No. 4. — A LONDON TUNING SHOP
OF my personal experiences of purveyors of speed, Messrs. Automobile Supertuners stand out as one of the most interesting. Situated in Roberts Mews, off the Hampstead Road, in this small but efficient workshop under the direction of R. F. Oats (with Alec Francis, the one-time designer of the very fast Beardmore cars well known in post 1914-1918 hill climbs, and of that ingenious twin o.h.c. twin mag. 350 c.c. Beardmore motor-cycle for the T.T. Races, as works manager), the elusive r.p.m. were successfully hunted.
Many and diverse were the cars that were handled during the 1933 season with which I propose to deal.
The two eight-cylinder 2,500 c.c. Maseratis, with their rather angular A.I. bodies in red fabric by Corsica, were those used in 1931 by Campari and Eyston, one being the property of the Australian, John Cumming, who had used it during the previous season as a sports-car, surely one of the fastest at that time. Cumming’s car was then being prepared for track events, and to that end the compression was raised and the car stripped. An inherent weakness in these Maseratis caused cracking of the electron crankcase at the clutch housing, owing to gearbox overhang and driving and braking strain. I spent many strenuous hours underneath, stiffening the weak parts with angles, webs and tensioning devices, but on a practice lap on the outer circuit at over 105 m.p.h. the tensioning bolts snapped, which meant some last minute work making up bolts of high tensile strength before the Easter Meeting, at which, off 23 seconds, the car finished second in the Second Addlestone Mountain Handicap.
After this event, the engine was stripped out, and the case built up by Lensen, the cold-welding magician, all acute angles being built up to radii, and the actual faces of the clutch housing thickened up. Improved tensioning bolts and an angle support under the gearbox with a large rubber mounting were further improvements. At the same time, an improved pattern piston was fitted, and a different mix of bearing metal used. In this condition the car finished fourth in one Outer Circuit race at the June Meeting, being badly baulked by slower cars. The other Maserati had similar attention to the crankcase, but in addition the top half of the clutch housing was stiffened by steel plating.
I remember some hectic work removing the rear axle of this job for loan to Whitney Straight for Shelsley, as his had burst in the International Trophy Race on the previous Saturday.
These motors were the real thing, and to ride as mechanic entailed being partially baked from the waist down, and frozen from the waist up, but it was indeed an experience never to be missed.
Two Salmsons also came under our care, those of Bartlett and Harvey Noble. The former was the then holder of the 1,100 c.c. Mountain record, and was being modified, the work on the engine consisting of removing the No. 8 Cozette compressor from its usual side-mounting, and driving it from the forward end of the crank through a short shaft and fabric universals, the front cross member being moved forward to accommodate it. The compressor was carried in straps from channel mountings across the chassis frame. The water pump was then driven from the usual blower drive. Special magnesium-alloy pistons weighing 5½ozs. with circlip gudgeon retainers replacing the usual Salmson taper-pin fixing, and a special balanced crank with a modified method of securing the centre main bearing were additional modifications. The flywheel was considerably lightened, and an entirely new double branch inlet manifold and more efficient water piping, designed by Francis, was constructed. The general chassis detail work included a re-designed front axle, 4 ins, lower than standard; wedged up and flattened springs with multiple clips, and fuel tanks in the tail and across the chassis under the propeller shaft and driver’s seat, pressure fed. A single seater aluminium body mounted on a light alloy angle sub-frame was fitted, and central steering with the steering column canted across to suit the two-seater chassis. Heavier triple-bladed Andre shock-absorbers were used all round (I recall the tough job I had lightening the arms of these), and the chassis was generally stiffened up at various points.
Using a No. 8 Cozette blower, the unblown compression-ratio was 4.8 to 1, and the car ran with a 12/45 or 12/48 straight-tooth axle assembly.
Harvey Noble’s car was nearer standard, having a No. 7 Cozette, side-mounted, an unblown compression-ratio of 6.5 to 1, twin Scintilla magnetos, and a Cozette carburetter. The flywheel was, of course, lightened, and the car looked unusual by virtue of its having an Amilcar body, flattened springs, and G.P. Salmson radiator cowl and scuttle tank, but it certainly went!
I see I timed an outer circuit lap at 95 m.p.h. on a valve timing of I.O. 12° before, E.C. 26° after, with an ignition advance of 48°, and tappet clearance of .018″. Later in the year we experienced piston trouble and circlip-locked gudgeons were used, and the bores linered. Very fine motors these old G.P. Salmsons!
The star car in the stable was, of course, Widengren’s Amilcar, which I mentioned in a previous article, and it would take many pages to describe the work put into this car, and the troubles experienced and overcome and the many nights and days we spent improving and modifying. No doubt, enthusiasts will be aware of general details of these beautiful six-cylinder cars, as they were at one time a standard production in France, and were exhibited here at Olympia. Widengren’s car was one of the special chassis with offset engine, the shaft passing alongside the driver. Alterations were many— special camshafts giving an overlap of 27°; larger valves; stronger triple valve springs; the Amilcar Roots blower boosting at 15 lbs. per square inch; and either a 40 mm. Solex or R.A.G. carburetter. Valve clearances were .018″ Ex., .014″ In., but depended upon the working hand, as the camshaft driving gears were fitted with a vernier, so that timing could be extremely accurately set.
