Original Communications. To the Editor of the London Journal of Arts, &c. SIR, THE specification of my patent for Axletrees intended to remedy the extra friction of carriage wheels when passing along curves upon rail-roads, having been inrolled, and I presume about to appear in your Journal, I request permission to communicate to the public through your medium, a few observations relative to the inconvenience of friction, which carriages now in use labour under when proceeding along curves of the line of railway, which observation will I consider shew the necessity of an invention of the kind, and its usefulness. Waggons that have hitherto been used are of such constructions that when passing curves in the rail-road (if the curve be not even more than two feet in twentytwo yards,) the friction is so great that it requires nearly double the power to propel the carriages that is necessary to produce the same speed on a straight line. It must therefore be evident that the extra power employed has the effect, merely of grinding and wearing away the waggon wheels and rails; various schemes have been put in practice to prevent these inconveniences, and each has proved ineffectual. Wheels have been used on tram roads running loose upon fixed axles, but they have proved unsuccessful; for this reason, they cannot be kept steady, nor can they be prevented having play. I wish it to be understood, that there is a great difference between the edge rails and tram roads, the former being but two inches and a quarter broad, the latter from four to five inches. It must be known to engineers that wheels of a large diameter run with much less friction than those of a small diameter. It is my opinion that a carriage that is to travel at the rate of six miles an hour, ought not to have wheels of a less diameter than three feet. If it be wished to increase the speed of a waggon running on rail roads, it must be evident that increasing the size of the wheel will do it. Suppose we take it on an average that the wheels be four feet in diameter, as the speed for carrying goods and passengers is wished to equal that of the coaches; the play that will soon take place in the loose wheels, will allow them to vibrate and spread not less than one inch and a half, and it is well known that rail roads cannot be kept to that gauge, without sleepers or bearers extending from rail to rail, in order to bind the road together; and it will alsɔ require an extra number of men to keep the road in order. Carriages with loose wheels are not at all calculated to rise and fall with the many irregularities of the road they must meet with, proceeding from various causes, such as the blocks being sunk, by the embankmeuts giving way, &c. &c., as their axletrees must be firmly fixed to the body of their carriages. It will be doubtless the case that when the carriage meets with the hollow parts in the road, it will be resting on three wheels, and the fourth will most probably be lifted higher than the depth of its own flange, therefore, if the carriage be e travelling round a curve with the hollow inside, it must inevitably be thrown off the road. In consequence of these inconveniences, loose wheels have been entirely abandoned on the edge rails, and those that are wedged firmly to a rotatory axle have been adopted, and appear to be far superior to the loose ones. In straight lines the waggons now in use may suffice, but when they meet with curves of six or eight feet to a chain, (or twenty-two yards) the friction that then takes place is enormous. I can with confidence say, that the carriages above alluded to in passing these curves will at least grind off the top of the rail one-sixteenth of an inch in twelve months. The thickness of the top part of that kind of rails generally in use is only about half an inch, and those are on the most improved principle; therefore, it cannot be disputed when I say, that in four years the rails in these curves will be reduced below the standard strength required for the passing of the loaded waggons. The enormous expense thus occasioned by this extra friction will be seriously felt by proprietors of rail roads; the malleable iron rail roads not having been long enough in use to prove to the public the real time they will last, and the disadvantages before named have not been yet fully ascertained by proprietors. The only malleable iron rail road that has been used for any length of time, is that which extends from Lord Carlisle's colliery to Brampton, in Cumberland, about ten miles in length, and has been made upwards of ten years. The straight line of rail road appears not to be much reduced, but the smallest curve lines have been replaced many years ago. From these circumstances I am led to believe that a straight line of rail road, where there is a great traffic, will not last more than forty years; and those of sharp curve lines, not more than four, with the waggons now in use. These disadvantages induced me to direct my attention to the constructing of a waggon that would obviate these difficulties, and the one I have made will, I doubt not, overcome them. The wheels on my waggon are firmly wedged to the axle, and yet will roll round the sharpest curve without any additional friction from the sliding of the wheels. Carriages of the ordinary construction that travel on rail roads having one side more exposed to the heat of the sun than the other, must have their wheels soon worn to a smaller diameter, by their being exposed to a greater heat, as every practical scientific man knows, that wheels exposed to the south wear away much sooner than those exposed to the north; but the two wheels being wedged upon one axle, as in the carriage at present used, the friction will be much increased, even if the carriage be moving on a straight line, in consequence of the wheels that have not been worn travelling over a greater surface than the others. Each wheel on my carriage is so adapted, that it will revolve with its own axle, and every wheel will travel over the surface required, either in a straight or curved line without any increase of friction, even though all of them should be of unequal diameter, (see the specification, page 169.) There are still many disadvantages not yet mentioned, which rail road carriages now in use labour under, for when they are lightly laden, and are moving at the rate of five or six mile per hour, and come in contact with sharp curves, they are generally thrown off the road; and should they be precipitated to the bot tom of the embankments, which are in some places fifty or sixty feet high, the consequences might prove dreadful, and the expenses great, for the carriages would doubtless be much injured. Suppose we conceive (which most likely would be the case,) that the waggon at that time would have many passengers, they must some of them, if not all, be killed upon the spot. My improved carriages will remove all the above named difficulties; and passengers may travel with the greatest safety. These carriages have been tried before scientific men, and have answered beyond all expectation; they will not only move round curves with the same ease as on a straight line, but will travel over the hollow parts of the rail road that may have sunk, in consequence of the embankments having given way, with perfect safety. I am, Sir, Your's, &c. ROBERT STEPHENSON. To the Editor of the London Journal of Arts. NOTHING appears to have been either more or longer overlooked and unimproved than the efficacy, necessity, and utility, of architectural ventilation. Sagacious ancients discovered indeed its useful effects, and ancient celebrated architects exerted efforts to introduce ventilation, on particular occasions; therefore, none need look far for records and proofs, that ventilation was always prized, when Vitruvius, Alberti, &c. flourished with immortal skill; yet no plain, perfect, and practicable means |