THE ENTHUSIAST'S IDEAL
THE ENTHUSIAST’S IDEAL
A New 1-1Litre Engine built specially for Fraser Nash.
UNIQUE in its all-chain transmission with its lightning gear change and high power-weight ratio, the marque of Fraser-Nash has found particular favour with the hard driver. On cars of this type, the owners are constantly demanding more and more power and with the aid of the special deflector cylinder-head the power output of the O.H.V. push-rod Meadows engine, which has been the standard power unit for the past two years, has been raised to over 60 h.p. on petrol-benzol. Any further progress could only be made by building an entirely new engine, and in deciding upon the final lay-out the latest developments in design and materials for high-efficiency engines have been used, while the practical experience of Mr. H. J. Aldington, the Managing Director, in races and trials has suggested
further detail refinements. A single overhead camshaft four-cylinder engine was considered to offer the best compromise between strength, light weight and efficiency.
The engine is a four-cylinder with bore and stroke respectively of 69 and 100 mm., giving a total capacity of 1,496 c.c. The cylinder block is little more than a framework carrying the bores, which are separate and completely surrounded by water. The sides of the block are sealed by aluminium covers. The lower part of the barrels fit down into the aluminium crank-case and the pistons can be removed from the bottom end without disturbing the block.
The water pump is carried at the rear end of the unit and forces water round each of the main bearing housings through ducts cast in the crank case, from which it is led upwards to the cylinder-block. The crank-case is an immensely stiff box-like structure, with numerous studs to secure the timing cover. The nitralloy hardened steel crank-shaft is carried in three steel-backed main bearings, and is fully balanced. The journals are 22in. in diameter. The weights, in each case, are secured to the webs by two bolts
on the sheer, and the .big-end journals are bored out to improve heat-dissipation. Oil is forced to the three main bearings, and is led through the hollow shaft to the big-ends, the centre ones receiving their supplies from both sides.
Steel connecting rods are used and the white-metal big-end bearings are cast direct into the rod. Research has shown that under stress the outer edges of plain bearings tend to open up, so that only the centre part remains in contact with the shaft, and to combat this strengthening rings of metal are left round the outside of the caps. The oil-holes in the journals are arranged slightly after top dead centre, so as not to be blocked when the maximum thrust takes place.
The Aerolite pistons are made of ” Y ” aluminium alloy, with two compression rings and one slotted scraper, and weigh only 12oz. each. The skirts are slit for some distance, and have shallow vertical grooves which take care of expansion. The gudgeon pins float in the pistons and the small-end bushes.
A. four-sprocket chain drive is used to drive the two auxiliary shafts and the oil pump.
This latter is mounted on the outside of the timing case and draws its supplies from the finned and ribbed sump, which holds two gallons, through a duct cast in the timing case. The main feed, of course is led to the main bearings, but ducts are also provided to lubricate the magneto drive and dynamo drive bushes, all under full pressure.
The cylinder head of the new FraserNash engine is of most substantial construction, and actually weighs more than the block. A single overhead camshaft is carried in four plain bearings, and is driven by a double roller chain at the front end.
This chain is interchangeable with the one used for the timing gear and has suitable spring-loaded tensioners. Pegs on the sprocket and a flange on the camshaft give a vernier adjustment of timing in steps of 1+ degrees. The valves are mounted vertically in the head with a finger interposed between each cam and its valve. These fingers can be moved aside against springs to facilitate the removal of the valve cups. Aluminium bronze valve guides are used, and the valve caps are extended so that they slide over them, providing a seal at all times. The valves are threaded and the clearance is adjusted by rotating the cap and locking it with a screwed nut. The camshaft is hollow and oil pumped up to the front bearing is carried to the others and also escapes through holes on to the working surfaces of the cams. Each combustion chamber is circular in plan view, with a lobe projecting into it from either side. This” deflectorhead,” which has been used with success on the Meadows engines fitted during the last six months, gives good turbulence, and permits of a high compression without pinking. Two sparking plugs per cylinder are used, with coil and magneto ignition, and they fire the mixture through screened holes of reduced diameter so as not to
disturb the turbulence The inlet valves are 1 +in. in diameter and the exhaust valves 12 in., both being made from K965 steel.
Two S.U. carburetters are used, and the starter, dynamo, and magneto are of Bosch manufacture.
A large quick-action oil-filler is fitted to the cam-case, and the rev-counter drive is taken from the rear of the camshaft. In spite of its massive appearance the new engine only weighs 325 lbs. or about 151bs. more than the Meadows. All the parts have been built with an ample margin of safety and should be capable of withstanding 150 h.p. which figure. would probably be reached if the engine were fitted with a large . supercharger. If this were used it would be driven off the front end of the crank-shaft, which
would be a special job with an extended front end, but for the present experiments are being confined to getting the best out of the unblown engine.
The new engines are coming through at the rate of one per week, and it is interesting to note that Messrs. A.F.N., the proprietors of the Fraser-Nash concern, have taken over the Anzani factory at Kingston, so that in a few months the new engine may be manufactured there.
The latest Fraser-Nash cars differ in several respects from last year’s models, the most important being of the standardisation of the 91t. chassis for the twoseater car in place of the 8ft. 6in. type formerly used. The increased length makes the cars steadier On corners with loose surfaces, and in conjunction with a new type of road spring made by Woodhead the cars are extremely comfortable on bad surfaces The chassis has been extended rearwards to carry the petrol tank, and the section of the chassis members has been increased. The centre cross-member now passes under the propellor shaft and this and the clutch may be withdrawn with the minimum of dismantling. The all-chain transmission, with its
silent direct drive on all ratios is naturally retained, but the bottom gear sprockets are now on the off-side instead of in the middle. This brings the back-axle sprocket in close proximity to the off-side bearing, and avoids the possibility of straining the axle through the heavy torque on bottom gear.
The price of the finished cars varies according to the type of engine and equipment required. The basic price of the two-seater car fitted with a twocarburettor Meadows engine is £475, while a de-luxe addition with outside exhaust system, telecontrol shock absorbers, and a number of other refinements costs £50 more. In the same way the two-seater fitted with the six-cylinder double-camshaft engine, either of 1,500 c.c or 1,657 c.c. costs £570, or with the extras £620. The Colmore three-four cars cost in each case £20 more than the corresponding two-seaters. It is interesting to note that all the latest bodies, which have particularly satisfactory lines, are being made at the Frazer Nash Works.