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article number 690
article date 11-09-2017
copyright 2017 by Author else SaltOfAmerica
Our Technology, 1922 - Part 1: Bridge, Pier and Concrete Construction Methods and Equipment
by Various Popular Science Magazine Writers

From issues of Popular Science Monthly, 1922.

* * *

California Has Unique Bridge with 142-Foot Concrete Girders

A BRIDGE crossing the Salt River in California has perhaps nabbed the record for the longest stretch of concrete girders between supports, with its measurement of 142 feet between the centers. The girder type of bridge was constructed at this point because of the greater clearance and lower cost, also because the salt fogs coming from the Pacific in this region would destroy steel construction.

Each span consists of two girders twelve feet in depth. These girders carry floor-beams at twenty-inch intervals, and between the floor-beams five inches of concrete is carried on nine by twenty inch reenforced concrete stringers. These stringers are placed at the third point of the floor-beams.

The under construction of the bridge showing floor-beams and stringers.

Main sections of the girder are seven inches thick and enlarge to twenty-four inches at the top and eighteen inches at the bottom. Pilasters opposite the floor-beams step up to a maximum width of thirty inches, with a thickness of eighteen inches.

The steel is continuous over the center pier and no expansion joint is provided there.

The bridge as viewed from a distance. After the forms were set, it required but eight days to pour all the concrete for the entire structure.

Trenching Machine Digs to Exact Level

THIS MINIATURE TRENCHING machine excavates the ground to the exact depth required, permitting the forms for concrete roads to be set accurately to the specified grade in about one tenth of the time required when the work is done by pick and shovel.

The grader is designed to excavate a trench eight inches wide.

It has been designed to avoid loosening the dirt below the point at which the bottom of the form should rest, since if the form is set on an unstable foundation, it sinks when the concrete is spread, making the surface of the finished road uneven.

A five-horsepower gasoline engine drives a cut-steel sprocket by a roller chain that has an automatic spring idler chain take up.

Four digger blades of tempered tool steel are moved down as they wear so that sharpening is unnecessary.

The cutter is raised or lowered by turning the automobile type steering-wheel. To cut exactly to grade, a guide-line is stretched one foot out from and one foot above the place for the bottom of the form.

As long as a gage-point on the grader is kept level with the grade line, the cutter will excavate to exactly the required depth. Thus, by raising and lowering the cutter, the bottom of the small trench is cut accurately to grade regardless of irregularities in the surface over which the machine travels.

The digger excavates from three hundred to seven hundred feet of trench an hour.

This trenching machine will cut a ditch to exact depth in one tenth time required by hand labor.

This trenching machine will cut a ditch to exact depth.

Outfit Equals Steam Shovel and Fifteen Men

OF practical size and suitable for the vast majority of contracting jobs, a gasoline “steam-shovel” is shown constructing a logging railway. The shovel is gasoline propelled and operated. The scoop capacity is one half cubic yard, and the gas consumption thirty gallons a day.

An air-compressor is run in conjunction with the shovel if air is needed for drilling holes for blasts, and caterpillar traction has been adopted to enable the shovel to travel over rough ground and to obviate the necessity of track-laying. These two improvements, the operators claim, enable the gasoline shovel to do the work of a steam-shovel with a crew of fifteen men.

Gasoline “steam-shovel.”

Lifting Magnet Especially Adapted to Flat Sheets

FLAT steel sheets and ship’s plating are being handled by a specially constructed lifting magnet in the yards of a Chicago steel company. The principle is a familiar one in the unloading of pig iron and small steel articles, and by making the magnet long and flat the same efficient stowage is obtained for large plates.

Large plates have always been awkward to handle, but with the new device, only one man is needed on the ground, and he merely guides the shapes into place.

Lifting Magnet for flat steel plates. © Ewing Galloway.

