Ok.
14000 rpm, with a gearbox turning 33% faster would have the output shafts going 18620 rpm.
4 inch pitch X 18620 rpm = 74480 inches per minute X 60 minutes = 4468800 inches per hour.
which is about 70 mph with no slip. take about 5-10% off that for a real number.
Sounds like a stretch, but I haven't seen your secret project. Who knows
