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14 MARINE REVIEW. [November 14, "LONG-ARM" POWER SYSTEM APPLIED TO BULKHEAD DOORS OF MANY NAVAL VESSELS--SUITED ALSO TO DOORS AND HATCHES OF MERCHANT SHIPS--DESCRIPTION OF THE SYSTEM. The "Long-Arm" System Co., Cleveland, has, since its organization, installed some 250 "Long-Arm" power doors on ships of the United States navy. Among the vessels which are thus equipped, or are being equipped, are the battleships Maine and Missouri, the monitors Arkansas, Wyom- ing, Nevada and Florida and the cruisers Chicago, Denver, Cleveland, Des Moines and Chattanooga. Official specifications call for a much larger number of these doors on the vessels which are now being designed. The com- pany has undertaken the man- ufacture of standardized ship fittings and is now in a posi- tion to offer both pneumatic and electric power systems and gears to operate and control its power doors and hatches. The company says that to those interested in passenger liners or ocean-going steam yachts it may at first appear that the "Long-Arm" system is com- plicated and expensive, but a brief investigation will show that when shorn of some de- tails required in naval ships, but not necessary in the mer- chant service, the "Long-Arm"' is a simple and direct means to accomplish a necessary result with reasonable and moderate outlay. In its argument the "Long-Arm" System Coe says that the most important and effective life-saving device on ships in case of collision or other skin puncture from shell, torpedo, derelict, iceberg or rock, is the hull itself rendered non-sinkable. Boats, life pre- servers and other devices of this nature, however good, are simply auxiliaries and make- shifts after the hull fails in its flotation. The main point in case of marine disasters has been and always will be to maintain flotation of the hull, ii not permanently, at least long enough to bring these auxiliaries into use. Without flotation first being secured in the hull all these auxiliaries are absolutely useless. What is Med =the best scheme to secure this Vertical Sliding Water-tight Door. flotation? Hitherto this has been sought through an ex- pensive subdivision of the hull by bulkheads. Doorways are abso- lutely necessary in many of these bulkheads for efficiency in work- ing the ship. These doorways are the points where the bulkhead system always fails and unless these doors can be closed water-tight, with cer- tainty and promptness, without danger of injuring or imprisoning the working force and without stopping necessary intercommunication, this expensive insurance by bulkheads becomes practically void. It is repre- sented that the "LLong-Arm" system secures real and efficient bulkhead insurance at a cost of much less than 1 per cent. of the cost of the ship. The "Long-Arm" power doors with their safety pneumatic and electric power systems have been practically developed by a constructing engineer and ship builder of long experience. They have been found acceptable and have been highly commended in sea service by most critical authorities because safe for the men as well as the ship. The doors and power devices have been standardized and are manufactured on the "interchangeable system" to the several types and sizes found desirable for naval and mer- chant ships. The company claims that the '""Long-Arm" central station power system with its liberty action is the cnly safe and practical scheme so far devised and adopted on any large scale for perfecting the stability structure and preserving the emergency flotation of modern ships, and there has been hitherto no successful attempt to perfect such devices to a practical state satisfactory to users and suitable for manufacture. The "Long-Arm" liberty action is the novel feature which has especially attracted the attention of experts, and it is this, coupled with good engi- neering and manufacture, which has made the "Long-Arm" pneumatic and electric systems successful. The successful system must win the con- fidence and co-operation of the crew instead of arousing fear and com- bativeness. This can only be done in two ways. The system must relieve the crew from the manual labor of handling heavy doors and hatches, and it must at all times give each man on board full control of any door or hatch which he may desire to use for his duty or safety, thus continually insuring both integrity of the compartments when needed and that inter- communication for duties which may be vital during emergencies. DESCRIPTION OF THE "LONG-ARM"' POWER DOOR. _ The ordinary sliding docr is totally unfit for power operation. It will jam, foul up and wedge fast and there is often too great an interval be- tween tighteners. A swinging door should never be used in an important bulkhead below the main deck. It is dangerous because it cannot be shut against rush of water. Therefore, whatever power system is used the door must be perfected before the power can be supplied satisfactorily. The "Long-Arm" power