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Merco 20

By John Goodall.
Originally published in 'Model Engine World', February 1999.

Exhaust side of the Merco 20
showing adapted silencer
The transfer side with
scaled down carburettor

This month an engine that might have been another success for the well known British manufacturer Dennis Allen Engineering, but which never reached production to join the famous Merco line.

The story starts some time ago at 'Runway South West' a model shop then run by retired reader Roger Howe, when in walked a customer and asked did he want to buy an engine? He did of course and was told that it came from an aquaintance who had found a young man flying a RIC model somewhere near Exeter, which turned out to be a Merco 20 prototype. He had managed to persuade the young man to part with it and basically that is how it came to Roger, who in turn sold it much later to me. These things go round in circles don't they?

Rogers customer must have been an aquaintance of the Merco maker Dennis Allen, because on enquiring about the engine Dennis had told him they had actually made six engines. Presumably in order to carry out an evaluation on possible production. This is born out by the number four stamped on the left hand lug upper side of the subject engine, this can be seen in the adjacent overhead shot I took of the engine.

The engine is typical Merco, if a little more chunky than usual and is embellished by the standard silencer and a scaled down carburettor, which show externally the Merco heritage. The silencer is fitted by using an adaptor plate and would have probably had a purpose made device once production started. Other typical Merco features are the basic construction, propeller drive assembly and the method of scavenging.

Twin ball races support the crankshaft with its front rotary valve and internal parts also conform to normal Merco practice. The capacity is just short of .20 cu ins and it would have been the smallest Merco produced (unless of course you know differently?). This engine is well made and castings appear to be sand cast as would be expected on a prototype engine.

I took measurements of the engine before my house move, but have mislaid them and the engine is still packed like most of my collection. One day I shall get sorted out!

Events obviously overtook the planned production and one can only guess on its possible market acceptance and susequent sales. It would be interesting to know if any other Merco 20's survived, or if any reader can add to the sparse background given here.

John Goodall.

Note engine number on lower lugTypical Merco from this view, note adapted silencer

John has copies of most issues of 'Model Engine World' from numbers 1 to 70 still available.
Tel/FAX: 01283 713715.

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