An Autobiography [126]
detail consisted in employing the waste steam in the upper part of the cylinder for the purpose of acting as a buffer to resist any undue length of the upward stroke of the piston. But for this the cylinder covers might have been knocked off. The elastic buffer of waste steam also acted as a help to the downward blow of the hammer-block. The simplicity and effectiveness of these arrangements form--if I may be allowed to say so--a happy illustration of my "Definition of Engineering," the application of common sense in the use of materials.
The folding-up steam pipe with which the steam was conveyed from the boiler to the cylinder at all heights, and the way in which the folding joints accommodated themselves to the varying height of the cylinder, was another of my happy thoughts. In fact, this invention, like most others, was the result of a succession of happy thoughts. The machine in its entirety was the result of a number of common-sense contrivances, such as I generally delight in. At all events, this most effective and novel machine was a special favourite with me.
I may mention, before concluding this branch of my subject, that pile-driving had before been conducted on what I might term the artillery or cannon-ball principle. A small mass of iron was drawn slowly up, and suddenly let down on the head of the pile at a high velocity. This was destructive, not impulsive action. Sometimes the pile was shivered into splinters, without driving it into the soil; in many cases the head of the pile was shattered into matches, and this in spite of a hoop of iron about it to keep the layers of wood together. Yet the whole was soon beat into a sort of brush. Indeed, a great portion of the men's time was consumed in "reheading" the piles. On the contrary, I employed great mass and moderate velocity. The fall of the steam hammer-block was only three or four feet, but it went on at eighty blows the minute, and the soil into which the pile was driven never had time to grip or thrust it up-- an impediment well known to ordinary pile-drivers. At the end of the driving by my steam hammer, the top of the pile was always found neat and smooth, indeed more so than when the driving began.
I may again revert to my interview with the Lords of the Admiralty on the occasion of my first meeting them at Devonport. I was residing at the hotel where they usually took up their quarters while making their annual visitation of the dockyard. I was honoured with an invitation to confer with Sir George Cockburn, Mr. Sidney Herbert, and Captain Brandreth on a subject of considerable importance; namely, the proving of chain cables and anchors required for the Royal Navy. The question was mooted as to whether or not some permanent injury was done to both by the test strains to which they were submitted before being put on board ship. This was a subject of vital importance. The members of the Board requested me to act as one of a committee to inquire into the subject. I felt much gratified by the invitation and gladly accepted it.
On discussing the subject with these gentlemen that evening, I found that Sir George Cockburn entertained an ingenious theory in support of his apprehensions as the effect of "over-proof" straining of cables and anchors. It was that they were originally in the condition of a strong man who had to lift some heavy weight, requiring him to exert his muscular strength to the utmost; and, although he might perform the feat, it was at the cost of a permanent injury, and that he might never be able to lift the same weight again. This, however true it might be with regard to flesh and bone structures, was scarcely true with respect to mechanical agencies. I proposed a simple experiment with chain cables, which, it occurred to me, would show quite a different result--namely, that the capability of resisting the severest proof-strain would rise rather than fall at each successive proof of the same chain cable.
To test the correctness of my supposition, we had a first-class chain cable put into the proof machine,and
The folding-up steam pipe with which the steam was conveyed from the boiler to the cylinder at all heights, and the way in which the folding joints accommodated themselves to the varying height of the cylinder, was another of my happy thoughts. In fact, this invention, like most others, was the result of a succession of happy thoughts. The machine in its entirety was the result of a number of common-sense contrivances, such as I generally delight in. At all events, this most effective and novel machine was a special favourite with me.
I may mention, before concluding this branch of my subject, that pile-driving had before been conducted on what I might term the artillery or cannon-ball principle. A small mass of iron was drawn slowly up, and suddenly let down on the head of the pile at a high velocity. This was destructive, not impulsive action. Sometimes the pile was shivered into splinters, without driving it into the soil; in many cases the head of the pile was shattered into matches, and this in spite of a hoop of iron about it to keep the layers of wood together. Yet the whole was soon beat into a sort of brush. Indeed, a great portion of the men's time was consumed in "reheading" the piles. On the contrary, I employed great mass and moderate velocity. The fall of the steam hammer-block was only three or four feet, but it went on at eighty blows the minute, and the soil into which the pile was driven never had time to grip or thrust it up-- an impediment well known to ordinary pile-drivers. At the end of the driving by my steam hammer, the top of the pile was always found neat and smooth, indeed more so than when the driving began.
I may again revert to my interview with the Lords of the Admiralty on the occasion of my first meeting them at Devonport. I was residing at the hotel where they usually took up their quarters while making their annual visitation of the dockyard. I was honoured with an invitation to confer with Sir George Cockburn, Mr. Sidney Herbert, and Captain Brandreth on a subject of considerable importance; namely, the proving of chain cables and anchors required for the Royal Navy. The question was mooted as to whether or not some permanent injury was done to both by the test strains to which they were submitted before being put on board ship. This was a subject of vital importance. The members of the Board requested me to act as one of a committee to inquire into the subject. I felt much gratified by the invitation and gladly accepted it.
On discussing the subject with these gentlemen that evening, I found that Sir George Cockburn entertained an ingenious theory in support of his apprehensions as the effect of "over-proof" straining of cables and anchors. It was that they were originally in the condition of a strong man who had to lift some heavy weight, requiring him to exert his muscular strength to the utmost; and, although he might perform the feat, it was at the cost of a permanent injury, and that he might never be able to lift the same weight again. This, however true it might be with regard to flesh and bone structures, was scarcely true with respect to mechanical agencies. I proposed a simple experiment with chain cables, which, it occurred to me, would show quite a different result--namely, that the capability of resisting the severest proof-strain would rise rather than fall at each successive proof of the same chain cable.
To test the correctness of my supposition, we had a first-class chain cable put into the proof machine,and