12 Apr
2013
12 Apr
'13
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