Page:The Building News and Engineering Journal, Volume 22, 1872.djvu/395

 May 10, 1872. THE BUILDING NEWS. De ——————————————————————————————— ——— ss] together. This is a 2-yard waggon when filled up to the top of the sides, as with gravel, or a 24-yard waggon when heaped up with clay or other earth. ‘The wheels are 2ft. 6in. diameter, of cast iron, with internal bearings, the axles being of wrought iron. The top of this waggon stands only 4ft. 3in. above the rails, and lowness of sides is a great ad- vantage in filling. The cost of this waggon is £17. Another form of earth waggon has the body set on an axle upon the frame, by which means the body only is tipped up, the frame remaining stationary on the wheels, but to enable this advantage to be had the top of the waggon stands a foot higher than in the other kind, and this is against it, as being so much labour wasted in filling. It is some- times necessary to have waggons that tip side- ways, and attempts have been made to combine an end and side waggon in one by making the body turn on a central pivot, but the plan did not answer the expectations. Indeed, removing earth in waggons on tem- porary rails in bad weather is very rough work, and the simpler the means adopted are the more likely is the work to proceed with- out hindrances. Ata busy tip, men, horses, and waggons are very apt to get in each other's way, and the simpler the construction of the waggons the better. As to the power required to lead the earth from the cutting to the embankment, a horse is usually understood to exert a force of 150Ib. in drawing a load at the speed of 24 miles an hour during 8 hours a day. The resistance which he has to overcome consists in all cases of the rolling friction—that is, the friction between the axles and the pedestals which bear apon them, and depends in a great measure on the attention paid to greasing the bear- ings; but when that is properly attended to the rolling friction is about 10Ib. per ton of the load—i.e., including the weight of the body of the waggon with the weight of the earth it may contain, but it varies from 10Ib. to 20Ib. according to the state of the bearings. ¥n going round a curve there is another kind of friction to be overcome—the sliding fric- 4ion—in addition to the rolling friction com- mon to all directions, for as railway waggon- wheels are keyed on to the axles, the outer wheels, in going round a curve, are obliged to slide over a distance equal to the difference of length of the inner and outer rail. Railway curyes traversed by earth waggons are in general of such considerable radius that this part of the friction may be neglected; but in order to ascertain the resistance on sharp curyes, the following experiments were made under the eye of the present writer :—Three men push 2 six-ton waggons on a straight line; 4 men push 1 six-ton waggon round a curve of 350ft. radius; 6 men push 1 six-ton waggon round a curve of 200ft. radius. The wheels were 3ft. diameter, and the axles 8ft. apart. From these experiments the following table is constructed :— Number of men to push a 6-ton waggon. Radius of curve in feet, Straight line 2,100 feet radius 1,340 606 550 500 450 400 300 oi 300 4 250 200 ” ” ” rh) ” ” ” 3” According to this scale the curve shown in Fig. 11 represents the rate of increase of the resistance compared with the radius. The following description of experiments on the work done by a horse was reported to the Institution of Civil Engineers by Mr. Beardmore. A quarry waggon, weighing 24 tons, carrying af average load of stone of 53 tons, was drawn by one horse along a railway 960ft. long, 260ft. of it being level, and the 138. During 48 working days the number of trips was 1,302, or an average of 27 trips per day. ‘The time of performing each trip was 4 minutes, or at a speed of 2°72 miles an hour, and the total weight drawn, including that of the waggon, was 23,959,000lb. Experiments proved that on the incline of 1 in 138 the waggons in their ordinary working state would just remain stationary ; the friction was, poe = 16-2lb. per By calculation it was found that the therefore, assumed to be VO ton. FIG.i0 ee RESISTENCES Fig. 11. horse raised 39,3201b. 1ft. high per minute during 8 working hours each day ; the useful effect, or net amount of stone carried, being 21,738lb., raised ft. high per minute. This great difference between the work done and the useful effect arose from the necessary strength and weight of the waggons. The animal employed was a common Devonshire cart-horse, eight years old, fifteen hands high, and weighed 10$ewt. He continued doing the same work during the whole of the summer, and remained in good condition, A lighter horse was found unequal to it. If we analyse the above statement we find that the weight of the waggon and its load together is 8} tons, but we may deduct three- quarters of aton for the wheels andaxles, leaving 7} tons as the bearing weight on the journals. ‘The friction was found to be 16-2Ib. per ton. Multiplying 16-2lb. into 74 we find tha traction of the horse to be 1201b., and, as ha moves at the rate of 2:72 miles an hour, 2°72 X 120 an : Sea SaM ae 1501b. at the rate of 24 miles an hour, which corresponds with what we said before. There is another resistance sometimes to be overcome, that of dragging waggons up an incline, the resistance to which varies as the sine of the angle of inclination, or as the gradient, aud although in the formation of a railway the gradients are so arranged that the full waggons have seldom to be drawn up an incline in the main, yet in the imperfections of a temporary road the wneyenness of the surface of the rails does offer resistances of this kind which are not compensated for by the corresponding depressions produced by the same defects; and on the whole the average friction of earth-waggons may be taken at 201b. per ton, although it sometimes amounts to 30lb. in bad weather, and in a very bad state of the road. In general, it is very much more economical to keep the road in good order and to grease the bearings well than to neglect these things, and throw greater labour upon the horse or other tractive power. In a former article we put down 3d. per cubic yard per mile of lead as the cost of keeping up the road; there can be no doubt that inattention to this matter will always entail a greater expense than that, although the various items which go to make up the greater expense cannot be exactly stated. At the Blechingley and Saltwood tunnels on the South-Eastern line it was found that in winding up earth at the shafts a horse working 3 hoursa day did work equal to raising 32,9431b. 1ft. high per minute, and working 6 hoursaday 24,360lb. These are averages of 112 trials in the first case and 212 in the second, but the maximum inthe first case was 47,875lb. and in the second 36,819]b. A waggon holding from 2 to 24 cubic yards is the most economical and convenient for use—that is, 2 cubic yards when loaded with gravel level with the top of the side boards, and 24 cubic yards of clay or other earth heaped up. If we take 24 cubic yards of excavated earth to weigh 34 tons, and the body of the waggon three-quarters of a ton, the load to bedrawn will be 4 tons each waggon. At the rate of 201b. per ton the resistance is, there- fore, 801b. each waggon, so that 2 waggons of this weight are as many as one horse can take away, on an average, of all states of the weather and of the road; but when the weather is dry and the road in good order, a horse will take 3 of such waggons, while at other times itrequires 2 horses to 5 waggons, the speed of transport being reckoned at 24 miles an hour. Thus, according to the length of lead and the number of roads that can be laid in at the tip head, so may the quantity of plant and the number of horses required to remove a given quantity of earth in a given time be caleu- lated. Allowance, however, in such calcula- tions must be made for hindrances at the tip head, caused by men, horses, and waggons, getting in each other’s way unavoidably, when the number is great. 800 cubic yards is the utmost quantity we can find amongst our notes ashaving been tipped at one head ina day of 10 working hours, and although it is on record that considerably more than that has been accomplished, yet it is certain that less is oftendone. The nature of the material makes some difference : when of a dry nature more can be done, but in working in clay or shale after a shower of rain, it is sometimes not easy to recover the waggons after they have been tipped, and to get them re-arranged in aset ready for being taken back again ; then, accidents are of frequent occurrence, either to men, horses, or waggons ; and all these things tend to reduce the average quantity per day that can be disposed of.
 * remaining 700ft. having an inclination of 1 in