door is, strictly speaking, not a door but a sliding gate-valve operated by power and working in guides with special arrange- ments for automatically tightening itself by its own motion when closed and freeing itself when starting to open. There are two types, vertical and horizontal sliding. The latter type is manufactured both "right- hand" and "left-hand." The door-plate is made light and somewhat flexi- ble, having the stiffeners, '"'plow-share" and seating strips cast on. When unlocked it rides freely in the guides with 4% in. or more clearance in all directions. Its edges conform to the action of the tighteners and make a safe closure of the doorway, even when the bulkhead and seat are considerably warped. The guide-frame is cast solid and as heavy and stiff as practicable; it is designed so as to protect all the tightening gear and the seat. The guide-gibs are separate and are bolted on to facilitate the manufacture and maintenance. The bridge, in the vertical type door, spans the guide-frame at the top of clearway to add stiffness and to hold the top-tighteners. The tightening wedges may be cast on the door-plate or on the guide-gibs or both. The tighteners are spaced not over 9 in. between centers throughout the periphery. In the ordinary door now used this spacing is 24 to 30 in. and each tightener is operated separately and by hand. The wedge surfaces throughout are made with an incline of 1 to 8. This prevents all "biting." A door having a wedge that will "bite" is not fit to be used as a safety power-door. Many doors now used have wedges with an incline of more than 1 to 100. In the '"Long-Arm" doors every wedge works'on a roller, which is another very important item in their success. The side tighteners in the vertical type, and the top and bottom tighteners in the horizontal type, are similar and consist of rollers held in roller-bars extending on each side the full length of guide- gibs, a roller for each wedge--all kept within the guiding gibs to avoid foul- ing. The roller bars are free and unused throughout the travel, except dur- ing the short tightening interval of less than 1 in. at the closing end of the stroke. Within this interval the roller-bars cause the rollers and wedges to engage and press the door-plate against its seat. The bottom tighten- ers, in the vertical type, are rocking toes secured on a rock-shaft running through eye-bolts which hold the bottom frame to the bulkhead. When Horizontal Sliding Water-tight Door. the door-plate is free these toes and their connecting web press against the seat by the action of enclosed springs, thus forming a seat guard. During locking the beveled bottom edge of door-plate and "plow-share" (with its slightly raised wedges) first close the clearway and then engage the rollers in points of rocking-toes, opening the latter out until their backs bear on the bottom frame; further movement wedges the bottom of door-plate against the seat. During unlocking the rocker-toes follow in and close on the seat before the clearway is opened. Thus in a coal bunker door, nothing can foul these bottom tighteners and the small amount of coal dust, when it is forced down in, falls throuch to the floor. It is important in coal-bunker doors to have from 8 to 6 in. drop between the base of frame and top of floor, otherwise these bottom tighteners cannot be expected to keep themselves free automatically. Properly installed these tighteners will remain unclogged when working in fine bituminous coal. as repeated and severe tests have proved. The remaining tighteners consist of plain wedges in the door-plate or frame, as the case may be, engaging rollers in brackets. They are not in a position to foul up and can be easily inspected and adjusted. DESORIPTION OF THE "LONG-ARM" POWER SYSTEM. The especially valuable and distinctive features of the "Long-Arm" system are: First, all the principal doors are constructed in such a man- ner that they will move freely, tightening and releasing positively and automatically, so that they cannot foul or jam and so that they can be shut against a rush of water. Each door must, at any time required, ope- rate independently and with certainty through appliances on the spot, either by power or by hand, and must automatically tighten on its seat by the last of the closing movement and automatically release itself by the first of the opening movement. Second, the system is under direct con- trol from one or more emergency stations placed where desired, so that all doors may be closed simultaneously at any moment by the person first cognizant of danger and so that such emergency closing shall leave abso- lute control in the hands of any man at the door for his own safety' and his own duties. Third, the present endless variation in types of doors, sizes of openings and design of fittings is simplified, standardized and reduced to certain well-considered sizes with interchangeable parts, thus placing this important item in ship fittings on the same footing with