DEVELOPING THE FRAZER-NASH
DEVELOPING THE FRAZER-NASH
Anyone who was associated with the sports car of ten or twelve years ago must be amazed at the change which has taken place since then. The average owner, accustomed to motorcycle standards of acceleration and comfort was interested in nothing but performance, and if he turned to four wheels, was content with small cramped bodies and harsh springing, as long as the car had the necessary urge. Nowadays, the designer is faced with no easy task, being asked to produce a smooth running car with luxurious coachwork, and to still preserve the snappy get-away of the modified racer. In 1922 we still had many things to learn about obtaining high power output, and so had to obtain our performance from a high power-weight ratio, and every part of the Frazer-Nash chassis contributed to this result. The chassis frame was very light and free from complications, simply two steel side members of channel section with three
cross-members. Quarter-elliptic springing all round saved weight, unsprung and total, and the front axle which was tubular still proved itself strong enough to resist the torque of front-wheel brakes.
Then we were fortunate in the engine which was a side-valve Anzani. Weighing only 166 lb., with a compression ratio of 5.8, it developed a maximum of 47 h.p. at 4,500 r.p.m. These little engines were extremely reliable and seemed capable of giving their output indefinitely. For your notebook, in case you are the owner of one of these motors, the ignition setting for full advance was 35 degrees before top-deadcentre, which worked out at 31 inches at the flywheel rim. Jet sizes are for the 30 mm. Solex 50 pilot and 120 main, with a 24 mm. choke. With the 35 mm. instrument the pilot should be 52.5-55 and 130-135 with a 26 mm. choke, the smaller jets giving better acceleration and the larger maximum speed. The original engines had cylinder heads with the combustion chambers sloping down to the pistons. A later development was the screened head, in which the combustion chamber sloped down abruptly, so that the top of the piston came very clOse to the head. This caused an increase in turbulence, and in conjunction with a new camshaft, raised the horse-power to 52. Unfortunately, this power was more than the rods could stand, and if you tune the engine to this pitch you will need special rods made of
100-ton steel. It is also advisable to replace the old-type pistons, which have the side round the gudgeon cut away to reduce friction, vvith a stronger pattern with straight sides. Incidentally, the screened head was very sensitive to ignition 18 degrees advance-47/8 on the flywheel being the correct setting. The old cars complete weighed only 14 cwt., and with the normal engine, a top gear of 4.1 WaS suitable giving a speed of 75 m.p.h. With the highefficiency or ” Boulogne ” engine, 3.8 was usual, and even on the standard type it could be used when low revs
SOME NOTES by T. W. DOMAN
(In an Interview)
were of greater importance than topgear acceleration. One of the great points of the FrazerNash is the ease with which one or more gear-ratio can be changed without altering the others, by changing the sprockets on the back axle. The standard ratios were 4.1, 5.4, 7 and 11.6 to 1, but for Shelsley, for instance, they could be altered to 5.4, 6.9, 8.8 and 12.5 to 1. Extra sprockets can be left permanently in position on the rear axle ready to be slid into, position when alterations in ratios are required. On the original cars, only three speeds were fitted, but a fourth can easily be added. ‘Stronger and larger double-dogs on the cross-shaft was a later development, and a wide front axle Which could be
installed without any alteration of the axle clips in place of the narrow track one much improved the road-holding.
Looking through my engine-test book the other day I came across two sets of figures which, though they have no bearing on the standard cars, are worth recording as showing what can be done with a side-valve engine. One of these was a special job with two carburetters, whieh were installed on the valve side of the engine just above the exhaust pipes. At 4,500 r.p.m. this engine gave no less than 61 h.p., a good figure even for nowadays. Unfortunately, very few of these blocks are in existence, the only ones I know being fitted to Mr. Metcalfe’s Abbott-Nash. This type was also used by Horstmanns in the 200miles race cars.
The other engine was the supercharged one fitted into the Terror, the little single-Seater with which Mr. R. J. G. Nash twice made fastest time at Shelsley. It was fitted with rollerbearing big-ends and could be run up to 5,000 r.p.m., the power being 105 h.p. For on short hill-climbs and sprints, these engines worked surprisingly well, and we even built a few road cars of this type, with engines giving some 80 h.p. Unfortunately, for continued full throttle work, the very compactness of the engine proved a disadvantage, as there was not sufficient water round the bores to allow continued cooling to prevent local overheating, and we had to look elsewhere in our search for further performance.
The engine we chose was the fourcylinder Meadows, a compact and strongly-built unit with vertical overhead valves operated by push-rods. It weighed 275 lb. and therefore increased our total weight by 1 cwt.:, but to balance that, gave a full 50 h.p. with the standard compression of 6 to 1. The performance remained much as it had been with the Anzani, but we soon found we could raise the compression by the use of ” higher ” pistons to a to 1, using as fuel 50 per cent. ethyl petrol and 50 per cent., benzol. This gave us A horsepower of 57 and an all-out speed of 85 with the car completely equipped while on the track with wings and lamps removed, one of the cars lapped at 95.5. How much more it would have done with a streamlined body we never found out, as we confined our racing to cars with standard coachwork. Continuing our experiments with the Meadows, we evolved a new type of cylinder head which had lobes or deflectors in the combustion chambers to improve the turbulence. This brought our power up to an even 60 h.p., with
compression raised to 10 to 1. Apart from giving smooth running the new head improved all-round efficiency, as was shown from the fact that the ;gnition advance, previously 54 degrees or 17i teeth on the flywheel, could be reduced to 35-40. This engine, like all the later ones, was fitted with two S.U. carburetters, and the settings I would suggest if you are tuning for speed are needles Fu. m5 and jets 5.090.
