Subject: Re: Coming up dry for Alps/Radio Shack/Atari/Commodore plotter gears

From: "Dwight K. Elvey" <[email-masked]>
Date: Wed Apr 23 13:02:59 2003

Hi
 As long as the load is not that great, one can whack
out the center with a drill and then notch it with a file.
The drill needs to be larger than the OD of the inner splins.
You then fill the voids with a mixture of epoxie and
fiber glass wool. Using something like JB Weld will
make the material as hard as most plastics. To keep
things aligned while the epoxie is setting, make a
jig to hold things by drilling some concentric holes
in layers of plywood that are bolted together, for alignment.
You need to put a wax surface on the plywood where
the epoxie will be so it doesn't stick.
 It isn't real clean looking but should be functional.
Dwight

>From: "Mail List" <[email-masked]>

>
>Hello Ethan,
>
>Internal splines, which is basically what that extrusion die would be are
>much harder to do than cutting gear teeth on the OD of a gear blank.
>The internal splines would have to be done on a slotter ( or possibly
>a shaper with the right set up, i.e. some cutting machine with a linear
>reciprocating cutting motion ) or cut into the die with EDM or wire
>EDM processes. Much more difficult, and therefore more expensive
>manufacturing processes. Original gears probably were shot in a
>plastic injection mold, but the mold making is very expensive too, and
>not something to do for very small production runs. Too bad you couldn't
>find someone with a broach, because broaching internal splines might
>not be as expensive a manufacturing process as long as you found
>someone with the broach already made up. To have a tool and die maker
>have to make a broach would also be expensive. Also extrusion die blank
>material would have too not be too hard to broach. But then you have to
>have the extrusion process set up and run. All in all, if you can't find them
>already made up, milling the teeth into blanks or slotting on a lathe are
>probably going to be your only really feasible options.
>
>Best Regards
>
>
>
>
>At 08:13 AM 4/22/03 -0700, you wrote:
>>Having worked out the pitch of the broken drive gears (120), and
>>having looked on a couple of web sites _and_ contacted someone
>>at Boston Gear, it's looking grim.
>>
>>According to the e-mail I got back, Boston Gear doesn't carry anything
>>finer than a pitch of 64.  When I asked who did carry such gears, the
>>answer was: "I am not familiar with any company that makes miniature
>>gearing." :-(
>>
>>My goal all along has been to find a company that has a bag of these
>>on the shelf.  I had no idea it was such an unusual item.  I don't
>>relish the idea of fabrication, but maybe that's what we're facing.
>>
>>Rather than machining each gear, I wonder how hard it would be to
>>make an extrusion die to pump out a long gear and cut it into 5/32"
>>slices?
>>
>>-ethan
>>The New Yahoo! Search - Faster. Easier. Bingo
>>http://search.yahoo.com

---

From: Ethan Dicks <[email-masked]>
Date: Wed Apr 23 13:03:14 2003

--- "Dwight K. Elvey" <[email-masked]> wrote:
> fiber glass wool...

That sounds interesting for a large enough gear, but in this case,
it's about 1/8" in diameter and 5/32" long with a bore of 1/20".

I don't think I'll be trying to whack and/or notch a chunk of
plastic that's smaller than a tic-tac.

-ethan

---

From: Tothwolf <[email-masked]>
Date: Wed Apr 23 13:05:42 2003

On Tue, 22 Apr 2003, Ethan Dicks wrote:

> That sounds interesting for a large enough gear, but in this case, it's
> about 1/8" in diameter and 5/32" long with a bore of 1/20".
>
> I don't think I'll be trying to whack and/or notch a chunk of plastic
> that's smaller than a tic-tac.

What type of plastic were these gears made from? I was thinking about
pulling out one of my plotters, but I don't exactly remember where I put
it right now ;P

If they are made of nylon, I'm surprised that they split. I really expect
to find that they were made of some kind of ABS or ABS blended plastic
that didn't handle the press-fit pressure very well.

Has anyone contacted Alps to see if maybe they might know where the gears
were made originally? It's certainly possible a set of molds might still
be sitting around somewhere...

-Toth

---

From: "Peter C. Wallace" <[email-masked]>
Date: Wed Apr 23 13:06:42 2003

> plastic that's smaller than a tic-tac.

How about making a silicone mold from an original gear and making copies out
of some kind  of plastic or epoxy resin?

> The New Yahoo! Search - Faster. Easier. Bingo

Peter Wallace

---

From: "Peter C. Wallace" <[email-masked]>
Date: Wed Apr 23 13:07:13 2003

Peter Wallace

---

From: "Jeffrey S. Worley" <[email-masked]>
Date: Wed Apr 23 13:08:16 2003

I've had good luck with a solid two-part epoxy you can find at most auto
shops - usually right by the register.  It comes in a clear plastic
cylinder about 1' in diameter and 3" long.  It is grey in color and has
the consistency of putty.  The two parts are together already in the
form of a core of one material and a shell of another.  You cut off a
piece and knead it til' it is fully mixed.  It will get warm and smell
like a ladies' old-style hair 'permanent'. When cured it is heat
resistant enough that I used it to seal the headers on my BMW R60/5, and
strong enough that I've used it in place of metal for lots of repairs in
printers, tape drives, you name it.

I think it is strong enough to make gears out of in that scale. It forms
very well and is cheap as dirt for what it does (about four bucks a
tube). For the gears, I'd let it cure for 24hrs before doing any
machining.

I mention this because someone else mentioned JBWeld.  JB is a great
product but is liquid which makes it harder to handle and unsuitable for
many of the jobs I've used the more solid product for.

Best,

Jeff

-----Original Message-----
From: [email-masked] [mailto:[email-masked]]
On Behalf Of Peter C. Wallace
Sent: Tuesday, April 22, 2003 4:41 PM
To: [email-masked]
Subject: Re: Coming up dry for Alps/Radio Shack/Atari/Commodore plotter
gears

> plastic that's smaller than a tic-tac.

How about making a silicone mold from an original gear and making copies
out
of some kind  of plastic or epoxy resin?

Peter Wallace

---

From: Tothwolf <[email-masked]>
Date: Wed Apr 23 13:08:46 2003

-Toth

---

From: [email-masked] (Tony Duell)
Date: Wed Apr 23 13:09:46 2003

> out the center with a drill and then notch it with a file.

Rather you than me. This gear is about 1/8" OD (that's from memory, 
whatever you do, don't make one on that spec :-)). I would not fancy 
trying to file internal splines on a hole about 2mm (i.e. the 'root' 
diamater of the gear) in diamater...

-tony