The Bioscope (Jul-Sep 1931)

Vi THE BIOSCOPE provision is made for the use of the maximum possible current. The carbon conductivity is very high, and matters are still further assisted by arranging for the positive to receive its current at a point immediately behind its crater. In this way it is possible to work an arc satisfactorily at currents up to 500 amperes, those taking 100 to 150 amperes being commonly met with in practice. But with such tremendous arc streams it becomes a matter of difficulty to keep a true crater formation, and, hence, to keep the luminous gases under sufficient control for arc steadiness and efficient optical utilisation. Unless some special means are adopted to keep the arc under control the edge of the crater burns away, forming a side, top or bottom lip, and the whole arc becomes unsteady. Now, it is in this method of crater control that we encounter the difficulties presented by the political aspect referred to. Making Carbons Under Difficulties It can be said that there is only one system of control which enables us to obtain the real high intensity effects associated with currents of 103 amperes and upwards. This consists of slowly rotating the positive carbon so that the shell is burned away evenly, thus maintaining the crater formation. This principle is, however, protected by jealously guarded patents, and, at the time of writing, is not found in lamps manufactured in this country. The principle of controlling the arc by means of magnetic blowers is, it is true, receiving much thought, and seems capable of development, even beyond the 75 ampere rating at which it is already giving such satisfactory results. Nevertheless, the fact remains that British carbon manufacturers, when producing carbons for operation in the true high intensity range of 100 amperes and above, are under the disadvantage that they are denied co-operation with the lamp manufacturers, The fact that, in spite of this, they produce carbons which are in most cases preferred to those claiming this advantage in no way alters the facts. How to Test H.I. Positives It will, therefore, be seen that external conditions often modify and limit the design of a carbon, making it necessary for the designer to subordinate his convictions to the conditions obtaining at the time. In general, however, the points to look for in a high intensity positive carbon are (1) intimacy between core and shell, allowing the carbon as a whole to carry the maximum of current. A good test in this respect is to stand the carbon on end on a hard surface — e.g., a concrete floor. Let it fall under its own weight ; it should give a metallic ring denoting homogenity, and it should not shatter or split. (2) Dead straightness throughout its length ; (3) Micrometrical consistency of diameter throughout its length. The necessity for this in rotating carbons will be apparent when you visualise upwards of a hundred amperes passing into the carbon through the jaws in which it has to make a sliding and rotating contact. (4) A smooth outer surface. For the same reasons as (3). (5) A shell which will stand up to the torsional stresses imposed when one end is twisted and the other end is gripped in a 100 ampere contact, and (6) consistency of material throughout its length, so that you can be sure that the automatic feed, once set, will not have to be corrected for irregularities in burning rate. MODERN CINEMA TECHNIQUE This is a notable week for Wurlitzer organs, for it has seen the formal opening of two unusually big instruments, one at the Granada, Tooting, and the other at the Paramount, Newcastle. The Granada instrument is one of the finest yet built. It is a four-manual instrument, has every conceivable modern improvement and has been built in three specially constructed rooms under the stage, the first of the big Wurlitzers to be housed in this way. The front of these chambers, opening into the orchestra-pit, consists of extended louvre fronts, operating either singly or collectively at the will of the organist. The instrument has the famous HopeJones second touch device, which enables the organist to obtain expression from his finger touch. In this way any particular note or notes can be brought out above the remainder of the organ without raising the hands from the keyboard. To each keyboard are fitted two distinct touches, the first playing the stops that are drawn on the firsttouch stop-keys and the second, which is made by a little extra pressure, bringing into use the stops drawn on the secondtouch keys. The Granada instrument is unique in that it is in many ways a big departure from Wurlitzer standards. Mr. Bernstein, on his recent visit to America, examined several different models, and came to the conclusion that the Granada instrument ought to be a combination of some of the features of a variety of models. The specification is, therefore, a unique one, and its purity and brilliance of tone will certainly astonish those who hear it in action. A feature is the " expressive ” piano, a beautiful white and gold grand-piano which can be moved about on the stage and is controlled from the main console. This is, we believe, the first European Wurtlitzer to contain this adjustment. On Sunday last, by the courtesy of the directors of the Pyrene Co., Ltd., the Guild members visited the company’s works at Brentford, where a lecture and demonstration was given by Pyrene’s special representative, F. Somerville. After the lecture the " Pyrene ” Automatic Extinguisher for projectors, already described in The Bioscope, was demonstrated in action. Great interest was shown in this device, which, the instant it operates, releases an inert gas, which is discharged throughout the film track. The gas is harmless alike to film and projector, and after the device has been in use it is only necessary to rethread the machine and carry on with the show. At the conclusion of this demonstration many questions were put to Mr. Somerville and Mr. Harrison, the sales manager, and projectionists were not left in doubt as to the great benefit of this device to the men in the box. After lunch in the Pyrene Restaurant the party adjourned to the grounds, where the technical staff staged a truly sensational series of real fires to demonstrate the efficiency of the company’s various fire extinguishing products. The first fire was the burning September 9, 1931 The splendid Paramount instrument is by far the largest instrument in the North, and its general specification follows on the lines of the Manchester Paramount instrument, It is a particularly big model built to standard Wurlitzer specifications, and is of a type likely to become standard in the Paramount group, for instruments of a similar type are, we understand, planned for Leeds and Liverpool. For hundreds of years only two methods of producing pipe tone have been used in organs, namely, the Flue-pipe and the Reed-pipe. Visitors to the Paramount will hear the Diaphone, which is an entirely new method of tone production, capable of expressive power by varying the wind pressure without altering the pitch. A notable Wurlitzer feature is the pizzicato touch, which produces a staccato or plucking effect on specific stops, very similar to a violinist plucking the strings of his violin with his fingers. With these means of finger touch expression a performer with one hand can be playing upon the Flute, by depressing certain fingers a little harder the melody can be brought out on the Clarionet, and at the same time have the Oboe horn playing pizzicato. The Paramount organ weighs 15 tons and occupied 70 tons of shipping space, and its blowing equipment calls for a 15 horsepower motor. The organ, with its accessory apparatus, occupies three separate chambers located on both sides of the proscenium arch. Preliminary demonstrations of the instrument have shown that it has an amazing variety of tone-colour even for a Wurlitzer, and the Paramount organ items are certain to be outstanding features in the Newcastle entertainment world. Alex Taylor, one of the Wurlitzer SuperSix, will be organist at the Granada, and Vincent Trippett, who has broadcasted all over the world, will be in charge of the Paramount instrument. of 2,000 ft. of film, piled up in the open field. It says much for the “ Pyrene ” fluid,, which turns into foam when released, that half the film did not burn at all, so quick was the action of the extinguisher. Secondly, a large barrel of petrol was distributed for a length of 60 ft. or so along a concrete road and then fired, to be extinguished in a few seconds by the demonstrator. Lastly, a pile of heavy wood boxes, filled with shavings and straw, was saturated with paraffin and set alight. When properly on fire from end to end, the extinguisher was brought into play and the flames were so speedily put out that the boxes were not even in pieces. This last test showed conclusively that however much hold the fire secured, as soon as the " Pyrene ” liquid was directed upon the flames they were immediately smothered. At the conclusion of this, the most practical and progressive demonstration the Guild has had the pleasure of attending, thanks were expressed to the Pyrene Co., Messrs. Somerville and Harrison and the technical staff for their efforts to make the meeting a success. If ever there was an instance of " seeing is believing,” this was one, and members of the Guild will not forget it. Wurlitzer’s Big Week Openings at Tooting and Newcastle Projectionists5 Guild Visits Pyrene Works