gear covers were removed. This makes
me ask will the public even see the gears? If they are
not visiable and its a static display why spend the time
and money doing anything to them?

"Chuck Sherwood"
wrote in message
...
They're not restoring this to use for road
building, they're
restoring it for a museum. It should be as
close to the
original as possible, or else why not just use
photos and
paper mache models?

In thg original post it was stated that the wear
was not
discovered until the gear covers were removed.
This makes
me ask will the public even see the gears? If
they are
not visiable and its a static display why spend
the time
and money doing anything to them?

Actually it was discovered when the covers were
removed. The machine will be a working machine and
not a static display. I hope to drive it at a
rally later this year.

Tom Miller

Both the English and the Swiss have standards for cycloidal gear
profiles, mostly for their (now almost vanished) horological industries.
However, if you examine them, you will find that they actually specify an
approximation to the true cycloidal curve; this consists of an ogival arch
(like a church window) constructed of segments of circular curves, with the
radii specified in a table. And even at that, most users modified the form
beyond recognition- at the Waltham Watch Co., for example, after
experimenting with the cycloidal form for years, they finally threw it out
and used a form of their own invention. The problems of constructing a
cycloid curve in metal are not easy to solve, nor are they new.
In addition, there is the problem of center distances Ed Huntress
mentioned. What he didn't say is that the form of the gear tooth also
depends on the tooth count of its mating pinion. So, to cut a true
cycloidal form with form cutters, one needs a set of cutters, for each tooth
size, which includes a range of forms for the range of gear tooth counts
(just as for involute) but for each pinion count as well. By the end of the
19thC, Brown and Sharp had gotten it down to only 64 cutters for each pitch
size, vs. 8 for involute (though they offered sets of 32 for non-critical
work.) You can see why involute took over.
Another reason might be that involute is better suited to gearing
down (e.g. the speed of a gasoline engine to the speed of a tire, or an
electric motor to a loom) while cycloidal is better suited to gearing up
(e.g. the once/day rotation of a grandfather clock winding barrel to the
once per minute of the escape wheel).
So you need to ask yourself, not only, do you really need to
reproduce cycloidal teeth, but also, are the old teeth really cycloidal?
Most guys think they can tell at a glance, but they're not looking at the
curve- they're looking at the whole tooth. Though clock wheel teeth are
usually sharp-pointed, and slenderer than regular gear teeth, those features
have nothing to do with the actual curve. In other words, cycloidal teeth
can be stout and truncated, and involute teeth slender and pointed. These
features have more to do with the overall wheel design (e.g., how deep the
mating wheel is gashed, or the ratio of tooth width to intertooth space, or
the required tooth strength) than with the mathematical curve the tooth
profile follows. And of course, the tooth root being rounded or square is
completely inconsequential to this. And don't forget, most horologists, let
alone gearheads, have never seen a true cycloidal tooth, or even an image of
one (as opposed to what I call an ogival tooth, i.e. what the English &
Swiss standards define as "cycloidal".)
On top of al this, I'd like to point out that the involute form
occupies the middle ground, or boundary, between the epicycloidal and
hypocycloidal curves. That's why any involute gear will mate with any other
of the same tooth size and pressure angle, whereas an epicycloidal wheel
will only mate with a hypocycloidal pinion.
But if you're still hell-bent on cycloidal, the book you need is
Willis's 19thC "Treatise on the Teeth of Wheels". It contains a handy
cardboard calculator he calls the "Odontograph" for generating cycloidal
teeth. There's really nothing practical on cycloidal tooth generation in
any of the 20thC books on gears (at least that I've seen, and that's a lot),
except that the textbook for the Swiss watchmakers training course (given
free to selected candidates in the U.S., but whose German acronym I can't
seem to extrude from my tired brain) has the Swiss "cycloidal" standard.
Good luck!


"Tom Miller" wrote in message
...

"Chuck Sherwood"
wrote in message
...
They're not restoring this to use for road
building, they're
restoring it for a museum. It should be as
close to the
original as possible, or else why not just use
photos and
paper mache models?

In thg original post it was stated that the wear
was not
discovered until the gear covers were removed.
This makes
me ask will the public even see the gears? If
they are
not visiable and its a static display why spend
the time
and money doing anything to them?

Actually it was discovered when the covers were
removed. The machine will be a working machine and
not a static display. I hope to drive it at a
rally later this year.

Tom Miller

In article , says...


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.


If you run into a dead end the folks at this place may be able to supply
some practical advice. I had a nice talk with the owner about what they
go through in order to cut the large epicycloidal gears for tower
clocks.

http://www.balzerclockworks.com/

Ned Simmons

Thanks Ned
I'm making a bit of progress I think. I'll email
them if my ideas don't work out.


Tom Miller


"Ned Simmons" wrote in message
...
In article ,
says...


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.


If you run into a dead end the folks at this
place may be able to supply
some practical advice. I had a nice talk with
the owner about what they
go through in order to cut the large
epicycloidal gears for tower
clocks.

http://www.balzerclockworks.com/

Ned Simmons

On Thu, 9 Feb 2006 19:58:41 +1100, "Tom Miller"
wrote:
One of the old steam rollers at the museum where
I spend a bit of time as a volunteer,is up for
restoration.
We have removed the wheels and gear train covers
to find that the final drive gears are badly worn.
The pinion has 14 teeth and the bull gear has 72..
The bull gear is about 1160 mm diameter on the
pitch circle. As we haven't removed the shafts
yet, I don't have exact centre to centre
distances. Looks like a straight forward exercise
in gear cutting, except for one problem. The gears
appear to be epicycloid in profile. The bull gear
, we (I) intend to draw in a cad program and send
a DXF file to a contractor with a CNC plasma
cutter.The pinion will have to be milled I think..
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.

Regards

Tom Miller
===================
Has anyone wirecut a cycloid gear?

Uncle George

"F. George McDuffee"
wrote in
message
...
On Thu, 9 Feb 2006 19:58:41 +1100, "Tom Miller"
wrote:
One of the old steam rollers at the museum
where
I spend a bit of time as a volunteer,is up for
restoration.
We have removed the wheels and gear train covers
to find that the final drive gears are badly
worn.
The pinion has 14 teeth and the bull gear has
72..
The bull gear is about 1160 mm diameter on the
pitch circle. As we haven't removed the shafts
yet, I don't have exact centre to centre
distances. Looks like a straight forward
exercise
in gear cutting, except for one problem. The
gears
appear to be epicycloid in profile. The bull
gear
, we (I) intend to draw in a cad program and
send
a DXF file to a contractor with a CNC plasma
cutter.The pinion will have to be milled I
think..
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.

Regards

Tom Miller
===================
Has anyone wirecut a cycloid gear?

Uncle George

Good Idea! It never occurred to me! I've already
made a DXF drawing of the pinion and was going to
check out waterjet cutting, but this would give a
better finish..
Thanks

Tom