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the belt. The tunnels under the hop- pers are unusually spacious.. The gate operating mechanism is_ thor- _ oughly accessible with liberal head room at the hand wheels. Ample room is also provided in outboard tunnels. The two hold belt conveyors are 42 inches wide and are carried on 4 inch diameter troughing idlers spaced 2 feet centers with return idlers at 9 foot centers. At the forward or discharge end the belts rise on a radius of 300 feet to a point about 15 feet 6 inches above the tank top, discharging on to cross-conveyors and thence to the pan conveyor. Each belt is driven by a 75 horsepower, 900 revolutions per minute, 440 volts, 3 phase, 60 cycle, squirrel cage motor. The belt speed is 350 feet per minute. The cross-conveyors, transferring the material from the hold belts to the pan conveyor, are 42 inches wide and of similar design. They are driven from off the head pulley of the hold conveyors by means of mitre gears with chain and sprocket reduction. The pan conveyors, elevating the ma- terial to the deck and discharging on the boom conveyor is 96 inches wide and has a capacity of 1800 long tons of stone per hour. The inclination is 42 degrees and the total lift about 48 feet. A 200 horsepower, 720 revolu- tions per minute, 440 volts, 3 phase, 60 cycle motor with a solenoid opera- ted brake drives the conveyor at a speed of 81 feet per minute. The drive is located at the head end, op- erating through a Robins-Falk her- ringbone reduction gear. From the pan conveyor the mate- rial passes through a cast steel chute to the boom conveyor which is 160 feet long by 48 inches wide. The belt speed is 460 feet per minute. The boom is pivoted to the deck at the tail end under the elevator discharge chute and may be swung over either side of the ship through a total are of 226 degrees and with a maximum inclination of 20 degrees amounting to a lift of about 55 feet at the head end. The boom drive is located at the tail end and consists of a 200 horsepower, 720 revolutions per min- UUULUOUALUUQUUNUUUUOUUOEOOGSUUUCCCULETCULHS Thunder Bay Quarries, one of three bulk car- riers converted to self-unloaders, showing the sub- stantial A frame structure with boom and belt jor discharging cargo over side of ship. Mazi- mum arc of swing of the boom is possible with this ar- rangement AUTTTEHTLTLUTTERLLUOMH LEE CEeUTAT AOL ute, 440 volts, 3 phase, 60 cycle motor with a solenoid operated brake. The entire conveying equipment, in- cluding belts and drives, was fur- nished by the Robins-Conveying Belt Co. All of the conveyor motors and solenoid brakes were furnished by the General Electrie Co. The main control panel for the .con- veying machinery is located on the starboard side of the main deck for- ward, enclosed by steel partitions. Control stations for the boom and pan conveyor are located on the spar deck port and starboard. The hold con- veyor station is at the head of the system, so that the operator can. watch the material coming off the cross con- veyors to the pan conveyor. The hold conveyors may be stopped at any time, port or starboard, by a pull cord run- “ning the entire length of the. tunnel. Each conveyor is operated inde- pendently or in sequence, so that if any conveyor is stopped, the conveyors ahead continue and those behind stop. Adjacent to each of the three main control stations is located a push but- ton with a horn in the tunnel, and by means of a code of signals, the entire system is under the control of the chief operator. Electrical energy to operate the con- veying machinery is supplied by a 500 UVTMETTUO VATU Under the hop- pers of the Thun- der Bay Quar- ries showing the gate controls from the hoppers to the two con- tinuous - belts which deliver the cargo to the forward end where in turn it is raised to the hopper on deck and deposited to boom for dis- charge over side PVPATUVTTTURUEATRUE UTED LULL LC MARINE Review—April, 1932 kilowatt, 3600 revolutions per minute, 480 volts, 3 phase, 60 cycle, Westing- house condensing turbo-generator set with direct connected exciter, taking steam at 175 pounds with no super- heat. The condenser is a Wheeler, 750 square feet, surface type, operating at 26 inches vacuum. It is interesting to note that the ship’s original boiler capacity was sufficient to take care of the unloading requirements with con- siderable margin. The tunnels are exceptionally well lighted with a double row of lights through the main operating tunnel and single rows: outboard. Additional lights are located between hoppers. Adequate lighting is provided at the head end of the conveyors. Flood lights are provided on the boom and “A” frame in addition to the deck lights. A 35 kilowatt, General Electric 11 x 8 inches Simplex engine gen- erator set has been installed aft in the fan tail to meet the extra lighting requirements. For draining the tunnels and for- ward recess under the pan conveyor, two Morris 4-inch motor driven dredge pumps were installed, one forward and one aft. Owing to the recess in the inner bottom, the ballast piping was relocated in the outboard tunnels on the tank top. Three 84% x 8 inches Lidgerwood re- verse valve steam winches were in- stalled for swinging the boom, two being used for the swing and the third for the tag line. These machines were located over hatch No. 29, which was decked over. A Clyde 10 x 12 inches steam, two drum winch was in- stalled over the pan conveyor housing above deck to serve as a boom hoist. Each vessel has a rated designed unloading capacity of 1800 long tons per hour of stone weighing 90 pounds per cubic foot, or 1120 short tons of coal. The equipment is capable of a 20 per cent overload when in opera- As converted, the sister ships Dta- MOND ALKALI and THUNDER BAy QUAR- RIES have a self-trimmed hold capacity of 363,200 cubic feet. The capacity of the Rogperts is 369,700 cubic feet. 51