A visit to Smiths Motor Accessories speedometer factory at Crickle Wood
Smiths Depot off the Edgware Road, where the Smiths Centre is situated, is tapped by an impressive clock.
All cars built after the end of September 1937 are compelled by law to be fitted with a speedometer and, in any case, this is the most-looked-at instrument in any car (for racing cars substitute tachometer), so I thought it might be instructive to visit the Motor Accessory Division of S. Smith & Sons (England) Ltd., who make most of the speedometers used in this country.
So along to Cricklewood, that area of factories beside London’s Edgware Road that was developed in the ‘twenties when instructional D.H. Moths still made their “circuits and bumps” out of Stag Lane Aerodrome, we went one wet winter morning and, after a brief fracas when the Commissionaire waited until I had carefully parked the editorial Mini-Minor and then told me to move it to somewhere down the road — I mention this only because, shortly afterwards, Motor Sport’s Production Manager’s gleaming white Porsche Super 75 was permitted to stay all day in the same place, which nicely illustrates the value of a prestige motor car — we met Gerry Ealson, Smiths P.R.O., in the tasteful Smiths Centre, and our education into the manufacture of speedometers had commenced.
Smiths association with the Motor Industry began in 1904, when they made watches for use on horseless carriages. From this speedometer manufacture developed and a Royal Mercedes was one of the first motor vehicles to be equipped with such an instrument. Serious-minded old-car enthusiasts should endeavour to visit Smiths Centre, where, in the gallery, there is a fascinating historical panorama showing speed and distance recorders from the earliest applications onwards; indeed, this display of “things Smiths make” goes back to 1851 and the rest of the 4,000 sq. ft. of the Centre is devoted to such modern Smiths products as automatic transmission as used by Rootes for the “gearless” Minx, oil-fired domestic boilers, all manner of industrial instrumentation, and some truly covetable timepieces, from pigeon-racing clocks to radio-controlled clocks. In all, I suppose Smiths supply over 350 separate items for domestic, industrial, motoring, aviation and marine requirements.
Back to speedometers . . . Speedometer manufacture throughout the World is almost entirely the monopoly of Steward-Warner, General Motors and Ford in America, Jaeger of Paris in France, Vdo in Germany, Veglia (or Borletti) in Italy and Smiths in Great Britain, supplemented by A.C. Delco who make speedometers for Vauxhall and Bedford and some 50 per cent. of Ford instruments.
Briefly, the evolution of Smiths speedometers goes something like this. There was the Governor type, expensive to make and mainly supplied to commercial vehicle manufacturers, of whom Albion were one. The Aigmo was another early speedometer, of magnetic type, in which there was no scale, m.p.h. calibrations being marked on the disc; this was fitted to the original Morris Minor. Next came the Nemag, in production in improved form today. which has total and trip milometers at 6 o’clock and 12 o’clock positions on the dial. There was also the A.T. speedometer, a more expensive instrument giving steadier readings, supplied to Rolls-Royce and to the police before they went over to the Nemag type. Another rather costly speedometer, having total and trip odometers in line, was the Smithmag, but this is on its way out, having been almost superseded by the Nemag Mk. II, which incorporates friction distance counters. To combat vibration in motorcycle and racing installations a geared mileage counter has been developed for the Nemag Mk. III.
Out of the past comes the Chronometric speedometer, found on the majority of motorcycles, a type using a complicated escapement mechanism and still made in improved form. Finally, the ribbon-reading speedometer is just emerging from Smiths factory for use on a new car shortly to be announced. At the other extreme, Smiths were asked some time ago to adjust one of their speedometers that had been supplied for a Daimler car in circa 1909. Judging by a Smiths clock that used to grace my 1914 “Alfonso” Hispano-Suiza and is still an excellent time-keeper their older instruments were also made to very high standards.
Turning to Smiths rev.-counters, or more correctly, tachometers, broadly there are three types, the Nemag Mk. I and Mk. II, etc as fitted to sports cars such as Austin Healey, M.G. and Triumph, the better-quality A.T. instrument supplied for Bentley and Rolls-Royce cars and the electric rev.-counters preferred by Aston Martin and Jaguar. These electric rev.-counters incorporate their own generators; a later development is the impulse tachometer actuated by the electrical impulses from the car’s ignition distributor, a system which is particularly applicable to racing cars on account of ease of installation, drive from dynamo or camshaft being eliminated and very accurate readings being possible.
