THIS is an affair which belongs to the era of London omnibuses running on “solids ‘ and sliding on the woodblocks at Hyde Park Corner, of quaint taxis and (they tell us) scorching-hot summers—of motor-boat racing on the Thames at Chiswick, Brooklands, and aero-engined racing cars.
The mystery starts with an announcement in The Motor dated April 26th, 1922, that Ernest Eldridge (known in later years as the intrepid driver of the 300-h.p. Fiat which took the Land Speed Record at Arpajon and constructor of the Anzani-engined Eldridge Specials) had produced an aero-engined giant for Brooklands racing by installing a Maybach engine in his 1907 IsottaFraschini. The Motor stated further that “For racing purposes several modifications have been carried out. The water is taken off each cylinder top and let in at the base of each exhaust port, while two Claudel-Hobson carburetters between cylinders Nos. z & 3 and 4 & 5 have taken the place of end-fitted carburetters. If oil-pressure drops below a pre-determined point the ignition is automatically switched off, and a similar arrangement operates if the engine exceeds pre-determined revolutions. Another modification is the increase in the number of valves from four to five per cylinder, three of these being exhaust, while an air-blast circulates through the crank chamber.”
Now I took this statement at its face value and quoted the Isotta-Maybach as having 30 valves in its T-head side-valve engine in my book about Brooklands.
There the matter might have ended, had not Douglas FitzPatrick discovered another giant car in which Eldridge apparently had a hand, in the form of a 1907 9.9-litre 60/8o-h.p. Metallurgique. It seems that this chassis was supplied by Eldridge to a Mr. Cole and partner, who, in 1919, put into it a Maybach airship engine. This engine was the 18o-h.p. T-head 160x 170 mm. AZ type, which Maybach had manufactured between 1910/12, with four valves for each of its six cylinders.
I came to know FitzPatrick’s monster Metallurgique very well, when taking its sensational performance figures (Moroa SPORT, January 1957). Naturally, its owner was interested in the origins Of his exciting Edwardian and in the course of his researches wrote to the Maybach Company. They informed him that the engine in his car was their first (AZ) series, being No. 30 of this type.
The Isotta-Maybach had an engine of the same type the tgo-h.p. model, and became a successful Brooklands car. type, Eldridge became obsessed with the resurrected Fiat “Mephistopheles ” he sold his earlier aero-engined creation to Le Champion, who won many races with it, lapping at 114.75 m.p.h., which was quicker than Count Zborowski’s Chitty-Bang-Bang.
It was FitzPatrick who queried the accuracy of my assumption that the Isotta-Fraschini had thirty valves. He pointed out that you couldn’t add a fifth valve as this would entail completely different water jacket castings. Yet, when Motor made FitzPatrick’s fine Metallurgique the subject of their Christmas Road Test in 1964, Charles Buttner wrote that the car had the fourvalves-per-cylinder T-head Maybach engine and not the later version with five-valves-per-cylinder. Confusion reborn! The solution is, I think, really quite simple. As far as I can ascertain, from FitzPatrick’s researches, which he has kindly
made known to me, the pattern of Maybach 6-cylinder aero motors runs as follows:
The Type CX engines can be distinguished from the AZ by an extra supporting foot cast each side of the crankcase, giving 6-point mounting, and timing gears transported to the back of the engine. The longer stroke of the CX engine (probably an increase of to mm.) gave an extra 30 b.h.p. The Motor of 1922 has a picture of the Isotta-Maybach ‘s engine, which was definitely a side-valve engine. It also states that this was the ISO-h.p. model. The war-time Maybach engine did have five-valves-percylinder but was a push-rod o.h.v. power unit. It seems inconceivable that if they could gain 30 b.h.p. by lengthening the stroke of the T-head engine they would have bothered with a 30-valve version, especially as the use of two large inlet and three smaller exhaust valves for their o.h.v. engine was presumably not a success, or unwarranted, as witness the use of four-valves-percylinder for the 300-h.p. o.h.v. version. Gout mud on page 772
