The Harker Special
A Brooklands Car in Road Trim
Pre-War Brooklands habituees will remember W. E. Harker and his remarkable eight-cylinder 1 1/2-litre Harker Special which won a Mountain Handicap in 1934, but it will be news to many of them that the designer-driver still has the car and, indeed, uses it on the road for long-distance touring and daily journeys to his office.
For a car of such decided technical ingenuity, the Harker Special is no mean performer, as we discovered for ourselves when we drove up to Derby last month to ride in and drive this fascinating “special.”
Harker commenced motor racing with a blown Austin Seven which went sufficiently fast to hold the class record at Shelsley Walsh from 1929 to 1932. With an Amherst Villiers Roots supercharger the Austin was developed to produce 60 b.h.p. and at Brooklands in 1930 it broke the Class H standing kilometre and mile records, at 63.01 and 68.58 m.p.h., respectively. As these speeds were achieved a fortnight after S. C. H. Davis had secured these records for Austin with the works car, considerable comment was occasioned, and the potency of Harker’s Austin will be appreciated.
From the Austin was developed the Mk. I Harker Special. An Austin Seven-type chassis with widened track was used and into it went a very special engine, consisting of two Austin Seven blocks on a common crankcase with two crankshafts geared together at the rear. The gears drove the clutch through a third, centre pinion. Harker took out a patent on this dual-crankshaft eight-cylinder assembly and the late Sir Herbert Austin showed considerable interest, but his company dropped the project due to manufacturing costs.
Undaunted, Harker developed his Mk. Il Harker Special. The chassis owed some allegiance to that small French sports car, the Lombard, but a new box-section chassis frame with dropped sidemembers was built by Rubery Owen, Bean Industries made a special straight-beam front axle which was mounted above the 1/2-elliptic front springs, rear suspension was also 1/2-elliptic, while new Moss gears were cut for the Lombard gearbox, giving, in conjunction with a Moss straight-tooth bevel back axle, ratios of 5.5, 6.7, 9.5 and 14 to 1. The Lombard-Perrot triple-shoe front brakes were scrapped in favour of two-shoe Perrot brakes, working in 13-in. diameter drums, the back brake drums being 16 in. in diameter.
The engine was a 1 1/2-litre two-crankshaft eight-cylinder, as before, but the late Cecil Kimber, of the M.G. Car Company, supplied Harker with racing-type M.G. cylinder heads, which were used in conjunction with special cylinder blocks. The o.h. camshafts — one per block, operating vertical o.h, valves in normal M.G. fashion — were driven by a long, exposed duplex chain, with tensioner sprocket, from the front of the engine. The chain is greased at intervals and has never given any trouble in spite of being exposed.
The Villiers Roots supercharger was driven from the front of the off-side crankshaft and as the cylinder blocks were not “handed” it fed mixture to the outside of one block and between the two blocks to the inlet ports of the other block. In the same way the exhaust pipes emerged, to tail pipes on each side of the car.
The crankshafts and connecting-rods (of H section) were specially made for this engine, each crankshaft running in three roller bearings. The big-ends were plain and the pistons were of “Y” alloy.
The engine was started by an off-set starting handle protruding through the radiator block and engaging the near-side crankshaft.
In the Mk. II form the engine had a compression ratio of 6.5 to 1 and a supercharge of 16 lb./sq. in. It won a Mountain Handicap at the 1934 B.A.R.C. Whitsun Meeting, averaging 67.5 m.p.h. and doing its best lap at 69.57 m.p.h.
In 1935 the Mk. III, or present, Harker Special was built. This was a 1,100-c.c. car, because the engine was the forerunner of the now popular “over-square” formula, the crank throws being altered to give a stroke of 55 1/4 mm., in conjunction with the bore of 56 mm. The Villiers supercharger was replaced by a Zoller M160 compressor as used on the 1 1/2-litre E.R.A. Driven at half engine speed this blower gave a supercharge of 30 lb./sq. in. The original lubrication system proved troublesome, too much oil being delivered at low speeds, which fouled the plugs, so Harker devised a hand feed, evolved from a drip-feed lubricator, drawing oil from a small cylindrical under-bonnet tank. As before, the blower drew from two downdraught S.U. carburetters, fed by hand air-purnp from an 8-gallon fuel tank in the tail. Ignition was by an eight-cylinder racing Scintilla magneto, modified to fire up to 8,000 r.p.m., which was the engine’s safe maximum speed.
