Designing a replacement Alps Plotter drive gear (was Re: looking for Daisy Wheel Printer)
12 Apr
2013
12 Apr
'13
12:57 a.m.
Message: 26
Date: Thu, 11 Apr 2013 18:49:25 -0400
From: Ethan Dicks <ethan.dicks at gmail.com>
To: "General Discussion: On-Topic and Off-Topic Posts"
<cctalk at classiccmp.org>
Subject: Designing a replacement Alps Plotter drive gear (was Re:
looking for Daisy Wheel Printer)
Message-ID:
<CAALmimn-amKc8rMuGmaua4hqmR527STr8B30qx_TJMPKSzr_Qg at mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1
[snip]
Mention of the Alps plotter reminds me that we've had various discussions
about all the plotter mechs with broken gears but we've never worked out
the details on fabricating replacement gears. I've learned a lot about
fabrication over the past couple of years, so I wanted to take another stab
at the discussion to fill in the parts I don't (yet) understand...
So I was looking at this gear generator...
http://woodgears.ca/gear_cutting/template.html
... thinking that you can't fabricate a good replacement until you
have the data on what you are replacing. I'd like to try to make
either a flat (DXF) design file or a 3D (STL) design file of a
gear replacement candidate. It's possible that with so few
leaves (teeth) and such a small size (1/8" / 3mm across the
face, 1/20" / 1.27mm shaft) that there will be fiddling for
undercut, etc., but I wanted to at least make *something*
that could be tried for good fit.
So that web-based tool can make a bitmap image of a
gear given the right data, but my own 2D CAD skills aren't
honed enough to draft up a DXF of a gear. Is there anyone
on the list here who is good with 2D CAD and has time
to make an image of a gear? I'm fine with turning that into
3D and seeing how things would all turn out. I still have
several broken plotters and would like to get them working
again.
Cheers,
-ethan
Ethan,
I may be able to draw up a gear like this, but like the "gear
generator," I'd have to have the correct gear data to know what to
draw. I'm willing to try.
What specs should I try to draw a gear to? I have access to both 2D &
3D drafting/modeling software (AutoCAD & SolidWorks).
Do you intend to use a 3D printer to try to manufacture the gear?
I suppose these gears are spur gears with involute gear teeth.
What is the pressure angle?
What is the total number of teeth?
What is the pitch diameter?
You said the face width is 1/8-inch and the shaft hole fits a 1.27mm
diameter shaft.
Wikipedia (https://en.wikipedia.org/wiki/Gear) has all this info and
more -- I'm pretty sure that you are interested in only spur gears
right now, so you can skim over the other gear-type information on
that page.
Knowing the gear specs may even allow someone to go to the "small
gear" catalogs and maybe even be able to select an "off-the-shelf"
gear for each needed gear. It's possible.
Let me know,
Bob
12 Apr
12 Apr
1:06 a.m.
On Thu, Apr 11, 2013 at 8:57 PM, Bob Vines <bobvines00 at gmail.com> wrote:
I forgot to add links to Stock Drive Products/Sterling Instrument
(http://www.sdp-si.com/index.asp), McMaster-Carr
(http://www.mcmaster.com/?m=true#standard-gears/=ma4xe6), or even a
big dog in the gear world, Boston Gear
(http://bostongear.com/products/open/sg.html). SDP/SI specializes in
small precision gears, et al.
Bob
Message: 26
Date: Thu, 11 Apr 2013 18:49:25 -0400
From: Ethan Dicks <ethan.dicks at gmail.com>
To: "General Discussion: On-Topic and Off-Topic Posts"
<cctalk at classiccmp.org>
Subject: Designing a replacement Alps Plotter drive gear (was Re:
looking for Daisy Wheel Printer)
Message-ID:
<CAALmimn-amKc8rMuGmaua4hqmR527STr8B30qx_TJMPKSzr_Qg at mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1
[snip]
Mention of the Alps plotter reminds me that we've had various discussions
about all the plotter mechs with broken gears but we've never worked out
the details on fabricating replacement gears. I've learned a lot about
fabrication over the past couple of years, so I wanted to take another stab
at the discussion to fill in the parts I don't (yet) understand...
