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| the Great Southern railway to cross the Riachuelo river at Buenos Ayres, Ar- -gentina; an electric railway and high- way bridge for the City of Dublin, 'Ireland; a bridge to cross the Lachine canal, Canada, for the use of the Cana- dian Pacific Railway. The bridge at Buenos Ayres is the third order received from the Buenos Ayres Great Southern Railway, and is a result of the satisfactory completion and operation of the first double track ibridge of the Scherzer type placed in service a short time ago. The traffic of this railway company is growing so rapidiy that a second double track span for use in connection with the first structure is now needed. It has been manufactured in the bridge shops in England and will soon be erected at Buenos Ayres alongside of the pres- ent double track span, the two double track spans side by side forming one four track bridge to 'be operated joint- ly or separately as desired. The pos- sibility of adding single, double or multiple track bridges to accommodate constantly increasing traffic is one of the advantages of the Scherzer rolling lift 'bridge as compared with the center pier swing bridge, which must be dis- carded, removed and replaced with a new bridge as soon as growing traffic requires additional tracks. AN IMPROVED STEERING ENGINE. The failure in the past of steering 'engines in which the movement of the tiller ropes was taken directly from a reciprocating piston instead of from a revolving drum has been due chiefly to their valve mechanism. Either the rudder movement was too THe Marine. REVIEW by means of which these objections are said to be completely overcome. As will be noted, there is an absence of a multiplicity of wearing and power absorbing parts such as drum, spur November, 1909 ing wheel to port or starboard as de- sired, operates the control lever wh'ch, swinging about the floating fulcrum, transmits its pull to a connecting rod, the other end of which communicates The by hand. Steam Sheaves Nash-Century Engine steam and hand operation. the clamps shown above are replaced by the sheaves and a _ standing part. duces by one-half the effort required to steer control not shown but is similar to that in diagram above. 3 Aare. free arranged for In this instance This also re- to move for steam steering, but are fixed by means of clamping screws for hand steering. Sheaves B are fixed for steam steering, but are free to move for hand _ steering. The liagram shows the rudder being operated by inder the steam gear. and worm gears, large bearings, etc. The piston rod is prolonged equally through both ends of the steam cyl- and carries, at each end, a sheave, through which the tiller ropes and rove so that the quadrant travel is twice that of the piston. Steam pressure admitted at each end of the cylinder acts upon both sides of the piston, holding it in position and at all times balancing it against the pres- sure on the rudder. The valves which admit pressure to the cyiinder are of the piston type and have a spindle common to both. When the control'ing gear is station- : is a SABLE TO HANQ ' - WHEEL. CLAMP er ee : The Nash-Century Engine -athwartships. - movement. co arranged for uring steam operation both clamps on the hand wheel cable are set to e : lf for steam operation only, the tiller ropes are made fast A Nectee ot passing through the third set of sheaves. : a ee abrupt or the rudder could not be 'maintained in the desired position sat- 'sfactorily. The Nash-Century steer- ing engine which we illustrate is con- 'structed with a novel valve movement steam and hand that 1s, CABLE TO HAND WHEEL operation. Cylinder placed ary these valves are in mid position; the va've rings -cover the steam ports with slight overlap and prevent admission of steam to the cylinder. The movement of the steer- forms with the valve spindle. The resulting movement of the valves uncovers the ports, admitting steam through the valve at one end of the cylinder and exhausting through the valve at the other end. The unbalanced cylinder pressure then shifts the piston and by means of the sheaves and cables attached to the ends of the p'ston rod the corresponding movement is imparted to the rudder. 'At the same time the movement of the piston causes the sprocket chain attached to the sheave b!ocks at each end of the piston to rotate the sprocket and its eccentric pinion. The sprocket and pinion are keyed to the same shaft and are practically one piece. The pinion meshes with an arc which swings about a center on a bracket on the cylinder casting. Extending from the center pivot of the arc and diametrically opposite to the toothed part is a projection which the fulcrum for the control lever. This explains why this fulcrum was previously referred to as "float- ing." The movement of the arc causes the fulcrum to travel in a radial di- rection and opposite to that taken by the valve spindle in opening for steam. Thus the instant the. piston reached the desired position it has by its own action as_ transmitted through piston rods, chain, sprocket, p-nion, arc, fulcrum and connecting rod, automatically closed the valve and shut off the steam. To keep the piston moving it is consequently nec- has