Monster Earth-Devouring Machine Digs and Lines Tunnels as It Creeps

- While Motor Driven Teeth Eat into the Ground, Automatic Masonry Layer Builds Conduits

PICTURE a giant, motor-driven bit that not only bores a clean hole through earth and rock, disposing of the debris, but simultaneously lines the walls of the tube with masonry as it creeps along, and you comprehend the possibilities of a new automatic tunneling machine invented by M. Roy Sheen, of Philadelphia, Pa.

In comparison, pick-and-shovel methods of open-cut and underground tunnel work appear crude; for the new machine completes the digging of a tunnel, the removal of the earth, and the bracing of the walls in a single operation!

In a recent test performance on a construction job in Philadelphia, one of the machines completed 18 feet 8 inches of tunnel, 52 inches in diameter, in four hours running.

The best run for one hour was five feet eight inches of finished tunnel. This boring was through schist rock; if the tunneling had been through earth or clay, undoubtedly the machine could have moved with much greater rapidity.

- Masonry Layer is Automatic

The only hand excavation necessary is the cutting of an opening large and deep enough to lower the machine to the depth desired for the tunnel.

Once its motor is started, the machine does all the work underground without breaking the surface. No back-fill and no bracing, forms, or shoring are required.

These advantages are obtained by a cutting head that eats into earth, clay, or soft rock, and a special masonry layer that automatically places a concrete block lining as the head moves forward.

It follows that the complete machine has three working sections—the cutting head, the earth conveyor, and the helical lining constructor.

The cut-away view above reveals the operation of the automatic tunneling machine that, like a huge bit, bores its way through earth and rock, simultaneously disposing of its “shavings” and building a concrete lining for the tube as it advances.

The cutting head consists of a steel drum with four revolving knives that loosen and scrape away the earth from the heading. Buckets attached to the arms collect the earth and throw it onto a belt conveyor, which in turn carries the earth to the rear and dumps it into cars. The cars run back through the finished tunnel to the shaft opening, where the excavated material is disposed of in the most convenient manner.

A 15-horsepower electric motor rotates the cutters and drives the conveying belt. In addition to this motion, the center of the cut may be shifted in any direction by the operation of hand wheels connected with adjustable eccentric cams that work against the outside of a set of movable teeth fitted on each of the revolving arms. Thus the course of the excavation may be changed.

The line of the tunnel is directed by indicators and sightings taken by a surveyor’s transit in the rear of the boring. A dial at the rear of the cams indicates the changes of direction, enabling the operator to take correct readings of the location of the cut made by the rotating knives.

Four guide fins on the outside of the shell keep the machine on its course, and prevent it from tilting.

Directly behind the excavating drum is a helical tunnel-lining constructor. This is propelled by a roller bearing consisting of an endless chain of trucks secured together by ball-and-socket joints. The bearing is placed against the last block of the masonry lining. The pressure exerted by the caterpillar rollers against the block causes the forward motion of the cylinder, and forces the cutters against the heading.

As the machine advances, specially modeled, dovetailing concrete blocks are laid in a spiral course, either dry or in mortar. The hexagonal blocks are so proportioned that when they are pushed into place an expansion occurs until they fit snugly against the surrounding undisturbed earth as if they were an integral part of it. Thus the masonry at once becomes a brace.

The shape and interlocking feature of the blocks produce a conduit with a perfect arch lining, it is claimed, so that cave-ins and settling virtually are impossible.

Hexagonal concrete blocks, interlocking, are laid as the machine advances, to produce a conduit with perfect arch action. The blocks are designed so that when they are pushed into place an expansion occurs that forces the tunnel lining tightly against the outer earth.

- Labor Costs Reduced

The advantages of the new machine are emphasized by a comparison of its work with the digging methods now in common use. The open-cut method requires the digging of a ditch and the piling up of excavated material near by for replacement.

Side bracing must be installed to prevent cave-ins. In busy sections of a city this method means interruption of traffic, as well as costly replacement of surface.

