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PROCESSE IN THE

21st April 1933, Page 46
21st April 1933
Page 46
Page 47
Page 48
Page 46, 21st April 1933 — PROCESSE IN THE
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PRODUCTION 0] THE BEDFORD THE monthly output of chassis from the Luton works of Vauxhall Motors, Ltd., is in the vicinity of 2,800, of which a large proportion consists of the well-known and suecessful Bedford commercial models. It will readily be understood that such a huge production figure not

• only demands very close coordination between , the many sections of the works, but the most rapid modern methods of machining, etc., whilst the quality of the chassis and the excellent after-sales service necessitate working to fine limits, so that spare parts are always interchangeable with those on the original products.

Over 3,000 employees are required, and 200 tons of materials enter the premises daily. Throughout the works there is an average of one inspector to every 10 men, and this alone is a factor which promotes good and accurate workmanship.

The Bedford is, of course, entirely British, and only such parts as stampings, frame members, banjo axles and cylinder and other castings are obtained from outside suppliers, but these are all machined at the Vauxhall works.

It is fully realized that it is much cheaper to detect and throw out faulty material before any work has been carried out on it; and, therefore, great importance is attached to the testing laboratory.

Each separate batch of material has to be passed. Steels, iron castings, etc., are analysed and inspected microscopically. In respect of many parts, each is B32 subjected to Brinnell or other hardness tests. One of the greatest difficulties has been the obtaining of stampings and castings made to a sufficient degree of accuracy to reduce considerably the machining required.

For the faces of certain parts, such as brake forks and gear-change forks, machining is dispensed with, the finish to the correct size being achieved by the use of a coining press, resulting in toughened and long-wearing faceS. Surface grinders, 5 ft. in diameter, are used for facing some castings.

Cylinder blocks a r e finished on three sides at once by a remarkable Cincinnatti milling machine, only one cut being taken, but this is to a depth up to 136in., and the clippings are all blued by the -heat. The blocks are put into the machine as received from the foundry and are held in a cleverly designed jig. The other machines must work to this standard, and a single tool taps over 40 holes in the cylinder block in one operation, taking 15-20 secs.

After boring, the cylinders are honed with carborundum slips. Each must be within .0005-in. for• ovality and taper, and after being finished the block is passed through a Crescent washing machine of the caustic-bath type. During our inspection we noted particularly that in every casting or stamping the holes in bosses, etc., are remarkably central. This prevents weakness and shows the standard of accuracy to which the suppliers of these parts have been brought. A difficulty with camshafts is their liability to warp while Wing hardened. Each is therefore brought from the furnace and inserted into a special cramp equipped with water jets, and the whole cramp is shut up so that the camshaft is firmly secured while being cooled.

A well-known tool maker, Drummond Bros., Ltd., of Guildford, has, at the request of the company, developed some excellent modern machines for high-speed work. Amongst these is the Drummond Maxi-cut lathe, which has up to 11 tools working simultaneously. Another Drummond ma5chine used for Bedford banjoaxle casings operates on both ends at the same time, utilizing 21 tools. Many small parts are surface-ground at one time on Churchill machines equipped with magnetic chucks.

Gearing naturally receives much attention. In some, after cutting, the teeth are ground, whilst in other cases they are burnished against hard master gears. Internal testing is carried out on a Lees-Bradner toothtesting machine.

To obtain the minimum of noise, the pinions are run together and marked up in pairs before assembly. They are tested in machines at various speeds just as If they were in the gearbox; this applies even to the reverse constant-mesh pinion. Helical gears, if slightly noisy, are rim in for 1i minute, using a special paste, and each gear is electrically engraved for mating purposes. This does not finish the testing process, for when the gearbox is complete it is put on another machine and the shafts turned at various speeds.

Every crankshaft and flywheel is carefully balanced and the assembly is mounted on ,horizontal knife edges upon which it can roll freely, and on which it should "stay put" in any position to which it is turned.

The working fits on the Bedford are just as close as on the Vauxhall. car, but a little more leniency is permitted in respect of gearbox noise. For instance, the limit for alignment and ovality of pistons Is .0001 in. It would be difficult to machine to such a fine limit, but the result is obtained by grading the pistons „Ticcording to their dimensions. Thus, taking the maximum tolerance as .001 in., the pistons can be graded into 10 bins.

Similar grading is carried out for gudgeon pins, which are quickly checked on a Zeiss optimeter, in which any variation is immediately shown by a band of light on a large scale. The allowance is .001 in. on the diameter, split up into 10 different grades, and .0001 in. in respect of taper and ovality on each pin. The grading system is also employed for connecting rods, in this case the important point is the weight. The gudgeon-pin bushes, after pressing into the pistons, are diamond-bored to impart a mirror finish.

The press and bodybuilding shops cover about three acres. Here, wings are stamped out from the sheet in one blow, one press, which exerts a force of 1,400 tons, stamps out the brake drums, in which the holes are punched, not drilled, and the only machining required is on the register for the hub. The round-headed studs securing the drum to the hub and passing through the former to take the wheel nuts have serrated shanks and are pened into position in a powerful press which, in one operation, forces a stud through its hole, at the same time pressing the drum against a peneing cone, which forces the drum metal against the serrated shank, thus forming a permanent lock.

Every engine is thoroughly run in before erection in the chassis, and each, as freed, is coupled to a Stiff one, so that it receives a further running in under power while freeing its mate.

Throughout the building great use is made of conveyer systems, these and the lifting tackle to various machines being products of Herbert Morris, Ltd. Chassis lines are also in constant motion, each erector carrying out his work as the chassis passes him.

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