The Works of the Sunbeam Motor Car Company Limited
Recent Developments in the Practice of a Well-Known Firm.

A brief description of the Sunbeam Works at Wolverhampton was given in the issue of The Automobile Engineer for January, 1924. Since that date important extensions have been made to the factory, and in certain directions the production methods have been improved. Modern plant has also been installed for gear grinding, as well as for the finishing operations on pistons, gudgeon pins, and other parts which call for a high degree of accuracy.

Originally the company manufactured several models, but they have now decided to concentrate on the 14hp. and 20hp. and 3 litre cars. The output of these three types is approximately fifty per week. In addition, a limited number of the new 30hp. model are being built. This car was shown for the first time at the recent Motor Show at Olympia. It is a particularly fine model, built on the same general lines as the smaller cars, except that it has an eight-cylinder engine.

The most important additions to the works consist of a new machine shop and a water-raising plant, by means of which an adequate supply of water for all purposes in the factory may be obtained if necessary. Few automobile firms experience any difficulty in this direction, but the scheme adopted by the Sunbeam Company is of interest as an example of enterprise in overcoming unusual obstacles.

Owing to the high ground on which the works is situated, and the uncertainty of the water supply in the neighbourhood, an expert was consulted as to the advisability of sinking an artesian well. As the result of this it was decided to undertake boring operations on the company's premises, and after reaching a depth of 301ft. an adequate supply of water was tapped.

The bore hole passes through strata consisting of conglomerate, hard red marl, soft red marl, sandy marl, and sandstone. The lower 200ft. is lined with a steel casing tube 10in. in diameter, whilst a 12in. diameter tube is used for the upper portion. In the portion of the bore which passes through sandstone, perforated casing tubes are used to allow a free flow of water. Plain tubes are inserted through the strata of sandy and soft marl to prevent any movement which might take place with the soft earth falling into the bottom of the bore.

The pumping plant consists of a Broom & Wade air compressor driven by a 30hp. electric motor in conjunction with two Rees Roturbo rotary pumps, each direct coupled to a 10hp. motor. The two rotary pumps have a combined capacity of 24,000 gallons per hour. In addition, a single motor and pump is installed as a stand-by.

A storage tank is situated in the pump room at the head of the bore hole, from which the water is raised by an air and water main extending to a depth of 170ft. from the surface. The air pipe is l½in. diameter, whilst the water main is 4½in. diameter, and these are connected together by a specially designed foot piece, so that the water is raised by air pressure. From the storage tank the water is raised to a reinforced concrete storage tower by the rotary pumps, which deliver through 2,450ft. of 6in. main. The base of the storage tower is 30ft. above ground level, and it has a capacity of 30,000 gallons.

To supply the works, the delivery main from the pump room to the storage tower is tapped at various points and connected to the existing pipe line. The yield from the bore hole varies as the head of water on the air pipe, being 12,250 gallons per hour with water at ground level, whilst after twenty four hours' continuous running the yield was 10,000 gallons per hour, the water level then being 67ft. from the surface. A float switch fitted between the motor starter and the storage tank provides automatic control of the pump, so that its delivery shall synchronise with the yield from the bore hole.

It will be apparent that the installation is quite an elaborate one, and has been carried through with every care and thoroughness.

The new machine shop is a lofty, well lighted building with a floor area of 48,024 sq. ft. Two views of the shop taken in opposite directions from a point near the centre are shown in figs. 1 and 2, though it is difficult to obtain a photograph showing the full extent of the shop, owing to the disposition of the machines and the intervening belts and girders. Incidentally, it may be remarked as somewhat surprising that more of the machine tools have not been equipped with individual motor drives.

An interesting point in the layout of the shop is the provision of two side galleries, each of which has an area of 3,312 sq. ft. These accommodate the lighter units of the plant, such as small automatics, capstans, brass finishing lathes, etc. Thus pistons and other comparatively small parts can conveniently be produced in the same shop as the larger components. It may be mentioned that pistons are at present finished on the outside diameter by grinding, machines having been installed in one of the galleries for this purpose. The limit worked to is exceptionally fine.

On the floor of the new shop, the heavier plant is laid out as far as possible according to the sequence of operations. Cylinders, crank cases, gear boxes, rear axle cases, and crankshafts are dealt with in this department. A small section is also devoted to gear grinding. Many of the machining operations on the larger components were described in the previous article dealing with the Sunbeam Works, so that further reference to them is unnecessary except in cases where the methods have been revised.

The gear grinding plant is a comparatively recent introduction, and consists of three Maag machines arranged as shown in fig. 3. Apart from the relative merits of these machines as compared with the Lees-Bradner and other gear grinders which are being installed by auto mobile manufacturers, mention may be made of one or two interesting points in connection with the Maag machine.

Amongst other things, the use of small abrasive wheels facilitates the grinding of cluster gears and such work as that shown on the table in front of the machines. It is also possible to employ two wheels for grinding both sides of the teeth simultaneously, the faces of the wheels being inclined at an angle equal to the pressure angle of the gear to be ground. The two faces thus correspond to the sides of a rack tooth.

Saucer-shaped wheels are employed, the comparatively heavy wear on the small wheel face being taken up automatically by an ingenious electrical device. This consists essentially of a diamond contact which is advanced to meet the wheel face at short intervals. As soon as appreciable wear has taken place, the diamond, in making contact with the wheel, overshoots a predetermined point, and in so doing it closes an electrical circuit, which operates a sensitive compensating device. This imparts a slight axial movement to the wheel spindle, which continues until the wheel face is brought back to its original position, when the feeding motion is automatically disengaged. In practice, of course, the movement is made in very small steps, so that the product is uniform within the fine limits which are permissible on this class of work.

