October 18, 1918. THE COLLIERY GUARDIAN. 807 imparted to the sand will be so small as to be negli- gible for practical use for stowing requirements. Let R = the hydraulic radius in feet, and V = the mean velocity in feet per second; then to impart movement to sand we get— R = 50’0 ... 23*3 ... 10-0 ... 5’0 ... 2’50 ... 1'00 ... 0’08 V= 6 0 4’5 . 35 ... 2 75 ... 2 16 ... 1 66 ... U5 R = 0-3 . 0’25 ... 0’15 ... 0-10 ... v 05 ... 0'02 ... 0’01 V = 1’4 .... 125 ... 118 ... 1 20 ... 1 40 ... ISO ... 2’50 It may be noted that as the hydraulic radius in- creases from 0-07 to 0-15, the velocity of the water necessary to move the sand decreases; while as the hydraulic radius increases from 0-25 to 50-0, the neces- sary velocity of the water increases. The depth of flow would be an important factor, as the water would first subject the sand to a motion of dragging, and later the particles would be lifted up into the stream, the motion being then converted to one of suspension. The water would carry a larger quantity of sand in its lower portion than the upper, and it could be generally assumed that the amount would be propor- tional to the depth. Regarding the wear due to friction of the sand on the pipe, it may be an advantage later to investigate carefully the relationship of this to the velocity, for it may be assumed that in pipes the greater amount of material carried will be along the centre portion of the water, and it remains to be determined to what economical limit the velocity of the water may be accelerated in order to increase the time of suspension of the particles and reduce the friction due to the dragging effect of sand particles. Where, however, the sand is washed into a bin and precipitated, while the water is allowed to overflow and run back to the pumps at the river bank, the proportion of water to sand may be high so that the inclination of the flume or pipe line can be reduced. Further, at the feeding point the tower can be ex- tended to a greater height so as to increase the -head, and this would reduce the requisite height of the other towers. In the open flume it is doubtful whether a coefficient of friction for sand on iron will be less than 1/5. bridging for a good proportion of the year and the mine is comparatively adjacent to the sand area. In the Jharia field the river is generally at a distance, and the lead involves a comparatively high capital cost. This may be dealt with either by the co-operation of a number of colliery concerns or the construction and running of the main lead by a private company. For transporting the sand endless haulage appears the most suitable, and with this system, if we have a four mile lead and assume each truck carries one ton, and the speed is two miles per hour, then one truck takes two hours to make the round trip. With 5,000 tons per day of twelve hours, equal to, say, 416 per hour, this means 832 full trucks and 832 empty ones in transit, total 1,664 plus those being loaded at the river bed. Possibly not less than 1,800 trucks or skips will be employed. Five thousand tons daily means 11,200,000 lb., and at 100 lb. per cu. ft. equals 112,000 cu. ft. A simple method of loading would be by running the trucks via a series of port- able tracks on the river bed, loading them by hand and shifting the tracks as occasion required. The loading, however, would be a much more difficult problem than this, as a truck load would have to leave every eight seconds; and if we consider the sand is excavated to a depth of 2 ft., then every day an area equal to 56,000 sq. ft. will be cleared, so that a simple loading device becomes absolutely necessary, the simplest method being to employ a conveyor, which by reason of its length is particularly adapted for work cf this kind. In America sand is often excavated and loaded by portable loaders, consisting of a frame with a number of buckets fixed to a chain running over head and tail wheels. The buckets are about 18 in. by 18 in., and deliver about one ton per minute. They are fitted with a chute, and only require about a 7 horse-power motor to drive them, the weight with the motor being about 7,000 lb. About eight of these machines would possibly help to solve the difficulty of labour trouble with regard to loading, and prove more economi- cal. The excavators at the river bed would then feed into a conveyor, and from experiments it is found that one man can load a conveyor with 6-75 cu. ft. of sand central power station, which could either be situated at the river bank, thus saving the poles and wiring to the conveyor motors, or we may assume a power unit with