Model Steam Locomotives
ago fo make an unsteccessful engine mure efiieient. It
cerlainly improved the ranning, but the real trouble lay
in the cylinders of the engine, and these were never pub
right.
Loco-type Boilers.— Undoubtedly the locomotive-type fire-tube boiler has the great merit of being trne to scale and realistic, and therefore much favoured by skil- ful model builders. For large passenger-carrying models it has no compeer, while there is a growing section of experimenters who favour the use of solid fuel and have made quite a success of loco-type boilers in gauges as small as No. 1 (4% in.). Solid fuel is very manageable, and with a well-made and proportioned boiler, efficient cylinders and proper blast arrangements, the most successful models can be made. At the Manchester Model Exhibition of 1913 @ 2h-in. gauge Pacific engine (see Mig, 280, page 220) was shown working by the writer. It was kept in sfeam six or seven hours a day for three davs; it could be left at any moment for considerable periods.
A successful loco-type boiler may be oblained by—
(4) A Jarge grate area.
(2} A large boiler diameter to provide sufficient tube heating surface and ample range of water. Diameter should, if possible, be above normal. In smaller models iength is uot a drawhack where solid fuel is used, as it helps the water range of the boiler.
(8) With a coal fire a deep grale at the tube-plate end is desirable. Where charcoa] is used the fuel may be heaped, and therefore the total capacity of the furnace is important’. With coal the capacity below the level of the tubes or “brick arch” line should be considered.56
