James Nasmyth: Engineer; an autobiography Part 35

Though the force of the blow was greatly checked through the measures taken for that purpose, and indeed so much so that the vessel itself suffered no very material injury, yet several of the ma.s.sive granite stones of the facing were driven some inches in, showing the enormous force used upon them. "Superior speed will be very essential to the successful action of the ram; but by the above circ.u.mstance we may a.s.sume that even a moderate speed would enable great effects to be produced, at least on any comparatively weak point of even ironclad s.h.i.+ps, such as the rudder."

In June 1870, I received a letter from Sir E. J. Reed, containing the following extracts: --"I was aware previously that plans had been proposed for constructing unarmoured steam rams, but I was not acquainted with the fact that you had put forward so well-maturerd a scheme at so early a date; and it has given me much pleasure to find that such is the case. It has been a cause both of pleasure and surprise to me to find that so long ago you incorporated into a design almost all the features which we now regard as essential to ramming efficiency--twin screws and moderate dimensions for handiness, numerous water-tight divisions for safety, and special strengthenings at the bow. Facts such as these deserve to be put on record....

Meanwhile accept my congratulations on the great skill and foresight which your ram-design displays."

Collisions at sea unhappily afford ample evidence of the fatal efficiency of the ramming principle. Even ironclad s.h.i.+ps have not been able to withstand the destructive effect. The Vanguard and the Kurfurst now lie at the bottom of the sea in consequence of an accidental "end-on" ram from a heavy s.h.i.+p going at a moderate velocity. High speed in a Steam Ram is only desirable when the attempt is made to overtake an enemy's s.h.i.+p; but not necessary for doing its destructive work.

A crash on the thick plates of the strongest Ironclad, from a Ram of 2000 tons at the speed of four miles an hour, would drive them inwards with the most fatal results.

1839. Invention of the Steam Hammer, in its general principles and details.

Described in text, p. 231.

1839. Invention of the Floating Mortar or Torpedo Ram.

For particulars and details, see Report of Torpedo Committee.

1839. A Double-faced Wedge-shaped Sluice-Valve for Main Street Water-pipes.

The late Mr. Wicksteed, engineer of the East London Water Company, having stated to me the inconvenience which had been experienced from the defects in respect of water-tightness, as well as the difficulty of opening and closing the valves of the main water-pipes in the streets, I turned my attention to the subject. The result was my contrivance of a double-faced wedge-shaped sluice-valve, which combined the desirable property of perfect water-tightness with ease of opening and closing the valve.

This was effected by a screw which raised the valve from its bearings at the first partial turn of the screw, after which there was no further resistance or friction, except the trifling friction of the screw in its nut on the upper part of the sluice-valve. When screwed down again, it closed simultaneously the end of the entrance pipe and that of the exit pipe attached to the valve case in the most effective manner.

[image]

Mr. Wicksteed was so much pleased with the simplicity and efficiency of this valve that he had it applied to all the main pipes of his Company.

When its advantages became known, I received many orders from other water companies, and the valves have since come into general use.

The prefixed figure will convey a clear idea of the construction.

The wedge form of the double-faced valve is conspicuous as the characteristic feature of the arrangement.*

[footnote...

At a meeting of the Inst.i.tution of Civil Engineers, May 23, 1883, when various papers were read on Waterworks, Mr. H. I. Marten observed in the course of the discussion: --"It has been stated in Mr. Gamble's paper (on the waterworks of Port Elizabeth) that the sluice valves are of the usual pattern. The usual patterns of the present day are in wonderful advance of those of thirty or forty years since. The great improvement originated with the introduction of 'the double-faced sluice-c.o.c.k.' This sluice-c.o.c.k, which had now superseded every other description, was the creation of Mr. James Nasmyth's inventive genius.

