Monday, November 10, 2008
Ranch Design kindly sent a small box motor for testing (GM14955, left above).
A test of RPM at 12.0 volts showed an average of 27,932 over a minute of free running, no load. Low RPM during that time was 26,762 and high RPM was 30,045. The wide variation was caused by front to back movement of the shaft during testing, which could be heard as an intermittent vibration.
This is a very lightly constructed, low power motor, with a short shaft that would not reach deep enough into the torque testing arm to allow torque tests to be completed. About 20-30gcm is estimated by feel. This motor will fit in a small space; the box is 19mm long, 17mm wide, and 9.5mm tall.
A second motor was tested, listed on the Ranch Design site as GM9330 (right, above). This is a slim can of the FF-050 general configuration, with an extra large oilite bearing on the can end. It revved to 39,312 average RPM over a minute of running, with very little variation. This is a very smooth-running motor. Torque tests showed approximately 105 gcm at 12 volts, averaged over several armature positions.
Both motors are sold by Ranch Design primarily for 1/43 slot cars, but the FF-050 could be used in 1/32 cars which would take that size motor. Due to the high RPM and good torque, it has racing potential. Power output computes to 10.3 watts.
Ranch Design also supplies pinions for these small-shaft motors, and a growing line of 1/43 car builders' supplies. Prices are remarkably low.