That's pretty interesting, Brian. 18.5 meters per second equals 43,701 inches per minute (18.5 meters × 39.37 inches/meter × 60 seconds). If it's a 7-pin 3/8" driver (5.25 inches per revolution) the stated speed is achieved with 8324 RPM. If it's a 7-pin .325" driver (4.55 inches per revolution) the stated speed is achieved with 9604 RPM.
18.5 meters/second converts to 41.4 mph or (The Bestial?) 66.6 kph.
Glen