GB918992A - Improvements relating to apparatus for calculation of depth, trim, bending moment and shearing stress in a loaded ship - Google Patents

Abstract

918,992. Electric analogue computers for the loading of ships. SINTEF. April 8, 1960 [April 28, 1959], No. 12622/60. Class 37. Depth, trim, bending moment and shearing stress are calculated for a loaded ship by assuming the ship divided into a number of sections and associating each with an apparatus section of an electric analogue computer which comprises resistors, potentiometers and adjusting means set according to depth, trim and load. In one section P11 is a variable resistor giving section load and R11 and R41 fixed resistors such that the sum of the currents through them when voltages e s and - e s are applied respectively and P11 is maximum (no load) equals the weight of the section- R51 represents the buoyancy factor of the ship's section and R61 the product of the buoyancy factor. and the distance of the section from midship. The current i o1 is proportional to the resultant weight of the ship's section. Similar references apply in the other sections. The voltage e D is adjusted so that the sum of currents i o1 , i o2 , &c. will be 0, e 0 on the potentiometer being a measure of D, the depth of the ship. e 01 is the voltage across a fixed resistor R 01 and itis applied over a fixed resistor RM 1 , where 1/RM is proportional to the distance from the plane about which one wants to determine the bending moment. The sum of all the currents iM 1 , iM 2 , &c. equals the total moment. The voltage e T is adjusted by potentiometer so that the sum of the currents iM 1 , &c., is zero by reference to one end of the ship, the value of e T then giving the trim angle. The bending moment and shearing stress at any plane are obtained by summing the currents iM n and i on respectively. Three of the eight sets of resistors for an eight-section ship are shown in Fig. 5 and more than one load, e.g. tanks, in any one section are indicated by several adjustable resistors, e.g. P 12 , P 22 , P 32 . Three areas are shown, B, C, D, E, the weight unit, C, D,F,G, the moment unit, and H, B, O, K, the control unit. Switch S in the weight unit has one position for determining depth, and other positions for determining shearing stress. The switch M in the moment unit is adjusted to the measurement of trim and by bringing in resistors R A5 , R A6 , R A7 , R A8 or R B6 , R B7 and R B8 , allows the bending moments between sections to be read on an instrument A 2 , or on a potentiometer P M with A 2 showing a null reading. The control unit consists of a voltage divider R 0 -R 0 and four potentiometers P D , P T , P S and P M , the positions of which give depth, trim, shearing stress and bending moment, respectively. Resistors P11 and R11 may be replaced by a potentiometer giving greater accuracy (Fig. 6, not shown).