The tunneling machine meets all these requirements automatically as it cuts its way; and in addition it cuts down labor costs. On the Philadelphia construction job, the test machine required only two experienced men to handle it.

Two common laborers took charge of the concrete blocks and earth in the tunnel, and three others unloaded the earth and sent in the blocks.

One engineer operated the gasoline-electric generating plant at the tunnel entrance by hand work.

This view through a tube constructed by the new tunneling machine shows the solid walls of masonry laid by the machine. In the background is a car receiving its load of earth from the automatic conveyor.

Rotary Machine Casts Concrete Shapes

SOLID concrete shapes can be successfully cast on a new centrifugal machine that will turn out four blocks every 60 seconds. A revolving table carries hollow molds into which concrete is fed by centrifugal action through a central orifice.

Excess water is squeezed out by centrifugal force during the spinning. The amount of water in the finished product may be governed by regulating the speed of rotation.

Hollow articles may be cast by placing cores in the mold. Similarly, the blocks may be reenforced by wires stretched across the interior. In both cases the concrete tends to pack solidly about the obstruction.

Filling the molds is completed in from 30 to 60 seconds. The mold is then opened along its bottom, and the shape falls on an endless belt, which carries it to the drying stacks.

When the shape is cast, there is usually a finlike projection from the mold into the central chamber. A cutter sliding up and down the walls of the feed-chamber removes this from the completed shape.

Rotary Concrete Casting Machine Layout.

Williamsburg Bridge Cables Dressed in New Suit of Wires

Photographs below © American Photo Service.

* * *

Before the four weather-beaten cables of the Williamsburg Bridge over the East River could be wrapped with wire for protection from rust, it was necessary to build a 2800-foot stairway scaffold along the entire length of each cable.
The picture shows workmen squeezing up the cable wires preparatory to wrapping them. Nine thousand parallel wires in each cable were put under 15 tons pressure before they were wound with outer wire.
An electric winding machine was used to bind the cables with soft steel wire an eighth of an inch in diameter and 970 miles long.
This photograph of one of the eight bridge anchors shows the manner in which the cables are attached to the concrete abutments.

Motor-Driven Drop-Hammers Used in Large Factories

THE individual motor-drive has been applied recently to board drop-hammers in large industrial plants. The hammers range from 300 to 2500 pounds in weight.

Each installation consists of two towers, one containing the hammer mechanism proper, while the other supports a 15-horsepower, 800-revolutions a minute induction motor, directly coupled to a shaft carrying one loose and one keyed pinion, with a flywheel at the extreme end to take the initial peak load off the motor when the hammer is drawn up.

The keyed pinion engages two beveled gears, which are directly connected to two pulley-wheels. The loose pinion simply acts as a spacer on the opposite side of the gears.

This arrangement causes the two pulleys to revolve in opposite directions. They are belted to a third pulley driving the shafts of the rollers that raise the hammer when they are forced together. The total speed-reduction is 8:1.

The motor runs continuously. The hammer is operated by a treadle control that separates the rollers and lets the hammer fall.

Motor Driven Drop-Hammer.

Hudson Bridge Presents New Engineering Problems

By: Gustav Lindenthal, designer of the Hell Gate bridge and consulting engineer of the Hudson River bridge project.

THE largest work in bridge construction ever undertaken will see its birth in 1922. This will be the giant bridge over the Hudson River to connect New York City with New Jersey. Its completion will require five years.

The bridge will be only a part of a gigantic scheme of construction which will include a large union railroad station on each side of the Hudson river.

Engineering science must solve in this project new problems of very deep foundations, of erection of very high steel towers and chains of steel eye-bars that will carry a double platform with 12 railroad tracks on one deck and a wide roadway with surface tracks and promenades, in all 235 feet wide, on the up deck of the structure.

Artist’s depiction of completed Hudson Bridge.

