Chapter 6

Messrs. J. & E. Hall, Dartford, exhibit at the International Health Exhibition, London, in connection with a cold storage room, two sizes of Ellis' patent air refrigerator, the larger one capable of delivering 5,000 cubic feet of cold air per hour, when running at a speed of 150 revolutions per minute; and the smaller one 2,000 cubic feet of cold air per hour, at 225 revolutions per minute. The special features in these machines are the arrangement of parts, by which great compactness is secured, and the adoption of flat slides for the compressor, instead of the ordinary beat valves, which permits of a high rate of revolution without the objectionable noise which is caused by clacks beating on their seats. The engraving shows the general arrangement of the apparatus. Figs. 1 to 4 show details of the compression and expansion valves, which are ordinary flat slides, partly balanced, and held up to their faces by strong springs from behind. The steam, compression, and expansion cylinders are severally bolted to the end of a strong frame, which though attached to the cooler box does not form part of it, the object being to meet the strains between the cylinders and shaft in as direct a manner as possible without allowing them to act on the cooler casting. Each cylinder is double acting, the pistons being coupled to the shaft by three connecting rods, the two outer ones working upon crank pins fixed to overhung disks, and the center one on a crank formed in the shaft. The slide valves for all the cylinders are driven from two weigh shafts, the main valve shaft being actuated by a follow crank, and the expansion and cut off valves from the crosshead pin of the compressor. The machines may be used either in the vertical position as exhibited, or may be fixed horizontally; and it is stated that the construction is such as to admit of speeds of 200 and 300 revolutions per minute respectively for the larger and smaller machines, under which conditions the delivery of cold air may be taken at about 7,000 and 2,600 cubic feet per hour. Messrs. Hall also make this class of refrigerator without the steam cylinder, and arranged to be driven by a belt from a gas engine or any existing motive power.

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A GAS RADIATOR AND HEATER.

There is now being introduced into Germany a gas radiator and heater, the invention of Herr Wobbe. It consists, as will be seen in engraving above, of a series of vertical U-shaped pipes, of wrought iron, 50 millimeters (2 inches) in diameter. The two legs of the U are of unequal length; the longer being about 5 feet, and the shorter 3 feet (exclusive of the bend at the top). Beneath the open end of the shorter leg of each pipe is placed a burner, attached to a horizontal gas-pipe, which turns upon an axis. The object of having this pipe rotate is to bring the burners into an inclined position--shown by the dotted lines in Fig. 2--for lighting them. On turning them back to the vertical position, the heated products of combustion pass up the shorter tube and down the longer, where they enter a common receptacle, from which they pass into the chimney or out of doors. Surrounding the pipes are plates of sheet iron, inclined at the angle shown in Fig. 2. The object of the plates is to prevent the heated air of the room from passing up to the ceiling, and send it out into the room. To prevent any of the pipes acting as chimneys, and bringing the products of combustion back into the room, as well as to avoid any back-pressure, a damper is attached to the outlet receptacle. The heated gas becomes cooled so much (to about 100° Fahr.) that water is condensed and precipitated, and collects in the vessel below the outlet. Each burner has a separate cock, by which it may be kept closed, half-open, or open. To obviate danger of explosion, there is a strip of sheet iron in front of the burners, which prevents their being lighted when in a vertical position; so that, in case any unburned gas gets into the pipes, it cannot be ignited, for the burners can only be lighted when inclined to the front. In starting the stove the burners are lighted, in the inclined position; the chain from the damper pulled up; the burners set vertical; and, as soon as they are all drawing well into the tubes, the damper is closed. If less heat is desired, the cocks are turned half off. It is not permissible to entirely extinguish some of the burners, unless the unused pipes are closed to prevent the products of combustion coming back into the room. The consumption of gas per burner, full open, with a pressure of 8/10, is said to be only 4-3/8 cubic feet per hour.

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CONCRETE WATER PIPES.

