Newsgroups: comp.robotics
Path: brunix!uunet!europa.eng.gtefsd.com!howland.reston.ans.net!spool.mu.edu!torn!watserv2.uwaterloo.ca!watmath!mwtilden
From: mwtilden@math.uwaterloo.ca (Mark W. Tilden)
Subject: Re: Minibot parts
Message-ID: <C9sr4x.F98@math.uwaterloo.ca>
Keywords: Motors etc for small bots
Sender: news@math.uwaterloo.ca (News Owner)
Organization: University of Waterloo
References: <miked.741710070@digibd>
Date: Wed, 7 Jul 1993 13:36:32 GMT
Lines: 62

In article <miked.741710070@digibd> miked@digibd.digibd.com (Mike Drew) writes:
>A while ago someone posted to this group that they were looking for very 
>small motors and other parts for microbots. I was at a local surplus store 
>yesterday and found a box full of drive assemblies for micro recorders. These
>assemblies contain two interesting motors. One is the main drive it is 8mm
>thick 3cm in diam and has a shaft that is 7mm long that is connected to a 
>pully and speed sensor. This motor has a small rubber drive belt that goes 
>around a large (3cm) brass wheel that drives the capstan. The other motor
>is used to load and unload the head. At first I thought this was a small
>solinoid but then I noticed it had a small worm drive on the end. It is about
>1cm in diam and 8mm long it has a shaft of unknown length with a worm gear
>on it. There are other misc gears and switches on the thing. They appear to
>be brand new.  Each is in a small zip lock bag. They are marked $3.50 but
>my instict tells me that if I buy enough that I may be able to get a deal on
>them. If anyone is interested, my email address id miked@digibd.com

Just to further Mikes observations, these devices really are an 
incredible wealth of bits including slip and one-way plastic ratchets, 
teflon pulleys, micro brass/copper washers (2mm), brass pistons,
gears, springs, low-friction rubber capstain, and zinc support trusses. 

The large motor sports a 16 pole, 400 mv magnetic tach built right on
to the shaft above the o-ring drive pulley.  It's sealed and mounted
fairly solidly on two support screws.  The motor itself is a 3Vdc 
efficient high-torque 6 pole pancake style with a massive flat drive magnet 
which takes up over half the motors volume (I have taken these motors
and made successful hovercraft by running them at 8v).  It's the main 
tape drive so it runs very quietly indeed.

The small motor is designed to load and unload the heads for the
'soft-touch' cassette mechanism.  I originally had high hopes for this
device as the worm gear and motor come off in one nice little package,
but alas the lack of a sufficient end bearing makes the motor stall
too easily if the gear undergoes excessive load.  It's a brass-worm/nylon
gear arrangement which makes it difficult to attach anything without
causing tooth damage.  Also the shaft the gear sits on is only
pressure fit, so it does come out easily.  The real advantage of this
device is the motor which can be liberated from the zinc worm assembly
with a knife to break the glue.  This motor is a 3Vdc 3 pole double
bearing 1.5 x 1 cm motor with two advantages: a half inch stainless
shaft, and a 4 brush comutator assembly that gives these things
running times in the hundreds of hours with very little electrical
noise.  The worm attachement can be removed by heating with a bic.

The best thing about these mechanisms is that they can be dissassembled 
with just a tempered fine Phillips screwdriver and an exacto
knife.  Also, the motor casings are steel so they can be soldered to
with a bit of filing.  Heating the cases has little effect on the
motors so long as they are allowed to cool slowly.

And yes, they're so sexy I bought 400 several years ago.  They're
great.  If there's going to be a bulk order, count me in.

Is all.



-- 
Mark W. Tilden.  "Gomi no Sensei des"       _    _    ________________________
MFCF, Un. of Waterloo, Ontario, Canada.    / \  / \  /________________________)
519/885-1211 <mwtilden@math.uwaterloo.ca> //\ \//\ \// ___o___________________
#include (standard.disclaimer);          //  \_/  \_/ (_______________________)
