James Nasmyth, Engineer: An Autobiography

by James Nasmyth

After finishing off the forging, my Lords gathered round the hammer again, when I explained to them the rationale of its working, and the details of its construction. They were greatly interested, especially Mr. Sidney Herbert (afterwards Lord Herbert of Lea), then Secretary to the Admiralty, and Sir George Cockburn, a fine specimen of the old admiral. Indeed, all the members of the Board were more or less remarkable men. They honoured me with their careful attention, and expressed their admiration at the hammer's wonderful range of power and delicacy of touch, in this new application of the force of steam.

The afternoon was a most important one for me in more ways than one, although I cannot venture to trouble my readers with the details. It was followed, however, by an order to supply all the Royal Dockyard forge departments with a complete equipment of steam hammers, and all the requisite accessories. These were supplied in due time, and gave in every case the highest satisfaction. The forgings were found to be greatly better, and almost absurdly cheaper than those done by the old bit by bit building-up process. The danger of flaws was entirely done away with; and, in the case of anchors, this was a consideration of life and death to the seamen, who depend for their safety upon the soundness of the forgings.

Besides my introduction to that admirable man, Mr. Sidney Herbert, I had the happiness of being introduced to Captain Brandreth, Director of Naval Works. The whole of the buildings on shore, including the dockyards, were under his control. One of the most important affairs that the Lords of the Admiralty had to attend to on their visit to Devonport was to conclude the contract for constructing the great docks at Keyham. This was a large extension of the Devonport Docks, intended for the accommodation of the great steamships of the Royal Navy, as well as for an increase of the graving docks and workshops for their repair. An immense portion of the shore of the Hamoaze had to be walled in so as to exclude the tide and enable the space to be utilised for the above purposes. To effect this a vast amount of pile-driving was rendered necessary, in order to form a firm foundation for the great outer dock wall, about a mile and a quarter in length.

Messrs. Baker and Sons were the contractors for this work. They were present at the first start of my steam hammer at Devonport. They were, like the others, much impressed by its vast power and manageableness. They had an interview with me as to its applicability for driving piles for the immense dock, this being an important part of their contract. Happily, I had already given some attention to this application of the powers of the steam hammer. In fact, I had secured a patent for it. I had the drawings for the steam hammer pile-driving machine with me. I submitted them to Mr. Baker, and he saw its importance in a moment. "That," he 'said, "is the very thing that I want to enable me to complete my contract satisfactorily." Thousands of enormous piles had to be driven down into the deep silt of the Shore; and to have driven them down by the old system of pile-driving would have occupied a long time, and would also have been very expensive.

The drawings were of course submitted to Captain Brandreth. He was delighted with my design. The steam pile-driver would be, in his opinion, the prime agent for effecting the commencement of the great work originated by himself. At first the feat of damming out such a high tide as that of the Hamoaze seemed very doubtful, because the stiff slate silt was a treacherous and difficult material to penetrate. But now, he thought, the driving would be rendered comparatively easy. With Captain Brandreth's consent the contractors ordered of me two of my steam hammer pile-drivers. They were to be capable of driving 18-inch square piles of 70 feet in length into the silt of the Hamoaze.

[Image] Space to be enclosed at the Hamoaze

This first order for my pile-driver was a source of great pleasure to me. I had long contemplated this application of the power of the steam hammer. The machine had long been in full action in my "mind's eye," and now I was to see it in actual reality. I wrote down to my partner by that night's post informing him of the happy circumstance. The order was for two grand steam hammer pile-drivers, each with four-ton hammer-blocks.The wrought-iron guide case and the steam cylinder were to weigh in all seven tons. All this weight was to rest on the shoulders of the pile. The blows were to be about eighty in the minute. This, I thought, would prove thoroughly effective in rapidly driving the piles down into the earth.

I have said that the steam pile-driver was in my mind's eye long before I saw it in action. It is one of the most delightful results of the possession of the constructive faculty, that one can build up in the mind mechanical structures and set them to work in imagination, and observe beforehand the various details performing their respective functions, as if they were in absolute material form and action. Unless this happy faculty exists ab initio in the brain of the mechanical engineer, he will have a hard and disappointing life before him. It is the early cultivation of the imagination which gives the right flexibility to the thinking faculties. Thus business, commerce, and mechanics are all the better for a little healthy imagination.

So soon as I had returned home, I set to work and prepared the working drawings of the steam pile-drivers. They were soon completed, conveyed to Devonport, and erected on the spot where they were to be used. They were ready on the 3d of July 1845. Some preliminary pile-driving had been done in the usual way, in order to make a stage or elevated way for my pile-driver to travel along the space where the permanent piles were to be driven. I arranged my machines so that they might travel by their own locomotive powers along the whole length of the coffer dam, and also that they should hoist up the great logs of Baltic timber which formed the Piles into their proper places before being driven.

The entire apparatus of the machine was erected on a strong timber platform, and was placed on wheels, so that it might move along the rails laid down upon the timber way. The same boiler that supplied the steam hammer part of the apparatus served to work the small steam-engine fixed to the platform for its locomotion, and also to perform the duty of rearing the next pile which had to be driven. The steam was conveyed to the hammer cylinder by the jointed pipe seen in the annexed engraving. The pipe accommodated itself to any elevation or descent of the hammer. The whole weight of the cylinder, hammer-block, and guide box, supported by the shoulders of the pile, amounting to seven tons in all, rested upon the shoulders of the pile as a "persuader;" and the eighty blows per minute of the four-ton hammer came down with tremendous energy upon the top of the pile head. No soil, that piles could penetrate, could resist such effective agencies.