The electric motor for the small prop pitch is a 24V DC motor. It is not a DC reversable motor that reverses direction by reversing the polarity of the applied power, but uses two different terminals for the application of +24V to reverse direction. A single common terminal is used for the negative power lead.

Many have run these motors on 24VAC and found that it is a real bad idea!

Using AC power to run the motors results in excessive commutator erosion and a relatively rapid decline in the longevity of the commutator.

The motors are not all the same. Some are Right handed, and others are Left handed. The field windings in the motor case are different between the two types. The armatures are the same. The pins on the motor that connect to the jacks in the input end of the gearbox are the same physical pattern, but different pins/jacks must be used for the common lead with each type of motor. See the wiring pagefor details.

Here is what a later model small motor looks like in its standard configuration as it was used in aircraft service.

On the left you can see the motor brake assembly at the top end of the motor case. The brake is activated by a coil when power is applied to run the motor. When the power is off the springs in the brake assembly apply the brake.

We don't need the motor brake to use a standard prop pitch for an antenna rotator. The 9576:1 gear reduction is enough to prevent uncontrolled rotator movement due to wind.

If the prop pitch has been modified to turn faster, via one of the normal methods used by amateurs, then the brake is probably a good idea because the rotator will probably not be able to hold its position in the wind. To properly use the brake for these modified gearboxes the brake coil needs to be powered separately from the motor with a delay to allow the rotator to come to rest before the brake is applied.

On the right is shown the end of the motor that connects to the gearbox. On this end are the four pins that are the electrical connections to the motor. These pins connect to jacks in the forward housing of the gearbox which are wired to the power source.

Here is the late model motor disassembled on the bench with the brake parts removed

Here is an armature with a severly worn commutator.

This normally should not happen very often, but this prop pitch was put in a tower with the original lubricant in it. The seal at the motor end of the gearbox leaked and all the oil ran down into the motor. Oiling your commutator/brush contact causes arcing and eats both the brushes and the commutator. Every used (by a ham) prop pitch that I have seen that dumped its load of oil on the motor has looked like this. When the motor is allowed to run dry there is usually much less commutator or brush wear.

This is what a new or rebuilt  one looks like.

Here is a sequence of photos showing a motor going together.

         Empty motor case with field windings & brush sockets                                   Brushes installed and output end shims

Armature is installed                                                                                   End Cap fasters and bearing shims

                   End cover is installed                                                Nuts for end cover and jumper  across brake lead terminals