Concrete water pipes of small diameter, according to a foreign contemporary, are used in parts of France, notably for water mains for the towns of Coulommiers and Aix-en-Provence. The pipes were formed of concrete in the trench itself. The mould into which the concrete was stamped was sheet iron about two yards in length. The several pipes were not specially joined to each other, the joints being set with mortar. The concrete consisted of three parts of slow setting cement and three parts of river sand, mixed with five parts of limestone debris. The inner diameter of the pipes was nine inches; their thickness, three inches. The average fall is given at one in five hundred; the lowest speed of the current at one foot nine inches per second. To facilitate the cleaning of the pipes, man-holes are constructed every one hundred yards or so, the sides of which are also made of concrete. The trenches are about five feet deep. The work was done by four men, who laid down nearly two hundred feet of pipe in a working day; the cost was about ninety-three cents per running yard. It is claimed as an advantage for the new method that the pipes adhere closely to the inequalities of the trench, and thus lie firmly on the ground. When submitted to great pressure, however, they have not proved effective, and the method, consequently, is only suitable for pipes in which there is no pressure, or only a very trifling one.

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THE SELLERS STANDARD SYSTEM OF SCREW THREADS, NUTS, AND BOLT HEADS.

_____________________________________________________ | | | SCREW THREADS. | |_____________________________________________________| | | | | | | | Diam. |Threads | Diameter | Area of | Width | | of | per | at root of | Bolt at | of | | Screw. | inch. | Thread. | root of | Flat. | | | | | Thread. | | |________|________|_________________|_________|_______| | | | | | | | | 1/4 | 20 | .185 | 13/64 | .026 | .0062 | | 5/16 | 18 | .240 | 15/64 | .045 | .0074 | | 3/8 | 16 | .294 | 19/64 | .067 | .0078 | | 7/16 | 14 | .344 | 11/32 | .092 | .0089 | | 1/2 | 13 | .400 | 13/32 | .125 | .0096 | | 9/16 | 12 | .454 | 29/64 | .161 | .0104 | | 5/8 | 11 | .507 | 33/64 | .201 | .0113 | | 3/4 | 10 | .620 | 5/8 | .301 | .0125 | | 7/8 | 9 | .731 | 47/64 | .419 | .0138 | | | | | | | | | 1 | 8 | .837 | 27/32 | .550 | .0156 | | 1-1/8 | 7 | .940 | 15/16 | .693 | .0178 | | 1-1/4 | 7 | 1.065 | 1- 1/16 | .890 | .0178 | | 1-3/8 | 6 | 1.160 | 1- 5/32 | 1.056 | .0208 | | 1-1/2 | 6 | 1.284 | 1- 9/32 | 1.294 | .0208 | | 1-5/8 | 5-1/2 | 1.389 | 1-25/64 | 1.515 | .0227 | | 1-3/4 | 5 | 1.491 | 1-31/64 | 1.746 | .0250 | | 1-7/8 | 5 | 1.616 | 1-39/64 | 2.051 | .0250 | | | | | | | | | 2 | 4-1/2 | 1.742 | 1-23/32 | 2.301 | .0277 | | 2-1/4 | 4-1/2 | 1.962 | 1-31/32 | 3.023 | .0277 | | 2-1/2 | 4 | 2.176 | 2-11/64 | 3.718 | .0312 | | 