What happened was probably had reporting on the part of The It is not apparent why a racing driver, who might be expected to watch his tachometer and oil gauge, should need the cut-outs described, and I think it likely that these were mentioned to the reporter concerned as modifications which might be made to the Isotta-Maybach. At the same time it could well have been implied that if Eldridge wanted more speed he would endeavour to find and install one of the 30-valye (/.h.,/Y. war-time Maybach engines. This could well have led to an error of reporting, implying that an AZ engine had been etm.t,erted into a 30-valve power unit., just as, 42 years later, Charles Buttner presumably confused the live-valves-per-cylinder Maybach engine with the T-head engines. A year or two before Eldridge coaxed more speed from his ancient Isotta-Erasehini by putting a 21-litre Maybach AZ engine into it, Count Zborowski had installed a 300-h.p. o.h.v. aerci-engine of this make into a pre-war Mercedes chassis to form the immortal Chitty-Bang-Bang I. Eldridge was presumably forced to give away 120 h.p. to his rival clue to the exigencies of using what was available. It is ironical that his car proved fractionally faster, a matter presumably governed by top-gear ratio, weight and frontal area. (FitzPatriek’s thesis that if Eldridge had wanted more power it would have been prudent to use a CX or later o.h.v. Maybach engine instead of trying to insert an additional valve into each “pot,” assuming this were possible, which he denies, falls -down if such werenot procurable. And, although vast numbers of surplus aero-engines were offered for sale after the Armistice, suitable ones for going motor-racing with may, for some inexplicit reason, not have been freely available—otherwise, why did Eldridge use a very-muchpre-war T-head Maybach, Zborowski settle for a 240-h.p. Benz engine for Chitty II after his 300-11.p. engine in the earlier Chitty, and Scarisbrick follow suit when having a replica Chitty built?)
The mystery hinges on whether it was possible to get another valve in each cylinder of an AZ Maybach, or whether there was an interim 30-valve version, also of 160 x 170 mm. Unless The Motor‘s reporter of 1922 defends his statement, or Bulmer his, or a Maybach expert can shed some light, I propose to resolve this minor Maybach mystery by suggesting casual reporting as an explanation, accepting the Isotta-Maybach as having an ordinary 24-valve AZ Maybach motor. Incidentally, after Le Champion had ceased to race it the Isotta-Maybach passed into the hands of a Mr. Frew of Cambridge and when he was building a house near Farnham a Mr. Sergeant who was employed by the local council was able to offer some assistance, and accepted for his services the old chain-drive racing car, for which the owner had no use. However, one run home was enough to convince him that this was no ordinary motor car and, despairing of ever taming it, he left it in the yard of the garage which serviced his ancient Triumph motorcycle and bullnose Morris. Over the years it was cannibalised and has completely vanished—a pity, otherwise I could have counted its valve stems!
The mystery does not quite end here, for the Maybach engine, whether 24- or 30-valve, was installed in the Isotta chassis by Aeromotors Ltd. of 5-11, Vauxhall Bridge Road, according to that 1922 report in The Motor. This firm apparently existed for the intriguing purpose of installing war-surplus aeroplane engines in cars and boats. But I have been unable to discover who ran it. A reader of my articles remembers the firm as renting the top storey of a building which was originally a horse-tram depot, the horses living on the first floor, which they reached by walking up a ramp. Apparently Aeromotors Ltd. pulled their cars up this ramp with rope and tackle, and my informant recalls a Mr. Fitzmaurice being in charge, and of hearing the deafening noise of the big engines being run up. At that time the bottom part of the building, today the Rosemex Service Station, was occupied by United Transport (London) Ltd., the proprietor of which was Major Jack Mills, brother of the late Bertram Mills of circus fame.
I think Eldridge acquired these premises although even this is not certain, because I think work on his Isotta-Maybach (like making floating gudgeon-pins, balancing the pistons and fitting tie-plates between the separate cylinders to stop the water joints from leaking, etc.) was carried on farther down the Vauxhall Bridge Road. And when he was putting the Fiat aviation engine into “Mephistopheles” the work was done at Hampstead. But Aeromotors may well have done the installation of the Maybach engine in the Isotta. Can any readers with long motoring memories tell us more?
Incidentally, when Mr. Scarisbrick put in hand his “Chittyreplica,” the work was done by C. H. Crowe & Co. of Upper Kennington Lane. S.E.11, a firm which specialised in Mercedes overhauls but which, like the short-lived Aeromotors Ltd., has disappeared.—W. B.
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