OM

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OM Cars

OM

 1899 - 1935
Country:
Italy
OM 665
The OM company was formed in Milan in 1899, representing the merger of two firms in the railways business, one of them making locomotives and the other rolling stock. Their first departure from this field was to make tramcars, Italy's first, which ran between Firenze and Fiesole. It was a rational step for a firm that recognised the increasing variety of mechanised transport; and the logical next step, car manufacture, was encompassed in 1918 by their acquisition of the Zust company which had been making big touring cars since 1905.

The first Zusts were very much in the Mercedes idiom, and were successful enough to prompt the Milanese firm to set up a new factory in Brescia (hence Brixia-Zust, from the Latin name for the city) until with their market success fading, they relied entirely on the Brescia works, where their last new model was produced in 1913. This was a 4.7-litre car known as the S305, with monobloc engine in Fiat style, and a 60 mph performance that its rear-wheel brakes could hardly match. This was the car that OM acquired with the Zust company, and it remained in production until 1923.

Lucien Barratouche



It was improved to suit the times, with electrical equipment being added, for example; but it was hardly competitive with the attractive machines being produced by the company's rivals in Italy, and the directors demanded a new car. To design it they employed an Austrian named Lucien Barratouche, who produced a car with the twin virtues of simplicity and scope for considerable future development. The engine was a very plain-looking side-valve four-cylinder affair, with a cast-iron block on a light-alloy crankcase; but the cylinder head was detachable and the crankshaft ran in three main bearings at a time when two were thought ample, the centre main being water-cooled.

The piston stroke was 100 mm, and this was to remain a constant in subsequent models; the bore was 65, and this with the number of cylinders gave the car its type number 465. Arithmetic gave it a displacement of 1327cc, and the dynamometer gave it a figure of 18 bhp as a modest boast, on a par with the 1.5-litre Fiat 501 that was so popular. Although its basic features were so terribly ordinary, the 465 revealed a good deal of loving care in its detailing.

The cooling might be by thermosyphon, the draught assisted by a wooden-bladed fan, but the electrics were 12 V with coil ignition by Bosch, and there was extensive use of light alloys not only in the engine but also the transmission and the main chassis bulkhead. Light weight was in fact one of the cornerstones of Barratouche's design: the connecting rods were machined all over, the chassis was formed from thin channel sections, and the rear axle even sought efficiency at the expense of noise by the use of straight-cut bevels for the final drive. The wheels were centre-lock wire-spoked types, but on the other hand all four had brakes.

The Coppa del Garda



Just as important, the standard open four-seater tourer body was light and well proportioned so as not to upset the inherently good balance of the chassis, which soon proved that the OM was a delight to drive even though not blessed with a very high performance. Its roadworthiness enabled it to win the Coppa del Garda in 1920, and to take second place in the general classification as well as a class win in the same event two years later. By this time, however, the want of power had been remedied to some extent: in 1921 a bore enlargement made it the type 467, and in the following year the 469 became a full 1.5-litre capacity that was to be a success in Italian sports-car competition.

By the end of 1923 one of the major developments implicit in Barratouche's original design was ready for production. This was the simple addition of another two cylinders to make the type 665, a two-litre car that dealt with objections about lack of performance. It was still a side-valve engine, and ought not to have been competitive with the numerous OHV machines being produced by opponents in Italy, Britain and elsewhere; but on the other hand, the complete car was still beautifully light (only 16t cwt) and superbly balanced, with steering of the finger and thumb variety and predictability in handling of a high order.

Amazing Reliability



It was also, for the era, incredibly reliable: the extension of the crankshaft called for another main bearing, water-cooled like the original central one of the four-cylinder engine; and so long as it stayed beneath the limits imposed by the three-per-revolution torsional flutter of an inline six-throw crankshaft, the four-bearing OM component had the smooth running characteristics typical of such engines up to crankshaft rates that were fairly high by the standards of the time. Peak power was developed at 4200 rpm, and the engine was happy enough up to 4500 - which was high for a side-valver. With a single carburettor it gave only 40 bhp in its original form, but this output was soon increased by 50%; and a twin-carburettor cylinder block, believed to have been designed at the same time as the original car, later came on the scene to endow the two-litre OM with even higher performance.

