MR. WHITELAW'S IMPROVED EXPANSION GEAR AND SLIDE-VALVES.

Sir,-I send you herewith an account of my plan of expansion gear, for insertion in the Mechanics' Magazine, for which I received from the "Royal Cornwall Polytechnic Society for the encouragement of the sciences, arts, and industry," their first bronze medal, in order that your readers may know to what extent this society encourages improvement. I sent the medal back to the Royal Cornwall Polytechnic Society: as my plan of a governor for regulating the time of cutting off the steam, is alone, in my opinion worth twenty times its value, I could not think of keeping such a trifle.

It is a pity that Mr. W. Baddeley, in his letter dated 5th July, 1838, was not able to answer my last letter fairly, but was obliged to prop up his notions respecting my feeding apparatus, by what were once the opinions of "Nauticus;" as the latter gentleman, at the time he entertained the same notions on the subject as Mr. Baddeley now does, believed also that the old feeding apparatus, in ordinary use, to be perfect; and of course, a person entertaining such ideas must laugh at every attempt at improvement, even the feeding apparatus of Mr. B. must, then, have appeared worthless in the eyes of "Nauticus." I have something more substantial than the opinion of others in favour of my plan, as Mr. B. will perceive, when I let him know that I was asked by a gentleman in London, about a month ago, to get a feeding apparatus on my plan made for him and from letters which are at present in my possession, I have every reason to believe, that there are two sets of this apparatus now making in one of the most extensive steam-engine factories in the kingdom.

Description of Improved Expansion Gear and Slide-Valves.-Figure 1 shows one form of myplan of expansion gear: in this fig. the steam pipe is shown at a, and the steam passes through a hollow belt b, cast round the cylinder into the chest c. dd is the slide valve which is of the D shape, so that outside the valve has the appearance of a pipe having a flat side with four ports in it, and a part of it taken away at each end. ef shows the passage through the valve by which the steam gets into the port g at the top of the cylinder, and hi is another Passage through the valve, by which the

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steam gets into the bottom port k of the cylinder. The cut off valves 11, are both fixed upon one rod. When the steam is cut off on the top side of the piston, the top valve marked 1, then covers the uppermost of the two middle ports on the flat side of the valve d d; and when the steam is cut off on the bottom side of the piston, then the bottom valve marked is upon the undermost of the two middle ports on the flat side of the valve. The eduction-pipe for the top end of the cylinder is seen at m, and n is the bottom eduction-pipe. The top end of the valve d d is packed by lifting off the top of the valve chest, and its bottom end is packed by taking away the cover o. The top port g into the cylinder has a part cast inside of it for the rod of the cut off valves to pass through; but this part being small it will not contract the port, as it (the port) may be made a little wider opposite the part. The slide valve d d is wrought by means of an eccentric, and p is the rocking shaft the cut-off valves are wrought by means of a wiper fixed upon the crank shaft, which communicates motion to the rod q. r is a small rocking shaft with two levers on it, the same as shown in the fig.; and the rod s communicates the motions of this shaft to the lever t t, which works upon a centre at u. If there were no more levers, &c. to work the cut off valves than now described, then, on account of the slide valve dd being always in motion, and the cut off valve making only one move in a half revolution of the crank shaft, the motions of the valve d d would shift the cut off valves from their proper positions on its face but as the centre u, of the levert t, works upon a stud fixed into the bell crank lever u vw, the centre v, being placed at a horizontal distance from the rocking shaft p, equal to the distance of the centre of the rod of the valve d d, from the centre of the rod for working the cut off valves; and the part v w of the bell crank lever u v w is connected to the lever p x, fixed upon the rocking shaft, by means of the link w x; and as vw is of the same length as p x, the end of the lever t t, to which the cut off valve rod is attached, will move through the same space as the slide valve, its other end being kept from rising or falling by the rod s. For these reasons the cut off valves can never shift from their positions on the slide valve dd, into which they are put by the wiper

