SCX makes a menagerie of RX-something motors that are known to run in a wide range of RPM. I recently tested several brand new SCX motors, on a standard 12 volts, under good testing conditions. I used my non-contact infra-red tachometer, and broke in the new motors by running for an hour (45 minutes on 6 volts, then a run for 15 minutes on 12 v). The motors were fixed to a base, and wired in parallel. All the motors were running through the whole test, only being shut down for a half minute at a time, to move the timing disc from motor to motor.
RX-41: 14,378 RPM
RX-42: 14,971 RPM
F1: 15,390 RPM
RX-81B: 17,184 RPM
RX-42B: 18,081 RPM
RX-41B: 18,256 RPM
I had recently tested a new Pro Speed at 20,700 RPM, so that remains the fastest of the available SCX motor range.
Now, some slot car racers feel the SCX range is too slow. The "B" motors address these concerns; and the 20k Pro Speed brings things into the range of standard Fly and Scalextric motors. However, other fast motors, particularly as used by magnet racers, rev into the 30k range.
I just happened to have a Parma 16D with pink endbell, now out of production, midway between the Death Star and Super 16D. I swapped the 16D armature into the SCX RX-42 case (very easy to do), as it is a perfect fit. At 12 volts, after only a minute of running, the tach read 43,950 RPM. Next time you take your unlimited magnet missiles to a track with a long straight, try an SCX RX-Parma 16D!
The Slot Car News Motor List has been updated with the above information. Thanks to SCX for supplying the test motors, and thanks to Bubba of Shoreline Model Raceways for supplying a pink-endbell 16D.