A BLOWN SEVEN-FIFTY

A BLOWN SEVEN-FIFTY

T0 the large majority of us, a run in anything approaching a sports car is, under present conditions, a very rare treat. When the car happens to be a very close approach to a racing car and one of the fastest. (if not the fastest) of its kind in one piece at the present time, then it is welland truly an occasion about which to write home. This was my good fortune ‘recently, when the happy coincidence Of a period of leave after service overseas, with its petrol allowance, and the purchase by a friend of a very potent Austin Seven enabled me to assist in its transference to its new home station in the Weybridge area.

The car in question is the blue competition 2-seater IV-Special, built for his own use by I.. Williams, of Auto Conversms, which will be known to many readers of Mo-roa SPORT from its appearances at Dancer’s End tied Markyate in 1939, and also from at least two occasions when it has appeared at the war-time meetings of the Seven-Fifty Club at Coulsdonand at Osterley.

Actually, its competition history has not yet really begun, as it was constructed durin,, late 1938 and early 1939, and pressure of other work and the outbreak of the present conflict limited its appearances in competition to two events. The first of these was at Dancer’s End in May, 1939, in which it was entered for the supercharged 750-c.c. sports-car class. The scrutineer spottis I the absence of both spare wheel and provision for carrying the same, so that the car was relegated to the under 1,100-e.e. racing class. Williams’s troubles were not yet over, however, as peak r.p.m. proved unobtainable due to a cause that remained obscure for some time, and only third place in the class resulted. Its second appearance was shortly afterwards at Markyate, for which occasion the blower was removed and twin downdraught carburetters on a special manifold were substituted. Once again misfiring became apparent at high speeds. It. was not until the Magneto was tested for the second time that an obscure short in the armature was located and rectified. Those readers who like little motor cars with tiny engines which go round very fast indeed to produce very respectable performance with extreme economy, will enjoy this account, by Capt John Moon, of the ex-Williams Austin Seven and his road impressions

of it.—Ed.

As far as it can be said to follow any particular model of the Austin Seven, it is on the blown ” Ulster ” that this car is based, but it is really a complete hybrid and illustrates well the versatility of Austin components.

The engine is a normal blown ” Ulster,” with the usual 11-in. hig-end journals and a crankshaft without. counterbalance weights, but drilled for pressure lubrication of the big-ends, oil being fed in through a bush which fits Over a parallel part of the starting-handle dog at the front end of the shaft. A set or racing Austin con.-rods, polished all over, are used, and the pistons are very light Martletts with very narrow rings. The valves and valve gear follow normal ” Ulster ” practice, with light, nonadjustable tappets. but the camshaft is a special one, giving a high lift and considerable overbip, so that. the engine can be run unblown and still give a respectable performance. The blown ” Ulster ” camshaft, as provided by the maker, is a very mild affair, giving approxiniately the same timing as, and 0.090 in. less lift than, the normal touring camshaft. The cylinder head is the unblown ” Ulster Ricardo ” type. giving about 7 to 1 compression ratio, and is copper plated. The gasket. is normally a standard-thickness C. & A. one, but a thin C. & A. gasket can be used. The blower is a Cozette (the blown ” Ulster ” has either this or a Rootspattern blower of Austin manufacture) and delivers at a maximum pressure of 5 lb. per sq. m. through the Y-shaped inlet manifold which curls round from underneath the blower to the two inlet ports above it. The carburetter is an Arnott, specially made for the car, and works on the constant-vacuum, variable

choke principle like t well-known S.U., and is mechanically very similar. but has a rather peculiar square appearance. It has the advantage that the mixture strength is readily adjustable without any dismantling, a great asset for competition work.

The exhaust manifold is an external one, specially made up to suit the narrow body, and is flat instead of being slightly upswept as the ” Ulster ” one is. It aLso avoids the rather poor feature of the ” Ulster ” manifold—the abrupt T-shaped junction where the third branch joins the main pipe.

The radiator actually started life on a ‘Nrolseley Hornet, but was rebuilt by Serck, the radiator people, to tit the car, with different header and bottom tanks, and with a hole through the core for the starting handle. It is mounted on two peculiar brackets which drop it just in front of the spring mounting, slightly more forward and lower than normal. In conjunction with the pump on the engine it is over-efficient, so that it has to be partially blanked Off, despite the absence of the fan with which the blown ” 171ster ” is normally equipped. Ignition is by an M.L. magneto, and three grades of plugs are normally used. The soft plugs which we used on our .delivery journey are K.L.G. 1{1, the medium plugs which are usually used for road work are M50, and the hard plugs used for sprints are M30. The extensively-lightened ‘llywheel carries the cast-iron linings of the ” 1,Ister”type clutch. which has heavier springs than the touring one, these making their presence felt %%lien traffic-driving is indulged in. The gearbox is a four-speed, close-ratio (” close-ratio ” is a relative term only, as third speed is 1.49 times the top gear ratio), having synchromesh on top and third and a constant-mesh, but plain, dog-engaged, second gear. The gear-change is remotely controlled by

means of an external rod with fork ends arid pin joints. The four-speed box necessitates the use of a geared-type starter motor. the switch for which is mounted on the dashboard.