Speedometers are made in five dial diameters, namely 60-mm., 80-mm, 4 in., 4.5/8 in. and 5 in. with the addition of 5¼ in. and 5½ in. cluster speedometer. The 5-in. size is popular for sports cars, although Austin Healey prefer the 4 in., while the 4 5/8-in. dial is found on Wolseley cars but is not in general use, although it was intended as an interim speedometer coming between the universally popular 4 in. and 5 in. instruments. Of rev.-counters, the 80-mm. instrument is uncommon, the 5-in, size being normal for sports cars. Clockwise or anti-clockwise movements are available, thus giving discerning car manufacturers the opportunity to have speedometer and tachometer needles moving in sympathy instead of in opposition. Smiths have a special section, under the care of Mr. John Nuttall, which looks after competition requirements, such as large-dial tachometers, impulse rev.-counters, maximum-reading needles, and special installations. In the last-named category were the speedometers driven from a back wheel on the Monte Carlo Rally Morris Mini-Minors, which proved to record distance 10 per cent, more accurately than the standard instrument, which in these conditions was cheated by excessive front-wheel spin, while it is interesting that John Cooper is amongst those who insists on a maximum-reading rev.-counter, which precludes impulse installations. Sometimes very high-reading tachometers are asked for, mainly for foreign racing motorcycles, although I gather the Camoradi Maserati engines call for readings up to 12,000 r.p.m. Another link Smiths have with motor racing is in K.L.G. sparking plugs, which they now manufacture but which were made in the first place specifically for Brooklands cars by the late K. Lee Guinness.
I discussed particular aspects of speedometer styling and presentation with Smiths Chief Production Engineer, who emphasised that whereas the French favour die-castings, Smiths employ pressings, and use transfer machinery, in speedometer manufacture. They are also very aware of the desirability of using easy-to-read calibrations and their latest methods of printing ensure a high standard of “life in the dials.” They pay heed to scientific tests carried out to see which layouts and colouring, etc., are acceptable to tired eyes but automobile design teams seem to ignore such advice and to some extent the customers’ — in this case the Motor Industry’s — requirements conflict with idealistic presentation. Smiths calibrations are in specially printed figures which respond extremely well to ultraviolet panel lighting, which is replacing the former “black” lighting. White figures on black dials are otherwise favoured.
One of Smiths major problems is that of making the great variety of speedometers called for by the car manufacturers, for if some standardisation of mechanism has been achieved, quite rightly, there remains complete individuality of styling. Ford, for instance, have very firm views when ordering speedometers, Rootes have decided preferences for particular shapes and styles and sizes and colouring of figures and B.M.C. know very definitely what they require, although always willing to co-operate with Smiths specialists.
It is common knowledge that speedometers and distance recorders are nearly always optimistic. Of 38 cars road-tested last year the average speed error at 60 m.p.h. was 5 m.p.h. fast and the average odometer read 1.7 per cent. fast, for instance. This is nor because Smiths cannot achieve nearly 100 per cent. accuracy — this “flatter” is ordered by the car manufacturers. Most of them like a speedometer to read +5 per cent. at 30 mph. but the police specify +2 per cent. fast. Tyre growth affects speed readings and while Dunlop can give Smiths exact data, they often have to rely on the car manufacturer’s figures when other makes of tyres are specified, which leads to further errors. Car makers explain away these optimistic speedometers by claiming that safety comes into it; they argue that if a driver is intent on demonstrating his car on a road such as M1 it is better that when the speedometer tells all concerned that, say, 80 m.p.h. has been reached, the car is, in fact, doing nearer to 70 m.p.h.! Incidentally, Smiths always calibrate their speedometers accurately by placing two tiny dots, usually at two different speeds, on the scale, these being hidden by the bezel in the installed instrument, the specified flatter being obtained by false calibration. The little figures you see on the dial, which some people think give the “flatter’ in code, merely indicate other revs.-per-mile at 60 m.p.h. and in ratio in the drive gearbox, which may be one of three types in general use.
To walk through the Smiths speedometer factory is to see precision instruments being made in a calm, unhurried atmosphere. They aim to produce some 45,000 speedometers and rev.-counters a week, employing some 45,000 operatives on a 42-hour week. The present recession in the Motor Industry is being felt at Smiths, but by making use of this recession to train unskilled workers, short-time working has been avoided.
I do not propose to explain in detail how a modern magnetic speedometer works, although practical-minded readers can obtain explanatory literature by writing to Smiths, mentioning Motor Sport. Briefly, the distance recorder consists of figure-drums pushed round by cam-operated ratchets, the adjacent drum being initially moved by friction when “9” comes up on the right-hand drum. This system is almost foolproof but to entirely obviate sticking or partial movement Smiths are contemplating, the introduction of a geared movement.
The speedometer consists of a metal drag-cup, which spins past a magnet to generate a magnetic force, the strength of this force increasing with the speed of the cup’s rotation; this pull, measured against a hairspring attached to the speedometer pointer, indicating speed in relation to the gearbox reduction in use. In the case of commercial-vehicle chassis with two gearboxes a speedometer has to have its own two gearboxes, to cancel out.
Absolute balance of the drag-cup is essential and Smiths ensure this with a highly ingenious machine in which, electronically, a blob of ink is squirted on the cup to show exactly where it is out of balance, a notch automatically cut in the flange then correcting this, whereas formerly balance had to be attained laboriously by trial and error.