So I was looking at this gear generator...
http://woodgears.ca/gear_cutting/template.html
... thinking that you can't fabricate a good replacement until you
have the data on what you are replacing. I'd like to try to make
either a flat (DXF) design file or a 3D (STL) design file of a
gear replacement candidate. It's possible that with so few
leaves (teeth) and such a small size (1/8" / 3mm across the
face, 1/20" / 1.27mm shaft) that there will be fiddling for
undercut, etc., but I wanted to at least make *something*
that could be tried for good fit.
So that web-based tool can make a bitmap image of a
gear given the right data, but my own 2D CAD skills aren't
honed enough to draft up a DXF of a gear. Is there anyone
on the list here who is good with 2D CAD and has time
to make an image of a gear? I'm fine with turning that into
3D and seeing how things would all turn out. I still have
several broken plotters and would like to get them working
again.
Cheers,
-ethan
Ethan,
I may be able to draw up a gear like this, but like the "gear
generator," I'd have to have the correct gear data to know what to
draw. I'm willing to try.
What specs should I try to draw a gear to? I have access to both 2D &
3D drafting/modeling software (AutoCAD & SolidWorks).
Do you intend to use a 3D printer to try to manufacture the gear?
I suppose these gears are spur gears with involute gear teeth.
What is the pressure angle?
What is the total number of teeth?
What is the pitch diameter?
You said the face width is 1/8-inch and the shaft hole fits a 1.27mm
diameter shaft.
Wikipedia (https://en.wikipedia.org/wiki/Gear) has all this info and
more -- I'm pretty sure that you are interested in only spur gears
right now, so you can skim over the other gear-type information on
that page.
Knowing the gear specs may even allow someone to go to the "small
gear" catalogs and maybe even be able to select an "off-the-shelf"
gear for each needed gear. It's possible.
Let me know,
Bob 
1:29 a.m.
On Thu, Apr 11, 2013 at 8:57 PM, Bob Vines <bobvines00 at gmail.com> wrote:
> Mention of the Alps plotter reminds me that
we've had various discussions
> about all the plotter mechs with broken gears but we've never worked out
> the details...
I may be able to draw up a gear like this, but like
the "gear
generator," I'd have to have the correct gear data to know what to
draw.
Understandable. If I had more numbers up front, I would have given them.
What specs should I try to draw a gear to? I have
access to both 2D &
3D drafting/modeling software (AutoCAD & SolidWorks).
Do you intend to use a 3D printer to try to manufacture the gear?
I do not. I was contemplating trying to laser-cut some out of Delrin sheet,
something I did not have access to the last time this conversation made
its rounds. As before, FDM printers do not have the resolution for such
a tiny part, and other technologies (sintered powder or UV-cured resin)
are likely to be too brittle, especially with such fine features.
I suppose these gears are spur gears with involute
gear teeth.
As far as I know that is true.
What is the pressure angle?
I do not know.
What is the total number of teeth?
What is the pitch diameter?
I do not know without digging out a printer to check. I used to have
4MP close-up pictures (taken with my gear in 2003 back when
Electronic Goldmine was surplusing the bare Alps printer mechs
for a few dollars) but I don't know exactly where those photos
are at the moment. My best approach right now would be to
drop one on a high-res flatbed scanner (1200 dpi) to get a
reasonable "to scale" picture, but I don't have a gear in front
of me at the moment (I do have them in town).
You said the face width is 1/8-inch and the shaft hole
fits a 1.27mm
diameter shaft.
That's what I've scraped from previous conversations about this
gear. I now own a micrometer so with a gear in hand, I have
a chance of confirming that to better accuracy.
Wikipedia (https://en.wikipedia.org/wiki/Gear) has all
this info and
more -- I'm pretty sure that you are interested in only spur gears
right now, so you can skim over the other gear-type information on
that page.
*nods*
Knowing the gear specs may even allow someone to go to
the "small
gear" catalogs and maybe even be able to select an "off-the-shelf"
gear for each needed gear. It's possible.
I think we (the cctalk community at the time) looked into that and nobody
had such tiny gears with so few large teeth in their catalog. There were
calls to remove a gear and make castings (most gears are already broken
making that difficult) or using a lathe to make a fresh brass gear, etc.
Someone apparently did take a stab at a homemade brass gear but
declared it too expensive to warrant starting up a small run. Perhaps
hobby CNC has evolved to the point now where one could do a gear
with less labor and make an individually cut gear easily enough to
justify selling it for around $5. Or not.