The propeller shaft is the solid type, with a fabric coupling at the front end and a lIardv -Spicer joint at the rear end, and it has been cut, welded, and sleeved in order to shorten it to suit the short wheelbase frame. The rear axle is a quite normal narrow-track one, with a 4.9-to-1 ratio at. present, though 5.67 to 1 and 5.25 to 1 have been used at times.

The frame is actually ” Ulster,” but is very much the same as any shortwheelbase frame of 1932 vintage. It is extended at the rear by two 11-in. by 1-in. angle steel members which pass under the axle to support the 7-gallon rear petrol tank and the tail of the body.

The front axle is dropped about 2 in. lower than the normal ” Nippy ” or Ulster” axle, and has a piece welded in the centre to make it wider than standard and so give the car a 6-in, crab track-3 ft. 10 in. at the front and 3 ft. 4 in. at the rear. The reversed camber front spring is a specially wide one to suit the wide axle, and the special radius rods were at one time boxed in, but are now normal channel section again.

The usual Austin worm-and-wheel steering is used, with a malleable iron steering box to prevent any risk of fracture. It is mounted on a forged-steel bracket to give increased rake, and is some 6 in. further back than on an “Ulster.” This, with the longest Austinproduced steering column and the deepest wheel hub available, brings the wheel right back into the driver’s chest. The steering wheel is a 17-in. Ashby—an inch larger than that normally provided on sports Austins—and an inch well worth having, as it seems to add a lot to the controllability.

The braking system is the Austin system, with Williams’s conversion to Bowdenex operation for the front wheels, the shoes and drums being the (relatively) wide type which were in standard production between 1932 and 1935, while the hand-brake is extensively cranked to bring it within reach of the driver.

The rear springs are of reversed camber and have the same number of leaves as the tourer, but have extra clips to prevent them spreading sideways. Incidentally, they are much softer than those on Austinproduced sports models, which have springs with the same number and thickness of leaves as the 5-ewt. vans ! The wheels will, I am afraid, shock people who hold that wire wheels are the only permissible wear for a sports car, as they are of Austin “Big Seven ” pressed-steel variety. Actually, I do not think that these wheels look out of place on a car that has a forwardly projecting radiator cowl as this one has. As a matter of fact, they are the only Austin wheels in standard production with 16-in, rims, are very little heavier than the wire type, and fit any Austin Seven hub when the dowels in the brake-drums have been removed. Incidentally, they provide the solution to a problem which I have been turning over in my mind for some time, namely, how to adapt bigger brake-drums to an Austin axle without having to replace

hubs and so on. Tyre sizes are 4.75 in. by 16 in. front and 5.25 in. by 16 in. rear. The body is built of ash with aluminium panelling, and is based in shape on the

i-litre single-seater Maserati racing car of a few years ago, except that it has been made just v‘ride enough to take two people. The beaten aluminium radiator cowl, carrying a neat ” W Special ” label, is reminiscent of the Brooklands Talbot of Dr. Roth. The. bonnet is hinged along the centre, has louvres cut along the top, and is held down by two external clips on each side. The fold-flat screen is mounted well forward on the scuttle, so as to avoid the cowl which is provided on the driver’s side only. The spare wheel rather mars the lines on the off side, but has to be carried to conform with Sports Car Race regulations, as has the hood, which, with its single hoop, stows away on the top of the tank in the tail. The proud new owner, incidentally, wanted to photograph the car with the hood erected, but soon changed his mind when he saw it so equipped, as it is a very comic-looking affair which merely serves to keep the scrutineer in his place.

As regards the other external features of the car, the wings are Mall flat-blade affairs, the front ones of cycle-type attached to the back plates of the brakes, a feature of which I do not entirely approve as it increases the unsprung weight by more than a little, though any other fixing would be a rather tricky matter. The car’s owner agrees with me that the rear number plate is in the wrong place, mounted as it is on the top of the tail, and the numbers will probably be painted on the sides of the tail at some future date, though this is only permissible when the sides of the tail are in a plane, and, anyway, makes illumination rather a problem. The exhaust system rather throws itself at one, I think, giving the impression of a “Promenade Percy ” motor-car, but it is difficult to see how it could be tucked away so as to be less obtrusive.

