A. On account of the high compression, that balances the pressure considerably.

Q. How is it given high lift?

A. By arranging a cam roller between the valve and the valve-lever fulcrum, as seen in Figs. 418 and 419.

Fig. 418.

Details of Poppet Valves and Lifting Mechanism, Unaflow Locomotive.

Q. How is coasting managed?

A. By raising the valves from their seats by compressed air admitted between small pistons formed on the valve tappits so that the roller will clear the cam. (See Fig. 419.)

CHAPTER LXXXVII

MOTION RECORDS

Q. How are "motion records" made?

A. Engineers who are called by the majority of manufacturers "efficiency men," altho they loathe the very appropriate term, owing to the number of fakers who have entered the field, employ instantaneous photography and "movies" to record and show unnecessary motions made in performing different operations, and compare them with those showing the same operations with all unnecessary and unduly complicated movements cut out. We have here illustrations showing the graphic records obtained, and the method of getting them.

The object here is to demonstrate the advantage of opening and closing a locomotive fire door by steam instead of by hand. A tiny incandescent lamp is attached to various parts of the fireman's person, and to the

shovel and the door, and connected by suitable wiring to a battery in the cab. Motion pictures are then taken of his movements under both sets of conditions; each

lamplet (the word is "a poor thing, but mine own") is shown on the film by a continuous line. The series of complicated lines here shown, was taken during hand management of the door; the other, much more direct and simple, illustrates the course of each tiny lamp where the door is operated by a tiny steam cylinder the valve to which is controlled by the fireman's foot. As each ton of coal averages 115 scoopfuls and ten tons are used on an average run, the steam assistant saves 11,500 body movements on the average run, as ten movements are saved each time the door is opened. Further, the door remains open only seven minutes per hour instead of over twenty. (See Figs. 420 to 422 incl.)