According to Richard W. :
Exactly. And for the times when it is beneficial to cut in reverse as well.
Of course, until I swap in a three-phase motor, there is no chance of rapidly reversing -- a single-phase motor typically wants to be down to near a stop before you can switch in the other direction. :-)
And no case of the chuck ever being too tightly screwed onto the spindle nose, either.
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Actually -- isn't that 5 belts going from the motor to the input shaft? I would expect gears between that input shaft and the spindle. And five belts -- 2HP per belt, I guess.
Good! Now all you need to do is to find the pulleys. Did they change both, or just one? (Or could it be that the pulleys will interchange between the motor and the input shaft, and are just enough different so they give 1000 RPM with one configuration and 1500 RPM with the other? If so -- that would mean that you don't even have to hunt down the replacement pulleys.
Good Luck, DoN.