The design of vaults and strong rooms to withstand earthquake, fire, explosion, or the scientific methods of burglary has demanded all the skill and ingenuity of the engineer

CIRCULAR EMERGENCY DOOR of a modern safe deposit. A manhole door of this type is provided as a means of access or egress if anything should interfere with the mechanism of the main door. The emergency door is built of a strength proportionate to that of the main door and is equipped with the same type of combination and time locks. It also plays an important part in the ventilation system of the vault, which is airtight when the doors are shut.

FEW things which man builds to-day have undergone such a transformation within recent years as safe deposits, those great chambers of steel with their doors of massive proportion, specially designed for the safe keeping of all kinds of valuables against loss and theft.

Safe deposits are found, as a rule, in the basements of public buildings. The vault is built of specially hardened steel, absolutely undrillable, resembling in design a huge steel box. Except for openings for the doors, the great chamber is entirely embedded, top, bottom and sides, in a bed of concrete reinforced with steel rods. The doors may be of the rectangular or circular type, 20-in to 36-in thick, and weighing from 20 to 40 tons.

Some of the latest American safe deposits have doors weighing between 80 and 90 tons. They are fitted with from twelve to twenty-four round bolts, each weighing 100 lb. There are no keys to the doors, their opening and closing being controlled by combination and time locks. There is invariably a passage about three feet wide running right round the vault, which is patrolled at night by an armed guard. The builders of these vaults claim that they are much more than burglar-proof, for they cannot be opened even when explosives are rained upon them. They are able to withstand mob force, burglars’ attack, flood and fire, earthquake, structural collapse, and even a possible bombardment by some enemy.

The evolution of the safe deposit is the story of the struggle between the safe-maker and the safe-breaker. Scarcely more than a hundred years ago man placed his treasures for safe keeping in great oak boxes, clamped with iron and provided with formidable clasps and locks. It was not long before man’s faith in strong boxes of oak was rudely shattered by the ease with which the burglar of those days opened them with a fine saw and chisel. Then came strong rooms built of bricks, followed by still more substantial receptacles built of hard Staffordshire blue bricks laid in cement. The openings into these chambers were closed by massive iron doors with heavy bolts and locks. But the burglar got through them.

To make the vault absolutely burglar-proof, as they thought, the vault-makers built the entire room of steel, the opening consisting of a double door having two locks, double hinges and many other ingenious contrivances calculated to daunt the most persevering thief. Special steel plates were made, of great hardness and toughness. This was to resist the vastly improved drills and jemmy of the burglar. Then burglars at once called science to their aid, and showed how they could attack and beat down the defence by a small pinch of nitroglycerine ingeniously applied and carefully exploded. The vault-maker turned his attention to ordinary armour plate, and built his strong rooms of this material. Yet again the burglar was successful. He produced a new cutting tool, by which the metal was penetrated.

CAST STEEL TREASURY DOOR of the London Safe Deposit. The door and frame are covered with stainless steel, relieved with bronze. The hinge and clenching gear are of polished steel. The door weighs 30 tons and is 33½-in thick; its clear opening measures 7 feet by 3 ft 3-in.

Here was the problem: how to produce something that was proof against dynamite or nitro-glycerine, the blowpipe and the extreme heat set up by the electric arc or material of the character of thermite. But the safe-maker was not discouraged. He recognized it was a question of increasing the strength and resisting power of his metal. He surmounted the difficulty by hardening his plates, producing an alloy and casting his doors and plates in one solid piece. The new material is absolutely undrillable. To make any impression upon it, the same heat must be applied as that in which it was cast. As the walls are cast in one piece there are no joints which can be forced.

The act of closing the door releases an automatic mechanism which carries the locking bolts into the locked positions, and there they stay until the expiration of a predetermined time. Then the time lock releases the automatic mechanism, which, in turn, withdraws the bolts, all without any assistance from outside the vault. In addition to the time lock there is also the combination lock, which makes it impossible to open the door unless the combination is known.

