A SMALL CAR WITH A BIG PERFORMANCE
SMALL CAR WITH A BIG PERFORMANCE:
THE FRAZER NASH SPORTS MODEL.
WHtN Capt. A. Frazer Nash announced his intention of producing a four cylinder model, a large body of motorists, sporting men in particular, looked forward to something quite unique in car construction, and had not long to wait before their most sanguine expectations were realised, for without doubt the Frazer Nash boasts a most extraordinary performance.
As our readers are aware, the design is based on the chassis which has been so successful in the past, in general use, in severe competitions, both in the hands of Capt. Frazer Nash and of private owners.
One of the most notable achievements obtained in competition was the winning of the Pickett Cup at the Boulogne Grand Prix in August, 1923, where the Frazer Nash car, which put up the best performance of the team, was entered and driven by an amateur. Three of these cars were the only team to finish the course, thus gaining the highest award of the meeting.
Other successes of great merit have fallen to the marque since that date, but as this article is confined to technical details, matters of history must be left for a more suitable occasion.
Unique Light Car Design.
In looking over this remarkable chassis one finds certain features which, had it not been for the enviable record for performance and reliability behind the name
of Frazer Nash, one might be inclined to characterise as almost freakish.
But the proof of the pudding is in the eating, and on examining all the details with the critical eye of an engineer, one can find nothing but the most robust construction, and a design which is really practical from start to finish.
The frame itself is built up of sturdy pressed steel members, suitably braced by stiff cross members, and the elliptical springs serve to give a good combination of comfort and road-holding qualities, though at first sight they appear to be very short.
Engine Details.
The four cylinder engine measures 69 mm. bore by 100 mm. stroke, giving a capacity of 1,496 cubic centimetres. When fitted with the super-sports camshaft and high compression head, the engine will develop 50 h.p. and will hold up to 4,500 r.p.m. for long periods without any decrease in the power curve. A special close-grain cast-iron is used for the cylinders, and the bores are ground and lapped to ensure accuracy and the best possible finish. The cylinder head is, of course, detachable, and the joint is so arranged that gasket renewals are seldom required, even after the engine has been de-carbonised several times, a process which is not required frequently, thanks to the careful arrangements of the ports and the free egress of the exhaust gases.
Side valves are used, which, while not in any way impairing the acceleration, enable the engine to maintain its tune without attention for very long periods compared with those usual where overhead meehonism is employed.
Die cast pistons made from a special hard wearing aluminium alloy are employed, and these are fitted with hollow gudgeon pins of the floating type, hardened and ground to fine limits and fitted with brass end caps to prevent all possibility of cylinder scoring.
Engine lubrication is effected by a geared pump working in the bottom of the sump, driven by a skew gear from the half-time shaft and supplying oil in the correct quantity to all parts of the engine under pressure. The cooling is by thermo-syphon, and the distinctive radiator of the well known Frazer Nash design allows ample cooling surface, besides giving an unmistakably smart appearance to the car.
In the interests of weight saving, the electric starter is omitted on the Super-sports model, but this can be fitted as an extra if desired. The vertical position of the dynamo places the commutator brushes and their adjustment in a very accessible place, and the electric equipment throughout is finished off very neatly.
A large Solex carburettor, gravity fed from a tank in the scuttle dash, provides the mixture, and the petrol consumption is between 35 and 40 m.p.g.
m.p.g. Transmission and Change Speed Mechanism.
Remarkable simplicity is to be found in the entire transmission mechanism, which is a very sound engineering job throughout, and as a matter of fact is immensely supenor in respect to robust construction and workmanship to that found in the large majority of light cars.
From the engine the drive is transmitted through a single plate Ferodo lined clutch, which has low inertia and imposes no end thrust upon the engine. This clutch is very smooth in action and has a light withdrawal, which further simplifies the ease of gear changing, for which the car is famous. The drive from the clutch is taken by a tubular clutch
shaft of 1 lin. diameter by means of a Hardy joint, the centre of which is spigoted to ensure the accurate alignment of the clutch shaft, to a pair of helical bevels to the bevel shaft. Mounted on the latter are the sprockets, from which the drive is taken to the solid rear axle. The various gears are engaged by dog clutches, moving laterally along the bevel shaft, the clutches being actuated through the ordinary form of gate mechanism. Owing to the bevel reduction, which is 3.5 to 1, the bevel shaft runs at a comparatively low speed, which facilitates the easy and silent engagement of all gears at practically any engine speed.
The change speed gear of the Frazer Nash car is one of the outstanding features of the design, and though slightly more expensive than the conventional gear box, has such advantages that its extra cost is fully justified.
The disadvantages of the sliding gear box have come to be regarded, through general use, as necessary evils, such as the difficulty of changing gear at high speed, with consequent liability of damage to the gear teeth, noise and double loss of efficiency when the indirect gears are in use. Of these disadvantages, the mastery of the gear change reduces the risk of damage, but the noise and loss of efficiency remain.
On the latter account many cars are geared on top below their most efficient ratio, to minimise the use of other gears, but on the Frazer Nash the gear can be changed with ease and certainty at any speed with no pause of double clutching, without risk of damaging the sturdy dog clutches, which, on all gears except reverse, bear the brunt of the change.
As all forward gears are direct, there is no loss of efficiency when the lower gears are in use, these advantages permitting the use of a high top gear and the remarkable acceleration of which the car is capable. The second speed, though nearly as high as the top gear of many other cars, will take a full load up really steep hills, while the low gear is suitable for any emergency. The adoption of chain drive may be regarded by some as being of doubtful advantage, but with the transmission system incorporated in this chassis, the method is certainly very effective. The life of the chains is very long indeed, 40,000 miles per set being quite usual, and
when replacement becomes necessary the cost is small, and the fitting takes but a few minutes.
The standard gear ratios are as follows :—Top, 3.8 to 1; second, 5.4 to 1; first, 11.6 to 1; and reverse, 12 to 1. Alternative gears can be supplied if required, and the particular construction of the transmission permits of easy changes of gear ratios for any class of competition work.
By the adoption of a patent interlocking device, the risk of double gear engagement is entirely eliminated, so that the respective dog clutches are locked in position in addition to the control of the selector mechanism by means of the change lever in the gate.
Adjustment of the chain tension is effected by spherically jointed radius rods, and as in practice it is found that all the chains wear equally, the one adjustment suffices.
The lay-out of the steering, front axle and suspension is decidedly interesting. The steering box contains a well cut bevel pinion and bevel sector, controlled by an 18in. steering wheel with a narrow rim. Thrust washers aad dust caps are fitted to the stub axle pivots, the design of which renders the steering quick and sensitive without causing any shocks to be transmitted to the driver.
The tabular front axle, lains. in diameter, is mounted on quarter elliptic springs tin. wide, working in conjunction with specially arranged Hartford shock absorbers. All cornering stresses are resisted by radius rods, and each front spring has a safety leaf above the main leaf, the forward end being brought well round the shackle pin.
Semi-cantilever springs lain. wide are used for the suspension of the rear axle.
Rubury front wheel brakes are fitted and are connected so that the shoes in both front and rear wheel drums are operated from the pedal, the hand brake lever controlling the shoes of the rear brakes only.
For those who require the exceptional performance of the Frazer Nash chassis, together with the roominess and full weather protection of the modern touring car, the four-seater model shown in our illustrations will make an undoubted appeal.