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Diagnosis by the Stethoscope.

27th May 1909, Page 4
27th May 1909
Page 4
Page 5
Page 4, 27th May 1909 — Diagnosis by the Stethoscope.
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A Description of a Novel Method by which Many Cases of Mechanical Faults May be Exactly and Readily Located.

A gentleman, whose chief business in life, at the present time, is to maintain, in first-class running order, a considerable fleet of commercial-motor vehicles, was, some two months ago. discussing automobile matters in general with a member of the staff of this journal. It happened that the meeting took place in a restaurant, and the first-named gentleman who, on a flying visit from the Provinces, had spent part of the morning shopping, was busy divesting himself of a number of parcels which he had collected during his peregrinations. The Last parcel to be deposited proved, to the astonishment of our representative, to contain an ordinary stethoscope. Although a man of varied interests, the individual in question had never been suspected of medical attributes, and, therefore, surprise was expressed at his possession of an instrument which, at first sight, seemed to be of little value to one whose diagnoses were, so far as a as known, all of the mechanical order. " You are wrong in your conjecture," replied the pseudo-physician, " that I intend to practise lung-sounding on myself or my friends, and you a re equally wrong in your opinion that a stethoscope is about as useful to a motor engineer as a punt-pole to a balloonist. That's the most useful instrument I've ever come across, for anyone who has to care for the running of motor vehicles. So convinced have I long been that, for the diagnosis of a number of the more-unusual types of faults on all kinds of motor vehicles, the principle of the stethoscope could be applied with success, that, some while ago, I persuaded a friend of mine to make exhaustive experiments on the subject. I, personally, hadn't the time—ancl he has now brought out an imgroved form of instrument which is specially adapted for fault-finding on machinery of all classes. This." said he, pointing to the stethoscope that he had pulled from his pocket, "is a second-hand instrument I picked up for a few shillings this morning, and I'm going to have it altered to suit my work."

Scenting " copy " of a fresh nature, our representative hunted up the experimenter, and was fortunate enough to secure for the readers of this journal some particulars of the many uses to which a properly-constructed stethoseope may be put, in connection with the location of faults on motor chassis.

It appears that our original informant has had an instrument of this kind in use for several years.

In the case of a very large number of motor-vehicle troubles, the existence of some unusual kind of noise i. more or less noticeable, as an indication that something abnormal is happening. In some cases, such as that of a valve's not closing correctly, the fact that there is an absence of a certain noise, for example, the click due to the fall of the valve on to its seat, should disclose that irregularity. Faulty running is, as a rule, attended by some change in the normal "tune" of the moving mechanism. It is remarkable how engineers in charge of running plant, whether it be of locomotives, marine engines, centralstation generators or of other large units, become entirely accustomed to run such mechanism by " note," and to detect the occurrence of anything unusual by an instantaneous change in such " note." Even in such cases as these, it is probable that moredefinite diagnoses could be ensured were a stethoscope to be employed in the region of the trouble. With small high-speed engines, such as those used for motor vehicles, the employment of the instrument becomes a necessity. On gearboxes, back-axles, water pumps, coils, magnetos and many other units, the location of faults becomes a simple matter with such an intensifying means of observation.

Most individuals have, at some time or another, made acquaintance with the stethoscope in the hands of a medical man. The word stethos is, of course, Greek for breast, and it is in its specific application as a means for the location of the actual seat of chest troubles in the human body, by the careful determination of the nature and position of abnormal sounds emanating from the distressed part. that the instrument evidently acquired its name. Two types are employed by doctors: the one for use with a single ear of the operator ; the other—the binaural stethoscope—for use with both ears. It is in its latter form that the application of the contrivance to mechanical requirements is to be recommended. The binaural instrument consists of a conical receiver, which may be either solid or tubular, and this is firmly fastened to one end of a metal branch piece which, at its other end, forks into two tubular extensions. A length of ordinary rubber tubing connects one of the two metal ear-tubes with each of these horns. The ear-tubes are joined by a piece of fiat spring steel, as may be seen in several of the photographs which we reproduce.