2-3/4 | 4 | 2.426 | 2-27/64 | 4.622 | .0312 | | | | | | | | | 3 | 3-1/2 | 2.629 | 2- 5/8 | 5.428 | .0357 | | 3-1/4 | 3-1/2 | 2.879 | 2- 7/8 | 6.509 | .0357 | | 3-1/2 | 3-1/4 | 3.100 | 3- 3/32 | 7.547 | .0384 | | 3-3/4 | 3 | 3.317 | 3- 5/16 | 8.614 | .0413 | | | | | | | | | 4 | 3 | 3.567 | 3- 9/16 | 9.993 | .0413 | | 4-1/4 | 2-7/8 | 3.798 | 3-51/64 | 11.329 | .0435 | | 4-1/2 | 2-3/4 | 4.028 | 4- 1/32 | 12.742 | .0454 | | 4-3/4 | 2-5/8 | 4.256 | 4- 1/4 | 14.226 | .0476 | | | | | | | | | 5 | 2-1/2 | 4.480 | 4-31/64 | 15.763 | .0500 | | 5-1/4 | 2-1/2 | 4.730 | 4-47/64 | 17.570 | .0500 | | 5-1/2 | 2-3/8 | 4.953 | 4-61/64 | 19.267 | .0526 | | 5-3/4 | 2-3/8 | 5.203 | 5-13/64 | 21.261 | .0526 | | 6 | 2-1/4 | 5.423 | 5-27/64 | 23.097 | .0555 | |________|________|_________________|_________|_______| _____________________________________________________________ | | | NUTS. | |___________________ __________________________________________| | | | | | | | | Short | Short | Long | Long | Thick- | Thick- | | Diam. | Diam. | Diam. | Diam. | ness | ness | | Rough. | Finish. | Rough. | Rough. | Rough. | Finish. | | | | | | | | | (Hex.) | (Hex.) | (Hex.) | (Square) | | | |_________|_________ |__________|__________|_________|_________| | | | | | | | | 1/2 | 7/16 | 37/64 | 7/10 | 1/4 | 3/16 | | 19/32 | 17/32 | 11/16 | 10/12 | 5/16 | 1/4 | | 11/16 | 5/8 | 51/64 | 63/64 | 3/8 | 5/16 | | 25/32 | 23/33 | 9/10 | 1- 7/64 | 7/16 | 3/8 | | 7/8 | 13/16 | 1 | 1-15/64 | 1/2 | 7/16 | | 31/32 | 29/32 | 1- 1/8 | 1-23/64 | 9/16 | 1/2 | | 1-1/16 | 1 | 1- 7/32 | 1- 1/2 | 5/8 | 9/16 | | 1-1/4 | 1-3/16 | 1- 7/16 | 1-49/64 | 3/4 | 11/16 | | 1-7/16 | 1-3/8 | 1-21/32 | 2- 1/32 | 7/8 | 13/16 | | | | | | | | | 1- 5/8 | 1-9/16 | 1- 7/8 | 2-19/64 | 1 | 15/16 | | 1-13/16| 1- 3/4 | 2- 5/32 | 2- 9/16 | 1-1/8 | 1- 1/16 | | 2 | 1-15/16 | 2- 5/16 | 2-53/64 | 1-1/4 | 1- 3/16 | | 2- 3/16| 2- 1/8 | 2-17/32 | 3- 3/32 | 1-3/8 | 1- 5/16 | | 2- 3/8 | 2- 5/16 | 2- 3/4 | 3-23/64 | 1-1/2 | 1- 7/16 | | 2- 9/16| 2- 1/2 | 2-31/32 | 3- 5/8 | 1-5/8 | 1- 9/16 | | 2- 3/4 | 2-11/16 | 3- 3/16 | 3-57/64 | 1-3/4 | 1-11/16 | | 2-15/16| 2- 7/8 | 3-13/32 | 4- 5/32 | 1-7/8 | 1-13/16 | | | | | | | | | 3-1/8 | 3- 1/16 | 3- 5/8 | 4-27/64 | 2 | 1-15/16 | | 3-1/2 | 3- 7/16 | 4- 1/16 | 4-61/64 | 2-1/4 | 2- 3/16 | | 3-7/8 | 3-13/16 | 4- 1/2 | 5-31/64 | 2-1/2 | 2- 7/16 | | 4-1/4 | 4- 3/16 | 4-29/32 | 6 | 2-3/4 | 2-11/16 | | | | | | | | | 4-5/8 | 4- 9/16 | 5- 3/8 | 6-17/32 | 3 | 2-15/16 | | 5 | 4-15/16 | 5-13/16 | 7- 1/16 | 3-1/4 | 3- 3/16 | | 5-3/8 | 5- 5/16 | 6- 7/32 | 7-39/64 | 3-1/2 | 3- 7/16 | | 5-3/4 | 5-11/16 | 6-21/32 | 8- 1/8 | 3-3/4 | 3-11/16 | | | | | | | | | 6-1/8 | 6- 1/16 | 7- 3/32 | 8-41/64 | 4 | 3-15/16 | | 6-1/2 | 6- 7/16 | 7- 9/16 | 9- 3/16 | 4-1/4 | 4- 3/16 | | 6-7/8 | 6-13/16 | 7-31/32 | 9- 3/4 | 4-1/2 | 4- 7/16 | | 7-1/4 | 7- 3/16 | 8-13/32 | 10- 1/4 | 4-3/4 | 4-11/16 | | | | | | | | | 7-5/8 | 7- 9/16 | 8-27/32 | 10-49/64 | 5 | 4-15/16 | | 8 | 7-15/16 | 9- 9/32 | 11-23/64 | 5-1/4 | 5- 3/16 | | 8-3/8 | 8- 5/16 | 9-23/32 | 11- 7/8 | 5-1/2 | 5- 7/16 | | 8-3/4 | 8-11/16 | 10- 5/32 | 12- 3/8 | 5-3/4 | 5-11/16 | | 9-1/8 | 9- 1/16 | 10-19/32 | 12-15/16 | 6 | 5-15/16 | |_________|__________|__________|__________|_________|_________| _____________________________________________________________ | | | BOLT HEADS. | |_____________________________________________________________| | | | | | | | | Short | Short | Long | Long | Thick- | Thick- | | Diam. | Diam. | Diam. | Diam. | ness | ness | | Rough. | Finish. | Rough. | Rough. | Rough. | Finish. | | | | | | | | | (Hex.) | (Hex.) | (Hex.) | (Square) | | | |_________|_________|__________|__________|_________|_________| | | | | | | | | 1/2 | 7/16 | 37/64 | 7/10 | 1/4 | 3/16 | | 19/32 | 17/32 | 11/16 | 10/12 | 19/64 | 1/4 | | 11/16 | 5/8 | 51/64 | 63/64 | 11/32 | 5/16 | | 25/32 | 23/32 | 9/16 | 1-7/64 | 25/64 | 3/8 | | 7/8 | 13/16 | 1 | 1-15/64 | 7/16 | 7/16 | | 31/32 | 29/32 | 1- 1/8 | 1-23/64 | 31/64 | 1/2 | | 1- 1/16 | 1 | 1- 7/32 | 1- 1/2 | 17/32 | 9/16 | | 1- 1/4 | 1- 3/16 | 1- 7/16 | 1-49/64 | 5/8 | 11/16 | | 1- 7/16 | 1- 3/8 | 1-21/32 | 2- 1/32 | 23/32 | 13/16 | | | | | | | | | 1- 5/8 | 1- 9/16 | 1- 7/8 | 2-19/64 | 13/16 | 15/16 | | 1-13/16 | 1- 3/4 | 2- 5/32 | 2- 7/16 | 29/32 | 1- 1/16 | | 2 | 1-15/16 | 2- 5/16 | 2-53/64 | 1 | 1- 3/16 | | 2- 3/16 | 2- 1/8 | 2-17/32 | 3- 3/32 | 1- 3/32 | 1- 5/16 | | 2- 3/8 | 2- 5/16 | 2- 3/4 | 3-23/64 | 1- 3/16 | 1- 7/16 | | 2- 9/16 | 2- 1/2 | 2-31/32 | 3- 5/8 | 1- 9/32 | 1- 9/16 | | 2- 3/4 | 2-11/16 | 3- 3/16 | 3-57/64 | 1- 3/8 | 1-11/16 | | 2-15/16 | 2- 7/8 | 3-13/32 | 4- 5/32 | 1-15/32 | 1-13/16 | | | | | | | | | 3- 1/8 | 3- 1/16 | 3- 5/8 | 4-27/64 | 1- 9/16 | 1-15/16 | | 3- 1/2 | 3- 7/16 | 4- 1/16 | 4-61/64 | 1- 3/4 | 2- 3/16 | | 3- 7/8 | 3-13/16 | 4- 1/2 | 5-31/64 | 1-15/16 | 2- 7/16 | | 4- 1/4 | 4- 3/16 | 4-29/32 | 6 | 2- 1/8 | 2-11/16 | | | | | | | | | 4- 5/8 | 4- 9/16 | 5- 3/8 | 6-17/32 | 2- 5/16 | 2-15/16 | | 5 | 4-15/16 | 5-13/16 | 7- 1/16 | 2- 1/2 | 3- 3/16 | | 5- 3/8 | 5- 5/16 | 6- 7/32 | 7-39/64 | 2-11/16 | 3- 7/16 | | 5- 3/4 | 5-11/16 | 6-21/32 | 8- 1/8 | 2- 7/8 | 3-11/16 | | | | | | | | | 6- 1/8 | 6- 1/16 | 7- 3/32 | 8-41/64 | 3- 1/16 | 3-15/16 | | 6- 1/2 | 6- 7/16 | 7- 9/16 | 9- 3/16 | 3- 1/4 | 4- 3/16 | | 6- 7/8 | 6-13/16 | 7-31/32 | 9- 3/4 | 3- 7/16 | 4- 7/16 | | 7- 1/4 | 7- 3/16 | 8-13/32 | 10- 1/4 | 3- 5/8 | 4-11/16 | | | | | | | | | 7- 5/8 | 7- 9/16 | 8-27/32 | 10-49/64 | 3-13/16 | 4-15/16 | | 8 | 7-15/16 | 9- 9/32 | 11-23/64 | 4 | 5- 3/16 | | 8- 3/8 | 8- 5/16 | 9-23/32 | 11- 7/8 | 4- 3/16 | 5- 7/16 | | 8- 3/4 | 8-11/16 | 10- 5/32 | 12- 3/8 | 4- 3/8 | 5-11/16 | | 9- 1/8 | 9- 1/16 | 10-19/32 | 12-15/16 4- 9/16 | 5-15/16 | |_________|_________|__________|__________|_________|_________|

