From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Product sheet detailing the features and applications of the Cambridge Universal Vibrograph.
| Identifier | ExFiles\Box 138\2\ scan0139 | |
| Date | 4th May 1938 guessed | |
| CAMBRIDGE UNIVERSAL VIBROGRAPH ALTERNATIVE ARRANGEMENTS Fig. 2 FOR VERTICAL VIBRATIONS Fig. 3 FOR HORIZONTAL VIBRATIONS Fig. 4 FOR SPOT TESTS Fig. 1 AS A TORSIOGRAPH Fig. 6 AS A DEFLECTOGRAPH This instrument is normally suitable for the investigation of horizontal or vertical vibration problems. By a simple interchange of additional parts, it can be adapted for rotational tests, or arranged as a portable unit in which the vibrations are communicated to the recording mechanism by bringing a projecting toe into contact with the vibrating body. It may also be adapted for use as a deflectograph for testing the deflection of structural parts, for example, on a bridge, when subjected to moving loads, or the displacement of one member of a structure in relation to another. The primary or recording unit contains the clock-work drive for the film, the recording stylus with linkage system, celluloid film, time-marking stylus with a clockwork mechanism which indicates 0.1 second intervals, missing each tenth interval to indicate seconds, and a signal-marking stylus. Terminals are fitted for connecting a 6-volt battery to supply the current for the time marker and signal circuits. Controls are provided for film speed, stylus pressure and for centring the zero position. For the recording of vertical or horizontal vibrations, a mass, mounted on a spring stirrup, is attached to the recording unit. The complete assembly is then mounted on a base in one of two positions, the mass being arranged for freedom in a vertical or horizontal direction as desired. Fig. 2 shows the instrument arranged as a vertical vibrograph, while Fig. 3 is a line sketch showing the horizontal vibrograph assembly. For use as a portable vibrograph (Fig. 4), a projecting toe is attached, the control spring slightly rearranged, and a handle fitted to the recording unit; the mass and base unit are not required. With this assembly, the projecting toe is lightly pressed on the vibrating surface, which can be in almost any plane. For recording the deflection of one body in relation to another, this same arrangement is employed, with the base added, and the instrument is attached to the fixed member of the structure under test. For recording bridge deflections, the mass is omitted, and a fitting carrying a sector is attached to the recording unit (Fig. 6). The instrument is clamped to a portion of the bridge, and a wire, suspended from above by a spring, is passed over the sector and down to a weight placed on the ground below. Any vertical deflection of the bridge will cause a slight rotation of the sector which is recorded by the stylus. For use as a torsiograph for measuring variations in rotational velocity, a flywheel unit forming the mass is mounted on the base and attached to the recording unit (Fig. 5). The recording stylus is operated by a connecting rod from the flywheel mechanism. Provision is made for alignment and adjusting the position of the flywheel unit relative to the shaft under investigation, a belt or direct drive being employed. Interchangeable stylus arms are provided to give mechanical magnifications of 1 to 1 or 5 to 1 for recording vertical and horizontal vibrations, and when used as a portable vibrograph. For rotational work, mechanical magnifications of 1 to 1, 3 to 1, or 5 to 1 are available. The recording unit takes spools of film 10 feet long and 20 mm. wide, which are easily inserted. The film speed is adjustable from 21 mm. down to 3 mm. per second. The whole outfit is fitted into a portable wood case, together with a six-volt battery for the time and signal marking mechanisms. The case also contains an optical system and a ground glass screen, and thus forms a viewer and photographic enlarger for the celluloid records, the illumination being provided by a 6-volt lamp run from the battery. The optical magnification on the viewing screen is x 10. Fig. 8 shows the case arranged for enlarging and viewing the records. Some notes on the unique characteristics of the records are given overleaf. Four typical stylus-on-celluloid records are illustrated in Figs. 9 to 12. Fig. 7 REPRODUCTION OF ACTUAL RECORD FULL SIZE When photographically enlarged records appear as shown below Fig. 8 CASE ARRANGED FOR VIEWING AND ENLARGING THE RECORDS SOME TYPICAL RECORDS Fig. 9 Angular vibration of a 90-ton flywheel, geared to a 400 h.p. turbine, and driving a 3-cylinder compressor with a ratio 100 : 3. Time marking 0.1 second ; lower record revolution. Note how the characteristic repeats with each revolution. Fig. 10 Horizontal vibrations in a large building, due to pile driving in adjacent ground (magnification about 120 x). Fig. 11 Vertical deflections on a 35 ft. span steel girder bridge during the simultaneous passage of a goods and a passenger train. The signal on the upper trace marks the arrival of the engine of the passenger train on the down track, the goods train being already on the bridge. Fig. 12 Record taken by the Portable Vibrograph on cabin window frame of a triple-engined Westland IX monoplane. The central trace shows 0.1 second time intervals. | ||