50Hz vs 60Hz fixed drive speed ?

Tom> A friend and I were discussing 8" floppy drives recently, in Tom> particular that they often have two pulley sizes so that the Tom> rotational speed is 360rpm regardless of 50Hz or 60Hz operation, Tom> assuming that they are setup properly. Tom> The question then turned to whether or not a fixed hard drive Tom> would typically be designed in a similar fashion, such that the Tom> spindle would rotate at the same number of RPM when configured Tom> for 50Hz or 60Hz operation, or if they did not worry about the Tom> speed differences as the media was not removable? Looking at some DEC drives in the Peripherals Handbook.... the RS04 fixed disk (head per track) drive spins slower with 50 Hz power. Various removable pack drives (RP04, RK03, RP03) all show a single RPM spec but two models, one 50Hz, one 60Hz. Of course, voltage is another consideration. A Maintenance manual would give more detail about whether there really are two different pulleys or the like, but the data suggest that this is indeed the case for the removable drives. paul