Leesil 2.4cc diesel

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One of the earliest and short-lived English diesels to emerge in the 1946/47 period was a known as the Leesil, manufactured in Bradford, Yorkshire. the rather cleverly contrived name which suggests the engine type is believed to derive from the two gentlemen involved in the initial production, Norman Lees and Silvio Lanfranchi. The best known Leesil is a straight Dyno clone, in other words, a side-port. These photos show the even rarer Rear Rotary Valve Leesil, slightly larger than the Dyno at 2.5cc displacement. The following description applies to this unusual engine and was provided by an Australian collector.

Measurement give the overall length (with prop fitted) as 4.8 inches, with a height 4.1 inches, a total weight (with prop) 8-1/8 oz, and bearer spacing of 1.4 inches. The piston has a conical crown here is no sub-piston induction, Unlike the Dyno, transfer is accomplished through four ports, two at the front and two at the back, drilled into liner at an upward angle. The crankcase appears to be a sand casting, machined at the front and rear with the sides and lugs hand finished with a file with the bottom of the case is left as cast. The purpose of the "sump-bump" cast into the case bottom is a complete mystery. We could speculate, but that would be all it would be: wild guesses!

The few remaining photos of the side-port Leesil show it fitted with a left hand prop (clockwise rotation as viewed from the front). As a side port, it would have happily run in either direction, but the RRV engine is actually set up for reverse rotation! The prop provided with the engine is about 10-1/2x4 and appears to have been purpose made for the engine.

The example is new and un-run. The Serial number stamped on the lower front of the crankcase is 1.107 and we have no idea what that means. Like some of the early Mills 1.3 Mk I's, the mounting lugs are hand finished and way out of whack with each other; if used in a model, the bearers would have to be bolted to the engine first, then the formers custom cut to fit. The engine was not frozen solid, having apparently spent its life in a shoebox lined with a 1947 newspaper. in Bradford, Yorkshire.

The internal fits seem very good. The piston feels like it's running in an un-tapered bore (and just a tad on the tight side) with the contra-piston not even being stuck! The photos show two Leesils. The one posed next to the Westbury Ladybird twin has a shorter fuel tank, plus one less cylinder fin than other example. Presumably there was considerable "machinists licence" in the (very low) production numbers.

Referring to the side-port Leesil depicted in Laidlaw-Dickson/Russell book, Model Diesels (p30), the authors state: "Leesil have now definitely scrapped their earlier design, and are replacing it with an engine that is virtually a Dyno of slightly larger capacity". So the question becomes where does the RRV engine sit in the Leesil chronology?

The answer comes from CE Bowden's book Diesel Model Engines, first edition, 1947 (p48), where Bowden notes,

"The "Leesil" is an engine of 2.5c.c., bore 1/2 in., stroke 3/4 in., with variable compression head. and nickel-steel crankshaft and duralumin connecting-rod fully machined are fitted (sic). The main bearing is a phosphor-bronze bush. The engine was evolved from the Swiss "Dyno," and at the time of writing is undergoing further development work, including a disc crankcase inlet valve on one version of the engine. The standard type will have a plastic tank when manufacturing permits. The tank will be close up on the intake tube".

Confirming the short life of the Leesil, Warring's 1950 book, Miniature Aero Engines lists the side-port only, but flags it as no longer in production.


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