Part-built 7 1/4 inch gauge Orenstein & Koppel rack locomotive

Since the ruling gradient at the new house Im trying to buy is about 1 in 4, Im half wondering whether I should keep this one myself.

A 7 inch gauge model of one of the Orenstein & Koppel rack & pinion locomotives supplied to the railway at Chambery, France in 1909 for working a combination of normal adhesion and rack sections over the route. The model design was done by Ken Swann (he of Bridget and Wren fame) in the 1980s and written up in Engineering in Miniature producing a unique engine of rather nice proportions and a high degree of technical interest.

The original O&K design was an 0-4-0 well and side tank. The cylinders were mounted high up at the front, driving a jackshaft mounted beneath the boiler, connected via gears to a crankshaft on which was mounted the rack pinion and two flycranks driving the wheels via a T-shaped connecting rod forming a Scotch crank. Since there were only two gears in the drive train, the jackshaft ran in the opposite direction to the wheels, which makes for an interesting sight. Ever the practical miniature locomotive man, Ken Swann interposed a dog clutch in the drive, allowing the engine to be run out of gear which is entertaining for spectators and useful for the driver, since the axle pump works off the jack shaft and can be used to fill the boiler whilst standing in the station!

Work to date is to a high standard and comprises the main chassis, incorporating a well tank, assembled including gunmetal axleboxes and roller bearings for the jackshaft. The rear subframe which supports the cab and dragbeam is largely complete and simply requires bolting on. The axles and wheels are keyed for accurate quartering and could be assembled, along with the cylinders to give a largely complete rolling chassis.

Chassis with well tank, gunmetal axle boxes, axles and wheels, buffer beams
Set machined cylinders, end covers, valve chest covers, ports to be drilled
Complete weighshaft
Jackshaft and machined flywheels
Dog clutch assembly complete
Rack pinion and final drive pinion assembly complete
Connecting rods, crankpins, nuts and bushes
Flycranks complete with crankpins
Smokebox tube, unmachined gunmetal back ring, flamecut steel front ring, steel smokebox door pressing
Set Riggenbach Patent plates
Dome casting
Brass tank sides

There are many more parts in a box with the engine and a complete set of the "Engineering in Miniature" articles in two ring-binder folders. There is very light surface rusting to some components, this comes off easily with Scotchbrite.

Although designed as a rack engine, many Koppels have now been built and acquit themselves admirably as adhesion engines on the typical club track. They are a good size to drive, being based on a 600mm gauge prototype.