Locomotive Types
The smaller model may be provided with a shallow.
firebox which can be extended backwards well over the
trailing axle. However, if a prototype which has a coupled
wheel base of over 9ft. is modelled no trouble will ensue,
more particularly if the cylinders are placed outside and
the consequent absence of a crank axle enables a slightly
longer firebox than is otherwise possible to be employed.
Further, if a high-pitched boiler and moderate-diameter
wheels are used an inclined grate will entirely get over
the difficulty.
Fig. 18. Model of the Famous L.N.W.R. "Lady of the Lake,"
Another drawback to the type is that the bogic wheels. are often, in many British examples especially, of large diameter, and if modelled to scale reduce the flexibility of the wheel base. If, as in the N.E.R. engine illustrated in Fig. 14, the bogie wheels are small and the frames are cut away over these wheels, this trouble to a great extent disappears. " Outside cylinder engines which drive on to the first pair of coupled wheels are usually arranged, as in the L.S.W.R. engine No. 593, with the connecting rod inside the coupling rod. This throws the crosshead very close. to the tyre of the trailing wheel of the bogie and seriously15