The dashboard, which is finished in a special blue paint giving a most attractive appearance, carries a complete set of instruments down to a grab handle— which is actually most useful in assisting the passenger’s entry and exit. The instruments, from left to right, are as follows : four tumbler switches, controlling the charging circuit, the ignition and the side and tail lights (which are all that are at present provided), plus a spare switch for the spotlight that will be fitted to act as the headlight ; underneath, the starter and choke controls ; then the airpressure gauge above the pressure pump for the petrol feed ; the ammeter ; the boost gauge above the strip-type [!—Ein.1 speedometer ; the 3i-in. Smith’s rev.counter, and, on the right-hand side, the water thermometer above the oil-pressure gauge. Incidentally, the body was made to measure to fit Williams, and for anyone much over his size entry is a matter of some difficulty. This recalls to my mind the groan of anguish loosed by the prospective owner who, having looked over the car and fallen in love with it, tried to insert himself into the cockpit and found that he could not make it. Fortunately, a demonstration by Williams taught him the correct technique, and he

now slips in and out with the greatest of ease ! My first impressions of this little car on the road were as a passenger during . the journey from Kew into the middle of Surrey, and I was soon completely fas

cinated, though after about 15 miles the car began to impress upon me the fact that it is not really intended to carry a passenger. as my right hand grasping the off-side wing stay was very close indeed to the rear wheel, so that I had to mind my knuckles when we went round corners, the exhaust pipe behind my left shoulder began to get quite warm in spite of the asbestos string binding, and my left leg got cramped, due to the restricted leg room caused by the battery living on the floor boards just behind the bulkhead. These, however, are very minor discomforts compared with the joy of travelling in a really potent little car again.

Later on, when the delivery journey was over and the car was taken out for a short run to try out its paces, I took the wheel and was able to sample its real fascination for myself. Certain acrobatics are necessary to insert oneself behind the steering wheel, but once there one feels completely at home with the big (for an Austin) steering wheel close to one’s chest, all essential instruments under one’s eyes, and the gear-lever just where one’s hand drops on to it from the wheel. The foot brake and the accelerator are rather close together—there is no room for them to be anything else so that it is essential to have narrow shoes, and in order to be able to feel what one is doing, it is desirable that these be light as well. When driving on the road, I prefer to use bottom gear for starting away from rest as second gear feels a little on the high side, but one’s getaway is rather spoilt by the change from first to second unless this is carried out in a very brutal manner (which I did not like it to be with someone else’s motor). On the other hand, when one really is in a hurry, an exceedingly rapid getaway can be achieved in second gear if the clutch is engaged with care. Once under way in second, 6,000 r.p.m. is attained in a very short space of time, and the same speed in third is reached just as effortlessly and nearly as quickly. The performance in top was limited by bad misfiring, which became apparent at just over 4,500 r.p.m:, which, according to my calculations, is somewhere around the 80 mark. This trouble was in all probability due to unsuitable plugs, as a medium hard set only was available at the time, but in any ease the very limited amount of fuel obviously precluded any serious attempt to trace the trouble, which was only apparent on top gear. In order to gauge the Austin’s accelerative ability, it was tried out against a 500-c.c. sports B.M.W. motor-cycle, which is one of its stable companions. The conclusion was, of course, inevitable, but the two-wheeler’s lead was much lower than we had expected. What impressed me most of all with the Austin was the way in which it sits down on the road. On roads with a reasonable surface, it remains glued down in a manner which completely belies its weight of only 8+ cwt., and which, if I, as a full-blooded Austin enthusiast,

may say so, is completely unAustin. The credit for this must, I think, go to the wide front axle and to the extra clips on the rear springs, which are firm enough to give steadiness at speed without being dead hard at low speeds. Over not so smooth surfaces, the front wings dance about like mad, but the fixings are sufficiently flexible to allow this movement without any detrimental effects. The brakes were definitely not up to the performance of the car (what Austin Sevens ever are ?), but as there was a lot of free play on the pedal which could have been taken up, it is not fair to criticise them adversely. A point which came in for adverse criticisin from both the owner and myself

is the external remote control for the gear change, which is made up with a piece of &-in. steel rod with fork-ends which pin on to the gear-lever stub and to the ball-jointed remote lever. The arrangement is light in weight but lacks any other virtues, as the pin joints are inadequate in size and the play that has developed through wear completely spoils the gear changes, especially through the gate. The present arrangement is to be replaced either by a welded-up enclosed type or by an open type with a thin tube for the horizontal extension and with large-size pin joints, such as those on the Allard Special, when the necessary facilities for that sort of job are available. Although a small blown engine such as this does not demand such dose gear ratios as an unblown one would, a closer set than those now fitted would make a great improvement. I have often wondered whether it would be a practical proposition to turn or grind the existing constant-mesh gears from the Austin four-speed primary and lay shafts and to press and key into position another set having one or two less teeth on the driven gear and one or two more on the driving gear, so making all the ratios closer. All these points, however, are passing thoughts which are far from being serious cril ii•isins, and which certainly in no way detract from a very interesting and potent little car, which it is confidently hoped will appear at the rst and at subsequent post-war sprint events. May this day be soon I