Using the motor from an original IBM 5 1/4 inch floppy drive for the propeller clock

Lots of you will will not be able to find the Sharp VCR reel motor that I used for the original propeller clock. I've found another motor you can use, and figured out how to modify it to use in the clock.

You'll need to find a Tandon full-height 5 1/4 inch floppy drive, such as used in the original IBM PC and many clones. Other manufacturers made similar looking drives, but Tandon made the best ones, with a motor made by Buehler. That's the one you want.

This motor runs a lot faster than the Sharp motor. The Sharp motor runs about 1800 rpm with 6.5 volts in, and this motor runs about 3000 rpm. You'll probably want to run it at 4.5 to 5 volts to slow it down. The side-effect of this is decreased brightness of your clock(remember, the clock uses the motor voltage minus about 1.25 volts). Use high-brightness LEDs and 47 ohm resistors instead of 120 ohms.



A typical Tandon full-height drive.


The Buehler motor.


Motor after disassembly. The brush assembly has two small brushes and  two small springs that love to fly. You might want to do some of the disassembly inside a clear plastic bag.


Discard the frequency generator assembly.

Disassemble the rest of the disk drive, in particular the main platter/flywheel assembly. It contains two bearings. Save the flanged bearing. It measures 0.625"OD and 0.25"ID.
Drill a 0.625" hole in the motor's end cap(the nose end, not the end with the brush assembly). A stepped drill bit does a nice job.
Get a 0.25" round threaded spacer. The disk drive does not contain one, although the main platter shaft might tempt you. It is probably harder than your hacksaw blade, so forget it. The spacer shown here is stepped down at one end. This is not needed, it was the only type I had with the right dimensions.

The end cap after drilling, the bearing, the spacer, and a step drill


Use a hacksaw to cut three notches in the spacer. The notches should run from end to end, and be big enough to fit a small insulated wire.  This is an enlarged picture showing one end of the spacer.


Grind off the end of the motor shaft, leaving about 0.2". Don't ruin your hacksaw blade trying to saw the shaft.


Glue the spacer on the motor shaft and let dry. I used "Automotive Goop", but you might also have success with "J.B. Weld" or epoxy. Clean all parts with alcohol before gluing.
You'll need three small insulated wires with a Berg connector on one end. The disk drive has lots of wires that are too big to squeeze into the notches in your spacer. The coaxial head wires will work if you strip off the outer insulation and shielding.
Thread the wires through the ball bearing. The bearing flange will need to be on the inside of the motor.
Solder the three wires to terminals on the motor's commutator. The commutator has 7 terminals, you have 3 wires, so symmetry is not possible. Best performance will be with two of the wires on adjacent terminals, and the third wire on the opposite side. Do not disturb the existing motor wires.
Glue the wires to the motor, embedding them in the spaces between armature sections and tying them tightly with thread or dental floss.


Assemble the motor, starting with the brush assembly.  The motor brushes need to be installed correctly, the curved ends towards the center, and the slanted ends to the springs. The grooves on the brushes should be visible as you assemble the brush assembly.  To catch flying parts, assemble the brush assembly inside a clear plastic bag.


The completed motor has a threaded shaft to mount the propeller clock  to, and a three-wire connector that rotates with the motor  to attach to the clock circuit.

 

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