The Tripoli Grand Prix



Sporting-bodied varieties could reach 75 mph, and maintain relatively high averages because of their excellent cornering and handling, not to mention the brisk acceleration that was as much a function of the car's low weight as of anything else. This was the car that really made the OM famous in competition and popular in the market place. In 1925 it won the Tripoli Grand Prix, driven by Balestrero, took a class victory in the 12-hour touring car race at San Sebastian, and fifth place in the Targa Florio behind four Bugattis. Perhaps the most interesting entry that year was of two cars at 1925 Le Mans: their engine displacement was given as 2005cc, an anomaly that was never been properly explained. It may have been that the desaxe crankshaft location would have accounted for the difference in capacity between calculations based on the actual piston stroke, and those based on the crankshaft throw; it may, alternatively, be that the cars were deliberately over-bored in order to take them out of the two-litre class where opposition from various French makes was considered sterner than what was anticipated from Britain's three-litre Bentley and Sunbeam teams.

1922 OM 469
1922 OM 469, which would remain in production until 1929. It was powered by a 1.5 litre 4 cylinder engine.

OM Type 465 competing in the Coppa del Alpi in 1922
OM Type 465 competing in the Coppa del Alpi in 1922. The 465 was fitted with a four cylinder 1327cc engine developing a modest 18 bhp, however the 465 was very light and handled extremely well.

OM Works drivers Morandi and Minoia posing with their OM 2000 prior to the start of the 1927 Mille Miglia
OM Works drivers Morandi and Minoia posing with their OM 2000 prior to the start of the 1927 Mille Miglia, which they won.


1931 OM 665 NV
1931 OM 665 NV.

The Rudge-Whitworth Cup



Whatever the case, the cars did respectably, dead-heating for fourth place at an average speed of 53.34mph, about 4mph slower than the winning 3.5-litre Lorraine Dietrich. The following year two OMs ran at the 1926 Le Mans again, winning the Rudge-Whitworth Cup and finishing fourth and fifth -again at a respectable distance behind the Lorraine Silken Six. 1927 was the great year for the two-litre OM, however, for this was the year that saw the birth of the Mille Miglia. It was almost an OM procession: the winning car was driven by Minoia and Morandi at an average speed of 40.27 mph, to be followed by two other factory-prepared cars of the same type. The following year OM would take first eight places in the two-litre class of the Mille Miglia, the best of them finishing second overall.

If a light touring car with a side-valve engine could do so well in events of such status, what might not OM achieve with a purpose-built racer? They were tempted to try the idea for the 1926 season, but the car that emerged was a curiously half-baked affair. At that time the regulations governing Grand Prix racing dictated engines of not more than 1.5-litres displacement, and OM embarked upon a twin-overhead-camshaft straight eight in the best traditions expounded by Fiat, Alfa Romeo, and in that same year by Talbot and Delage. Perhaps it was a good engine, but the three-speed gearbox was an inexplicable handicap to it at a time when the little straight-eight Delage was making the most of - and demonstrating the need for - a five-speed gearbox.

The European Grand Prix



Worse still, the chassis created some handling problems that were not at all the sort of thing to which the OM factory drivers were accustomed. The car was entered for the French Grand Prix at Miramas, but did not start-a circumstance that brought no more disgrace upon OM than upon the numerous other manufacturers who treated this event in the same way, leaving it to Bugatti to win unopposed. In 1927, two Grand Prix OM straight eights were entered and did in fact start in the European Grand Prix, held at Monza. To cover 500 kilometres around that particular circuit demanded nothing very extravagant in the way of transmissions, nor did it make any great demands on the handling abilities of the cars: so although a Delage ran away to win, as happened in all but one of the year's important Grands Prix, an OM finished second, and another fourth, behind that other three-speed fish out of water, the Miller.

