[GeeTwo]

I calculated it:
top speed = efficiency * free-speed-of-shaft * wheel-radius

For a 1 inch diameter wheel (1/2" radius), a CIM on a 1:1 gearbox, and an 80% efficient drive train, and converting all the units:

0.8 * 5310 rpm * (2 * pi radians/rev) * 0.5in (radius) / (60 sec/min * 12 in/ft) = 18.5 fps.