Thousand Tons of Rails Test Strength of Concrete Piers

A THOUSAND tons of steel rails were piled upon a concrete pier in Chicago recently, to determine whether piers extending only to a layer of hardpan, and designed for a four-story building, would support the weight of a 16-story structure on the site of the Chicago Union Station.

The soil at this point is composed of 65 feet of soft earth over an eight-foot layer tf hardpan. Beneath the hard pan a second layer of soft clay and sand is encountered before rock is reached. The tests were conducted to avoid, if possible, the expense of excavating to bedrock, and to find h,w many additional piers would be required to support the 12 additional stories.

- Tremendous Weight Applied

To conduct the test successfully it was necessary to apply a tremendous weight, and at the same time to install very sensitive measuring apparatus to register the exact distance the pier sank as the weight was piled upon it. The top of the concrete column was protected by a steel casting. On this was set a hydraulic jack, through which pressure could be applied. The rails served as a dead weight to bear the upward thrust of the jack, and did not rest upon the head of the pier.

The jack used is the largest of its type ever constructed. It will lift 1000 tons when the water pressure on the ram is 6000 pounds to the square inch. To register the effect on the pier, a special inclined draft level, filled with gasoline because of the cold, was set up directly on the concrete head. This gage is so sensitive that it registered the passing of a trolley car over the Adams Street bridge, fully 100 feet away.

The test revealed that the pier settled .18 inch under a pressure of 680 tons, and sank an additional .09 inch when the weight was increased to 1000 tons. When pressure was removed, the pier rose .26 inch. The settling, represents the elasticity of the hardpan.

How the tremendous weight was applied to the concrete pier and bell-shaped footing through a 1000-ton hydraulic jack is described in the cut - away view above.

Concrete River Wall Poured into Portable Steel Forms

By the use of a flexible system of steel forms for placing concrete under water, a great saving in time was effected in building a concrete coffer dam at the Buffalo Terminal of the New York state barge canal. The new method was developed by Frank C. Hibbard, of Buffalo, New York.

Instead of the tedious and expensive process of driving sheet piling, then pumping out the water behind it, and erecting wooden concrete forms, huge steel forms were prepared in units 40 feet high and 20 feet long.

Each unit consisted of a rigid frame, strengthened with trusses both vertically and horizontally, from which the wooden forms for the front and back of the concrete wall were suspended and supported by means of screw-jacks.

The two forms, front and back, were lowered into the water by a 60-ton derrick, and the concrete was poured under water.

After the mud and silt had been dredged from the rock bottom of the river, the huge steel forms were lowered by a 60-ton derrick, as pictured above.

To make the bottom of the form conform to the irregularities of the bed rock, a lower wooden section was sawed to fit the rock bottom as its irregularities were ascertained by divers and a series of accurate soundings.

Before placing the forms, the mud and silt lying above the rock bottom of the river was removed by clamshell dredges. The surface of the rock was then cleaned by divers, who played high-pressure water-jets on it until the last trace of mud was washed away.

Soundings were made at each corner of the form, and four adjustable posts attached to the steel framework were set at the correct height by passing bolts through a series of holes in the frame.

A raft was next anchored in place, and a second series of soundings taken with a gage pole. The depth was measured along every foot of the outer surf ace of the forms.

The soundings were then transferred to the wooden planks on the bottom of the form by measuring from the lower edge of the steel plates and driving in nails at the proper point. Finally, the planks were sawed along these points.

“Well” holes 30 inches in diameter were left in each section so that the concrete could be tested.

One of the form units, front and back. Each unit consisted of a rigid frame supported by trusses, vertically and horizontally.

Self-Loading Screw Conveyor Handles Thirty Tons an Hour

A PORTABLE screw conveyor, driven by an electric or gasoline motor, has recently been adopted for mechanical loading where only small volumes of material are handled. Because of the small amount of headroom required, the device is especially useful for indoor work.

