AN ENGINE WITH MOVING' CYLINDERS.
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Details of a New Power Unit Possessing Unusually Novel Features.
IT might be thought by many that after all these years of experience there is but a remote possibility of producing petrol engines possessing really novel features, but from certain recent designs which we have studied and actual engines which we have examined it would appear that this is far from being the case.
For instance, in this respect a specific example is afforded by the new engine designed and patented by Mr. H. C. Heckman and constructed for him by the Rose Engineering Co., 49-51, Selkirk Road, Tooting, London,
S.W.17, the patent number of the unit being 257,314, of 1926.
To begin with, the engine employs the two-stroke cycle. This in itself, of course, is not novel, and to bring out its new points it will be best to describe the actual form of the unit. That which we examined consisted of two horizontally 'opposed stationary cylinders containing sliding sleeves with the outer ends closed, and which form the cylinders proper in which combustion takes place. These two sleeves are rigidly secured to each other by an intermediate member formed in longitudinal halves which are bolted together and grip the inner ends of the sleeves, in which suitable locking grooves are provided.
In each half of the intermediate member is a central slot through which passes the crankshaft, thus the intermediate member, with its sleeve-pistons, can move to and fro without interfering with the crankshaft.
Connecting Cylinders and Crank shaft.
At each side of the crank are ar ranged two pairs of rollers. One of these pairs makes contact with two cam grooves of approximately elliptical form ranged in the intermediate member. These grooves are interrupted by vertical grooves extending both above and below the slot for the crankshaft, and the second pair of rollers is arranged to work in these. The rollers of each pair are in alignment with one another, and the pairs are at angles of 180 degrees apart. An imaginary line joining the centres of the pairs would make an angle of about 26 degrees with a similar line joining the centre of the crankpin and that of the crankshaft. This angle can be modified between certain limits, and it is of great importance because upon it depends the fact that there is an overlapping of the dead centres of the crankpin proper and of the rollers.
Mounted on the crankpin are two connecting rods to the ends of which are secured pistons of ordinary form working in the moving sleeve-pistons, which are provided with rings above and below transfer ports in the head and a single ring about half-way down, below which, again, are the exhaust ports.
Poppet inlet valves of the ordinary pattern are controlled by a cam on the crankshaft and are in communication with ports in the upper portions of the stationary cylinders. Exhaust ports are also provided at the lower ends of the last-named.
We will now describe the cycle of operations, and will begin by' assuming that there is a charge in the combustion space between one sleeve-cylinder and its piston. The arrangement of the crankpin and rollers is such that compression takes place through the piston rising in the sleeve-cylinder while the latter is descending, a fresh charge being simultaneously admitted into the space between the fixed cylinder and the sleeve cylinder, but as the sleevecylinder has moved downward the inlet ports in it are closed. The mixture ik then ignited by an electric spark, the piston moves downwards, performing work on the crankshaft, and the cylinder-sleeve is forced upwards, also performing work on the crankshaft, through the medium of the rollers which engage with the intermediate member and which take the form of small annular ball hearings.
How the Mixture Enters the Sleeve-piston.
Just before the completion of this movement the exhaust port is uncovered, and shortly after this the new mixture, which has been compressed above the sleeve-cylinder, is forced into the combustion chamber, the ports of Which are now uncovered, whilst the piston rises and closes the exhaust ports. This completes the cycle of operations.
The need for two pairs of rollers can be seen from the fact that the pair coacting with the elliptical grooves inthe Intermediate member is only operative, as 'regards the transfer' of the movement of the sleeve-cylinders, for that portion of the stroke when the crankpin centre is in the vicinity of the axial line of the cylinders, whilst for the remaining portion of the stroke the movement of the sleeve-cylinders is controlled by the second pair of rollers coacting with the vertical grooves.
Combustion Between Opposed Pistons.
The principle of the design somewhat resembles that employed on the GobronDrilli6, in that the explosion takes Place between what amounts to a pair of pistons in each cylinder.
Mr. Beckman does not restrict the scope of his invention to two-stroke horizontally opposed engines. He points out that the principle of operation could be applied to other arrangements of cylinders, also ; instead of coupling the sleeve-cylinders to the crankshaft in the manner which we have described in this article, other forms of mechanism could. be employed.
The engino of this type which we saw running was the first experimental model and, in this ease, the sleevepistons and intermediate member were made of phosphor-bronze, purely for ease in manufacture, so that it was not possible to run the engine at any great speed as fracture might have occurred. However, the running was sufficient to show that the invention is certainly practicable, and it remains to be seen whether it will be possible effectively to balance the respective moving parts, for the pistons being connected to one crankpin they do not balance each other as in the case of the ordinary horizontally opposed engine, and there is the further complication of the movement of the rigidly connected sleeve-pistons. However, the Progress made so far is certainly satisfactory, the unit appears• to be one possessing much promise, and we shall be extremely interested to follow its development. •