How to time a GWS EPS300C Motor

The GWS EPS300C Motor/Gearbox unit uses a Mabuchi 370 (speed 300) motor. These motors are pretimed at the factory for forwards rotation. In a normal tractor prop configuration (Prop at the front of the plane) the motor will need to run in reverse due to the spur gearbox. This mismatch will give poorer efficiency and reduced motor life and power. By correcting the timing we can improve the power output by as much as 25% for the same power in.

Step 1

First you need to unsolder the capacitors from the case.

 tb-unsolder.jpg (10K)
tb-mark.jpg (9K)

Step 2

Next mark the case and endbell with a felt tip pen so you can return the endbell to its original position if needed.

Step 3

Prise back the four small metal tabs with a small pair of side cutters. This will help loosen the endbell.

 tb-tabs.jpg (9K)
tb-rotate.jpg (8K)

Step 4

Using a pair of needle nose pliers rotate the endbell clockwise by 7mm. Bend back the tabs to lock the endbell in place. Don't forget to solder the Caps back on!

NOTE: For a more accurate adjustment hook your motor up to a 5v power supply (With no prop!) with an accurate ammeter in series. Measure the current with the timing in the original position, it should be about 0.80A. Monitor the current while rotating the endbell clockwise. You should see the current drop and then rise again. Stop the rotation when the current reaches 0.80A again.
Back to Articles