On the Motion of a Vessel and the Change of the Thrust and Torque acting on the Shafts during Starting, Stopping or Backing

Abstract

It is feared that the excessive thrust and torque of the shock type may act on the shafts of a vessel during starting, stopping or backing etc. and cause damages on the propeller blades, the thrust block, or the reduction gear in the case of a turbine steamer. But it is difficult to obtain a general conclusion because this phenomenon depends not only on the ship form, characteristics of the propellers and the propelling machineries but also on the operation of the machineries.The authors prove the existence of the four “Humps and Hollows” of the characteristic curves of a screw propeller working under conditions of whole range of speed eoefricient J=va/nD=-∞ to+∞. And they give a thorough explanation theoretically on the three conspicuous fluctuations appeared on the “torque-time” curves plotted from the data of the backing trials of U.S. Destroyer Roe published by Comdr. P.D. Gold and of U.S. coast guard cutter Compbell by Comdr. Curry. The change of the thrust thus obtained theorectically can be used to calculate distance run, the speed of a vessel etc. during stopping or backing.The train ferry-boats repeat arrival and departure time after time every day, and serve conditions of starting, stopping and backing on all such occasions as compared with ordinary large ships. The authors make a detailed numerical calculations after the above-mentioned theory about the train ferry-steamer “Ishikari Maru” of the Aomori-Hakodate line as an example.