All About Engines

26o All About Engines cylinders, and the <( Great Bear had four. Then, consider the relative weights of the engines—for it is this which gives rise to the friction between rails and wheels, and enables the engine to draw heavy loads. So that when we find that the weights on the driving wheels of the “ Locomotion was only 6J tons, while that on the driving wheels of the AB Axle box AP Ash pan BC Break cylinder BP Blast pipe BTP Back tube plate C Cylinder CR Connecting-rod Fig. 146.—General arrangement of a modern locomotive FA Fire arch HP Horn plate S Super heater FB Fire bars MF Main frame SB Smokebox FBS Firebox girder P Piston SD Steam dome stay PR Piston rod SP Steam pipe FBX Inner firebox PV Piston valve ST Smoke tubes FD Fire door R Regulator SV Safety valve FR Foundation ring RH Regulator handle VG Valve gear FTP Front tube plate RW Reversing wheel 11 Great Bear ” was 60 tons, there is no wonder that the draw bar pull of 1,000 lb. of the earlier engine looks small compared with the pull of 26,000 lb. of the later one. The general arrangement of a modern locomo- tive is shown in Fig. 146, and though the drawing is