. Electrical news and engineering . tingeffect on one sample it is seen that the heatingeffect is not directly proportionalto the increase in current, but itis proportional to the square ofthe current increase or decrease,and directly proportional to theresistances. The safe limit ofheat for rheostat wires is a mat-ter that depends on ventilation,as much as anything else. A cur-rent that would heat a wire toa red heat in a confined spacewill be perfectly safe when coolair circulates around it freely. Knowing the current thatthe rheostat will want to shunt (maximum), it will be safet
. Electrical news and engineering . tingeffect on one sample it is seen that the heatingeffect is not directly proportionalto the increase in current, but itis proportional to the square ofthe current increase or decrease,and directly proportional to theresistances. The safe limit ofheat for rheostat wires is a mat-ter that depends on ventilation,as much as anything else. A cur-rent that would heat a wire toa red heat in a confined spacewill be perfectly safe when coolair circulates around it freely. Knowing the current thatthe rheostat will want to shunt (maximum), it will be safeto allow about one square inch of radiating (cooling)surface of rheostat for every ten watts absorbed by it. J. B. writes from a Western Ontario town, asfollows : I am in charge of a Wheelock engine, buthave never seen the valves of this engine nor even a cutof the valves. I have seen instructions in mechanicalpapers for setting valves of other engines, but never aWheelock. Could you tell me where I could get theinformation I want ?. \alve of Wheelock Engine--Showing Valve Motion atEnd of Cylinder. Answer.—The accompanying cuts and diagram, forwhich we are indebted to the Goldie & McCulloch Co.,of Gait, Ont., the Canadian manufacturers of theWheelock engine, will doubtless enable our correspond-ent to understand the valve mechanism. The diagramshows the dashpot and a portion of the valve motionfor one end of cylinder. On the arm of cut-off valvewill be noticed the letters R and L. When the valve isat rest and the hook detached, the line R should be Febniary, 1896 CflNflDIflN EliECTRlCAb fJEWS perfectly perpendicular ; the dashpot will be down andthe spring closed. Should the line not be perpendicular,the stud B has- an eccentric pin on the end and the dash-pot can be raised or lowered by loosening- the set screwand turning stud. Sometimes this is necessary owingto the leather under dashpot getting worn thin. Withthe crank of engine on dead centre and the hookattached so as to
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