Fig. 4 shows how my plan of expansion gear can be applied to the short slide valve; in this fig. aa shows part of the cylinder; b is the port leading to the top end of the cylinder, and c is the port leading to its bottom end; d is the cut off valvewhich opens and shuts the passage through the slide valve which leads to the port b, in connection with the top end of the cylinder; and the cut off valve e opens and shuts the passage f, leading

through the slide valve into the bottom port c of the cylinder. The rod g,which works the cut off valves, passes through the rod of the slide valve. h is the eduction port. Fig. 5 is a front view of the cut off valves; the rods ii, shown in this fig. form the connection of the one valve with the other. Fig. 6 shows an arrangement of shafts, rods, and levers for working the valves: in this fig. a is the lever, which works the slide

valve, and the lever b communicates motion to the cut off valves; c is the rocking shaft, and the lever b is fitted so as to work loose on it. The lever shown by dotted lines is the one into which the rod from the eccentric for working the slide valve gears; d is the rod which receives its motions from the wiper for working the cut off valves, which is fixed upon the crank shaft of the engine; e is a rocking shaft, the journals of which work into two levers fixed upon the rockng shaft c one of these levers being placed exactly behind the other; f shows them both; g is a lever fixed upon the rocking shaft; e and h is another lever fixed upon the same shaft. The levers g and h communicate the motions of the rod d to the lever b, by means of the rod i. A similar arrangement of rods, &c., as now described, may be used for working the cut off valves when they are placed in figure 1.

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Fig. 7 shows another form of my plan of expansion gear. In this fig. it will be seen, that the cut-off valves work upon the back of the face-part of the large slide-valve of the engine: a is a small rocking-shaft, supported upon brackets which may be fixed at a convenient distance, above or below the rocking-shaft b, which works the large slide-valve. The rocking-shaft b is cranked, in order to let the end c, of the lever d c, be so near to the centre of motion of the shaft b, as that the motions which this shaft gives to the large slide-valve, will not shift the cut-off valves from any position on the large slide-valve into which they may be put, by means of the wiper on the crank-shaft. The centre of the lever de works upon a pin, which pin is fixed into the levers in connection with the links which work the large slide-valve. e is part of the rod which communicates the motions of the wiper, fixed upon the crank-shaft, to the rods, &c., shown in the fig., which carry its motions to the cut-off valves: f is the eceentric rod.

Fig. 8 shows the crank-shaft, and the wiper upon it which works the cut-off valves. The large valve, shown in fig. 7, is a modification of the D leech-valve. The pipe h which forms the connection with the top and bottom ends of the valve is stationary, and the valve slides past it. The eduction pipe h rests, and is prevented from rising by means of narrow flanches cast near its bottom end, which are guided by means of similar

flanches cast inside of the bottom part of the nozles. As the working part of this slide-valve is very light, it may be made entirely of brass, and cast in one piece. Behind the rod which connects the top and bottom cut-off valves a light rib is shown: one of these on each side connects the top and bottom parts of the valve.

In a factory engine, the part of the stroke at which the steam is cut off must be regulated by the governor. Fig. 9 shows a plan of a governor, which shifts the wiper for working the cut-off valves, so as to cut off the steam later, whenever the engine goes too slow; and if the engine happens to work above its proper speed, it puts the wiper into a position to give the piston the full pressure of the steam during a shorter portion of its stroke; and, in this way, the governor keeps the engine going at nearly the same speed, whether it is doing much or little work. The wiper a gives motion to the cut-off valves by means of a similar arrangement of rods, levers, &c., as shown in fig. 1, 6, or 7; and it is of the same form as the wiper shown in fig. 8. bis a spur-weeel, and d is a pinion which gears into it. The part e of the governor is connected to the pinion d in such a manner that, if the part e rises or falls, it will carry the pinion d along with it; but the connection of these parts does not hinder the pinion from revolving on the governor shaft or rod. The wheel and pinion are calculated so as to cause the shaft c, upon which the wiper a is fixed, to make the same number of revolutions as the crank-shaft of the engine. The pinion d is bored out and fitted to the governor-rod, so that it can revolve and work up and down on it; and the feather, which forms the connection betwixt the rod and the pinion, runs in a spiral direction, as shown in the cut, and not, as in ordinary cases, straight up and down. By this arrangement, if the pinion d is raised or lowered, by means of the governor, the screwed feather will carry it round upon the rod, and shift the position of the wiper, so as to cut off the steam sooner or later, according as the balls are up or down-if the screwed feather winds in the proper direction. If the teeth of the spur-wheels b and d wind in a spiral direction on the surface of their rims, as in White's wheels, the pinion d, as it rises or falls along-side of the wheel b, will cause the

Sir, I beg to submit to your readers, directions for making, managing, &c. the best of all possible boilers for steamengines in general, and marine engines in particular.

