Monday, December 21, 2009

Radio Shack Motors for 1/43 and small 1/32

These three Radio Shack motors are the same size as the SCX 1/43 motor (a Scalextric standard FC-130 motor is shown for size comparison). The small Radio Shack motors will fit in 1/43 cars, and may be used in very small 1/32 cars, including narrow F1 racers from the mid 1960's with full drivers. The FF-030 size is the same in cross section as the familiar F-050 "slim can" motors made for BWA, Scalextric, etc. Shaft is 1.5mm diameter. An oilite bearing is fitted on the metal can end, while the other end of the shaft appears to run in a plastic bearing molded in the end bell.

The three "Rat Shack" motors are in packages labeled 6 volt, 7.5 volt, and 9 volt. Performance specs on the packaging indicate the following:
6v motor 17,000 RPM +/- 15%, 8 gcm minimum stall torque
7.5v motor 20,000 RPM +/-12%, 21 gcm min. stall torque
9v motor 24,000 RPM +/- 12%, 26 gcm min. stall torque

RPM tests with a tachometer showed all motors revving within their stated variability band, at their given voltage:
6v motor: 16,283 RPM at 6v
7.5v motor: 20,458 RPM at 7.5v
9v motor: 23,558 RPM at 9v

Torque was assessed at a uniform 4.07 volts, showing they all have about the same torque:
6v motor: 15.7 gcm at stall at 4.07v
7.5v motor: 14.3 gcm at stall at 4.07v
9v motor: 16.4 gcm at stall at 4.07v

When converted to their rated voltage, we find that all exceed their rated torque:
6v motor: 23 gcm at 6v (8 gram minimum stated on the package)
7.5v motor: 26 gcm at 7.5v (21 gcm minimum)
9v motor: 36 gcm at 9v (26 gcm minimum)

And finally, the moment of truth. What will they do on 12 volts, a more or less standard voltage for slot cars? Torque was extrapolated upward from the 4.07 test voltage, and RPM was directly read when the motors were given a full 12v:
6v motor: 29,326 RPM/12v, 46 gcm stall torque/12v
7.5v motor: 31,674 RPM/12v, 42 gcm stall torque/12v
9v motor: 29,849 RPM/12v, 48 gcm stall torque/12v

It appears that all three motors are the same, given the natural performance variation of very small DC motors of this type. Even though they are labeled at three different performance levels, and three different voltages, I could not detect any meaningful, significant differences between the motors.

The SCX Compact 1/43 motor is rated 22,000 RPM/12v, 33 gcm torque/12v. No tests of the SCX Compact have been conducted, but it looks like the Radio Shack motors may make your little slot cars go faster.

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