McKechnie was a motorcycle produced in 1922.
This machine had a novel design, but failed to have any impact on the market. It had an unusual spring frame in which engine, gearbox, tank, foot-boards and saddle, etc., were all suspended as a unit by means of a leaf spring. The assembly lay between straight duplex tubes connecting steering head to rear-wheel spindle, while a Montgomery leaf-spring fork controlled the steering. It was powered by a 688cc sv Coventry-Victor flat-twin engine, with a four- speed Jardine gearbox and all-chain transmission.
ORIGINALITY IN A SPRING FRAME.
CASUAL observers of motor cycle development may be excused if they remark. that spring frame design has gone into a groove nowadays, and that the designs which do break away from the conventional seldom get further .than the Patent Office. With one or two notable exceptions, the observation is, unfortunately, true. It is therefore distinctly encouraging to encounter a promising new suspension system, which has survived its early road tests with honour, and which has iiow reached the marketable stage.
The machine which embodies the system in question, the invention of Col. Mackechnie, is being built at the works of Morton and Weaver, Ltd., Coventry, makers of the 5-6 h.p. Coventry Victor engine, with which it is fitted. It will be shown at Olympia as the Mackechnie Coventry Victor.
Perhaps the three chief advantages of the Mackechnie design are (1) that lateral instability of the rear wheel is no more possible than on a rigid frame; (2) that the single 4ft. long leaf spring permits more than 4in. up and down vertical movement to the sprung portion; and (3) its promise of almost indefinite wear with a minimum of attention. These qualities are gained as follows :
Two pairs of slightly curved and cross braced tubes extend from the steering head to the rear axle, forming a cradle rigidly connecting the rear wheel to the head of the machine.
The engine is carried in a sub-frame, hanging between the main longitudinal members, and is slung from the centre of a five-leaf semi-elliptic spring which extends from a cross brace behind the steering head to the bridge of two vertical stays pivoting near the rear axle. Also, on this sub-frame are carried the petrol tank, Sturmey-Archer gear box and footrests, and mounted on the spring at the point of attachment is the saddle, which thus moves directly with the footrests. The chain stays are pivoted behind the gear box bracket, and at their rearward extremities - in both cases on Skefko self-aligning ball races. Incidentally, although the range of movement of the sprung portion is unusually great, only a very slight deviation of the chain stays takes place. As these are also well braced, there should be no cause to fear lack of lateral rigidity of the engine unit at this point.
Provision is made for lubricating the substantial mounting for the spring in front, and at the rear it is pinned to a cross-piece, which, on future models, will be carried in "oilless" graphite bushes. As the spring is so securely carried, and of such massive dimensions, there is no danger of the upper portion of the sub-frame developing side play.
Transmission Variations Slight.
Variations in transmission tension are so slight as to be quite negligible with the Brampton spring chain fitted, which the even torque of the 5-6 h.p. Coventry Victor flat twin engine adds to the exceptional comfort of the machine, as we discovered on trying the first machine within half an hour of its completion; and considering its newness, it gave a very fine impression of comfort combined with security, particularly at high speeds.
In detail specification this machline resembles the touring model Coventry-Victor, 28x3in. tyres, dummy belt rim brakes on both wheels, Best and Lloyd latest type drip feed, M-L lightweight magneto, and Amac carburetter being standard. There is only a slight increase in weight, and the selling price, althoug not yet fixed, will similarly be not much greater.
Modifications which will be made in the future include a gaiter tor the spring and combined engine and legshields, which may be conveniently fitted to the outside of the main frame members, thus shielding the rider from the flywheel and exhaust pipes.
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