sufficient power to operate, in conjunction with the main lead, the endless haulages for mines adjacent to it. The latter is the more expensive arrangement, but it is taken as the grade to the mines is favourable to the load, as a rule. Even assuming the friction of the rolling stock to be 20 lb. per ton, the power plant given below is extremely high, and although a supplementary engine is allowed for the lead from the main track to the mines, the power at the main station would possibly cover this, and the switch-board arrangements are entered at a high figure to admit one central plant only if necessary. Also another supplementary conveyor 500 ft. long, in addition to the two already mentioned, is allowed for, so that the area of supply may be distributed as much’ as possible across the river bed. Owing to the absolute necessity of a reliable power plant, two sets of engines, each of 150 kw., must be provided, so that a failure of one would not absolutely stop the work. NORTH OF ENGLAND INSTITUTE OF MINING AND MECHANICAL ENGINEERS. Mr. John Simpson presided over a meeting of the members of the North of England Institute of Mining and Mechanical Engineers, held on Saturday after- noon last in the lecture theatre of the Wood Memorial Hall, Newcastle-upon-Tyne. The following gentlemen were admitted into thte Institute:—Associate member: Dr. S. Smith, geolo- gist, University College of Wales, Aberystwyth. Asso- ciates : Mr. Wm. A. Flint, colliery overman, 27, Middle Row, Isabella Pit, Newsham, Newcastle-upon- Tyne; and Mr. P. Kay, colliery surveyor, 54, Rosa- lind-street, Ashington, Northumberland. Overhead Koepe Winding Plant. “ Notes on the Overhead Koepe Winding Plant at Plenmeller Colliery, Haltwhistle, Northumberland ” E,LE.vaTior2 nlrernsre tjec-viorx pi |K| leal K4 i£il Figs. 10 to 12.—Bank Tower for Flume. Figs. 13 and 14. Thus for water to carry 1 lb. sand 100 ft. requires 100/5 = 20 ft. lb.; if the proportion of sand to water is 1 to 10, then 10 lb. of water must fall 2 ft. in 100 to give this energy. However, while the water imparts motion to the sand there is a tendency for the former to run at a higher velocity over it, so that the inclination would need to be more than this. Possibly for feeding the sand, in the place of the flume it would be better to employ a pipe, and we may then roughly assume that the grade will be in proportion to the mixture; if one part of sand be used to 25 of water, the grade would be also in this proportion, or 4 ft. in 100. The necessary head might be increased at the feed tower, so as to reduce the height necessary for the intermediate towers. The flume bearing the return water to th# pumps could be carried across the river (when necessary) below the supply pipe and on the same supports. The area of the receiving bin would in this case have to be of sufficient extent to admit of the requisite precipitation of the sand with sufficient rapidity to allow a large proportion of, the water to overflow. For this reason it may be suggested that the bin would be provided with a well in its floor and the surface would be graded to meet this, so that an adequate sand sump would be provided. The feeding pipe from the rivfer would terminate comparatively deep in the bin, so as to keep the sand at as low a level as possible to aid its precipitation, and from the bottom of the well the sand could be led straight to the mine or a supplementary feeding bin. Near the surface level of the feed bin the flume for taking back the surplus water would emerge. A strainer might be put at the entrance of the flume to assist in keeping out the sand, and it would be found convenient for its alignment to follow directly under the supply pipe, though possibly set on the ground until carried across the stream to the pumps on the same support as the upper pipe. Owing to the low grade required for the return water, it is possible that the flume could meet the feed tower at a point considerably above the level of the river, and the pumps be here situated so as to reduce the head necessary for a considerable proportion of the water. It is, of course, doubtful if this project would prove economical or convenient, but it is possibly worth con- sideration, particularly where the location of the sand areas necessitates crossing a river which may need in twelve minutes with the material at a distance of 18 ft. from the conveyor. In practice the conveyor could possibly be moved in such a way that the men would be close to it all the time, and would at the •most have to carry the sand about 3 ft. In the con- dition under review it was found