1. Let your chief care be to make the boilers very complicated, and of such form and strength that the most trifling

accident shall eventually cause them to explode.

2. Connect them all to one steam-pipe; and take care that the openings into it. are so formed that it is almost impossible for the steam to pass through; and then, to make the steam obedient to your will, put in immense fires, and thereby gene

rate steam very fast, and, by that means, oblige it to pass through the aforesaid awkward openings, somehow or other.

3. Be sure to form the flue so that a great part of the heat is appropriated to scorching the hull of the vessel, instead of to boiling the water; it may, perhaps, set the vessel on fire, which will cause an amusing excitement among the passengers, and relieve the dull monotony of the voyage.

4. Do not by any means neglect to place the chimney in such a situation as will give the engine-men a lively idea of the heat of the abode of a certain old gentleman, whose name is commonly abreviated to the first syllable.

Having made all these admirable arrangements, you may expect an explosion every hour. After it has occurred,

5. Employ some clever engineer to examine the boilers; and make a great parade of your own anxiety for a full and fair inquiry; if the engineer says the boilers are every thing they ought to be, all well; if he does not say so, bring forward as many persons as you can, who may safely swear they do not know why the boilers are not every thing they ought to be, and that, therefore, they consider they are;-declare you know they areand mystify the jury until they return a verdict which amounts to saying they have tried to understand the matter, and have failed in the attempt.

You may, however, think it prudent to make a few alterations, which you can easily do by sticking a few steam chests on the tops of the boilers, which will enable you to assure the people that, although they were perfectly safe before, they are a vast deal safer now; and that you are decidedly certain no accident can possibly happen. You may say all this with a safe conscience, because you will take care to be profoundly ignorant of every thing which would render your opinion worth one straw.

But you will prudently provide for contingencies: that is, as you will not know whether the boilers are any safer or not, you will prepare yourself, as well as may be, to encounter another explosion; for which purpose the following hints may be useful:

Impress upon the mind of some one on board that, as soon after the explosion as possible, he is to go and look at the feed-cocks, and call some one else to look

too; if they can see that all the cocks are shut, and the boilers red-hot all over, it will be glorious; if not, the more red they can see the better.

Be prepared to state, that the men who have been killed, were very carefully chosen-that they were the most sober, experienced, and efficient engineers that could possibly be selected-that they were never guilty of inattention until they were employed on board your vessel; but that, when that was the case, they formed a perverse determination to do what they had manifestly no motive for doing, and which they must have known would end in their own destruction. You can intimate a suspicion, that they had agreed among themselves to commit suicide; or that they were quarrelling, and that some of them exploded the boiler for the purpose of giving the others a more effective "blowing up " or any thing else that may occur to you, and which you think may do your cause some service, however monstrously inconsistent it may happen to be; for you must not think of sticking at trifles.

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Possibly, about this time, the coroner will be kind enough to tell the jury, that he thinks they know as much of the matter as they ever will know, and the jury may think so too, and return much such a verdict as the first jury did-in which case you can try again, and kill a few

more.

But if the case happens to be before a jury who are most inconveniently determined to arrive at the truth,-declare most emphatically, that is your only object; if you can make them believe this, you will have the better chance of leading them wrong. To assist you in doing so, bring forward some one who will declare, that the strength of a steamboiler is "merely a matter of fancy." And do not by any means neglect to try figures; tell the jury" there is a matter of figures to go into," and do your best to bother them that way. For, if any one should be unkind enough to declare in print, that " any pretence to calculate the strength of your boilers would be absurd, or something worse," and give good reasons why, you have nothing to do but to say no more about the 'figures," and you are but where you were before you made the attempt.

If an eminent engineer should be called upon to give an opinion of your