As a further precaution many safe deposits are so designed that an electric alarm is sounded should an attack be made anywhere upon the vault, or else the basement containing the safe deposit is flooded with water the moment the mechanism is tampered with. Some of the devices in the more recent American safe deposits are most ingenious. Should an attack be made upon the vaults, tear gas is let loose and at the same time the nearest police station is automatically, signalled by telephone.

One of the latest safe deposits in London is the London Safe Deposit, in Regent Street. Although situated in the basement of a public building, it is an entirely independent structural unit. Before work could be begun the London clay was excavated to a depth of 37 feet. Then came the building of the shell, or outer casing, which envelops the steel vault or safe deposit proper. This outer covering consists of concrete, several feet thick, reinforced with special steel bars. Forming what is in reality a lining to it is the steel vault, built of sheets of a toughened steel which is undrillable.

Emergency Bolt-Securing Device

Fob all practical purposes the huge steel chamber is one solid piece of metal. Before a would-be burglar could reach this steel-lined vault he would have to penetrate the bed of concrete with its tangled mattress of steel bars, whether he approached the vault from above or below, or from the guard passage that runs round it. In the modern safe deposit, walls, floor, and roof offer equal resistance against attack as the door itself. The vault builder works on the principle that the strength of a chain is the strength of its weakest link.

The main entrance door to this stronghold is of the rectangular type, 6½ feet high, 3½ feet wide and over 2 feet thick. It throws sixteen round bolts weighing about 100 lb each, and weighs over 20 tons. The door, apart from its mechanism, was cast in one solid piece. It is equipped with the most modern keyless combination and time locks. There is also an emergency bolt-securing device, an interesting but valuable innovation. In the event of an attack upon the locks, either by blowpipe or by explosives, the securing device would immediately come into action, making the bolts of the door effectively secure irrespective of the usual locks.

There is also a small manhole door for use in emergency. Proportionately it is as massive and strong as the main door. Emergency doors of this type play an important part in the ventilation of the vaults. When the doors are closed the vaults are airtight. There are several methods of ventilating vaults. The usual method is by a ventilating gate or shaft connected to the entrance door; the gate comes into operation only when that door is opened. Then by ventilating fans attached to the emergency doors a current of air is made to pass through the chamber.

MAIN ENTRANCE DOOR to a modern safe deposit, with the emergency entrance to the right. The main door is built up in steps and weighs 26 tons. It is 6 ft 6-in high, 3 ft 3-in wide and throws sixteen round bolts. The bolts and the lock fittings alone weigh 5 tons. The electric buttons on the wall at the left raise and lower the gangway which leads across the steps of the entrance.

The safe deposit at Regent Street is divided into four sections - the treasury, the annexe with its grille divisions, the strong rooms and the storage accommodation. The treasury is an attractive hall the metal of which it is composed being of polished stainless steel illuminated by concealed electric lighting. It contains 1,520 receptacle safes of various sizes arranged in batteries.

A most up-to-date system of electrical and other burglar alarms has been installed. All over the safe deposit are bolts, a pressure upon which sets bells ringing in the building and also at the nearest police station. These signal bolts, which cannot be distinguished from the others, are known only to the attendants. In a receptacle in the treasury, behind a sheet of glass, is a telephone, attached to which is an envelope containing instructions for the use of anyone who found himself shut in and unable to get out.

The first safe deposit to be built in Great Britain was that known as the National Safe Deposit, situated in Queen Victoria Street, within a stone’s throw of the Bank of England. The safe deposit is in many ways a remarkable structure, and one of the few in London that consist of an island site. There is first an outer wall of solid concrete lined with hard bricks 10 feet thick, to penetrate which would prove a momentous if not an impossible feat. Within this outer wall, and separated from it by a 3-feet passage, is a wall of hard Staffordshire bricks, lined with undrillable armour plate 4½-in thick, dovetailed in sections and further strengthened by wrought-iron framing. This forms the true deposit building, and within it are the vaults, thirty-two in number, built up in four tiers one above the other.

Protective Reservoirs

Under the lower floor of the vaults is an enormous subterranean cistern, 6 feet deep, and below that again a solid bed of concrete 20 feet thick. The vaults themselves extend to a depth of 50 feet below the street level. The foundations reach down to a total depth of 76 feet.