In order successfully to bring the medical stethoscope into line with the requirements of mechanical engineers, certain detail alterations have to be effected. In its application to the surface of a living body, the conical receiver, which is usually made of hard wood or vulcanite, is readily seated on the yielding surface of the skin or bide. For the detection of unusual sounds which are proceeding from parts of a machine, this receiver has to be provided with a specially-formed rubber diaphragm; this addition enables the user to secure an almostentirely airtight joint between the stethoscope and the metal casing, and, furthermore, it has the effect of intensifying and increasing the sounds which it collects. If air be permitted to pass between the receiver and the metal surface, a noise similar to that in a sea-shell will be heard, and this will drown all other sounds. The -other important modification is the lengthening and strengthening of the connecting tubes. In order properly to isolate the particular sound which shall indicate the trouble whose existence it is sought to prove, it is found by experiment that the longer tubes are more efficient. These, moreover, enable the user to locate sounds without the necessity for him to crane his neck into abnormal positions. A form of armoured tube, which does not impair the efficiency of transmission, may usefully be employed, when the instrument is liable to meet with _occasional rough usage.

As an example of the delicacy of the instrument which we are considering, we would instance a simple experiment which may be performed in this connection. If the under surface of a thick wooden table be gently rubbed with the soft tip of a finger, the actual spot under which this slight friction is taking place will be unerringly indicated as the stethoscope receiver is passed over the surface of the table. Nothing will be heard until the region of disturbance is closely approached ; then, a distinct noise will be detected, and this will rapidly increase until it will reach a maximum as the receiver cornea directly over the spot which is being rubbed : the volume of noise now resembles a violent scratching and scraping.

Our illustrations show the method adopted when the new type of stethoscope is employed on the various parts of a motorcah. It is difficult to indicate the many different uses to which the instrument may be put, but it will suffice if we describe the location of a few of the more common faults which are likely to occur on a petrol-engined chassis.

An engine knock, which it is difficult to locate, and which may be due to pre-ignition or to sonic mechanical mal-adjustment, can, in almost every ease, be diagnosed by the careful application of the receiver to various parts of the engine case. If all the valves are not closing equally, the defaulter can readily be located. When the receiver is as near as possible to the valve seating, the actual closing of the valve itself can he distinctly detected. If a valve be baelly burnt or otherwise prevented from seating correctly, the difference in the noise made by closing can be remarked by careful comparison, with the sound made by the other valves. The grating of a broken piston ring may, with care, be noticed by the application of the receiver to that part of the, wall of a cylinder which is not surrounded by a waterjacket. An internal "short" in a coil can be diagnosed without trouble, by the placing of the cud of the stethoscope on the case while the current is switched on. If a " short " he taking place, a distinct ticking will be noticed when the receiver is in a certain position. When the trouble occors on a multiple coil, the unit which is affected can be, selected without trouble. Big-end knocks, as a rule, are self-evident, but, in the case of timing-gear wheels with defective or

missing teeth, of defective pumpvanes, of faulty valve-tappet gear, or of any one of many other similar engine troubles, the stethoscope may invariably be applied with success, and this nature of the trouble decided.

Loose brasses, and ball-races which are split or worn, or in which a fractured ball is lodged, can be detected by the small localised noises to which tiler give rise. If there be an unnatural incise in a gearbox or an axle, the exact seat of the trouble eau be found by the systematic moving of the receiver until it is exactly over the source of generation. Under normal conditions, in the case of a gearbox fitted with four or five ball-races, it is often difficult without the opening and stripping of the whole box, to decide which_ of these is defective. The stethoscope enables the grating noise of the faulty bearing to be located to a nicety. Innumerable other forms of application of the instrument will readily suggest themselves to those who have to deal with the adjustment and repair of motorvehicle mechanism, and similar more oe less intricate machinery.

The time-honoured and haphazard method of holding a 12-inch steel rule in the teeth and of closing the ears, while the free end of the rule was placed on the suspected part, will give way in time to the more-scientific and, certainly, more-efficacious method available by the use of the stethoseope.

We would strongly advise those who are constantly having to diagnose faults on commercial-motor vehicles to procure an instrument, and we would suggest that particulars and prices be requested from the people who have been experimenting on this subject for some while, and who now, we understand, have applied for patents to cover the improved form of device which is adapted to the detection of faults in the moving portions of all classes of machinery. The Autoseope !.-.4ripply Company, of 49. Illawson Road, Cambridge, is the address to which such aiiplication should be made.


Locations: Cambridge

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