. Science of railways . ngth of card the standard drum instrument, the pencil has a move-ment of while with the smaller drum, the pencil motionis limited to inches. The ratio of travel between thepencil point and piston is 5 to 1 in both the outside and inside LOCOMOTIVE APPLIANCES. 603 spring indicators with either size drum. The drum spring is ofa design which practically maintains a constant tension on thedrum carriage throughout all parts of the stroke, giving asmoothness and uniformity of action which insures the mostaccurate results. The tension of the drum sprin
. Science of railways . ngth of card the standard drum instrument, the pencil has a move-ment of while with the smaller drum, the pencil motionis limited to inches. The ratio of travel between thepencil point and piston is 5 to 1 in both the outside and inside LOCOMOTIVE APPLIANCES. 603 spring indicators with either size drum. The drum spring is ofa design which practically maintains a constant tension on thedrum carriage throughout all parts of the stroke, giving asmoothness and uniformity of action which insures the mostaccurate results. The tension of the drum spring may bevaried to suit conditions of high or low speed engines, althoughthe one setting is suitable for a large range of speeds. Thisspring is very durable and will hold its tension for longperiods. A Detent Motion is regularly supplied with all Tabor Indi-cators except instruments which are equipped with theHoughtaling Reducing Motion in which is incorporated aDetent Motion. By the Detent Motion the drum can be stopped. Cord Take-Up. for the insertion of a new card, without disconnecting thecord from the engine crosshead. This mechanism consists ofa handle operated pawl which engages a ratchet on the drumcarriage. When the Detent Motion is employed a convenientmethod of taking up the slack cord is found in the introduc-tion of a rubber band as shown in the accompanying illustra-tion, Fig. 6. This band must be of sufficient strength andlength to take up all slack in the cord, which slack is equalto the stroke of the drum. This arrangement shown in theaccompanying view, will prevent breakage of the cord whenthe drum is stopped. When this takes place, the rubber bandcontracts, taking up all slack between the points where it isknotted to the cord. 604 LOCOMOTIVE APPLIANCES. The Cord Guide Pulley of the Tabor Indicator permits thecord to be led off in any direction. After being adjusted itcan be securely locked in position. The adjustment pre-vents breakage of cord, due
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