Rudimentary Treatise on the Construction of Locks

by A. C. Hobbs; George Dodd

fig. 50.

The next step in the operation is to raise the tumblers to the proper height. For this purpose a second pipe m n is made to slide upon the first with an easy motion, and by means of the cross handle h h can be turned round or slid backwards and forwards on the tube a b. This tube m n is also furnished with a single projecting bit or step n o, corresponding with one of the six steps of the key, [fig. 32], and made of the proper length for entering the key-hole.

Now for the operation of opening a tumbler-lock with this simple apparatus. Referring to [fig. 31], page 56, it will be evident that if the pipe a b, [fig. 49], be passed over the pin of the lock and turned round towards the left, and the weight be attached, there will be a tendency in the bolt to shoot back, which tendency will bring the stump s, [fig. 31], up against the inner angle or shoulder of one or other of the tumblers, whichever happens to project, however slightly; or, as Mr. Hobbs expresses it, “one or more of the tumblers will bind.” By moving forward the pipe m n and turning round the bit n o in the lock, it is easy to ascertain, by delicate touch, which of the tumblers it is that binds. It may be found that all are free to move except one or two against which the stump is pressing with the force of the weight w, [fig. 50]. The bit n o is therefore brought gently under the bellies of the tumblers which bind, and they are moved slightly upwards until they cease to bind. As soon as they are set free another tumbler will bind; that is, the bolt will move through a small space, so as to bring the stump into contact with that particular tumbler which now projects; this in its turn is relieved, another tumbler binds and is relieved, and so on until the tumblers are, one by one, raised to the proper height for the stump to pass. When the last binding tumbler is raised to the proper height, the weight w being no longer resisted, shoots the bolt back, and the work is done.

Now it must be evident that in this operation the detector apparatus need not come into operation. But if, as has been proposed, a detector-spring be added to each tumbler, it may be converted into a friend or a foe according to the use that is made of it. If the tumblers are lifted too high, they will be detained or detected in that position, and the operator will have to release them by turning the bit round in the opposite direction before he can begin his work again. The same force, however, which detains the tumblers when they are lifted too high will obviously detain them when they are lifted only just high enough, and thus the detector-springs would really be of great assistance to the operator in picking such a tumbler-lock.

The apparatus which we have described for picking the tumbler-lock must be varied to suit the form of key employed in opening the lock; but it is not difficult, in the case of most locks, to ascertain this form through the key-hole, without examining the key itself.

It is but fair to state in this place, that since the above method of picking tumbler-locks was made known,[8] Mr. Chubb has added a series of teeth and notches to the stump and tumblers; the effect of which would evidently prevent the application of the above method of picking, because any permanent pressure applied to the bolt would send a tooth of the stump into a notch of the tumbler, and prevent all further motion. But recurring to the principle, that whenever the parts of a lock which come in contact with the key indicate the points of resistance when any pressure (whether permanent or temporary) is applied in attempting to withdraw the bolt, that lock can be picked, it follows, if this principle be admitted, that although the notches prevent the application of the form of instrument described, yet there is sufficient indication afforded by the pressure to enable a skilful operator, with proper instruments, to form a false key, as was done in the case of the lock referred to at [page 104]. We now proceed to the second stage in the lock controversy of 1851.

[8] We believe the method was first made publicly known at a special general meeting of the members of the Institution of Mechanical Engineers, held at the rooms of the Society of Arts, London, on the 30th June, 1851, when a paper was read by Mr. Paul R. Hodge “On the progress of improvements in locks in the United States of America.” A report of this paper, together with the discussion thereon, was published by Waterlow and Sons, London Wall, 1851. Plate 34 (figs. 9 and 10) of this report contains representations of the lock-picking apparatus, from which we have copied our figures.

Soon after the picking of the Chubb lock in Great George-street, and consequent on the excitement and discussion to which that operation led, a committee, consisting of Mr. G. Rennie, Professor Cowper,[9] and Dr. Black, agreed to superintend the arrangements for a more severe testing of Mr. Hobbs’s power to open locks. There had been for many years exhibited in the window of Messrs. Bramah’s shop, in Piccadilly, a padlock of great complexity and beauty; to which an announcement was affixed, that a reward of two hundred guineas would be given to any person who should succeed in picking that lock. This challenge was accepted by Mr. Hobbs; and the committee managed all the arrangements, as arbitrators between Mr. Hobbs on the one side and Messrs. Bramah on the other. The lock was removed to an upper room in Messrs. Bramah’s establishment; where it was placed between two boards, and so fixed and sealed, that no access could be obtained to any part of it except through the key-hole. The room was to be given up to Mr. Hobbs; he was not to be interrupted by the presence or entrance of any other persons; and he was allowed a period of thirty days for opening the lock. If the lock was not picked at the expiration of that period, Mr. Hobbs was to be considered as having failed in his attempt.