If I have a DXF or EPS of the face of the gear, I can see if the laser
cutter can make an approximation out of Delrin for nearly free (I just
spend a few minutes when I'm already working on a run and as long
as I don't work past the quarter-hour billing tick on the tool, the time
is already paid for by the other job). I'm not positive that this will
work, but the cost is so low that it's worth a stab. Just need the
silhouette to scale and I'm good to go.
-ethan
1:59 p.m.
On Thu, 11 Apr 2013, Ethan Dicks wrote:
I do not. I was contemplating trying to laser-cut
some out of Delrin sheet,
something I did not have access to the last time this conversation made
its rounds. As before, FDM printers do not have the resolution for such
a tiny part, and other technologies (sintered powder or UV-cured resin)
are likely to be too brittle, especially with such fine features.
Ethan, you might try talking to Shapeways or Ponoko and having the gear
printed out of stainless steel. A very small gear shouldn't cost that
much and may last longer than a delrin part.
There's a very nice gear program here: http://woodgears.ca/gear/index.html
I own a copy and it produces excellent DXF files suitable for laser
cutting.
g.
--
Proud owner of F-15C 80-0007
http://www.f15sim.com - The only one of its kind.
http://www.diy-cockpits.org/coll - Go Collimated or Go Home.
Some people collect things for a hobby. Geeks collect hobbies.
ScarletDME - The red hot Data Management Environment
A Multi-Value database for the masses, not the classes.
http://www.scarletdme.org - Get it _today_!
2:34 p.m.
On Fri, Apr 12, 2013 at 5:59 PM, geneb <geneb at deltasoft.com> wrote:
Ethan, you might try talking to Shapeways or Ponoko
and having the gear
printed out of stainless steel. A very small gear shouldn't cost that much
and may last longer than a delrin part.
I've thought about that, but, if you haven't seen one of these Alps gears,
there is very little material at the bottom of the "teeth", which is why the
gears all split - weak spot combined with either mechanical or thermal
stress. I don't have measurements to quote, but it's only a few hundred
microns of material at most.
I'm not sure what the surface smoothness is of Shapeways printed SS,
but this gear is about the size of a match head with something like
a dozen teeth (think back to the old "slot cars" and the grape-sized DC
motors and the brass gear on them - it's about that size). It's going
to mate with a plastic gear that's smaller than a dime.
There's a very nice gear program here:
http://woodgears.ca/gear/index.html
I own a copy and it produces excellent DXF files suitable for laser cutting.
That's the same website that I linked to at the start of this thread.
-ethan
2:52 p.m.
On Fri, 12 Apr 2013, Ethan Dicks wrote:
Ah, didn't see that.
g.
--
Proud owner of F-15C 80-0007
http://www.f15sim.com - The only one of its kind.
http://www.diy-cockpits.org/coll - Go Collimated or Go Home.
Some people collect things for a hobby. Geeks collect hobbies.
ScarletDME - The red hot Data Management Environment
A Multi-Value database for the masses, not the classes.
http://www.scarletdme.org - Get it _today_!
On Fri, Apr 12, 2013 at 5:59 PM, geneb <geneb at
deltasoft.com> wrote:
Well you might want to replace the tiny pinion gear with a larger one and
reduce the size of the gear it mates to. As long as you've got the space
and can keep the ratio the same, you should be fine.
Ethan, you might try talking to Shapeways or
Ponoko and having the gear
printed out of stainless steel. A very small gear shouldn't cost that much
and may last longer than a delrin part.
I've thought about that, but, if you haven't seen one of these Alps gears,
there is very little material at the bottom of the "teeth", which is why the
gears all split - weak spot combined with either mechanical or thermal
stress. I don't have measurements to quote, but it's only a few hundred
microns of material at most.
I'm not sure what the surface smoothness is of Shapeways printed SS,
but this gear is about the size of a match head with something like
a dozen teeth (think back to the old "slot cars" and the grape-sized DC
motors and the brass gear on them - it's about that size). It's going
to mate with a plastic gear that's smaller than a dime.
There's a
very nice gear program here: http://woodgears.ca/gear/index.html
I own a copy and it produces excellent DXF files suitable for laser cutting.
That's the same website that I linked to at the start of this thread.
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