To reach the vaults from below or from the outside is virtually impossible. Protection against any possible form of attack from above is provided against by a bomb-proof roof, consisting of semicircular arches lined with undrillable armour plate and further strengthened by wrought-iron plating. Then over all, at the top of the external building, there is a tank, always kept full, containing 50,000 gallons of water.

The massive steel doors leading to the vaults are 12-in thick and weigh nearly 5 tons each. They have no locks or bolts and are operated in an ingenious way by hydraulic power. To close them it is necessary for three or four officers of the company to be at separate posts. Once the doors have been closed there is no power on earth that can move them until the proper machinery is brought into action. Any one attempting to reconnect the machinery would release the water in the cistern above the vaults, which would mean that the whole place would be flooded.

The vaults in the old Bank of England were also protected by reservoirs of water in this way. There were two vaults, built one above the other. In the bank’s new building there are three vaults, also one above the other, and they go down to a depth of 60 feet below street level. When the Bank moved to its temporary home in Finsbury Circus there were taken from its vaults £120,000,000 in gold bars and coin, as well as securities to the value of £128,000,000.

TWENTY-FOUR ROUND BOLTS, each weighing 100 lb, are incorporated in this circular door of a safe deposit. The door has a diameter of 7 ft 6-in and weighs 25 tons. Of this total, a weight of 21 tons was cast in one piece, the remaining 4 tons being accounted for by the boltwork and time lock fittings. The door is opened by a keyless combination system.

The largest safe deposit in London is in Chancery Lane. It is a veritable nest of strong rooms and safes, comprising some 40,000 receptacles in all. Since it was opened it has enlarged its area some four or five times. It is used a great deal by the diamond merchants of the district. It is a common occurrence for a broker to hasten down the broad white steps leading to the vaults just before closing time with £20,000 worth of diamonds in his pockets.

The safe deposit is an American idea. During the American Civil War (1861-65) bank robberies were so frequent in America that the banks refused to take care of their customers’ valuables. One of these institutions referred its clients to the porter as willing to accept the risk. For a small sum he took charge of the boxes and safes and made a fortune by doing so. This suggested to the ever-alert American brain the safe-deposit companies.

INTERIOR OF THE LONDON SAFE DEPOSIT, in Regent Street, London. All the visible metalwork is of polished stainless steel and more than 50 tons of special steel were used to build this single chamber. The whole room is embedded, walls, floor and roof, in a thick bed of concrete reinforced with steel bars. This room contains more than 1,500 receptacle safes of various sizes and in the background is the door which leads into the strongroom. The door on the right is the main entrance to the vault.

In all the great cities of the United States there are public safe deposits which have cost from £100,000 to £200,000 to build. The Carnegie Safe Deposit Vaults, in New York, are a typical example of these American institutions. The vaults are in reality two huge steel boxes, placed one on top of the other, situated in the basement of a skyscraper. The lower box is 108 feet long, 31 feet wide and 10 feet high, and the upper box 85 feet long, 20 feet wide and 10 feet high. They are fashioned of best harveyized (specially hardened) nickel steel armour plate. In all some 1,400 tons of this metal were called into requisition, for the building of these New York vaults.

None of the plates with which the vaults are built weighs less than 5 tons, and some of them tip the scale at 50 and 60 tons. The biggest two plates were, at the time, the largest pieces of armour ever forged. Before the metal was accepted it was subjected to a stern test. Three 5-in 50-lb capped armour-piercing shells discharged against a sample plate had no harmful effect upon it. The deepest penetration was three quarters of an inch, and no cracks or fractures appeared on any part of the plate. It is estimated that no charge of explosive which it would be possible for a human being to direct against these plates would avail to break through them.

No bolts or rivets were used in fixing the plates together. The design of the vaults provided for the forging of the plates with wedge ends and channels which were to lock together by a system of interlocking wedges on the inside of the vault. This has made the structure a unit of such character that any force applied to any of the joints will have the effect merely of tightening the grip of the wedges. It is calculated that the tensile strength of these wedge ends is 240,000 lb to the running inch. The engineers declare that, if it were possible to explode a quantity of explosives of sufficient power to raise the whole structure into the sky, the vaults would still remain intact. If the skyscraper above collapsed and piled itself upon the vaults it would not crush, bend or crack the plates.

