184.9.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



305 



This kind of sector, w; he believes is in.i(le by his firm only, 

 has the tenth number at .e twelfth division from the starting 

 point; the two divisions being added for the depth of tooth beyond 

 the pitch-line. There are two scales on each of these sectors, one 

 on each edge; which scales are marked according to the number 

 of teeth to the inch diameter (pitch-line) they are adapted for. 

 They are made in sets ranging from 3 to 30 in the inch. t)ne set 

 of tiiese sectors is used for sizing working-wheels, and another set 

 for sizing pattern-wheels; the latter is one per cent, coarser than 

 the former, to compensate for contraction of the metal in cooling. 



4. Sheet-Metal 3IoiMinri-machine. By Mr. Richard Roberts, of 

 Manchester. — {JVith an Engraving, Plate XIX.) 



This machine is furnished with two shafts, B, and B', which pro- 

 ject beyond one of the side frames in which the lower shaft B, 

 turns; the upper shaft B, is mounted in a balanced swing-frame, 

 and is connected by spur gear with the lower shaft in such a way 

 that the distance betwixt the shafts may be adjusted to any re- 

 quired extent without altering the depth of the wheels in gear. 



On the projecting ends of these shafts the rollers D, E, are put, 

 with which the mouldings are to he formed; the lower roller is in 

 one piece only; but the upper roller is made in one or more parts 

 transverselj>, as may be best adapted to form the required mould- 

 ings, as shown in the enlarged figure; the wliich parts, when more 

 than one, are made to approach each other by being slid along the 

 shaft B', whicli is hollow, by means of a screw F, that acts within 

 on the back part of the top roller D, by means of a cotter, which 

 passes through the shaft and the screw, and on the front part by a 

 nut/, which is screwed from time to time by hand. Tlie advantage 

 of making the rollers in two or more parts is, that it allows the 

 met.-il to be gradually compressed sideways as well as vertically, 

 and avoids puckering. 



The curved mouldings, shown in the engraving, were made on 

 the first machine of the kind that was constructed; and the 

 straight mouldings on a similar machine subsequently made. Al- 

 most any degree of curvature may be given to the moiilding by 

 means of the third roller H, which, with its shaft and sliding bear- 

 ings J, is lowered, by the gearing h (fig. 1) in front of the pair of 

 rollers, to produce the requirM curvature. 



The engravings A (fig. ]) and A' (fig. 4) are representations of 

 two pairs of rollers for forming simultaneously the cap-mould of 

 each of the two brass domes for locomotive engines; the rollers A, 

 fig. 4, being for the purpose of creasing the metal, and the rollers 

 A', fig. I, for finishing the two cap-moulds, which may after- 

 wards be divided in the middle by a lathe or with a saw. Two 

 mouldings are in this case made together, owing to the peculiar 

 form of the moulding rendering it more facile to do so than to 

 make one separately. 



Fig. 5 shows three pairs of rollers for forming the "astragal," to 

 which the ui)per and lovver plates of the chimney of the locomotive 

 are rivetted; tliese rollers B, B', B-, are used in the order the 

 drawings are lettered. 



Fig. 6 shows a pair of rollers for forming the "base mould," and 

 fig. 7, rollers for forming the body of the l)rass dome of the loco- 

 motive engine; one pair of rollers only being used in both these 

 last-mentioned cases. 



5. A Centrifugal Pump for Draining Marshes. By Mr. J. G. 

 Appold. 



The pump consists of a disc with two side-plates, hollow between 

 and an opening in the centre; between the two plates are spiral 

 fans or vanes as shown in the anne.xed diagram. The disc is 



^~-<;a 



/T 



mounted on a shaft, and turned by the aid of multiplying wheels, 

 for the purpose of getting up a great velocity. The'water flows 

 into the disc through the centre opening, and by the rapid velocity 

 with which the disc is turned, and its centrifugal force, the water 



passes out from the outer edge of the disc, and is elevated to a 

 height according to the size of the disc and its velocity. — The 

 model of a pump capable of discharging ten gallons of water per 

 minute was exliibited. The disc was only 1 inch in diameter. 

 One the same shape, and \i inclies diameter, will discharge at the 

 same speed of the outside circumference, or one-twelfth the num- 

 ber of revolutions, 1,440 gallons per minute, which is according to 

 the square of the diameter, and not according to the cubic con- 

 tents. Mr. Appold considered that one 10 feet diameter, of the 

 best shape, will puni)) 140,000 gallons per minute, and so on in pro- 

 portion. 



6. The late Accident at the Britannia Bridge, Menai Straits. 



Mr. Stephenson, at the request of the meeting, explained the 

 cause of the accident which lately occurred in lifting the tube at 

 the Britannia works. He first explained the macliinery adopted 

 for raising the tubes, vvhich it is unnecessary for us now to report; 

 and stated that the plan originally proposed was by lifting tlie 

 tube to the height of (i feet at a time, and then allowing it to be 

 suspended by chains to the cross-head during the time the m.a- 

 sonry below was carried up: but this plan was abandoned, fearing 

 that if an accident should take place, either by the bursting 

 of the press or the breaking of a link of tlie chain, the tube 

 would be totally destroyed if it fell through such a heiglit as 

 6 feet, or even of G inches. He then considered that the only way 

 to proceed was by packing in timbers, inch by incli, under the 

 tube as it was being lifted; so that in case an accident did 

 take place, the tube would not have to fall through a greater 

 space than an inch,— and this was the plan adopted at the time 

 of the accident. To show how necessary it was thus to proceed, 

 Mr. Stephenson explained that although the tube fell through 

 the space of only an inch, it broke down iron beams each sufficient 

 to bear 500 tons weight. It will be seen that by this process the 

 tube was never allowed to be suspended in the air; and as a far- 

 ther precaution, he intended in future, when the raising was 

 again in progress, to pack in 

 underneath the cross-head of 

 the press, by driving in iron 

 wedges as the tube is raised, 

 as well as under the tube; 

 thus, if the press were to 

 break down, neither the 

 cross-head nor the tube 

 could fall through a greater 

 space than an inch. — He 

 then proceeded to describe 

 the nature of the fracture, 

 which he showed by a sketch 

 as per annexed figure. The 

 press was 20 inches diameter, 

 and the thickness of the me- 

 tal 10 inches. 



It was very curious to find that the fracture took place at that 

 part of the press which was the strongest, for it broke through 

 the angle of the bottom at F; and when it fell out, tlic piece 

 formed the frustrum of a cone. At the time the presses were at 

 work there was nut one ton pressure to the square inch, the area 

 of the fracture being l,31fi square inches, and the weight sus- 

 pended on the press 1,000 tons. The press was calculated to be;ir 

 3i tons, a pressure to which hydraulic presses are frequently sub- 

 jected for manufacturing purposes. The ram at the time ot tlie 

 accident dropped 2 ft. 6 in.; if it had been wedged up, as now 

 proposed, the accident might not have occurred. 



Fi^. 1. 



Fig. 3. Fig. 2. 



When lifting the Conway tubes, they commenced by lifting both 



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