Speedometers are assembled in one vast hall, almost entirely by skilled girl workers, on a piecework basis. Assembly proceeds from stage to stage, the girls sitting at separate stations, putting the minute parts together by hand or aided by small automatic screwdrivers and other tools, the growing assemblies being placed on a shoulder-high conveyor-belt for passage to the next station. Early in the manufacturing process the drag-cup spindle bearings, etc., are lubricated with molybdenum disulphide from hypodermic syringes, the girls concerned being responsible for inserting just the right amount of oil, which lasts the life of the instrument.
After the odometer mechanism has been assembled each one is given a visual check of 68 separate items and each movement is then tested for a period ranging from 35 min. to 85 min., depending on the drive-ratio in use. For this test the speedometer heads are mounted on manifolds, of which some 14 are available, each accommodating 96 heads, a 1-h.p. electric motor driving them for the required time. After they have been geared the recorders are checked for readings of from 3 to 5 miles. When the motor is stopped any head giving a false distance reading is rejected. When geared odometers are introduced a different system of testing will be necessary as this type is not easily re-set to zero, bad news for the dubious fringe of the Used-Car Trade!
Every Smiths speedometer is also tested for accuracy of speed recording. This is done on an electrical machine which can simulate any one of 18 speed readings by loading the drag-cup with the equivalent magnetic flux, after demagnetising, to prevent magnetic saturation. The girl in charge usually selects four readings by plugging in the required electronic service and she can see at a glance whether the needle takes up its correct position. Afterwards the dial is fitted, on which any required “flatter” shows up:
A typical speedometer which was being made on one of the eight assembly lines was the combined speedometer, fuel contents and temperature gauge for Fords. This has bi-metal indicators common to both auxiliary dials, in conjunction with a voltage regulator and thus you have the accurate petrol level reading found also on the Standard Vanguard Vignale Six, etc. An oil pressure indicator working on a similar basis will soon be in use.
Other inspection checks are made to ensure that warning-lights, etc., within the speedometer cluster are functioning correctly, and rejected instruments are put right in a separate bay to obviate interrupting the assembly lines. This extreme and painstaking care in speedometer assembly and inspection reminds one that Smiths are noted for their clocks and watches, in the manufacture of which they achieve accuracy by the precision of mass production machinery, whereas the Swiss still make watches by hand — the old conflict of model-T Ford versus Rolls-Royce.
On the first floor of the MAI speedometer factory Smiths print the dials to designs styled by their draughtsmen and approved by the car-manufacturers, by two methods, the cliche or offset and screen printing. Lithographic printing did not give the strength or “body” they expect from a speedometer dial and screen printing is applicable only to flat surfaces, which have to be shaped subsequently. So the offset method predominates, the gravure plates being etched to a depth of 2-thou. for the main figures, 1½-thou. for smaller figures or letters. Probably one hundred different dial designs have to go through this printing process. It is interesting that two grades of gelatine are used, one in the winter, another on hot days, this being far easier than enclosing the machines in rooms maintained at a set temperature. Just as every speedometer mechanism is tested individually, so each dial is checked for clarity, two inspections being made of white numerals on a black dial — the inspector’s shirt takes on a blue hue when he passes his arm under the ultra-violet lighting, causing one very distinguished visitor to remark promptly “Washed in Tide!”
The printed dials certainly are vividly “alive,” and so easy for the motorist to read. They are either air-dried or baked for six minutes in a big infra-red oven.
Apart from the mechanical aspect of speedometer manufacture and the design and printing of the dials, there is the question of the finish of the case to be considered. Justifiably, Smiths are proud of a very costly new Canning plating bath in which up to 70,000 bezels a week can be nickel and chrome plated. The brass parts are hung from an overhead conveyor and automatically immersed, moved on for swilling and further immersion, entirely automatically on the transfer system. The nickel-plating process needs care if the brass is not to be rendered brittle, causing breakage of the attachment tabs when these come to be bent over, but skilled chemists ensure that the contents of each bath and the time of each machine-controlled dip„ obviate this. This fine British plant will soon extend down the entire length of the factory, and only zinc plating will remain a manual operation.
The impression I gleaned during this three-hour visit to Cricklewood was of happy workers making precision instruments to an extremely high standard. The girls all look contented, are permitted to smoke, and strike a cheerful note by wearing overalls of varying colours, a further brightness being imparted by their open umbrellas, of many hues, drying on a convenient shelf, reminder that we were in the heart of the British Isles, where the changeable climate is looked after by another Smiths product, in the form of car-heaters.
Apart from the main speedometer, factory there is another 40,000 sq. ft. factory a mile away and the old Bentley Motors works in Oxgate Lane is now Smiths London service station.
So I came again to the restful Smiths Centre, opened by H.R.H. the Duke of Edinburgh in 1959, where this great industrial organisation’s products, made of twenty or more manufactured units, are tastefully displayed. The motif on the entrance hall is a mural depicting the elements of time and space, very accurately depicted, which might well be headed by the motor car manufacturers who wickedly specify how much “flatter” they want when they order Smiths speedometers for their cars! — W. B.