THIS is the second Blackburn agricultural engine built by Mrs Cherry Hill. This one dates from 1863 and the first one from 1857. Cherry has a fascination for novel and unusual steam traction engines from this period and these have formed the basis of her work in recent decades.

As usual the process begins with research, the richest sources being Patents and contemporaneous magazine articles especially in the Mechanics Magazine and The Engineer. This phase is particularly challenging and goes beyond simply researching the engine to be modelled as detail is often not available, and so the research extends to other items from the same period. In this case research extended, for example,  into diggers from a number of contemporary companies.

In the case of this 1863 engine only a sketch type drawing was included in the Patent, no mention was found in magazines of this engine. It must be a matter of conjecture whether it was ever built. The model most certainly was built, and has been extensively tested successfully on compressed air.

The design has the boiler and crankshaft positioned inside a large diameter drum which acts as a single driving wheel. Cylinders are placed at the front of the engine frame, either side of three wheels used for steering. the boiler is connected to the frame to which are also fitted flanged wheels which run on rails fixed on the inner side of the drum, which is open sided. These wheels keep the drum parallel with the ground.

The boiler is parallel with the length of the drum. Fire doors, ashpan doors, smoke box and chimney are at one end of the boiler, and the combination chamber  at the other.

The model is built to 1:16 scale giving the 9ft 2in diameter of the full-sized drum a scale diameter of 6.8in. Drum width is 3.75in. At 60 rpm, the model has a scale speed of 2mph.

No castings were used in construction of the model, everything is fabricated from stock metals. Every last part was made by Cherry - spur gears, internal gear, worm wheel, chain links, chains and sprockets, name plates and chequer plates, and even the nuts, bolts and rivets. The boiler is made from mild steel with copper flues and tubes. The drum is also mild steel.

The research phase took two years; drawing, building a mock-up and construction seven, and then painting five months. The ‘bare metal’ is actually finished to look like the wrought iron of the day.

The model includes approx 7,400 parts and occupied some 7,500 hours work over a 9 1/2 year period.

It was awarded a Gold Medal, and needs no hyperbole.

Photos courtesy Cherry Hill.