The Wurlitzer Compensating Perforator
By Matthew Caulfield
|[ Editor's Note:|
[ Last August Matthew Caulfield sent to me and David Wasson this
[ description of the Wurlitzer perforator and its automatic tempo-
[ compensating mechanism. The Wurlitzer master rolls, to our
[ understanding, were punched at constant "steps-per-beat". The master
[ roll was pulled by a capstan reader at constant speed (hence constant
[ tempo), and the perforator's tempo-compensating mechanism pulled the
[ output paper at continually increasing speed, just as though it was
[ accumulating on a take-up spool at constant shaft speed.
[ Robbie Rhodes
There is a push rod moving back-and-forth horizontally which ratchets the gear which moves the tractor device which pulls the paper layer through the perforator under the jaws of the perforating dies. Each cycle of the machine and each back-and-forth motion of the push rod advances the paper approximately half or three-fifths of a punch. The push rod does not connect directly to the ratchet gear wheel but is threaded to move up and down a long (about 8-inch very finly threaded rod which is attached to the side face of the gear wheel.
When the operator starts to perforate a roll, beginning at tune 1, he turns the crank on the head of the threaded rod so as to bring the push rod all the way to the top of the threaded rod. Thus the travel of the push rod moves the gear wheel to its most minimal degree, whereas when the push rod is in its lowest position, closest to the center axis of the gear wheel, each motion of the push rod turns the gear wheel to its maximal degree, advancing the paper to the maximum extent. This is the position the machine finds itself in when it is punching the last few feet of a ten-tune roll.
Each complete cycle of the perforator performs many operations, one of which is to turn, by means of another ratchet, the same finely threaded rod the operator set to its starting position, in the opposite direction, each ratcheting out of the thousands needed to perforate a complete roll having the effect of miscroscopically increasing the paper travel at each cycle and correspondingly lengthening the size of each perforation.
Thus, as was told to me, the operator sets the tempo conpensation device only once (at the start of a roll); everything thereafter is done by the machine. Any master can thus be used anywhere in the series of ten tunes making up a roll. However, to normalize the tempo of all tunes to some universal standard, no matter how large or small spatially and lineraly the arranger marked the measures on the master, a "gear" system is used, each master being marked as being of a certain "gear" ("use 48 gear" or "use 32 gear").
No actual gears are changed. There is merely a lever on the side of the perforator, with a pointer to a scale with numbers on it indicating "gear"--much like the tempo scale on a player piano. Each time the operator put a new master on the perforator, he sets the "gear" pointer to the proper number before starting to perforate. That's all there is to it. The gear setting then controls the speed of the master past the index rods that mechanically read the master.
(Message sent Mon 5 Aug 1996, 18:03:13 GMT, from time zone GMT-0500.)