By this time the two-litre OM was finding a lot of enthusiastic customers in England. The enthusiasm was carefully nurtured into something a little short of an obsession by the British concessionaires, L. C. Rawlence & Company. For a start they retained Major R. F. Oats, previously notable for the improbable competition successes he scored in the little 11.9 horsepower Lagonda, to develop and race OMs in British events at Brooklands and elsewhere. Next they developed an astonishing range of high-performance conversion equipment, enabling them to market OMs the like of which were never seen in the OM catalogue. From 1926 there appeared two almost completely separate strains of OM cars, the standard machinery issued by the Brescia factory, and the extensively modified Rawlence hot-rods.

There were numerous variations in body style, from a simple two-seater to a long six-light Weymann saloon, but it was the mechanical options that were the most astonishing. There was a heavy duty ENV gearbox, a special Ricardo cylinder head with two spark plugs to each cylinder, and Dewandre servo operation of the brakes. Before long there was an overhead valve conversion with three carburettors as well as twelve spark plugs, and other variations included a low underslung chassis frame, a raked radiator, and special axle ratios-though by now OM had made a concession to modernity in fitting spiral bevel gears in their axles instead of the old straight-cut noisemakers.

The Irish Grand Prix



Eventually the factory cottoned on to the possibilities still inherent in the 665 and started making their own high-performance versions. In 1929 they built some low-chassis cars with finned cylinder heads and Roots superchargers. These cars developed 80 bhp at 4000 rpm. The following year the capacity was increased to 2.2 litres, though the type number 665 was retained; and if the designation in the Rawlence catalogue was anything to go by, these blown sports versions developed 95 bhp. The factory went one better for its own team of sports racers, with three cars of 2.35 litres capacity. These were entered for the Irish Grand Prix and the Tourist Trophy to be held at Phoenix Park, Dublin, but the race ended disastrously for OM with the complete disappearance of the cars' brake linings which were of a new type.

Within the confines of Italy the OMs were still a force with which to reckon; outside they seemed consistently unlucky. In any case the Italian company was losing interest in car manufacture. It may be that they could foresee the coming of the slump that was to spell an end to the hopes of so many other manufacturers; it may simply be that the resurgence of Italy in political and economic terms was enough to prompt them to concentrate on truck manufacture, especially since OM had always been able to look to the Italian government for a worthwhile amount of business. It may be, too, that they recognised the impossibility of doing much more with a basic design that derived from 1920, and were not at all confident that if they were to try again they would be so lucky a second time.

Esperia



Accordingly OM began to run down the car business, as they built up their manufacture of commercial vehicles powered by Saurer diesels built under licence. It was a long drawn out business, the entire stock of private cars at the Brescia factory was sold in 1930 to a firm (run by two former OM management staff) called Esperia, yet in 1931 there was ostensibly a works entry for the Mille Miglia that netted a second place. In England things were even more extraordinary: no new cars were delivered to Rawlence after the end of 1930, and yet there were new models announced at the 1931 and 1933 Motor Shows at Olympia. Even in 1934 Rawlence showed something they called a 667 sports four-seater, but it was really a 1930 car, built (like so many of the other OMs delivered to English customers up to as late as 1935) from the big stock of spare parts stored underneath the railway arches at Waterloo.

The Alcyone



In Italy derivatives of the cars, designed as vans or taxis, remained in production for a little while alongside light military vehicles that saw service in World War 2, but by 1933 any prospect of returning seriously to car manufacture was finally doomed by the sale of OM to Fiat. There was a rearguard action, based on a new car called the OMV or Alcyone, which was announced in 1934: it had overhead exhaust valves, a synchromesh gearbox and hydraulic brakes, but it never went into production. In 1975, OM still existed and played a significant part in the overall Fiat strategy, concentrating on trucks that, like the cars before them, were beautifully made and had an unexpectedly high performance.
The OM Factory at Brescia, circa 1921
The OM Factory at Brescia, circa 1921.
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