Wurlitzer Chest Repetition Speeds

The following is a letter which first appeared in the March/April 1984 issue of Theatre Organ.

The issue has been raised on page 21 of Theatre Organ., September/October 1983, about the speed of electro-pneumatic action. The subject has been discussed for many years without positive conclusions published. A few years ago my partner, Bob Jacobus, and I were visiting Roy Emison in Kansas City, Kansas. During a happy three-day visit this subject came up and as a result Roy agreed to set up the necessary test equipment to research the subject and try to establish conclusions based on reasonably accurate test procedures. On a subsequent visit, we three reviewed the test equipment and procedures that Roy had set up, and the results he obtained. We ran through the series of tests selecting at random to double-check Roy's findings. We all agreed that the results were as accurate as the testing equipment could produce.

The equipment used was:

1. Strobotac stroboscopic tachometer used to measure speed without drag on the action;
2. Stewart-Warner magnetic speed indicator;
3. Veeder counter used for checking;
4. Facsimile of a Wurlitzer relay and chest built to scale by Roy from measurements taken from his residence-installed Wurlitzer, Style 260, Opus 1173, originally installed in the Newman Theatre, Kansas City, Missouri; and
5. A Wurlitzer Open Diapason pipe, G# number 33 on the 8' scale. It was chosen being near the middle of the compass and for its promptness of speed, a middle-of-the-road choice.

Wind was supplied to the facsimile relay and chest at 10" pressure from he organ blower, a 10-hp Orgoblo. Temperature was controlled at 68° Fahrenheit. Very thin Brown leather and Zephyr skin was used to cover the pneumatics. The facsimile chest and relay were built with a side window for observation purposes.

The following input was important to the test results:

1. Relay contact bar was set to travel ¹⁄₁₆" (¹⁄₃₂" open, ¹⁄₃₂" closed);
2. Slack in the secondary chest pneumatic was made by cutting the flex material oversize to allow for ⁷⁄₆₄" travel of the striker felt before it hit the valve arm spoon; and
3. Magnetic travel of the magnet armature was set at ¹⁄₃₂" using a Wurlitzer Brass Plug magnet.

Observations

The speeds shown on the chart were an average of several readings. It was discovered that the complete relay (both primary and secondary pneumatics) continued to operate after action had ceased on the pipe valve, and continued to operate up to 1700 cycles/minute (28.3 cycles/second), the top limit of the test equipment. As a possible reference point, the speed of a Xylophone hammer was measured up to 700 cy/min (11.7 cy/sec). Bypassing its reiterating contact allowed it to be accelerated up to 800 cy/min (13.3 cy/sec) before it faded out. The term "faded out" refers to the failure of an action to follow the speed of the input. It was observed that the speed of the action (key contact through relay and chest) may be increased from 680 cy/min (11.3 cy/sec) to 1050 cy/min (17.5 cy/sec) (approximately 50%) by changing adjustments and pneumatic covering material. This fact emphasized the importance of correct adjustments for maximum performance.

Comments

A Wurlitzer relay/chest combination operates faster when ultimate adjustments obtain and when pneumatics are covered with Zephyr skin. However, the time elapse difference is minimal (1.5 cy/sec).

Summary

The fastest reiterating speed obtained by the pipe pallet valve in the chest, figure (a) on the chart, was 1150 cy/min (19.2 cy/sec). This was obtained by bypassing the relay with electrical input directly to the chest magnet. Zephyr skin was used on the primary and secondary pneumatics, with travel adjustments as noted. The fastest reiterating speed using brown leather on the pneumatics was figure (b) on the chart, i.e., 1050 cy/min (17.5 cy/sec). This finding definitely proves that Zephyr skin-covered pneumatics are faster. However, the time elapse difference is minimal, i.e., 1.5 cy/sec. Including the relay in the circuit produced the results as shown at figures (c) and (d). The time elapse difference is now much more significant, i.e., 4.2 cy/sec. This greater differ- ence reflects the operation time of the relay pneumatics and travel adjustments. It should also be noted that a combination of Zephyr and Brown leather in the pneumatic circuit increased the speed somewhat over that obtained using only Brown leather. The question raised by the above-listed findings would naturally be the apparent result to an organist. With the assistance of Mr. Gordon Kibbee, noted organist and organ consultant, it was determined by tests he made that a manual key could be played at a Speed of 20 cy/sec, which extends to 1200 cy/min. This figure was obtained using two fingers, one on each hand, striking the same key. Using one finger only, the result was between 16 and 17 cy/sec. The differ- ences between the above and the relay/chest action results indicate a loose relationship between the demands of a competent organist and he response of the organ action.

Reiteration Speeds of Wurlitzer Standard Relay and Chest
Chest					Relay		Maximum Speed
Primary		Secondary			Primary	Secondary
Pneumatic Material	Valve Travel	Pneumatic Material	Valve Travel	Pneumatic Slack	Pneumatic Material		(cy/min)	(cy/sec)
Br. L	¹⁄₃₂"	Br. L	¹⁷⁄₆₄"	¹⁄₃₂"	Relay By-passed		790	(b) 13.1
Br. L	"	Br. L	⁵⁄₃₂"	"	"		1000	17.7
Br. L	"	Br. L	"	⁷⁄₆₄"	"		960	16.0
Br. L	"	Zephyr	"	¹⁄₃₂"	"		1050	17.5
Br. L	¹⁄₁₆"	Zephyr	"	"	"		1030	17.2
Zephyr	¹⁄₃₂"	Zephyr	"	"	"		1150	(a) 19.2
Br. L	¹⁄₃₂"	Br. L	¹⁷⁄₆₄"	¹⁄₃₂"	Br. L	Br. L	680	11.3
Br. L	"	Br. L	⁵⁄₃₂"	"	Br. L	Br. L	800	(d) 13.3
Br. L	"	Br. L	"	¹⁷⁄₆₄"	Br. L	Br. L	770	12.8
Br. L	¹⁄₁₆"	Zephyr	"	¹⁄₃₂"	Br. L	Br. L	810	13.5
Br. L	¹⁄₃₂"	Zephyr	"	"	Br. L	Br. L	830	13.8
Zephyr	"	Zephyr	"	"	Br. L	Br. L	980	16.3
Zephyr	"	Zephyr	"	"	Zephyr	Br. L	1000	16.7
Zephyr	"	Zephyr	"	"	Zephyr	Zephyr	1050	(c) 17.5