It sounds more extreme than it is—“forced exercise” is simply tandem riding in which patients are required to pedal 80-90 rpm.
Meanwhile, they kept up a jabber that sounded like a 33-1/3 rpm record being played 78 rpm.
Portions of the turbine also volitized; idling at eight thousand rpm, it became unstable.
Later tests would put the rim through check-out tests to as high as 1.59 gee, but "normal" operation had been fixed at two rpm.
The out-of-balance fan, turning at close to 35,000 rpm, flew to pieces and the air cushion vanished.
1906, initialism from revolutions per minute.
rpm or r.p.m.
revolutions per minute