The dimensions given for diameter at root of threads are also those for diameter of hole in nuts and diameter of lap drills. All bolts and studs 3/4 in. diameter and above, screwed into boilers, have 12 threads per inch, sharp thread, a taper of 1/16 in. per 1 inch; tap drill should be 9/64 in. less than normal diameter of bolts.

The table is based upon the following general formulæ for certain dimensions:

Short diam. rough nut or head = 11/2 diam. of bolt + 1/8. " finished nut or head = 11/2 diam. of bolt + 1/16. Thickness rough nut = diameter of bolt. Thickness finished nut = diameter of bolt - 1/16. Thickness rough head = 1/2 short diameter. Thickness finished head = diameter of bolt - 1/16.

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AN ENGLISH RAILWAY FERRY BOAT.

The illustrations above represent a double screw steam ferry boat for transporting railway carriages, vehicles, and passengers, etc., designed and constructed by Messrs. Edwards and Symes, of Cubitt Town, London. The hull is constructed of iron, and is of the following dimensions: Length 60 ft.; beam 16 ft.; over sponsons 25 ft. The vessel was fitted with a propeller, rudder, and steering gear at each end, to enable it to run in either direction without having to turn around. The boat was designed for the purpose of working the train service across the bay of San Juan, in the island of Puerto Rico, and for this purpose a single line of steel rails, of meter gauge, is laid along the center of the deck, and also along the hinged platforms at each end. In the engraving these platforms are shown, one hoisted up, and the other lowered to the level of the deck. When the boat is at one of the landing stages, the platform is lowered to the level of the rails on the pier, and the carriages and trucks are run on to the deck by means of the small hauling engine, which works an endless chain running the whole length of the deck. The trucks, etc., being on board, the platform is raised by means of two compact hand winches worked by worm and worm-wheels in the positions shown; thus these two platforms form the end bulwarks to the boat when crossing the bay. On arriving at the opposite shore the operation is repeated, the other platform is lowered, and the hauling engine runs the trucks, etc., on to the shore. With a load of 25 tons the draught is 4 ft.