Mr. Marten said he well remembered the first reception of this useful invention, as he happened at that time to be a pupil of Mr. Thomas Wicksteed. He was present when Mr. Wicksteed explained to Mr. Nasmyth the want he had experienced of a sluice-c.o.c.k for Waterworks purposes, which should shut and remain perfectly tight against a pressure coming from either side. Mr. Marten had a lively recollection of the instantaneous rapidity with which Mr. Nasmyth not only grasped but provided for the requirement; so that almost by the time Mr. Wicksteed had completed the statement of his want, Mr. Nasmyth had drawn upon the back of an old letter a rough sketch of the first double-faced sluice-c.o.c.k; and in less than an hour had converted this rough sketch into a full-sized working drawing; in the preparation of which it fell to Mr. Marten's lot to have the honour to a.s.sist. In his 'Autobiography' Mr. Nasmyth referred to the conversation with Mr. Wicksteed, and introduced a print of the drawing made upon the occasion. The invention has been of the greatest use to the Waterworks Engineer, especially in connection with the constant supply system, in which it frequently happened that the pressure was sometimes against one face of the sluice-c.o.c.k, and sometimes against the other."-- See Proceedings and Discussions of the Inst.i.tution of Civil Engineers, 1883, pp. 88, 89.

1839. A Hydraulic Mattress Press, capable of exerting a pressure of Twenty thousand tons.

Being under the impression that there are many processes in the manufacturing arts, in which a perfectly controllable compressing power of vast potency might be serviceable, I many years ago prepared a design of an apparatus of a very simple and easily executed kind, which would supply such a desideratum. It was possessed of a range of compressing or squeezing power, which far surpa.s.sed anything of the kind that had been invented. As above said, it was perfectly controllable; so as either to yield the most gentle pressure, or to possess the power of compressing to upwards of twenty thousand tons; the only limit to its power being in the materials employed in its construction.

The principle of this enormously powerful compressing machine is similar to that of the Hydraulic Press; the difference consisting princ.i.p.ally in the subst.i.tution of what I term a Hydraulic Mattress in place of the cylinder and ram of the ordinary hydraulic press.

The Hydraulic Mattress consists of a square or circular water-tight vessel or flat bag formed of 1/2-inch thick iron or steel plates securely riveted together; its dimensions being, say 15 feet square by 3 feet deep, and having semicircular sides, which form enables the upper flat part of the Mattress to rise say to the extent of 6 inches, without any injury to the riveted joints, as such a rise or alteration of the normal form of the semicircular sides would be perfectly harmless, and not exceed their capability of returning to their normal curve when the 6-inch rise was no longer necessary, and the elevating pressure removed.

[image]

The action of this gigantic press is as follows. The Mattress A A having been filled with water, an additional quant.i.ty is supplied by a force pump, capable of forcing in water with a pressure of one ton to the square inch; thus acting on an available surface of at least 144 square feet surface--namely, that of the upper flat surface of the Mattress. It will be forced up by no less a pressure than twenty thousand tons, and transfer that enormous pressure to any article that is placed between the rising table of the press and the upper table.

When any object less thick than the normal s.p.a.ce is required to receive the pressure, the spare s.p.a.ce must be filled with a suitable set of iron flat blocks, so as to subject the article to be pressed to the requisite power.

As before stated, there may be many processes in the manufacturing arts in which such an enormous pressure may be useful; and this can be accomplished with perfect ease and certainty. I trust that this account of the principles and construction of such a machine may suggest some employment worthy of its powers. In the general use of the Mattress press, it would be best to supply the pressure water from an acc.u.mulator, which should be kept constantly full by the action of suitable pumps worked by a small steam-engine. The great press would require the high-pressure water only now and then; so that it would not be necessary to wait for the small pump to supply the pressure water when the Mattress was required to be in action.

1840. A Tapping Square, or instrument by which Perfect Verticality of the Tapping of Screwed Holes is insured.

[image]

The letter X shows how Screws are frequently made when tapped in the old mode; the letter T as they are always made when the Tapping Square is employed.

