Sold June 2022 Back to Archive

A compound undertype engine, to Henry Greenly's design, published in "Model Engineer" magazine in 1903, to a scale of 1 1/2 inches to the foot with key dimensions based on a Marshall 48 i.h.p engine.

Commissioned by the editor of the magazine at that time, the design was acknowledged by Greenly as being challenging, both in size and detail. He wrote:

"Our editor required a [design], and, as the subject should be to some extent novel and yet one finding favour with model engineers, a semi-portable compound undertype engine and boiler, with governor, was chosen.

Some readers will perhaps say the model is too big, being beyond their capabilities... In reply to this, it may be said that it is as well to set the highest standard of work... Care should be taken not to detrimentally modify the elements and principle of the design in reducing or enlarging any part of the model.

I will endeavour... at a later date to put into black and white, drawings [for a model] which will require much less time than the one now described to construct."

So, after that didactic introduction, one wonders how many model engineers in 1903 started on this design - and how many waited for the simpler version!

Beyond stating the obvious - that the model was built sometime between 1903 and now - we don't know how old this one is. Work on the engine is to a high standard, machining is crisply done, Greenly's design has been followed in all its detailed glory (we love the gear-driven horizontal Watt governor).

Boilermaking was not our builder's strong suit - in putting it together more heat, less solder and thicker material would all have contributed to a happier outcome. Whilst it could be finished off for display purposes, better by far would be to start again from scratch with an all silver soldered job.

The engine itself is stiff to turn over although not seized. Largely complete, there is some work remaining including fixing the flywheel to the crankshaft with a key.

There is a single general arrangement, pasted to a wooden board, of prehistoric appearance although still readable. Details of the construction and drawings can be found in Greenly's articles, published in volumes 8 to 11 of "Model Engineer" magazine, 1903-4 (the simpler "small undertype" design he mentioned came out later, in 1907).

Pretty much the rarest type of stationary engine we see, the undertype enjoyed popularity between the wars but nowadays is rarely modelled.

This one deserves sympathetic restoration, it will make a fine model when finished.