The photo above shows the smallest of the three mini motors sitting on a dime. All three motors work the same and are based on experiments done on another motor that was published in Instructables a couple of months ago. You can view that instructable here: http://www.instructables.com/id/Simple-dc-motor-with-forwardreverse-and-self-start/
Plastic covered paper clips are the "secret" to making these mini motors. The plastic covering works as an electrical insulator that helps prevent battery shorts and the clips are steel (a magnetic material) that works with the magnet and the battery to keep the motor parts stuck together. Insulated copper wire (non-magnetic) will not work the same, and standard bare steel paper clips give too many chances for electrical shorts. Vinyl covered clips are widely available.
Button batteries power all three motors - I was pleased to find that button batteries are inexpensive when purchased at "dollar" type stores. Typical cost per button was about 50 cents when bought in packages of 4 or more.
Step 1: Video shows all three mini motors working plus some motor build details
Step 2: Parts and tools used for all three mini motors
Motor Wire Magnets Battery Paper Clips
(Neodymium) (Vinyl covered)
Small #30 (2-4) 1/4x1/10 1.5v AG2 1-1/8x3/8
Medium #26 (1) 1/2x1/8 1.5v 357 1-1/8x3/8
Large #26 (1) 3/4x3/16 3v CR2032 1-3/8x3/8
Beads are optional but in general they will make for a smoother running motor - 2 plastic beads per motor.
Batteries are selected to roughly match the diameter of the magnets. I found that there are a number of battery designations that "replace" other battery designations.
I bought a "sampler set" of 50 rare earth magnets (neodymium) from Lee Valley for about $20. I bought the 3/4 inch magnet for the Large motor separately. Here's the Lee Valley link: http://www.leevalley.com/en/wood/page.aspx?p=59362&cat=1,42363,42348,59362
The weight of the armature would often topple the small motor so I ended up using 3 and sometimes four magnets to give it more stability and more "go". A coin containing magnetic material makes a stable base too.
The wire is "enamelled copper magnet wire" - you will need 2-3 feet of wire per motor.
Paper clip dimensions are not too critical but they need to be plastic covered.
All but one of the batteries I tried was non-magnetic (a particular brand of CR2032) - it's best to have magnetic material in the batteries to help keep the motor parts tightly together. Go shopping with a magnet :)
Long nose pliers
Utility knife (an X-acto or craft knife might be easier to use)
Diagonal wire cutting pliers
2 pens used as forms for winding the armature wires (any tapered form of suitable size will do)
A block of wood for a mini work bench when stripping the enamel off the wires
A toothpick or other small non-magnetic stick to give the motor a flick to get started
Step 3: Start with the armature
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With a little practice you can make up a functioning armature in a just few minutes. The video (above) shows the procedure that I use. Except for differences in diameters and wire sizes the armature coils have roughly the same number of turns. I tried more and fewer turns as well just to check any differences in operation. Suggest you go no less than 12 turns when experimenting.
A wire winding form with a taper works best. I used a Sharpie pen for the medium and large coils (inside diameters about 1/4 and 3/8 inches) and a smaller ball point pen tip (3/16 inch) for the small motor coil. Once wound, a few wraps of the wire ends made directly opposite each other on the coil, is sufficient to stabilize the coil and to create fairly stiff axles.
The enamel insulation must be completely removed from one axle and half removed on the other as shown in the sketch. A utility knife or craft knife works fine - just be careful not to nick the wire too much. Once the insulation is stripped check the armature for balance on the axles. A little manipulation of the axle wires will usually get a good enough balance.
The second last photo in this step compares the mini motors with the larger one referred earlier. The final photo in this step shows a variety of armatures that I made up to test with the different motors.
Step 4: Paper clips parts - aka Torms
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The 2 motor components made from the vinyl covered paper clips all have the same general shape, just the size varies to suit the particular motor. Tricky to find a good name for these components as in these motors the paper clips function as:
The photos and video show how the torms are made from paper clips. Because the vinyl covers help prevent the torms from shorting out the motor battery, it's best to leave as much vinyl on as possible. I stripped just the bottom part of the vinyl from the upper torm on the large motor - just enough wire exposed to make good electrical contact.
All torms must be sized and shaped so that the armature is above the top magnet and offset from the center of the magnet to get efficient motor operation.
This series of photo show the steps to duplicate the top torm for the large motor.
Step 5: Final shots and notes
The main photo here compares the three magnet sizes with Canadian and US dimes and quarters.
I also played around with different numbers of magnets and batteries in the medium and large motors. It's easy to connect two batteries in series to double the voltage (just stack them together) as the magnets take care of keeping them together Also, sandwiching a torm between two magnets can often help keep an unstable motor under control.
I also played around with various paper clip colors... as my oldest adult son would say, "it doesn't take much" :)