An essential feature of the invention is the large screw-head that bores into the pile of material to be moved, breaks up all lumps, and prepares the earth for the conveyor. The screw conveyor, placed in an inclined position, is turned like the cutting head, by a motor at the upper end of the conveyor trough.

The lower end of the machine is mounted on wheels, and the entire mechanism swings around a movable pivot at the upper end of the conveyor trough. This arrangement makes it possible to reach a large section-shaped floor area with the loader.

The capacity of the device is 30 tons an hour.

Boring into a pile of earth, the screw-head breaks up lumps and carries the material to the screw conveyor. The motor driven mechanism swings on a pivot.

This Truck Mixes Concrete on the Way to Work

CONCRETE-MIXER mounted on a motor-truck chassis in place of the truck body is an interesting development by a Middle Western manufacturer. The ordinary batch body with its hoist is replaced by a specially constructed frame fastening on to the chassis and supporting a rotably mounted concrete mixing-drum.

Power to operate the drum is derived from the truck motor through a power take-off.

The charge is put in the drum from measuring-bins at the road-builder’s yard and the batch is mixed while the truck is on the way to the place where construction is going on. Mixing is usually completed on the final stretch, just before discharging, but the drum may be rotated at any truck speed either forward or reverse or when standing still.

The mixed batch of concrete is discharged by gravity into a chute delivering the material to the rear of the truck and as the truck moves forward the chute spreads the concrete so that only a small amount of hand spreading is necessary

Concrete is mixed in the rotary drum driven by the truck motor.

Steam Shovel-Pile Driver Removes Pavement

BY converting a steam shovel into a pile driver, a street railway company in Detroit, Mich., improvised a method of removing a heavy concrete pavement from its right of way with a minimum of time and expense.

A framework of steel rails, about 18 feet high, was bolted together and attached vertically to the derrick boom of the shovel. A sliding weight was arranged to move up and down inside this frame, lifted by a wire cable that had been disconnected from the shovel, yet was operated by the shovel winch.

A “war nose” was fitted to the bottom of the sliding weight, and this shattered the concrete into pieces so small they could readily be removed with a shovel.

The steam shovel moved along under its own power, since by raising the boom slightly, the improvised pile-driver frame could be lifted clear off the ground.

Steam Shovel-Pile Driver shatters concrete.

Steam Hammer Pulls Pile from Frozen Ground

PULLING a 20-foot pile out of the ground with a steam hammer was the task accomplished recently by a contractor of Detroit, Mich., when the usual method of pile removing had failed.

After the derrick had proved itself powerless to budge the pile, the steam hammer was reversed, so that it struck upward. A three-quarter-inch steel cable was passed around it four times. This cable also passed through a U-bolt attached to the pile, and the derrick was fastened to a sling threaded through the head of the hammer.

With the derrick pulling full force, the hammer delivered several short, quick blows on the tightened cable. The pile was raised several inches. This broke the grip of the frozen ground, and the pile was then removed by the derrick alone.

Steam Hammer rig with U-bolt attached to the pile.

Bucket Loader Now Does the Shoveling

SHOVELS are almost unnecessary tools for the contractor who makes use of a new industrial loader that employs the bucket principle in filling wheelbarrows or wagons with crushed stone or other loose material.

The machine is designed primarily for road-building and concrete construction work, and consists of a sloping framework eight feet wide, up which travel four bucket conveyors. These pick up the material and drop it into bins, from which it is distributed by gravity.

Double capacity from the concrete mixer wherever the new machine is in use, is claimed by its inventors.

A gasoline engine runs the conveyors at any desired speed, and also moves the loader itself along the road fast enough to keep pace with the other equipment. One man controls the loader, and the adjustments include a method of raising or lowering the elevator buckets to conform to any unevenness in the ground.

Bucket Loader designed primarily for road-building and concrete construction work.

Engineers Hang 500-Foot Bridge in 13 Hours!