As a result of racing experience, we developed special lightened con-rods, light rockers and valves and a balanced crankshaft, and these refinements, especially the con-rods, are desirable if you want to get the best out of the engine. Finally we succeeded in taking the compression up to 14 to 1, when we got 74 h.p., running on racing Ethyl. This power gave us a Broolclands lap speed of 103 m.p.h. on a car stripped of lamps and front wings. Supercharged, with ten pounds pressure, Commander Grogan’s engine gave off 120 h.p. which resulted in a lap-speed of 113 m.p.h. Here again, after more than doubling the original horsepower, we had reached the limit to which the engine could be brought without drastic redesign. Instead, we branched out into a 6-cylinder car. The engine used was a Blackburne, a double-overhead camshaft job with a capacity of either 1,500 or 1,660 c.c. At 4,800 r.p.m., the larger engine gives 75 h.p., while the weight, which seems to increase almost in proportion to power output, is just 3 cwt. Being longer than the 4-cylinder, we were compelled to use the long chassis with a wheelbase of 9 feet as compared engine has proved a great success. Fully equipped, and using standard fuel, Mr. Fane’s car laps Brooklands at 106 m.p.h. and, during the M.C.C. High Speed, where the car was fitted as an experiment with a low top-gear ratio, held 5,000 work rather than racing, little has been done to the 6-cylinder engine, which in its standard trim has proved completely reliable. The latest departure is to supercharge them, using a Centric blowing at 6 to 8 pounds. The blower
with the short one of 8 ft. 6 in. Far from being a disadvantage, the longer chassis was appreciably steadier on corners, and so was used to house the latest 4-cylinder Frazer-Nash engines. Being intended primarily for road
is mounted at the side of the engine and chain driven by a sprocket mounted on the torque damper, which insulates the drive from sudden variations in speed. The driven shaft is supported in two bearings and drives the Centric through
a flexible coupling, avoiding any side-strain on the blower bearings. Tests of the supercharged ” 6 ” have not yet been completed, but we hope to reach 100 m.p.h. with it.
Now we come to the special Frazer-Nash engine, which first became available in 1934. It was built with two special ideas in view, firstly to give a high output with continued reliability, and also, with a view to supercharging, crankshaft connecting rods and other heavily stressed parts were made particularly strong. The standard compression is 8 to 1, and thanks to the efficient design of the single overhead camshaft head, the engine runs quite happily on Cleveland Disco], with an output of 56 h.p. at 5,000 r.p.m. With a 10 to 1 compression 70 h.p. is produced, with 50 per cent. ethylised petrol and 50 per cent. benzol as fuel, while about 4 h.p. more is secured by the use of two sets of sparking plugs. For maximum outputs, however, single ignition has been found more successful, as the aperture in each combustion chamber, through which the second plug fires, reduces the turbulence. We are not yet in a position to publish details of the latest moves, but I can say that by various small alterations we have reached 87 h.p., which should give us a road, or rather track, speed of 110 m.p.h., not bad for an unsupercharged engine. In supercharged form the new
r.p.m. for an hour. With higher compression and using 50 per cent. benzol, the all-out speed is about 114 m.p.h.
For Grand Prix racing we have developed the new single-seater cars, which are identical in chassis design with the standard cars, but have an additional tubular cross-member amidships. The compression ratio stands Et 10i to 1 and with a ” blow ” of 16 lb. we have reached 148 h.p. The all-out speed is some 130 m.p.h. while the car weighs just over 14 cwt. In a short time we are bringing out an entirely new model called the Ulster Hundred, which will have a guaranteed speed of 100 m.p.h. The price will be £750. The chassis will be similar to the SheIsley type, with the new cantilever front springing and cable-operated brakes. The engine will be a modified Frazer-Nash Four, unsupercharged, with the cylinder block, crankcase and all
other possible parts made of elektron. A new form of clutch-operating mechanism brings the pedal lower and requires less pressure, but otherwise the transmission is unchanged. The radius arms, which carry the back axle, will be tubular instead of being built up from steel plates. The rear springs are underslung and the chassis frame passes under the axle. The body is of semi-racing type with a long sweeping tail. It is constructed om sheet aluminium over a frame of bent ash formers. An undershield runs the length of the body, the only projecting’ part being the front end of the 2-gallon sump. A sheet-metal bulkhead in front of the engine will divert all the air which passes through the radiator out through large louvres at the front end of the bonnet, and a second, acting also as a fireproof bulkhead, reaches down to the under-tray behind the engine, and there disposes of engine
fumes through further louvres: These two measures should prevent the interior of the car from becoming hot and also reduce wind-resistance by cutting down eddies.
Driver and passenger sit well down in the body, the seats being level with the side-members. Behind the seats and forward of the rear axle is the 15-gallon petrol tank, which has two fillers. The spare wheel is carried vertically and enclosed in the tail, with its front part between the two centre sprockets on the rear axle.
Up to now, we have been handicapped in sports-car races by running cars with standard coachwork, which has no pretensions to streamlining. The new model will give us a chance to compete on equal terms with cars specially built for road-racing.