The lubrication system was normal wet-sump, with an oil pump above the sump level, feeding at 100 lb./sq. in. Two filters, one a Tecalemit pressure filter on the side of the chassis, were used.
The body was that used in the Mk. I days, an aluminium “1 1/2-seater” on a duralumin frame, built for Harker at Weybridge. It weighed 25 lb. and cost £25. 6.00-16 tyres were used on the back wheels for Brooklands, since replaced by 6.50-16. The two crankshafts are “timed” to give even-firing intervals, the firing order of each block individually being the normal 1. 3, 4, 2. In this form, this technically advanced 1,100-c.v. engine, running on methanol, was bench-tested to develop 160 b.h.p. at 7,000 r.p.m.
In this, its present form, the very successful Harker Special saw little racing service, for the war intervened. It was laid up by T. & T.s during hostilities but after the war Harker brought it up to Derby and prepared it for road use. This consisted of eliminating the few remaining “bugs,” clearing up the various installations, arranging the oil pump so that it didn’t require frequent priming, and adding cycle wings, side and rear lamps, a bulb horn and the number plates issued to the car when it was used previously on the road back in 1933. The compression ratio was reduced to 5.5 to 1 and the blower boost to 20 lb./sq. in. Another remarkably ingenious alteration was that of removing the float chamber from one S.U., which now functions as an extra air valve instead of as a carburetter, the other S.U. remaining unaltered, so that the correct air/petrol ratio is maintained although the fuel is now pump fuel and not methanol, which requires less air. A recent modification has been that of boxing in the carburetters so that they draw in cool air. Two huge cylindrical silencers quieten the exhaust.
In road trim the Harker Special weighs 15 cwt. It has very vivid acceleration and excellent roadholding from stiff suspension. The front Hartford shock-absorbers act as radius-arms to absorb front-axle torque under brake application.
Harker put his “special” on the road in April, 1951, and since then it has been in regular use, proving exceedingly reliable and starting promptly with a single pull up on the starting handle. Indeed, it is far less temperamental than it was in its Brooklands days, which Harker attributes to present-day fuel and particularly to modern platinum-point plugs; he uses Lodge HMP. The engine has been known to consume “Pool” petrol without protest; it normally runs at full advance, and the fuel consumption is 18 m.p.g., which is excellent for a high-boost power unit.
We were able to drive the Harker and there is no doubt but that it is very definitely a motor car! In road trim the car has done a mean rolling start to 80 m.p.h. in 12.4 sec.
The cockpit is cramped, its sharp metal edges devoid of padding, while the only protection is from a small aero-screen before the driver. The dashboard is well stocked with small, businesslike dials, as well as with the fuel and blower lubricator hand pumps, rotating hand-throttle, etc. The ride is hard, but directionally stable. The clutch is heel-operated and heavy, all the pedals are closely spaced, and the crackle of the exhaust and howl of the straight-cut back-axle gears are music to the enthusiast.
The Harker Special is not an easy car to drive, although its taut feeling of being in one with its driver and the delightful gear-change by a truly diminutive, very powerful little lever working in a rearward-inclined ball-gate, are delightful, and the fly-off central hand-brake lever works very nicely. We give full marks to Mr. W. E. Harker for the impeccable manner in which he handles the car on the road — as he did all those years ago at Brooklands. Moreover, there can be very few people who have so satisfactorily developed an advanced design that they can use on the road as reliable everyday transport twenty years afterwards.
By all count the 1,100-c.c. eight-cylinder Harker Special is a remarkable motor car and our visit to inspect and sample it quite an event. One wonders how many of the present generation would have the technical ability to maintain it or the physical stamina to enjoy driving it! — W. B.