Ledyard Colburn, of Birmingham, Conn, has taken measures to secure a patent for a new railroad brake. The invention consists of a wrought-iron shoe, which is suspended on either side of the wheel in the ordinary manner, and worked like the common brake. It can also be used in cases of extreme' danger by the engineer pulling a leter,' Which springs the knuckle joints of the Shoes, and causes them to fall on the rail i dsr the wheels, thus raising the latter slightly- from the track and stopping them, as well as throwing the friction and wear on the shoes. The Albany and Susquehannah Railroad has been so far located as .to be ready for contract. Bids for its construction have been invited, which will be opened on t Q 1st of December. Machinery and Tools as they are --The Steam Engine. (Continued from page 75.) Before dismissing the subject of the side- lever engine, we will make a lew remarks on some parts of the” machinery which are common to all the varieties of the marine engine, and foremost in importance is the subject of the condenser. Singular as it .may seem, it is nevertheless certain, that the condensing engine is an invention of older origin than the high pressure engine, which latter is much less complex, and would appear likely to have first occurred to the inventor. The use of the condenser is to convert the steam, after it has done its duty in the cylinder, into water, which is effected by exposing the steam to the chilling influence of a jet of water, which passes from the sea through a pipe into the above- named vessel. At each successive stroke of the engine it is necessary to remove the water that is in the condenser; this is effected by the air- pump, the arrangement of valves for this purpose being as follows :—The foot-valve opens to permit the water and uncondensed vapor to enter the air-pump, from which they are removed by the air-pump bucket, which is furnished with a valve opening upwards.— Another valve, termed the delivery-valve, prevents the return of the water from the hot- well into which it is pumped. The present shape ot the foot and delivery valves is that of a rectangular plate working on a joint, so as to close against the valve seating which inclines at an angle. The valve of the bucket is either simply a circular plate with a hole in the centre, through which the air-pump roll. passes, so as to allow the valve to slide up and down, or if that shape is rejected, the buttercup valve is used, which is merely a semi-circular flap on each side of the bucket. It is evident that, in engines of high power, these valves are of great size; the diameter of the air-pump is about one-eighth of the diameter of the cylinder, and the area of the delivery- valve is one-third ol that of the air-pump, so that the continual .jarring of these valves against their seats is an evil which requires a remedy. Canvas and india rubber have been employed in the air-pump valves for this purpose, with considerable advaatage. The feed- water for the boilers is taken from the hot- well and forced into them by the feed-pumps. These operations, it will be perceived, consume a considerable amount of the power, and to reduce this item of consumption is of great importance. We have mentioned that condensation is often effected by passing the steam through a great number of small tubes, which are surrounded by cold water; this allows of the employment of a much smaller air-pump, and consequently saves the power, because the condensing water has not to be pumped out, but only the water arising from the steam. The saving is, however, counterbalanced by other objections, the chief one of which has been already stated. Another mode of attaining this object, which has hitherto failed, is to expose the steam to be condensed, to the impinging on a cold metallic surface, but it is difficult, by this plan, to condense rapidly and efficiently. Could any such system be made available, the evil of employing salt water in the boilers would be ' got rid of, and thus cause a saving of these vessels, a diminution in the amount of fuel,and render unnecessary the operation of blowing off. The slide valves regulate the entrance and exit ot the steam to and' from the cylinder, and are usually of the box or else of the D description, not having been much changed for some years. The D slide is generally preferred if the engines are of great size, being sometimes made in one long valve, and in other cases being formed of two short D slides connected by a spindle. It derives its name from the shape, which is that of a semicircle, with a strip at top and bottom, designed to close the steaM ports, a, projecting a little forward ; the circular part, which is the back of the slide, is kept steam-tight by packing. The box slide-valve requires but little description, its name explaining its shape; suppose, for example, a shallow cast-iron box placed on the cylinder facing with the recess downwards, top and bottom rim made rather broad, and it will give a sufficiently accurate idea of this valve. The last-mentioned valve has been somewhat improved in many engines, by being rendered a balance-valve, of which the main object is to obviate the great pressure exerted by the steam on the back of the slide. This is effected by t lacing a .metallic ring on the above-mentioned part of the slide which is made steam-tight by spring packing. By admitting the steam between the slide and this ring, the pressure is counterbalanced, for the ring bears against the valve- box cover as much as the face of the slide bears against the cylinder. If this construction is adopted, the valve-box cover of course must be planed and brought to a surface. The above contrivance is particularly serviceable when the engineer requires to shift the position of the valve. Until the epoch of transatlantic navigation, marine engineers were indifferent or incredulous to the advantages of expansion; it is now, however, generally used in all large vessels. It will be unnecessary to dwell upon its benefits, as in America its economy has been long appreciated. With reference to its employment in steam vessels, the only point in dispute is, how tar it is advisable to sacrifice the saving of fuel, realized by its use, tor the slight additional speed obtained by admitting the steam during the whole stroke of the piston. It is well known that expansion can be effected by a proper arrangement of the slide valve, and tor this purpose some marine engines have been lately provided with the slide gearing first intr )duced by Stephenson, in England, for his locomotives. It is, however, generally considered preferable to use a sepa. rate valve to cut off the steam, and thus to allow the slide its lull stroke. The expansion valve is regulated by a cam fixed on the main shaft, and consisting ot a series of curves arranged side by side, like steps, so as to shut off the steam at any desired part of the stroke. The valve itself is a balance or equilibrium valve, and is generally of the form known as the Cornish double-beat, so that the pressure of the steam is neutralized. We shall conclude our account of the Side- lever Engine with a few remarks on the mode ot operation tor connecting or disconnecting, as may be required, the crank-shaft and paddle wheels. When, from any cause, the machinery is not in operation, although the vessel is under weigh, it is requisite to cast the paddle shafts loose from the engine, for the water acting on the floats of the paddle-wheel retards the pro grp.ss of the vessel. This was formerly accomplished by removing the strap ot the con necting rod, so that the whole length of the shaf with the wheels would revolve freely. Such was a tedious mode, and various plans have been introduced to simplify the, opera tion. The main idea, however, is the same in all, namely, permitting the paddle shafts to revolve while the crank or intermediate shaft re mains stationary. (To be Continued,)
This article was originally published with the title "Railroad Brake"