- Every Beam and Cable, Cut in Advance, Fits to the Fraction of an Inch as Long Suspension Structure Is Assembled

ERECTING in 13 working hours a 500-foot suspension bridge across the Willamette River, at Oregon City, Ore., engineers of the Oregon State Highway Bridge Service recently gave an amazing demonstration of the construction speeds now obtainable as a result of modern methods of preliminary mathematical calculation.

Every beam, cable, hanger, and plank in the entire structure was cut to the exact size and laid out on the river bank before any actual building was attempted. Because every element in the complicated structure fitted to the fraction of an inch, the building was accomplished almost as quickly as an automobile can be assembled.

- A Temporary Structure

Speed in the work was necessary because an old suspension bridge, built across the Willamette in 1888, was to be taken down and replaced by a new arch viaduct, and it was necessary to build a temporary footbridge to allow hundreds of people to cross the river to their work. Traffic could not be suspended, even for a day, and it was also necessary to avoid interference with navigation on the river.

The first step in building the temporary bridge was to frame the towers. On each bank of the river six piles, each 90 feet long, were laid horizontally and bolted together. Emplacements — consisting of substantial timber footings embedded on solid rock — were prepared, and the towers, hoisted in place by a floating derrick, were braced and guyed. The instant this was accomplished, two gangs of men set to work, one gang erecting the approaches while the second swung the suspension span.

Two parallel wire cables, each composed of four one-inch ropes, were passed across the river and over the towers, then fastened to anchorages.

Two men then climbed to the top of each tower, placed a plank across the cables, and took their positions at the ends of the plank, each man straddling one of the cables. To these men were handed the hangers, or vertical ropes with which the roadway was to be hung to the cables. The hangers had already been cut to the correct length and fitted with clamps ready to attach to the cables.

The bridge during construction, showing floor beams being suspended from the two main cables by hangers of carefully calculated length.

The workmen moved out along the bridge, fastening the hangers as they went, while a second crew of two men following, laid the framework and spiked down a temporary roadway as fast as the hangers were fixed.

In constructing the roadway, each floor beam was suspended from two opposite hangers by slipping each end into a U bolt already clamped to the lower end of each hanger. To the beams, spaced at equal distances by a space gage, four 2 by 12 inch planks were spiked lightly.

This process was repeated in suspending and planking each of the 48 floor beams, providing a temporary footway across the bridge by which material could be carried out as the construction proceeded.

In the meantime the framed approaches to the bridge were being bolted into place, all the wooden truss members having been shaped previously. The crew that followed the men laying the floor beams, put down the permanent deck. As a result of this concerted effort, the bridge was opened to the public without any interruption of traffic.

The details of the construction offer an interesting example of the engineering design of a temporary structure. This bridge is not intended to remain in service more than a year — hence the extensive use of wood, especially in the towers.

- Bridge Holds 500 Persons

The span is for pedestrian traffic only, and is planned to carry a maximum live load of 500 persons at 160 pounds each — that is, about as many people as could crowd upon the bridge. It is built with a factor of safety enabling it to support three times the maximum load.

For example, each of the eight strands in the main cables will withstand a tension of 58 tons. The combined weight of the bridge and its maximum live load will produce a total tension of 160 tons in the cables. Dividing by eight, each strand need carry only 20 tons — about a third of its safe working load.

The main span is 496 feet between towers, with a navigational clearance of 75 feet at low water. Each of the 48 hangers is of six-strand flow steel cable with hemp centers. Since these must often bear heavy loads for a few seconds at a time, the factor of safety is raised to five.

The stiffening truss is of laminated timbers, and is 10 feet wide by 10 feet high. All joints are bolted and spiked.

To maintain street clearance under the approaches, the angles of approach vary from a grade of 20 per cent on one side of the river to 14 per cent on the other. While this might not be tolerated for a permanent bridge, the variance is of no consequence for this temporary structure.