The equipment for handling the larger components in this shop has in many cases been designed for dealing with two or more components at one setting. This applies to the majority of the milling operations on the cylinder blocks and cylinder heads, as well as to the operation of machining the cylinder bores.

The machine employed for this operation is illustrated in fig. 4, the component being the cylinder block for the 20hp. engine. It may be seen that a fixture of unusually large size is mounted on the work table, so that it accommodates two six-cylinder blocks simultaneously. The machine is one supplied by G. A. Alexander & Co., Ltd., Birmingham, although it differs somewhat from their usual range of cylinder boring machines, having been specially designed for the work in question.

Attention may be directed to the massive construction of the fixture, which is made with a central wall so that the boring bars can be piloted in the centre as well as at both ends. Two separate cutters on each bar are employed for boring both cylinder blocks simultaneously, and the same machine is used for roughing and finishing cuts, the bores being finally finished by grinding on Heald machines.

Another interesting operation on the cylinder blocks is the milling of the inspection cover facings. Actually this operation is carried out prior to boring the cylinders and after the bottom faces have been milled, Owing to the fact that the inspection cover faces are inclined to the vertical, two conical milling cutters, mounted side by side, are employed for milling the facings on two cylinder blocks simultaneously.

Another component on which some interesting operations are carried out is the water-cooled cylinder head. This is an intricate casting, calling for much more careful treatment than the usual type of detachable head. After heat treating, the top and bottom faces are finished, this operation being now performed by surface grinding in place of the former method of milling the faces. The bolt holes and valve guide holes are then drilled at two separate settings on a multiple-spindle machine, after which the holes are drilled and tapped on a radial for taking the unions by means of which the casting is coupled up for the water test.

A further drilling, facing, and tapping operation is also carried out on the sparking plug holes prior to milling the inlet and exhaust faces. The last-named operation is carried out on a Hendey duplex milling machine in the manner shown in fig. 5. This affords an excellent example of the type of multiple fixture employed by the Sunbeam Co. for handling large components.

The fixture takes the form of a substantial box casting open at the sides so that four castings can be milled simultaneously by means of inserted tooth cutters, which are sufficiently large to machine the two sets of facings with one traverse of the work table. Following this operation, the inlet, exhaust, and rocker stud holes, as well as the drain hole, are drilled on an Archdale machine, and the casting is next transferred to a vertical miller for machining the combustion chambers. Boring the valve pockets on a radial then completes the component apart from testing.

Fig. 6.  A typical multi-spindle drill head.

Extensive use is made in this department of multiple-spindle drill heads fitted to single-spindle machines. One of these is illustrated in fig. 6, which shows the equipment for drilling the bolt holes in rear axle casings.

The component is a steel pressing, which is first of all machined on the ends, after which it is mounted in a large face plate fixture for facing and boring the central portion to take the differential housing.

It should be noted that, in the operation of turning the centre, multiple tools are employed, so that both sides of the casing can be machined at one setting, thus avoiding the necessity for reversing the work in the fixture.

The head employed for the drilling operation is of light construction with ball bearing spindles, the driving gears being enclosed in a simple sheet metal casing.

On this particular component drilling is carried out from both sides, the two jig plates being clamped in position by a central bolt and nut, whilst feet are provided for the fixture to raise it clear of the work table. The same head is also employed for drilling the rear axle cover and the housing which is bolted to the rear axle casing, the fixture employed in this case being a plate which is supported on pillars so that the component may be clamped upwards against the underside of the jig plate.

Another type of tool equipment which is employed extensively in the Sunbeam works is the rotary continuous milling fixture. Two examples of typical operations are shown in figs. 7 and 8, these being representative of a large number of similar operations on such components as brackets, forks, small casings and covers, stub axles, etc. The method is employed to a much greater extent than in the majority of automobile factories despite the fact that the number required of any one component is relatively small. The moderate outputs are dealt with by making the fixtures comparatively simple and arranging them so that they can be quickly changed on the machine tables.

The component shown in fig. 7 is the rear spring bracket and cap, and it will be observed that a gang of cutters is employed for finishing both the inside and outside faces of the two lugs simultaneously. Previous operations consist of milling the faces of the two halves, milling the bosses for the bolt holes, and bedding and bolting up the cap ready for boring. The milling operation is, however, carried out before finishing the bore. The components are located in the fixture shown by spigots, which are a loose fit, whilst the studs projecting from the base of the fixture prevent the parts from rotating about the spigots under the action of the cutters. A substantial bracket bolted to the column of the machine supports the lower end of the cutter arbor, thus effectively preventing any possibility of springing.

With regard to the erection of the Sunbeam chassis, no attempt has been made to carry out the work on an assembly track. Such methods are, of course, of doubtful value, unless an output running into hundreds per week can be obtained. In addition, the firm hold the opinion that the practice is not applicable to the production of a high-grade car. Instead, the wheels, complete with tyres, are bolted in position at an early stage, so that the chassis may easily be moved along the shop as it nears completion.

Runways extending throughout the assembly shop also facilitate the handling of heavy units. These runways may be seen in fig. 9, which illustrates one section of the erecting shop. Separate tests are carried out on the engine, gear box, and rear axle prior to assembly, whilst the completed chassis is submitted to a severe road test before commencing coach building or body fitting.

In conclusion, it may be mentioned that the social side of the organisation has received its share of attention in the improvements which have been made, a well-ordered institute and sports ground having been provided for the convenience of the Sunbeam employees.