FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1951
1951 - 1330.PDF
13 July 1951 A 1903 ENGINE RE-BORN Working Replica of Wright Brothers' Power Unit Constructed in D.H. Technical School THE Wright Brothers began their experiments on flightwith gliders, later fitting small internal-combustionengines to their aircraft. The outcome of their experi- ence was an aircraft fitted with an engine of their own design, since automobile engines had proved too heavy. (It will be recalled that Sir Geoffrey de Havilland started his work, in 1908, by designing an engine.) When the original Wright biplane left the Science Museum in London, the de Havilland Aeronautical Technical School undertook the building of a replica, and the Stag Lane branch was asked to make the engine. The 1903 engine, which embodied a number of progressive ideas, was fairly large, having a 4in bore and a 4|in stroke. Its weight was 176 lb. The only performance figures available are those of the replica and they indicate that it would clock over i,qoo r.p.m. This figure was not exceeded for fear of damaging the engine, though it is quite possible that the replica is a better engine than the original since machining and measuring "apparati" have improved considerably since 1903 ! In the replica the aluminium crankcase is one of the originals, cast at some date before 1903, and it arrived at the School in its rough state. It was immediately checked up and marked off, and machining operations began with the facing and boring, both of which were carried out on a radial drilling-machine. This was the most important job of all, as any damage to the crankcase would have been fatal to the project. Whilst the machining was in progress, patterns and core boxes for the cylinders, pistons, and combustion-chambers were being made by other apprentices, as were the cores for the big- and little-end bearings and flywheel. These patterns were eventually sent away for the casting operations. The crankshaft, which has five main bearings, was machined from a solid steel billet, this job being undertaken by the Machine Section under the watchful eye of Mr. A. Lake. The Machine Section also finished the bearings for both crankshaft and camshaft, which had previously been cast in white-metal in moulds made, again, in the same Section. The cylinders of the engine are of cast iron and are screwed directly into the crankcase. The pistons are also cast iron, and have three compression rings. All the machining of these parts was successfully carried out with the tools, jigs, and fixtures which had been made previously at the School. Though there were five each of both piston and cylinder castings it is noteworthy that the spare ones were not required. The connecting rods are of simple construction. They have bronze big- and little-ends, which were cast and machined, with a tubular centre-section. The tubes were simply screwed into the ends. The valves have steel stems with cast-iron heads, to with- stand temperature. The inlet valve is most interesting, as it is automatically operated by the suction of the induction stroke. The exhaust valve is of a more usual type, being worked by a rocker from the camshaft, which is driven by a block chain direct from the crankshaft. The camshaft drives both the oil pump (by a worm mechanism) and the TO build a non-working replica of an historic power unitis a comparatively easy matter; to construct a working replica by "cheating" with the use of disguised moderncomponents calls for ingenuity; but to build an engine that is a replica of the original in every respect except that ofmaterial-specifications, and which produces a performance comparable with that of the original, demands real en-gineering skill. That it is not beyond the powers of de Havilland Aeronautical Technical School apprentices isproved by this article reprinted from 'The' Pylon,' the School's journal. J. R. Andrews is the author. ignition shaft (by spur wheels arranged to give advance and retard). The apprentices both wound and heat-treated the valve springs. Low-tension ignition is used, with a make-and-break in each combustion chamber. The electrical generator for the ignition is driven by a leather friction disc, which is held by means of a spring on the periphery of the flywheel, giving three times the engine speed and developing 10 volts at 4 amp. It is wired up to the contact points in the combustion chambers, and a spark occurs when the points break. A surface-type carburettor is fitted, the petrol feed being controlled by hand with an ordinary petrol tap. There are in fact two taps, an on-off type and another in the nature of a metering tap. A considerable time was spent by a student in producing these taps, which are decorated. A mould was made, and after several attempts two taps were cast. When machined, they were seen to be remarkably good considering that our friend had done none of this type of work before. The many components were collected and assembled and then run in by means of a belt-drive from a lathe. This done, the engine was stripped for inspection to ensure that no damage had occurred in the running. None was apparent, and so it was re-assembled and run for short bursts under its own power to make final adjustments to the ignition tim- ing, and to find the approximate air-fuel mixture. These runs completely stopped work in the school workshop, as everyone was greatly interested, and because the noise and the smell of exhaust gas were most disturbing. After a number of runs, the duration of which increased every time, the engine was run very satisfactorily on November 29th, 1950, in the presence of Sir Geoffrey de Havilland, Mr. Hearle, Mr. Brodie, and Mr. Sumner of the Science Museum. The engine left a few weeks later to be put on exhibition at the Science Museum. The enormous amount of work which went into this job can be gauged from the fact that it took about 8,000 working hours. Nearly every part required tools which had to be made first, a task which often took longer than the production of the part itself. The fact that the engine would eventually run under its own power gave the apprentices great reason for enthusiasm. Without their keen interest and patience, the machining and other operations could not have been carried out, especially when one considers that their experi- ence amounted to three months' filing. Again, we must re- member the patience and understanding of Mr. E. A. Fresher, the instructor in machine tools, who supervised the job throughout.
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