1840. A Mode of turning Segmental Work in the Ordinary Lathe

In executing an order for twenty locomotive engines for the Great Western Railway Company, there was necessarily a repet.i.tion of detail parts. Many of them required the labour of the most skilful workmen, as the parts referred to did not admit of their being executed by the lathe or planing-machine in their ordinary mode of application.

But the cost of their execution by hand labour was so great, and the risk of inaccuracy was so common (where extreme accuracy was essential), that I had recourse to the aid of special mechanical contrivances and machine tools for the purpose of getting over the difficulty.

The annexed ill.u.s.tration has reference to only one cla.s.s of objects in which I effected great saving in the production, as well as great accuracy in the work. It refers to a contrivance for producing by the turning-lathe the eighty bands of the eccentrics for these twenty engines. Being of a segmental form, but with a projection at each extremity, which rendered their production and finish impossible by the ordinary lathe, I bethought me of applying what is termed the mangle motion to the rim of a face plate of the lay, with so many pins in it as to give the required course of segmental motion for the turning tool to operate upon, between the projections C C in the ill.u.s.tration.

[image]

I availed myself of the limited to-and-fro horizontal motion of the shaft of the mangle motion wheel, as it, at each end of the row of pegs --in the face plate (when it pa.s.ses from the exterior to the interior range of them) in giving the feed motion to the tool in; the slide rest, "turned" the segmental exterior of the eccentric hoops.

This it did perfectly, as the change of position of the small shaft occurred at the exact time when the cut was at its termination,--that being the correct moment to give the tool "the feed, or advance for the taking of the next cut. The saving, in respect to time, was 10 to 1 in comparison with the same amount of work done by hand labour; while the "truth" or correctness of the work done by this handy little application of the turning-lathe was absolutely perfect I have been the more particular in my allusion to this contrivance, as it is applicable to any lathe, and can perform work which no lathe without it can accomplish. The unceasing industry of such machines is no small addition to their attractions, in respect to the production of unquestionably accurate work.

1843. Invention of the Steam Hammer Pile-driver.

Described in text, p. 261.

1843. A Universal Flexible Joint for Steam and Water-pipes.

[Image]

The chief novelty in this swivel joint is the manner in which the packing of the joints is completely enclosed, thereby rendering them perfectly and permanently watertight.

1844. An Improvement in Blowing Fans and their Bearings.

The principle on which Blowing Fans act, and to which they owe their efficiency, consists in their communicating Centrifugal action to the air within them.

In order to obtain the maximum force of blast, with the minimum expenditure of power, it is requisite so to form the outside rim of the Fan-case as that each compartment formed by the s.p.a.ce between the ends of the blades of the Fan shall in its course of rotation possess an equal facility of exit for the pa.s.sage of the air it is discharging.

Thus, in a Fan with six blades, the s.p.a.ce between the top of the blades and the case of the Fan should increase in area in the progressive ratios of 1-2-3-4-5-6.

[Image]

If a Fan be constructed on this common-sense principle, we shall secure the maximum of blast from the minimum of driving power. And not only so; but the humming sound--so disagreeable an accompaniment to the action of the Fans (being caused by the successive sudden escape of the air from each compartment as it comes opposite the s.p.a.ce where it can discharge its confined block of air)--will be avoided. When the outer case of a Fan is formed on the expanding or spiral principle, as above described, all these important advantages will attend its use.

As the inward current of air rushes in at the circular openings on each side of the Fan-case, and would thus oppose each other if there was a free communication between them, this is effectually obviated by forming the rotating portion of the fan by a disc of iron plate, which prevents the opposite in-rus.h.i.+ng currents from interfering with each other, and at the same time supplies a most substantial means of fastening the blades, as they are conveniently riveted to this central disc. On the whole, this arrangement of machinery supplies a most effective "Noiseless Blowing Fan."

1845. A direct Action "Suction" Fan for the Ventilation of Coal-Mines.

The frequency of disastrous colliery explosions induced me to give my attention to an improved method for ventilating coal mines.