Tube Construction Research Articles

Electronoptical observation of metal surfaces: I. Iron: formation of the “crystal pattern” on activation

Summary After an introductory part regarding the construction of the cathoderay tube, the phenomena are discussed, and illustrated by means of a number of photographs, taking place on activating iron with strontium (starting from strontiumcarbonate), so that an intensive emission pattern of its crystalline texture is obtained. It is suggested that the applied method of activation has some features in common with the activation of thoriated tungsten.

A 100-kw vacuum tube

The construction of a new vacuum tube having a rating of 100 kw is described herewith. <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∗</sup> This tube has been made possible by the development of water cooling and a satisfactory copper-glass seal.

The design and operation of a high-speed cathode-ray oscillograph

Following an Introduction reviewing the essential requirements of a high-speed cathode-ray oscillograph for the recording of short-time transients, consideration is devoted to the design and construction of an instrument of this description adapted to both internal electron-blackening and to external light-blackening photography. The problems discussed include the construction of a cold-cathode discharge tube, the disposition of deflection plates, the operation of the time-sweep and beam-trap circuits, and the methods of synchronizing these with the transient under examination; this last leading to questions of voltage-division and delay necessary for synchronization.

On a determination of the pitot-static tube factor at low reynolds numbers, with special reference to the measurement of low air speeds

1.1. Of the numerous instruments that have been devised for the measurement of the speed of flowing gases, the pitot-static combination alone has proved itself suitable for use as a standard. It owes its superiority in this respect mainly to the fact that its calibration factor has been found to be constant over a large range of Reynolds number and is affected only by mechanical damage of a kind that can easily be detected by cursory inspection. A single calibration therefore endures throughout the life of the instrument. For this reason the combined pitot-static tube, in one or other of a few types differing only in unimportant details, has been universally adopted as a standard and, although in many circumstances other apparatus or instruments may be more conveniently used for measuring gas-flow, the calibration of such apparatus or instruments has always ultimately to be referred to pitot-static measurements. 1.2. The construction of a pitot-static tube will be clear from fig. 3 ( a ). It consists of two coaxial tubes A and B arranged over part of their length with their axes parallel to the direction of motion of the flowing gas. This portion of the instrument is known as the “head,” while the “stem” comprises those parts of the tubes perpendicular to the head. The stem is generally considerably longer than the head for convenience in mounting the instrument in the required position without interfering with the flow past the head. Tube A is open to the stream only at its end C, which must be arranged to face the motion, while tube B is sealed from tube A entirely and from the stream except at the series of small orifices shown at D. Provision is made at the other ends of the tubes in the stem to connect each to one side of a differential manometer. There is then no flow through the tubes and it is found that if the shapes and proportions of the head are properly chosen, the pressure acting at the aperture C is the total head in the stream (that is the velocity head plus the static pressure), while that at the orifices D is very nearly equal to the static pressure. The differential head indicated by the manometer is thus substantially equal to the velocity head. An empirical calibration factor allows for any discrepancy between the static pressure and the pressure at the static orifices D.

Stroboscopic and Slow-Motion Moving Pictures by Means of Intermittent Light&lt;!--&lt;xref ref-type="fn" rid="fn110.5594_J05547"&gt;*&lt;/xref&gt;--&gt;

In a paper published in the June issue of the Journal the author showed that mercury-arc lamps when excited by quick violent electrical transients make a practical source of intermittent light which is very actinic and has a short duration of flash. The timing of the flashes is easily controlled. — In this present paper, further information regarding the duration and the quality of the light are given. Also improvements upon the mercury-arc tubes are described which simplify the construction of the light-pulse tube and the electrical circuits. — Uses of intermittent light for taking motion pictures are described and illustrated by examples. There are in general two methods of using the intermittent light. One method is used to take pictures where the light is caused to flash for each frame and the film runs at a continuous speed. The second is used to take stroboscopic moving pictures of rapidly moving objects by causing the light frequency to approach the frequency of the motion of the object. Examples of the later method are shown, these being stroboscopic motion pictures of a crude motion picture claw mechanism operating at 30 fps. and of the surges in the valve springs of a gasoline engine running at 1930 rpm.

