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Except in extraordinary cases, all equipments of this gear are exactly alike for outside admission, no matter what the class or type of engine; and the same is true for inside admission. Further, the yokes and radius bars are the same for both admissions. The combination lever would have to suit the requirements as to lap, lead, and the stroke of the piston. All parts are interchangeable, and the castings—including the gear frame—are the same for both sides of the engine, excepting the gear-connecting rods; the combination levers are rights and lefts, but they are forged. The gear frame is one piece of cast steel and can be used on either side of the engine without refitting; one type for inside admission, and another for outside admission. The gear frame is designed with an extension, so that it can be applied to a variety of engines, thus reducing the number of kinds of frame that a road must carry in stock. Hence, if an engine with this gear meets with an accident it is a short job to repair the gear and put the engine in service again.
Valve Events in General.—The Baker-Pilliod improved valve gear gives a constant lead of the valve the distance of the steam lap, but a variable preadmission; at full gear we get practically no preadmission, but as the cut-off is shortened preadmission begins and increases until there is ample for high speeds, with no bad effects for the slow-speed, full gear position. The man
ufacturers direct particular attention to the squareness of the cut-off, in back-up gear as well as the go-ahead. And they claim the longest release for given cut-off and lap condition of any locomotive valve gear in practical use to-day.
Whenever certain persons who are familiar with the “Stephenson” link motion are brought into association with a modern, radial valve-gear their first inquiry usually is as to the directions for “valve setting”; they cannot get clear of the idea that every valve motion requires constant tinkering with “to keep it square.” All engines with radial gear should have adjustable valve stems, however. Before the gear is taken apart, tram the valve rod and the reach rod; put them back in the same place, test the lead and cut-off in one position of the reverse lever, equalizing the travel of the valve—if this should be necessary—by adjusting the valve stem, and the engine is ready for the road.
QUESTIONS AND ANSWERS ON BREAK-
ON THE ROAD
Question 1.-In case of breakdown with the engine disabled on one side, how may the valve be blocked centrally on its seat so as to cover all ports—is it necessary in the use of this gear, to carry a valve-stem clamp for the purpose?
Answer. It is not necessary to carry a valve-stem clamp on an engine with the Baker-Pilliod improved valve gear. The valve-stem crosshead is provided with a set-screw by which it can be clamped to its guide, after the valve has been centred; and it holds the valve immovable.
Q. 2.-In case the eccentric crank or eccentric rod should break, what should be done?
A.—When the gear was first erected, after the valves had been set the reverse lever was placed in mid-gear and a hole drilled through the gear frame and bellcrank arm (see a and a', Figs. 49 and 50). You now remove the broken parts—if a broken eccentric crank remove the eccentric rod, of course; move the bell crank until holes a and a' are in register, insert a bolt through
the holes, and you are ready to go. With the gear bolted in this manner the valve will get the lap-and-lead movement, and will permit a port opening equal to the lead for all cut-offs, from the motion received through the combination lever from the crosshead.
Q. 3.—With what other breaks should the bell crank be bolted to the frame and the valve be able to receive its lap-and-lead movement, as directed above?
A.-In cases of breakages of the gear-connecting rod, radius bars, reverse yoke, short reach-rod, or horizontal arm of bell crank, remove the eccentric rod, and the lower arm of the bell crank can be bolted to the gear frame; and as previously stated, the engine will not have entirely failed on that side, the lap-and-lead movement of the valve supplying enough steam to the cylinder to give a certain amount of turning effort to the main pin.
Q. 4.-What should be done where the union link or crosshead arm has failed?
A.-In such cases it will be necessary to block the valve over the ports, by tightening the set-screw that clamps the valve stem to its guide, and to disconnect the valve rod, proceeding with the engine working on one side. Or, if it is possible to do so, chain the lower end of the combination lever in the position in which its pin hole F will be on the same vertical line as the fulcrum pin E of the bell crank; it will not then be