I well remember the trouble we experienced before the International Trophy Race in 1933, when in practice, late on the Friday evening, the car started to slow up and burn out the hottest plugs. Hurried removal of the head revealed that the exhaust valves were pulling through the valve seats, the heads having cracked. An urgent ‘phone call to Clayton produced a set of exhaust valves, and an all night sitting dismantling, machining and hardening a set of end caps, and re-assembling, saw the car on the line on the morrow, when it finished eighth after many pits stops, lapping at 86 with a peak r.p.m. of 6,200.
I should like here to make a correction to my previous article in which I stated that the Avus Grand Prix was a week after the record attempt. It was, in fact, a week after the International Trophy, which week saw a complete engine overhaul, modifications to blower and water pump, and also to body and exhaust system! On the Avus, the car completed 3 laps, attaining over 120 m.p.h., when a valve dropped in, causing a spot of trouble entailing further complete rebuilding of the unit, modifying the gudgeon pin fittings, and substituting a spare head of Bill Humphreys’s, with the smaller valves, and steel valve guides. Endless work saw the car ready for the British Empire Trophy, when, after lapping at 110.9, the driver knocked the tank pressure release tap on, and retired on the spot! So often the obvious escapes notice.
The marvellous Thomas Special, one of the 1½-litre “flat-irons,” was at the time being fitted with a Francis-designed cylinder block of great technical interest. The block and head were cast together in pairs, and bolted up by longitudinal bolts, to make a complete eight-cylinder block assembly. This simplified and cheapened the pattern and thereby the production of the casting. It was intended to produce four, six, and eight cylinder engines using a multiplication of the two bore block castings.
The fixed head block used twin o.h.c. opening valves inclined at 60°. Twin plugs, masked, to enable larger valves to be used, were fired by twin eight-cylinder B.T.H. magnetos mounted on the top of each bronze o.h.c. cover, and driven by spur gears from the camshaft gear. With these masked plugs 67° ignition advance was given, and the valve overlap was 41°. The pistons were extremely short-skirted and light, and fitted with two compression and one scraper ring, all above the gudgeon pin; the engine was designed to give 95 b.h.p. at 6,000 r.p.m., unblown.
The block was mounted on the original Thomas-Special malleable iron crankcase, using the 1,100 c.c. crank and rods; particular attention was given to the water circulation round the exhaust valve seats, and four Solex carburetters with double chokes provided the mixture. An amusing incident occurred during the construction of the involved linkages required to operate the eight throttles in that depression of the accelerator pedal shut instead of opened them— a defect which was very quickly rectified.
After a tremendous amount of work the car was got down to the Track for test, where apparently the power developed by the new top rig was too great for the rods, which shot in all directions ‘
Apart from the engine details above the crankcase, the car was original Thomas, the 8″ diameter, multi-plate clutch, horizontal steering column, sledge pattern chassis, and sheet steel bodywork being typical of the master’s design. It was later fitted with a Perkin’s Diesel and took oil-engine records.
Other interesting cars included the big six-cylinder o.h.c. Napier, owned by Capt. Miller, and one of the Segrave supercharged 2-litre Sunbeams, with which I had the misfortune to ram the firm’s hack 0.M. when being started up one day (luckily the damage was confined to the radiator and the car did well in Ireland at a later date, driven by McCalla). Another Sunbeam was the blown 3-litre o.h.c. sports job, originally driven by Malcolm Campbell and later by B. 0. Davies in Ireland. Actually we stripped the engine, a lengthy job with this type, and welded a crack between the valve seats, which unfortunately went again in a very short time. This car was imposing with its side-mounted Cozette blower, twin A.C. fuel pumps, and distinctive lines.
There was a special eight-cylinder G.P. O.M. with its extremely complicated engine, in which each cylinder was separate, with fixed head and sheet steel water jacket; nine bearing balanced -crank; roller big-ends; and Amherst Villiers blower. The tubular front axle was carried on very short, flat, half-elliptic springs, and cast iron liners on steel shoes operating on steel drums looked after the braking. The chassis was of inverted “U” section, filled with lead, to give correct weight distribution, and it went remarkably well unblown, on eight R.A.G.s driven by the Great Man himself.
The four-cylinder “12/50” Alvis driven up to a recent date by Chas. Follett, also came in for a lot of attention. Especially, I remember working on conversion to dry sump, and days spent at the bench in the blazing sun, lapping cylinder block and head to obtain that perfect joint! This car was amazingly reliable and successful over a period of years.
Sundry “Speed 20” Alvis came in for additional tuning, among them Widengren’s private car, and a very fine dark blue saloon, the property of Sir Ronald Gunter. Replacing broken valve springs on these cars prior to the multiple spring design was a routine job. There were also divers 0.M.s including R. P. Oats’s personal blown 2-litre saloon, which we had fitted with special vernier blower gear wheels. There were also occasional visits from H. G. Dobbs, the Riley driver, for whom Francis had designed a set of rods, and countless other interesting jobs which occupied my time fully until I cracked up in late ’33 with a dislocated spine, which put me out of active participation for many months.
Our staff also was not without interest. There was old Terry, who had worked at Chas. Friswell’s in Albany Street in the very early days of motoring, and could discourse learnedly on cars which to us were merely names. Owen Finch, who had been with me at Frazer-Nash, I was able to introduce to the firm, and, strange to say, we are now again together, supervising the conditioning of Civil Defence Vehicles. Other mechanics I still meet in places many miles away from the Hampstead Road, and I regret that space compels me to deal with machines and men in such a cursory fashion, but there it is!