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).
Instructions and applications for the 'CAPAC' Bin-Aural, a device for knock detection and sound standardisation.
| Identifier | ExFiles\Box 76\3\ scan0140 | |
| Date | 20th October 1921 guessed | |
| The “CAPAC” Bin-Aural General. In introducing this instrument to the engineer, we feel certain that a moment's consideration will be sufficient to give a clear idea of the practical applications of the device to any particular class of work. The time lost in locating faulty or worn parts on machinery is always considerable and this instrument permits instant examination to be made of the condition of all such parts under actual running conditions, and in effect permits the user to place his ear ON the part it is desired to test, at the same time all other sounds are cut out so that the sound of the part being tested is the only audible noise. The difficulty of detecting which part is worn or faulty in operation is complicated by the other sounds of the machinery or engine; with the Capac Bin-Aural ANY particular sound can be located and examined by itself, and therefore it is a very simple matter to determine which bearing is slack, or any similar test. Some Applications. The scope of the instrument is so large that it is impossible to do more than indicate a few of the most obvious uses, such as detecting slack bearings, slack pistons, broken rings, worn or broken gear teeth, faulty ball bearings, defective lubrication, condition of any machinery, vibration caused by machinery in the structure of buildings, ships, or vibration in any structure caused by either running machinery or passing traffic. Used in connection with a “ Standard Reference ” and damping valves, an approximate value can be given to the above, and in fact to any sound which it is desired to examine. Motor. For Automobile work the instrument may be applied to any part of the car, and can be fixed by a special clamp so that the driver may wear the head spring and note back axle, gear box, or engine sounds when in actual use on the road or track. Marine, Aero. The above also applies, of course, to Marine work with internal combustion or steam engines, or turbines; also for Aero engines. Instruments have already been supplied to many firms engaged in all branches of engineering, and it is safe to say that no shop is fully equipped without at least one instrument, many have a number, and as the cost of the simple form is only a matter of a few shillings the device can be tested at a cost which will be saved in labour alone on the first job in which the instrument is used. Special Types. The number of purposes for which the device is used prevents description of many special types, but if your conditions are not fully covered by the standard instrument we can always supply special fittings and accessories for any particular duty. Operation. The use of the instrument requires no special ability or training, as the sound of the part is not altered in ANY way, but is conducted to the ear and all other sounds are cut out or reduced to a negligible value. In effect you can place your head inside the engine, and at the same time stand up to eight or ten feet away. INSTRUCTIONS FOR KNOCK DETECTION To locate a knock proceed as follows: Connect tubes to the headpiece and instrument, screw in test rods of required lengths (the lower end must always be the plain round ended rod). Place head spring in ears, with the ear plugs facing forward. Apply test rod to the suspected part at three or four points well apart; note position giving loudest noise and repeat from this point. The maximum position having been found, the nature of the sound and knowledge of the construction will indicate the defective part. Treat the entire instrument with care. NOTES If the diaphragm is damaged send for a replacement, a bent or damaged diaphragm is not accurate. If the noise is excessive adjust the damping valve. For gear box, back axle, and similar tests, a clamp can be supplied to enable the instrument to be attached some distance from the operator (attach to any convenient part), the driver or passenger wearing the head spring. This also applies to engine tests on road and track. To prevent vibration steady the instrument by thin rubber tape and support the tube. We are always pleased to advise and will supply any special fittings. Write us fully. NOTE.—For locating noises on machinery we recommend the Tectoscope. For locating squeaks, rattles, etc., use the Tectophone, as no actual contact is required. COMPARISON OF SOUND VOLUME The importance of an instrument to compare sound emitted by any machinery, etc., is obvious, and the many uses of the device prevent details being given of various applications. Comparison may be made: (1) To a duplicate of the part being tested. This is not recommended, as lubrication and wear affect volume, therefore results are not regular. (2) To a “ Mechanical Sounder,” this giving more regular results, as lubrication is not used, and periodicity and volume are adjustable. We can supply either a fixed or a portable type, and shall be pleased to quote to requirements. Standardisation of Sound Volume General. The Capac Bin-Aural in addition to the service of sound location, can be supplied with fittings for the comparison of the sound of any two or more components, say, for example, a batch of gear boxes can be tested for comparative silence and held up to a definite standard. We do not think it necessary to draw attention to the importance of this development, but we believe that very soon it will be regular practice to inspect components for silence, as it is to hold all such components up to a rigid view room inspection for mechanical accuracy. Briefly, comparison is effected by the use of two instruments, both being connected to the same head spring, and one instrument being placed on the STANDARD REFERENCE, and one instrument on the TEST PART. Dual control valves are interposed between each instrument and the head spring, and the position of the control levers indicates the amount the test part is ABOVE or BELOW the standard which has been set for the part. Experimental. Except for experimental work it is not usual to make use of a duplicate of the part to be tested for a STANDARD, as wear and lubrication affect the results and prevent a constant figure being obtained. We have designed special mechanical sounders for STANDARD purposes and we can supply to meet any particular requirements; these are hand or clockwork driven and produce a standard sound which does not vary through wear, and no lubrication is used on the sounder parts. Efficiency. In addition to use as a means of standardising the noise of any component, the device is useful for purposes of testing the efficiency of either different forms of construction, grades of lubricant, or forms of casing, and we believe it is the first instrument to enable such work to be conducted in the shop as apart from a specially equipped laboratory. Limits. When the convenience of an instrument with these points is considered, it is a matter of surprise that it has not been carried out years ago. As the demand for such assistance on many engineering problems (which occur every day, even in a small shop) is well known, we can only conclude that formerly engineers have been content to trust to personal opinion, which after all is similar, and no more accurate, than judging the size of a shaft by eye in place of measurement, although it is granted that practice will make an approximation more or less correct in either case. Is it reasonable to hold parts up to close micro-meter limits, and at the same time trust to opinion and guess work for the equally important matter of sound? (Diagram 1 text) Dual Valve Test (Bin-aural) Connect as above (X) valve full open, with S valve full open. The standard sound must stand out clear above (X). The standard sound under that will satisfy requirements in part X under test. Part to be rejected if, with standard full open, X is louder then S. To avoid confusion, the standard should have a very distinct sound to test part. If S has to be damped to hear X, X=less than standard. If X has to be damped to hear S, X=more than standard. (Diagram 2 text) Dual Valve Test (Independent) Connect as above, first set S valve to damp out and adjust Zero, then set X valve on the standard and set Zero. The scales will now read the same for both ears. Proceed as usual, always damp down, as it is far easier to detect the cessation of sound. Usually this method requires more practice than the Bin-Aural, and in many cases the latter is preferable. In any case, the independent method requires elimination of all external sounds. REMARKS.—Generally speaking, we recommend the Tectoscope for both Standard and X when it is desired to compare the mechanical sounds for efficiency purposes. Example. Most efficient and silent form of gear tooth, rigidity of shafts, etc. The Tectophone on X and the Tectoscope on Standard are used when it is desired to compare either the general running silence, or the effect of different forms of casting, lubrication etc. Example. Most suitable construction of gear-box to give general silence of operation externally, effect of different forms of lubrication, etc. STANDARDISATION OF SOUND (Diagram 3 text) Examining internal Mechanical Sound, for standardization or efficiency purposes. Tectoscope on both X and Standard. (Diagram 4 text) Standardising external noise, comparing degrees of silence with various lubricants, etc. Tectophone on X and Tectoscope on Standard. IMPORTANT.—A piece of machinery may be noisy when tested with the Tectoscope, although from the nature of the construction such noise may be barely audible externally; therefore, for external noise use the Tectophone, for interior sound the Tectoscope. | ||