BEAM Pieces is a BEAM
What to look for, and how to roll
As is the case with many BEAM parts, you can either
or build the
geared motors you'll need for your 'bots. If you just wanted
to buy off-the-shelf, geared motors are generally expensive;
I generally resort either to salvaging or building mine.
You can buy
some nice gearmotors; although it's tough to find any motor
that's both readily available and affordable. The best deals
will generally be from surplus companies that are selling
goodies that they have salvaged themselves. Here are some
Micro -- These folks sporadically have one, very
nice, gearmotor for sale. Currently, it comes as a part
of a lens assembly, and is listed as part LEN
1022. $10 (US) plus shipping; shipping's much cheaper
if you order just the motor, rather than the whole
assembly. I have details and test results on this
particular motor here.
Pang -- just an average guy, but he's got Copal
motors (part #020, down at the bottom of the page) for
As for salvage,
I've got some preferred salvage sources for gearmotors:
drives -- One of the most-reliable sources of salvage
gear motors is from Macintosh computer floppy drives. The
drive mechanism is essentially the same for either
internal or external floppy drives; buy whatever's
cheaper (you can often buy these at swap meets on
for $3-4). I've got pictures of a representative example
floppy drive mechanism here.
In the process of disassembling one of these beasties,
you'll find that they are full of interesting and useful
hardware. You'll want to hang on to the circuit boards,
fasteners, and micro switches for later use in your
projects. If you're really careful, you can also drive
out the drive's main bearing (a tiny little ball bearing
race, press-fit into the drive frame).
Primarily, though, you'll want to pull out the 2 reusable
motors -- a gear motor, and a stepper
motor. The gear motor is used to eject the floppy,
and has many BEAM uses. The stepper
motor is used to move the read / write heads in and
By the way, while the gear motors from floppy drives
are cheap and durable, they won't run at low voltages
(see my gearmotor
comparison page); most likely you'll want to save
these for battery-powered 'bots.
Motorized lenses -- You can occasionally find a
projector, camera, or camcorder lens that has built-in
focus and / or zoom motors. These are generally small,
high-quality, low-current motors, and accordingly are a
real treat for BEAMbots. If you have a friend (or
make a friend) at a camera store, you can
occasionally get one of these from junked equipment.
If you haven't either bought or salvaged the gear motor
you need, you'll just have to build
your own. I'm aware of just two ways to get there from
- Add a gear train to a small
- "Hack" a hobby servo
Let's take 'em in turn...
Adding a gear train to a small
This can be the cheapest way to go, if you have the
patience and mechanical skills (oh, and lay off the coffee
for a bit...). You'll also need to find gears. You can get
them from a number of places...
(Kitchen Timer Units) -- those little, wind-up timers for
the kitchen. Generally, this isn't cost-effective
(off-the-shelf, these can cost up to $10; there are
cheaper ways to get gears); keep your eyes open, though,
for freebies at yard sales, and the like.
(Oven Timer Units) -- you can find these in old ovens,
washing machines, dishwashers, even an occasional clock
radio (the old kind with the mechanical guts -- the
source of this shining example in the image to the
- Replacement servo gears -- you get these from hobby
shops (about $3 US per set
Hobbies), they're intended as replacement parts for
the gears in hobby servos. You will, of course, have to
build the "gearbox" that will hold your gears together
with respect to each other, and together with your motor.
But more on that in a bit...
Once you have your motor and your gears lined up, it's
time to put them together. If you salvaged an OTU
you already have the gearbox and are ready to go. Otherwise,
you probably have to build your own gearbox as well.
As for the assembly, I'll just point you to the excellent
descriptions and tutorials already out on the web:
If your tastes lean to KTUs,
Robert Stein ("Eisbot") has a good tutorial here
on building a gear motor from a surplus "Walkman" motor
and wind-up kitchen timer.
(your one-stop BEAM shop...) has a neat tutorial on
building a gear motor from an OTU
The end result winds up looking like this:
(image courtesy of Solarbotics
Meanwhile, if you'd like to look at using servo
gears to free-form your own gearbox, Ian Bernstein has
pix of such a beast here.
"Hacking" a hobby servo
Good hobby servos can be found for under $10 (US), but
bear in mind that they're designed for a lifetime of just a
few hundred hours (pager and "Walkman" motors will, in
general, last longer). Hobby servos can easily be modified
for use in BEAM robots.
has a quick tutorial on servo "hacking" here;
"hacking" micro servos is a bit more intricate, but
Jim Brown of the
Personal Robotics Group has a tutorial on that here.
For more information...
The 12/1999 issue of RC MicroFlight has a nice
writeup on micro servos -- go here
to read it.
Rigter wrote up an article on a BEAM controller
for stepper motors here.
This material is oriented toward the use of the
4-wire stepper motors found in Mac floppy drives,
so this'll allow you to make fuller use of your
I've now got a comparison of
commercially-available gearmotors (straight off the
shelf, salvaged, hacked servos) here.