This and the other tower were framed on the ground and hoisted into position. Above is the completed bridge.

Submarine Torch Saves Cities from Water Famine

- Divers Mend Great Main with Electric Burners in 53 Feet of Water

WORKING desperately in six-hour shifts, in the murky depths of New York harbor, three divers, using a newly designed oxyelectric torch to repair a broken cast-iron water main, recently saved 110,000 residents of Staten Island from a serious water famine.

In the gloom and muck of the river bottom, where the pipe lay buried in 26 feet of mud, the (livers, with steadily flaming torches, cut through 30 feet of metal from 1 5/8 to 3 1/2 inches thick, removed a broken section of pipe 12 feet long, and replaced it with a new section, relieving a serious situation in a third of the time that would have been required by sawing and cutting with pneumatic tools.

The broken main is a siphon made up of flexibly jointed 12-foot sections crossing the harbor at the Narrows between Long Island and the Borough of Richmond. It was broken by a harbor dredge that dropped its spud, or vertical anchoring pile, on or near the pipe, knocking a hole in one section.

With the flames of their oxyelectric torches blazing steadily in 53 feet of water, three divers swiftly cut out and removed a 12-foot section of cast-iron water main in the manner shown above.

- Tons of Mud Dredged Away

To permit the divers to work on the break, 26 feet of mud covering the pipe was dredged away. It was then necessary to remove the broken section under 53 feet of water, without disturbing adjoining lengths.

The divers worked simultaneously at three points. First they completely severed an adjoining pipe length. To cut the joint at the other end of the cracked section they were forced to cut away the upper sector of a bell, or flare, 3 1/2 inches thick.

Before they could reach this bell, they found it necessary to make two cuts and release an encircling wrought-iron band 1 1/2 inches thick and four inches wide.

Then to cut the lower portion of the pipe, a diver crawled inside the main, which he could enter only after the fracture had been enlarged.

In the face of these difficulties, the efficiency of the new torch made it possible to complete the cutting in nine working days.

The broken pipe section after its removal. A diver is demonstrating the use of the electric torch for outside cuts.

Once the cracked section was cut loose and removed, the repair was completed by lowering a new section into place, and making the joint watertight by packing it with lead wool — also a new invention. To hold the new section firmly, encircling steel collars were placed over the bell ends and drawn together by long, threaded bolts.

Cutting cast iron under water is a new achievement. W. E. Kirk and R. E. Chapman, of New York City, had worked for several years on a torch for this purpose.

Their invention was inspired by underwater cutting torches invented in Germany, which, while unsuccessful, had proved that an oxyacetylene torch, when equipped with a bell-shaped shield over the burner, would burn under water if it was ignited at the surface and carried below in a position permitting expanding gases in the bell to force the water out of and away from the flame.

However, if the position of the mouth of the bell allowed the water to enter, or if the pressure was not great enough to keep the water back, the torch was extinguished and it was necessary to carry it to the surface to be relighted.

By a radical change in design, Kirk and Chapman devised a torch that could be lighted under water. The unstable acetylene was eliminated and the electrical features of the torch became the principal rather than a subsidiary part of the apparatus.

In cutting, the metal is fused by an electric arc, and then cut by a blast of “cutting gas.”

Layout of Kirk and Chapman oxyelectric torch.

This flame is hot enough to turn water into steam, creating a zone of vapor within which the electric are does its work. Inside the bell there is a carbon electrode through which pass two small brass tubes that feed the cutting gas at the point of the arc.

The gas is supplied from the surface by a hose, within which are the electrical connections. One wire goes to the carbon electrode and the other side of the electric current supply is connected with the work to be cut.

- How the Torch Is Lighted

To light the torch, the diver simply touches the tip of the electrode to the work, then draws it back about a quarter of an inch. The arc invariably results. To stop cutting, the electrode is drawn beyond the arcing range. The temperature of the electric arc is nearly twice that of any oxyacetylene flame.

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