HR 118 Progress

The chassis is separate from the superstructure, being held in place by a bolt, which engages with a nut hidden in the smokebox, a tongue and groove arrangement secures the rear. An ABC Gears Mini 7E with an M1824 motor and flywheel fits comfortably into the boiler which is cut away to accommodate the mechanism. Pick-ups are 0.5mm phosphor-bronze wires bearing on the back of the left-hand driving wheels, while those on the right are uninsulated. I'm working on a pick-up from the front carrying wheel too, which should further improve performance. There's a surprising amount of detail on this little engine and it won't be complete before its first trial outing on the the club layout in Carlisle early next month.   

The motor is supported on a cross bearing just behind the flywheel to keep it from resting on the axle.

Using an M1824 motor allows just enough clearance inside the cut-away boiler. A sand box will be mounted behind the motion plate.

Buffers are from Roxy Mouldings and are mounted high on the buffer beam, so the retaining nuts are too big to fit under the footplate and an alternative needs to be designed.

 

HR 118 Making a Start.

HR118 Chassis in progress 

My model of HR118 will illustrate the engine, as rebuilt by Sharp Stewart, towards the end of its service with the Highland Railway, when it had lost its former name, Gordon Castle, had its number plate removed and was working as a humble shunting engine. There's a photo of the engine at the end of its days, laid aside at Culloden Moor in 1923, in unlined olive green, which is a useful source for details of the engine; I won't make my model in quite as decrepit a state as this though. Only three photos of the engine are known to survive, along with a side elevation drawn by L Ward using the photos as reference. It's enough to build a model, though there are one or two details I don't understand to be resolved and I have no information at all on the cab interior.

There is no kit for this prototype in any scale so I'm scratch building it or, as I prefer to say, "modelling without the aid of a kit", though with reliance on the trade for suitable castings.  

Driving wheels are from Walsall Model Industries, these are cast iron, turned to size and drilled 12BA for the crank pins; they match the pattern of the prototype. The off-side drivers are insulated midway along the spokes. The frames are 0.7 n/s, set 26.6mm apart.

I made the coupling and connecting rods myself from 1.2 mm nickel silver sheet as I could find no trade source for this type of rod with marine big ends. The front crank pin seen here is a 10BA screw, the coupling rod runs in a brass bush and the connecting rod is held in place by a top hat bush threaded to match the screw. The slide-bars and cross-head are commercial castings of unknown provenance. A guard-plate will be fitted later behind the slide-bars, presumably this kept dirt away from the cross-head. The carrying wheels are held in place by a central keeper-rod, mounted on a transverse plate, which can be unscrewed to drop the wheels out of their slots.

The axle screw is inaccessible behind the slide-bars. The horizontal rod acts as a keeper for the carrying wheels which are easily removed from the frames. 

For detailed information on the prototype and its vicissitudes in service see...Cormack and Stevenson's Highland Railway Locomotives Bk.1, pubs. RCTS.