that the 6-75 cu. ft. were deposited in the conveyor in twelve minutes. This represents 675 lb. in twelve minutes, or 1-6 tons per hour. With a conveyor 500 ft. long and a man every 3 ft., 166 men could be employed each side of the conveyor, and these could load about 500 tons per hour, but for the purpose of calculation it would be advisable to figure on not less than 400 men. Assuming the conveyor could be practically moved in a circle, we get a superficial area of 783,828 sq. ft., or, at a 2 ft. depth, about 1,567,656 cu. ft., equalling about 70,000 tons or 14 days’ supply. This conveyor then would feed into' one leading up the bank* and 600 ft. long. Since the loading point at the bank is being continually shifted from the bank terminal of the main lead, a supplementary haulage would have to be introduced running parallel and close to the bank; a portable bin would need to be provided into which the conveyor running up the bank would feed, and as the area was evacuated in the river bed, and the conveyors were shifted, the bin would, be moved from time to time to suit conditions. Owing to con- veyors being more expensive than a track, the former is not to be recommended for feeding direct to the main haulage. This loading bin would have a capacity of about 100 tons, and this equals 2,240 cu. ft., and if 40 ft.' long would accommodate eight trucks at a time, and this would enable loading at the speed required to allow them to leave at their eight-second intervals. In Jharia, the point for depositing the sand from the main lead would be about 80 ft. higher than the river bank, the grade being 1 in 230 or 0 deg. 15 min. The load on the rope equals 832 tons, and for a rough calculation we may ignore the weight of the return trucks as they will have a slight grade in their favour. Assume pull of 900 tons; by Ende’s formula we get 0-0043 x 900 tons equals 3-8700, add 25 per cent, for friction, gives 4-84. Taking a factor of safety of 7, we get a breaking strain of 30-88 tons. To deal with this, a one-inch rope may be estimated at, say, 10 lb. per fathom, and for eight miles of rope this would be 800 cwt. It will possibly be advisable to have a (Colliery Guardian, June 7, 1918, p. 1141), by Mr. George Raw, were open for further discussion, but none was offered. Replying on the whole discussion, Mr. Raw re- marked that Mr. Hanley and Mr. Halbaum were each evidently dissatisfied with the rope adjustment screws and links, Mr. Hanley suggesting the introduction of “ the. principle of the extension carriage,.” and Mr. Halbaum “ something more worthy of an engi- neer’s brain ” than the “clumsy links.” Incidentally, the Plenmeller plant was designed and constructed, though not erected, prior to his association with the colliery. At that stage, however, he carefully re- viewed the principle of the sliding carriage, but it was found that the new stresses introduced would have involved reconstruction of the whole tower, so that, although admittedly clumsy, he found the ad- justment screws and links the best compromise for a completed if unerected plant. He also formed the conclusion that the arrangement chosen was preferable to the hinged platforms which were frequently used to get over the difficulty and, when the winding rope was too long and the cage in consequence too low, caused the tubs at the pit bottom to jump into the cage much too vigorously. The idea of the extension carriage was, of course, an old one, but it allowed the driving pulley to be double-grooved and to engage the winding rope for roughly times the periphery of the pulley instead of only half or, as in the present instance, 0-583 of the circumference. That .increased very considerably the frictional grip of the rope or, if Mr. Hanley preferred it, the “ strictional ” grip in the same way, although probably not to quite the same extent, owing to the separate groove, as a sailor looping a rope round a capstan, when the grip on the capstan increased as the power of the number of turns of the rope. It would scarcely be practicable to raise and lower in an overhead plant the whole driving pulley, a.s the motor or engine would have to accompany the pulley in its travel, and the whole device would be a most ponderous one. Were he, how- ever, to have to design a new Koepe winding plant, he should very carefully consider, for adjusting the rope length, the introduction of a sliding pulley, utilising the same for operating the depth indi- cator, etc. He found himself in disagreement with Mr. Hal- baum regarding the side friction of the pulley groove in the rope. The wood segments, hard wood though