The seats shown on the deck are for the convenience of foot passengers, and the whole of the deck is protected from the sun of that tropical climate by a canvas awning. The steering of the vessel is effected from the bridge at the center, which extends from side to side of the vessel, and there are two steering wheels with independent steering gear for each end, with locking gear for the forward rudder when in motion. The man at the wheel communicates with the engineer by means of a speaking tube at the wheel. There is a small deck house for the use of deck stores, on one side of which is the entrance to the engine room. The cross battens, shown between the rails, are for the purpose of horse traffic, when horses are used for hauling the trucks, or for ordinary carts or wagons. The plan below deck shows the arrangement of the bulkheads, with a small windlass at each end for lifting the anchors, and a small hatch at each side for entrance to these compartments. The central compartment contains the machinery, which consists of a pair of compound surface condensing engines, with cylinders 11 in. and 20 in. in diameter; the shafting running the whole length of the vessel, with a propeller at each end. Steam is generated in a steel boiler of locomotive form, so arranged that the funnel passes through the deck at the side of the vessel; and it is designed for a working pressure of 100 lb. per square inch. This boiler also supplies steam for the small hauling engine fixed on the bulkhead. Light to this compartment is obtained by means of large side scuttles along each side of the boat and glass deck lights, and the iron grating at the entrance near the deck house. This boat was constructed in six pieces for shipment, and the whole put together in the builders' yard. The machinery was fixed, and the engine driven by steam from its own boiler, then the whole was marked and taken asunder, and shipped to the West Indies, where it was put together and found to answer the purpose intended.--_Engineering._

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[For THE SCIENTIFIC AMERICAN.]

THE PROBLEM OF FLIGHT, AND THE FLYING MACHINE.

As a result of reading the various communications to the SCIENTIFIC AMERICAN and SUPPLEMENT, and _Van Nostrand's Engineering Magazine_, including descriptions of proposed and tested machines, and the reports of the British Aeronautical Society, the writer of the following concludes:

That, as precedents for the construction of a successful flying machine, the investigation of some species of birds as a base of the principles of all is correct only in connection with the species and habits of the bird; that the _general mechanical principles_ of flight applicable to the _operation_ of the _same unit_ of wing in _all_ species are alone applicable to the flying machine.

That these principles of _operation_ do not demand the principles of _construction_ of the bird.

That as the wing is in its stroke an arc of a screw propeller's operation, and in its angle a screw propeller blade, its animal operation compels its reciprocation instead of rotation.

That the swifter the wing beat, the more efficient its effect per unit of surface, the greater the load carried, and the swifter the flight.

That the screw action being, in full flight, that of a screw propeller whose axis of rotation forms a slight angle with the vertical, the distance of flight per virtual "revolution" of "screw" wing far exceeds the pitch distance of said "screw."

That consequently a bird's flight answers to an iceboat close hauled; the wing _force_ answering to the _wind_, the wing _angle_ to the _sail_, the bird's _weight_ to the leeway fulcrum of the _ice_, and the passage across direction of the _wing_ flop to the fresh _moving_ "inertia" of the wind, both yielding a maximum of force to bird or iceboat.

That the speed of _reciprocation_ of a fly's _wing_ being equivalent to a _screw rotation_ of 9,000 per minute, proves that a _screw_ may be run at this speed without losing efficiency by centrifugal vacuum.

That as the _object_ of wing or screw is to mount upon the inertia of the particles of a mobile fluid, and as the rotation of steamship propellers in water--a fluid of many times the inertia of air--is _already_ in _excess_ of the highest speed heretofore tried in the propellers of moderately successful flying machines, it is plain that the speed employed in _water_ must be many times exceeded in _air_.

That with a _sufficient_ speed of rotation, the supporting power of the inertia of air must _equal_ that of _water_.

That as mere speed of rotation of propeller _shaft_, minus blades, must absorb but a small proportion of power of engine, the addition of blades will not cause more resistance than that actually encountered from inertia of air.

That this must be the measure of load lifted.

That without _slip_ of screw, the actual _power_ expended, will be little in _excess_ of that required to support the machine in _water_, with a slower rotation of screw.

That in case the same _power_ is expended in water or air, the only difference will lie in the sizes and speed of engines or screws.

That the _greater_ the speed, the _less_ weight of engine, boiler, and screw must be, and the stronger their construction.

That, in consequence, solid metal worked down, instead of bolts and truss work, must be used.