Written by Paul Pavlinovich
Wednesday, 07 October 2009 22:19
This is the story of a model engine built by Alby Smith of Sunbury in Victoria.
Empirical commenced life as a set of castings purchased in England under the design name of RLE. The supplied sketches were rejected at the beginning because of the relatively crude design. For example, the valve rocker was a piece of 1/4" square mild steel with a bush less pivot hole and no provision for tappet adjustment. The connecting rod was a piece of steel bar stock with an oil can hole to allow lubrication of the big end. The crankshaft; unbalanced of cut and "glue" construction with unbushed main bearings. The primitive cam follower operated via Meccano gears.
Empirical was built from rough free hand sketches. The overall design (appearance) is loosely based on full sized engines of pre-1920 period. The engine is hopper cooled with exhaust activated hit and miss governing.
Bore 1.25" stroke 2". Compression ration 6.5:1. The one piece balanced crank shaft has been electroless nickel plated for wear resistance. All bearings are bronze bushed, including the valve rocker.
Located in the "toolbox" is the reliable and efficient spark ignition system manufactured by Floyd Carter USA. The Ni-Cad battery energised coil provides a spark more than 1/4" long. The spark is initiated by a Hall effect device mounted on the frame near the off side flywheel. Three rare earth magnets are mounted on a disc which is attached to the crankshaft. As the last magnet moves past the device the spark is initiated. No magneto is used on model engines as it is almost impossible to scale them down and still prevent internal arcing.
The miniature spark plug is commercially manufactured for model aircraft engines. Home made plugs have been tried, however, the engine performance is down when compared to the commercial plug. Experiments are to be made with home made plugs of different design in the near future.
Fuel; unleaded petrol. The fuel tank was made from a shortened oil filter outer shell.
The skid frame is made from blackwood.
Construction of the engine was completed using a Myford ML7 lathe with vertical milling attachment. 1/2" pedestal drill. Large flat surfaces were accomplished with the aid of files and scrapers. The lousy (PP:looked pretty good to me) brush painted finish provides a base for the professional sign writing - Empirical.
"Empirical" : Experimental - Observed - Practical - Pragmatic - (anti)Theoretical - Hypothetical.
TAYMITH Engineers, Sunbury Vic, Australia. A mythical engineering firm. "Taymith" is a combination of family names.
Editorial Comment by Paul Pavlinovich
Note that the manufacturer of the casting set used in "The Empirical Engine" article wrote to me demanding that the article be removed from the server as it was not exactly complimentary to the casting set used. I trust the model engineering abilities and judgment of the author Mr Alby Smith who is a dedicated member of the Australian Army Engineers. Steam & Engine being a magazine site reserves the right to publish articles which are not always complimentary as I consider the truth to be more important. It should be further noted that I did offer right of reply to the manufacturer in question which was ignored.
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