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Turbine or Diesel Drive in Stern Wheel River Boats HEN the attempt is made W to install in river boats mod- ern machinery involving either steam turbines. or diesel en- gines connected directly or by means of electric transmission to the stern wheel, those making the installation are confronted with the problem as to how to effect the mechanical con- nection between the prime mover or the electric motor, and the wheel. In small sizes this has been suc. cessfully accomplished by means of shafts and gears, or chains, but these are said to offer great difficulties when applied to boats demanding 1000 to 2000 horsepower and over. With the large torques involved in consuming this horsepower at speeds of 15 to 30 revolutions per minute, it is not surprising that this feature has been a cause for concern. After careful analysis, several groups studying the problem independently have arrived at the conclusion that the use of connecting rods, or pit- mans, offers the most satisfactory so- lution. This type of connection has been successfully used for many years with the old grasshopper type of steam engine and has demonstrated its merit. However, difficulty arises with the pitman type of connection in apply- ing any type of modern power which delivers practically a uniform torque throughout a revolution of the wheel. In the case of the grasshopper reci- procating engine, steam is cut off be- fore the end of the stroke and the idle pitman is carried over the dead center by the working one. How- ever, with any type of motive power delivering practically constant torque, there is grave danger that during maneuvering the driving cranks on either side of the boat will be in op- position to each other. This is due to the clearances which naturally de- velop in the bearings and which will permit of a driving crank, when near dead center, dropping by and caus- ing a cramping action. This analy- sis is by no means based on theory only, as actual experience has been had with electric locomotive design incorporating similar features. A solution for this problem has been worked out by the General Electric Co. which it believes meets the requirements fully. The idea is to install in the pitman a hydraulic connection, shown in Fig. 1. In this illustration, A is the forward end of the pitman and B is, in effect, this forward end made to surround and include the driving crank. The driv- ing effort of the crank is delivered through the connecting rod H, to which is attached a piston D. This piston works in a cylinder C filled with a hydraulic medium, such as oil. Mounted on top of the cylinder is a piston valve E, which is actuat- ed by the crank through the linkage F. During the advantageous work- ing angle of the crank, the two ends of the cylinder on either side of the piston are sealed off from each other by the valve E, so that a rigid con- nection is maintained; as the crank approaches dead center, the two ends of the cylinder on either side of the piston are interconnected, so that the piston is allowed to float freely, thereby permitting the working pit- man to carry the other past dead center, much as is the case with the grasshopper type steam engine. The portions of the mechanism filled with the hydraulic medium are all self- contained; that is, there is no pip- ing external to the device itself. A reserve supply of oil is con- tained in the valve chest, which is used to keep the working passages filled as any slight leakage may oc- cur; this is accomplished through the medium of a piston actuated by spring K. For the purpose of indi- cating the necessity for refilling the system, the stem of the piston upon which the spring K _ operates is brought external. The makeup medi- um may be supplied without disas- sembling the .mechanism, through means of an ordinary hand pump. As the forward end of the pitman Right — Fig. 1 — . Hydraulic connec- tion installed in pitman. Above— Fig. 2— Arrange- ment of motors and gearing in- stalled well for- ward MarRINE REviEw—July, 1931 is made to surround the crank, as il- lustrated at B, there is no tendency for the pitman to buckle due to the interposition of the hydraulic link between the driving and the driven members. This arrangement has the addi- tional advantage of setting a definite limit to the stresses set up in the crank pins, pitman, ete. This is due to the ability to choose the point at which the load is relieved on side approaching dead center. It should be understood that with this arrangement the driving cranks will be cross-connected; that is, elec- tric motors or other constant torque motive power will not be independ- ently connected to the driving cranks. If this cross shaft were not provided, its individual motor would accelerate each crank a little when it became idle and as each dead center was passed, until all the clearance pro- vided for by the hydraulic connec- tion would disappear. The cross- shaft may be placed at any conveni- ent point in the reduction system be- tween the motor and driving cranks, so that it may be placed below the deck and remove the objection that it interferes with the use of this space for stowing cargo or other purposes. In Fig. 2 an arrangement is shown whereby the weight of the motors and gearing is placed well forward. This is understood to be a very de- sirable feature for this type of boat. ° As the ordinary pitmans would be too long with such an arrangement, they are shown divided in two parts and supported at approximately their center points by sliding crossheads. Foreign Traders Meet The eighteenth annual convention of the National Foreign Trade Coun- cil was held in New York on May 27, 28 and 29. Delegates from every state in the union and from foreign countries attended, giving the meet- ing an international significance. An excellent program of papers was read at both the general and group ses- sions. Chairman James A. Farrel _ opened the convention with an ad- dress on the world trade outlook. Subjects covered in the group ses- sions included export merchandising, imports, co-operation in export trade, credits and credit information, export advertising, and foreign trade banking. iia ae | NS D 35.