How to Colonize an Asteroid
How to Colonize an Asteroid
While this motor is very crude and inefficient, it cost me less than $5.00 to build from parts I mostly had around the house, and total construction time was under four hours. The hardest part was winding the field magnet and the armature coils.
Note that you can click on many of the smaller images on this page to see larger versions.
The wooden frame of the motor was
constructed from various bits of scrap lumber I had laying around. If you
build your own, look through all of these pictures and you can rig something
up based on what YOU have laying around.
I could have used permanent magnets for the
fields on this motor, but this is a section on electromagnetism -
and I couldn't find any. I made my field coil by winding 75 feet of 26 gauge
enameled magnet wire onto the "U" of a 2.5 in iron Muffler clamp. Note the
fence staple on the left to provide a route for the wires. The coil is wound
in several neat overlapping layers, with a layer of electrical tape between
each. Wind a layer, then wrap with a single layer of electrical tape, and
wind back over the coil you have already wound. Just make sure that you always
wind in the same clockwise or counterclockwise direction in which you started.
The arms of the
"U" bolt are passed up through holes drilled in the bottom of the wooden
frame. The whole assembly is held in place by gravity and by the nuts on
the top of the frame assembly.
The bearings for the shaft are simply screw eyes screwed in to the sides of the wooden frame. The brushes, which will transfer current to the slip rings in the commutator assembly are made from 22 gauge solid copper wire with a couple of inches of the insulation stripped from each end. Note that one is mounted on the top of one wooden cross piece, while the other is mounted to the bottom of the other. This wire must be stiff enough to hold a shape, but not so stiff that it puts too much friction on the commutator assembly.
The armature is made from
a section of iron nail which was cut to fit cleanly between the arms of the
"U" bolt. Before winding the coil for the armature, wrap one turn of 12 gauge
solid copper insulated house wiring around the very center of the nail. Bend
the wire in such a way that it comes straight off the piece of nail, and
that the nail is positioned in a ninety degree angle to the wire. Place the
nail and wire on a chunk of waxed paper and place some two part epoxy on
the union to bind them together.
Wrap one layer of electrical tape around each half of the iron nail, then wind four layers of 26 gauge enameled magnet wire and tape onto the iron nail, making sure to always wind in the same direction. Simply cross over the 12 gauge wire shaft in the center and continue each layer on the other side, as if the shaft were not there.
The commutator in my motor is made from a
section cut out of a broken shovel handle. Drill a hole in the center into
which the wire shaft will fit fairly snugly, and cut a groove into each of
it's sides. Slide this onto the short end of the shaft. The next step is
to fashion the slip rings. I used a tuna fish can, and cut it into 2 strips
the width of the commutator using tin snips. The ends of the strips should
be folded down into the grooves in each side of the commutator. Use a small
screwdriver to fold them neatly into the grooves in the wooden piece. It
is important that the slip rings are as round as possible when the commutator
is assembled, and that none of the metal extends past the edges of the wooden
part or your motor will not function properly.
Cut
a small notch in the folded part of the slip rings so that you have something
to which you can attach the wires from the armature. Using a small butane
lighter, burn the insulation from the ends of the armature wires and clean
with a piece of steel wool. You can solder the wires in place if you wish,
but I simply used some miniature alligator clips to hold it in place. Snap
the slip rings onto the wooden block, and wrap half of them tightly with
electrical tape to hold them in place. Make sure that they are as round as
possible, and that they do not touch each other in the notches.
Make sure that the 12 gauge wire shaft is straight and even, and that the slip rings on the commutator are as round as possible. The gap between the slip rings should be at about a 90 degree angle to the armature assembly. Try spinning the shaft in your fingers to be sure that the assembly is fairly well balanced.
Slide the armature
assembly into the front bearing (a.k.a. a screw eye) from the center of the
wooden frame until the armature is against the frame. If the other end of
the wire shaft is too long to fit in the rear screw eye, trim it off a bit.
Insert the back end of the shaft into the rear bearing, and slide the whole
assembly back until the slip rings line up with the brushes.
You should have to bend the brushes slightly outward
to get the commutator between them. If they don't touch the slip rings when
you are done, slide the assembly forward enough to bend them in toward the
shaft, then gently slide the commutator back between them.
There is not much to the electrical wiring of the motor - I did not even use an on/off switch. The use of the terminal strip in the back of the motor is optional, but does make life a lot easier. Apply power to the motor by connecting a 12 volt lantern battery, and it should spin merrily away. If the armature wants to lock in position, then you have the wires to the commutator reversed, causing an opposite magnetic field. Even if you have the magnetic poles in the correct orientation, to get the motor to run properly you may have to disconnect the battery and adjust the position and tension of the brushes. You can also slightly adjust the speed of the motor by slightly rotating the commutator on the shaft so that you change the angle between the armature and the field coils.
If your motor still does not work properly, connect a couple of "D" cell batteries (3 volts dc instead of 12) and manually turn the shaft. You should be able to feel the magnetic fields as resistance or attraction at certain points in the rotation and you should then be able to figure out where the problem lies. Do not leave the motor connected to the batter for very long or the coils will get very hot, and the battery will get drained quickly, due to the extremely poor efficiency of this design.
If you want your motor
to work better than mine, and possibly at a lower voltage, figure out how
to reduce the friction of the brushes, and use a more rigid shaft mounted
in bearings for the armature.
© 1998, Robert Lyon Richards