A Useful Revolution Counter
Page 59
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U1NGINEERS frequently find the I 'I need for a method of determining shaft speeds when constructing auxiliaries for vehicles, or executing installations in workshops. The commonest practice to-day is to use a revolution counter in conjunction with a stop-watch.
A marked improvement on the working principle referred to takes the form of a combined stop-watch with 60second calibration and a revolution counter with a four-digit indicator. The stopwatch has a free wheel and is started The revolution simultaneously with counter is the counter when the directly above spindle is applied to the time-red the rotating shaft. cording dial.
In practice, the first requirement is to determine the most suitable connection to the shaft, the speed of which has to be judged. A shaft having a centre hole is best suited by the pointed, triangular end of the spindle of the instrument, whilst a pointed shaft requires the use of the concave-tipped cap supplied with the device. For work with hardened shafts or spindles, a convex tip is employed. Immediately the instrument is applied to the rotating spindle, the stop-watch is automatically started and the revolution counter begins to work. At the end of a pre-determined period—either 30 seconds or 60 seconds—the instrument is removed, when the counter and watch stop simultaneously.
The counter works irrespective of the direction of rotation, whilst the screw which is employed to reset both watch and counter to zero also serves to wind the clockwork mechanism.
-This instrument, which is sold by A. B. Busfield, 46, Corn Exchange. Leeds, and is priced at £2 2s., should be of marked use in any case in which the end of the shaft is exposed.