Today in Motorcycle History

Black Prince Motors

of Thorngate Mills, Barnard Castle, County Durham.

Black Prince motorcycles were produced from 1919 to 1920.

This remarkable and advanced machine was designed by E. W. Cameron of Doncaster, Yorkshire and produced at Prince Motors.

1919 The engine used was either a single-cylinder 292cc Union or a 396cc flat-twin two-stroke with a single spark plug that was designed and patented by H. Singleton of Liverpool. Also unusual for the time was the use of flat top pistons and off-set big ends. The rest of the engine was conventional, but the motorcycle as a whole was not. The pressed steel frame had two sides joined at the headstock. It ran down and back to fully enclose the mechanics and form the rear mudguard. The fuel tank was set in the top - a design that was to be seen three decades later on the Velocette LE. Suspension comprised bottom-linked forks at the front and spring-controlled pivot-forks at the rear. The engine was built and successfully tested, but the machine failed to reach the market as it was too advanced and too expensive. Also used unusual 497cc flat twin two-stroke.

1920 All future prospects were lost when E. W. Cameron committed suicide. With him went the motorcycle and the Black Prince Runabout, a three-wheeler designed by A. G. Cocks which was expected to go into production.

1919 Another £100 proposition is the Black Prince runabout, a small four-wheeler embodying several features which depart from the conventional. The springing is by coil springs, and the power is provided by two Union two-stroke engines having a. total capacity of 584 c.c. These are placed side by side in a vertical position, and depend upon a 180 degree magneto for ignition. An epicyclic two-speed gear is fitted at one end of a countershaft, at the other end of which is the pulley for the final single belt drive. The frame and body are made in one, and the total weight is said to be tinder 3 cwt. The manufacturers are Black Prince Motors, Ltd., Barnard Castle, Co. Durham.

Black Prince 1919

The Black Prince motor cycle, a design in which all mechanism is enclosed.

Black Prince 1919 Cardan Shaft

The bevel drive of the shaft transmission. Note the construction of the disc wheel.

Black Prince 1919 Engine

Cross section of the engine, showing the automatic valve for transfer of gas.

OPT 1919 HO Engine

An "O.P.T." engine - a flat twin two-stroke with common combustion space.


Pressed Steel Frame, Rear Springing by Volute Springs, Mechanical Units Enclosed, Shaft Drive, and Opposed Two-stroke Engine with Common Combustion Space.

THERE have been many attempts on the part of designers of motor cycles to break away from the conventional "diamond" frame, and for some time past there has been a decided tendency for more thought to be given to the great possibilities of pressed steel. Usually, however, such designs have been from the board of more or less pseudo designers who have aimed at the ideal without much regard to the commercial aspect. In addition, we know of several manufacturers who are experimenting with machines which reduce as much as possible the use of steel tubing, as it is thought that pressed steel construction will greatly assist in overcoming several inherent faults of the conventional motor cycle, by enclosing the engine and gear box as in a car, and so removing the possibility of oil reaching the driver. By enclosing the "machinery" it is also possible to produce a machine which can be washed down by a hose, thus reducing the amount of work necessary to keep a machine in first-rate condition.

A Built-up Frame.

One of the most interesting designs on these lines which we have seen recently is that of the Black Prince motor cycle, which Mr. E. W. Cameron, of Askern, Doncaster, advises us that he hopes to produce shortly as a marketable proposition. The machine, however, departs so much from the conventional that several manufacturing difficulties are likely to be encountered which will tend to retard its production on a large scale without special facilities.

As will be seen from the illustrations, the machine, while unconventional, is by no means " freakish " in design, and when given an "all black" finish, which, we presume, is the intention to be in keeping with the name, the appearance should be quite pleasing. The frame is composed of two side panels of pressed steel connected by means of a sub-frame, the steering head and the tank, which latter becomes part of the frame construction instead of an "accessory." Two transverse members pass through the engine plates and hold the frame rigid. These cross members carry an undershield, the crank case, engine plates, and gear box.

In addition to the ordinary mudguards, there are wide wing pieces at the front of the side panels with a camber forward which induces a draught into the centre part of the machine and should assist in cooling the engine.

The rear springing is quite simple, and should be less expensive to manufacture than the average leaf spring device. The wheel is carried in a substantial fork hinged at its inner end, and volute (1) springs attached at their wider ends to the rear extension of the frame bear upon bosses on the rear ends of the lower stays.

The front wheel springing, too, is simple.

Not the least interesting feature of the design is the type of disc wheel used. As will be observed from the drawing, wire spokes are dispensed with, and in their place two dished discs are used which, with a centre rim piece, form the wheel. Roller bearings carry the wheels, knockout spindles will be used, and it is intended to fit internal expanding brakes on both hubs.

The steering head is of the usual tubular construction, with two substantial lugs for the bolts, which secure it to the pressed steel members and the tank.

The Transmission.

Following the ideas of many "advance" thinkers, Mr. Cameron has included shaftt drive in the specification. The primary transmission is by chain to the gear box, whence the drive is taken by cardan-shaft to the rear wheel through bevel gears.

The centre of the driving member of the gear box coincides with the hinged rear wheel frame. No particulars are yet available regarding the gear box, but we understand that this is to have two speeds, a clutch, and pedal starter.

O.P.T. Engine.

Equally interesting as the framework is the flat twin two-stroke engine, which is the first of a new type which may become to be known as the O.P.T., i.e., one plug twin. This is to say that, although the cylinders are opposed, they have a common combustion space, therefore one plug fires both cylinders with, of course, perfect synchronism, the impulse effect and the mechanical balance being the same as in a four-stroke opposed twin.

By this form of construction long induction pipes are obviated, and as the new gas enters at the centre of the combustion space and exhausts at the bottom of the stroke, a straight through flow is provided, which ensures that no dead gases remain near the sparlcing plug on the following power stroke.

As will be appreciated, there is considerably more radiating area on the combustion chamber than in any other type of engine, and in an air-cooled engine o£ the two-stroke type this may be found a very desirable feature. In a water-cooled type, however, it may be found that such an engine would not show up to great advantage, as in all probability it would be over-cooled.

To Eliminate Four-stroking.

From the crank case the new gases enter the combustion space through an automatic valve directly opposite the plug, therefore four-stroking, even at low speeds, should be almost, if not entirely, eliminated.

The overall length of a 60 x 61 mm. engine of this type is only 15 1/2 in., and we are informed that 4,000 r.p.m. have been attained.

It is also intended to market a model fitted with a single-cylinder two-stroke engine, and for this model the Union engine, made by Messrs. Josiah Parkes, of Wiflenhall, may be chosen.

Without doubt the Black Prince is a most interesting design, and at a later date we may be able to record our impressions of its performance on the road. In the meantime we congratulate the designers in producing on paper what is a really serious attempt to attain a machine which so many have prophesied to be the type of the future - a weatherproof motor cycle at a low cost.

The Motor Cycle JULY 24th, 1919. p86

Sources: Graces Guide, The Motor Cycle

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