CAST IN ONE SOLID PIECE, with the exception of the boltwork and mechanism, the main entrance door of the London Safe Deposit weighs 20 tons. It is 6 ft 6-in high, 3 ft 6-in wide and has a thickness of 2 feet. The door has sixteen 100-lb bolts and is equipped with keyless combination and time locks. It is capable of defying all known methods of forced entry.

The foundation laid under this mammoth steel structure is exceedingly interesting. The bedrock was dressed off to a level and then, for a thickness of 10 feet, there was built up a solid mass in alternating layers of concrete and railway rails laid flange to flange. Upon this bed armour plates 5-in thick were laid, to form the floor of the lower vault. This foundation is calculated to act as a cushion in the event of an upheaval of Manhattan Island, so that, even were the underlying rock to be split, the strain upon the armour plate would be dissipated and the structure would remain intact. There is no opening anywhere through the exposed skin of the vault or through its foundation bed.

The columns supporting the building run through the vaults. Each of these columns is encased in 5-in armour plate, as are the walls of the vault. Neither the columns nor the foundation walls are in any way attached to the vault. Communication between the upper and lower vaults is afforded by a hatchway 12 feet square encased by a neck of the 5-in armour plate. The

3 feet of space between the ceiling of the lower vault and the floor of the upper vault are filled in with solid concrete.

Access is gained to the vaults by two round doors, 7½ feet in diameter, each weighing 25 tons. Twenty tons of this weight are in one solid mass of material, the remaining 5 tons being accounted for in the boltwork and mechanism operating the lock. The doors are fitted with both time and combination locks.

The latest time locks operate from one to 120 hours - that is, five days. Lest the time lock should fail to operate, it contains either three or four separate chronometer movements, any one of which is capable of setting the lock “off guard” at the desired time. When the doors have been closed and the timepiece has been set, it is impossible to open them again until the clock has run its allotted time. The time lock is a British invention, though it was first used in America. Bank managers and others in the United States were continually being held up by armed robbers demanding the keys or the combination of their vaults or safes. When the time lock appeared they saw in it an additional means of thwarting the would-be thief.

Over 96 Million Years

In addition to the timepiece there is also the keyless combination lock. This is an ingenious device. There is no key to be broken, bent, lost, stolen or copied. There is no aperture leading direct to the most vital part of the door. The possible combinations run into many millions. The combination may consist of figures or letters. Some locks have four sets of twenty-four letters of the alphabet, which can be set to a sentence in most modern languages. When one letter is used in one alphabet, and another in the second set, and so on, it becomes a complicated matter to detect the combination. There is the initial problem of what language it has been keyed in. If numerals are used instead of letters - and they are the more common - the combinations that may be used are almost endless.

The lock is set on the figures 3,030,303,030,303,030. It would take a burglar who set himself the task of unlocking such a vault, beginning with the lowest figure and working upwards, 96,090,278 years 269 days 30 minutes 30 seconds, working at the rate of sixty numbers a minute, to arrive at the proper combination.

Any one can rent a safe, or integer, as the smaller receptacles are called, in a public safe deposit, by paying the necessary rent. Each renter is supplied with his own key and if he loses it his integer has to be broken open.

After the safe deposit had had a successful run of twenty years in the United States the idea was brought to London. At first, however, British citizens did not take kindly to the idea of storing their valuables in public vaults. Now they have appreciated the wonderful security against loss and theft offered by these institutions. The British repositories are to all intents and purposes as strong as those in America, and can justify their claim to be fire-, burglar- and mob-proof.

QUADRUPLE TIME LOCK MECHANISM is incorporated on the door of a modern safe deposit. Once the doors have been shut and the clocks have been set for any predetermined time during the next 120 hours, the locks cannot be opened until that time. Four chronometer movements are provided to make sure that the mechanism shall not fail to operate because of faulty timing mechanism.

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“Calculating Machines”,

“Harnessing Light” and

“How Gold is Mined”

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