Welded Tube Construction

THE firm of A. V. Roe &amp; Co., of Manchester, is the outcome of the early efforts of the two brothers Roe, of whom A. V. was responsible for all the early practical work, and, with the writer; is the oldest aircraft constructor in Great Britain so far as really practical work is concerned, though there had been several others who had made experiments and had generally toyed with the idea of free flight prior to the serious experimental work undertaken by A. V. Roe. In recent years the actual design of the firm's products has been in other hands, but his original ideas are still easily traceable in the design of the present‐day machines produced by this company; which would seem to prove that some of the early designers knew a good deal more about the subject than the later generation of designers and constructors would care to admit.

SOME THERMIONIC PROPERTIES OF BARIUM FILMS ADSORBED ON TUNGSTEN

An investigation has been made of some thermionic properties of a barium film adsorbed on tungsten for various values of θ, the fraction of the surface covered with barium. The experimental tube was so constructed that the measurements could be made on a small area of the filament in order that errors due to lead losses, non-uniformities, and voltage drop along the filament might be minimized. An electrometer vacuum tube was used to measure the electron currents. The experimental results obtained by Eglin were confirmed, i.e. the thermionic activity of the composite surface was found to increase with θ until an optimum value was reached after which further deposit of barium caused the activity to decrease. As a result of prolonged deposition, a steady value of the activity was reached which did not change appreciably or regularly with further deposition. The change in C.D.P. was found to be directly proportional to the change in Tθ, the absolute temperature of the filament required to give an arbitrarily fixed value of electron emission. It is significant that the factor of proportionality for all values of the activity higher than the steady value reached after prolonged deposition was found to be different than that obtained for the values which were lower. The distribution of velocities of the emitted electrons was found to be Maxwellian for all values of θ. The construction of the experimental tube was found to be unsuitable for studying the effect of field intensity on the activity. Thus the results obtained pertaining to this effect are of little significance.

A New Method for the Calibration of Ammeters at Radio Frequencies

This paper describes the construction and operation of a thermionic vacuum tube which is designed for the measurement of radio-frequency currents. The input circuit consists of a filament whose cross section is small enough that the "skin effect" is negligible at thefrequencies used. The filament is heated first by currents of known magnitude (at a low frequency) and again by radio-frequency currents to be measured. Electrons emitted by the heated filament are drawn to an anode sealed into the tube and a comparison of the resulting space currents indicates, if the necessary precautions are taken, the amount of current in the input circuit.

Notes concerning the Sprengel pump

The Paper describes an improved design of the modified Sprengel pump described by the author in the Proceedings of the Physical Society, Vol. 36, p. 291. The walls of the pump are freed from gas skins by electric means, and the shattering of the mercury pellets (which tends to liberate gas) is checked by a special construction of the fall tube.

Welded Steel Tube Construction and The Development of Cantilever Wings

Welded Steel Tube Construction and The Development of Cantilever Wings

XIV. Account of the construction of a standard barometer, and of the apparatus and processes employed in the verification of barometers at the Kew Observatory

After stating the results of experiments, made under the superintendence of the Kew Committee, for the construction of a barometer tube of large diameter by the usual method of boiling the mercury in the tube, the author proceeds to describe a method of filling a tube with the aid of an air-pump. In this process, which is fully detailed in the paper, the tube is so constructed, that when the air has been extracted from it, the mercury enters by atmospheric pressure, provision being made for entirely removing the air which the air-pump has failed to extract. By this method a barometer tube of 1.1 inch internal diameter has been satisfactorily prepared at the Kew Observatory. The author then describes the mounting and mode of observing the standard barometer, proceeds to explain the processes adopted in the verification of barometers, and gives a detailed description of the apparatus for determining the errors of barometers at different atmospheric pressures.