STATIONARY ENGINES.

243

gland, and it should have a brass guiding socket at the other endfor taking the valve spindle, which passes through a tube cast alongwith the valve, and to which it is secured by means of a nut andjam nut at each end. Some makers dispense with this guide, andattach the rod to the valve by a screwed part at its end, having anut let into the valve, with a jam nut to lock it securely when thevalve is properly set.

The valve is actuated by double eccentrics and link motion.The eccentric sheaves are of cast iron, of the usual construction,and may be cast all in one piece, or have the means of taking themoff the shaft without disturbing the main parts of the engine. Thestraps should be cast in brass, or they may be forged on the eccen-tric rods, and lined with Strips of brass rivetted on. The link,Suspension rods, weigh shaft, and reversing handle should be madeof wrought iron, and all the working pins case-hardened; and thesliding block for the link should be of Steel. All the bearings forthe weigh shaft should be bushed with brass, and the whole motionadjusted in a strong and substantial manner.

The starting handle should be a plain lever, fitted with quadrantand catch for holding the link in position. The starting platformshould be placed so as to command a good view of the pit head.Its position depends, of course, on the method of fitting up themachinery, but in ordinary cases the platform may be arranged atthe back of the winding drum, and of sufficient height to see wellover it. In this position, when the fly wheel is placed at the centreof the engine shaft, the friction strap and hand gear for working itis greatly simplified, and the attendant has the two important handlesfor reversing and applying the friction brake in a direct line withthe pit head. The handle for working the stop valve of the equili-brium type should be placed here likewise, on the centre of thesteam pipe between the two engines. The handles are, however,at times arranged on the outside of the left-hand engine lookingtowards the pit head, with a cross shaft, as in the former method,for the reversing gear placed underneath the bed plates or abovethem, supported at the end and middle with suitable pillow blocks.On this shaft the lifting arms are fitted, with a weight arm at thecentre of the shaft, or between the end and middle pillow block,having a suitable weight, which may be placed on the startinghandle, for balancing the links and rods, and thus easing the labourof starting and reversing the engines. The handle will of course