rises, owing to the pressure exerted on the shoulder formed by the difference of diameters of the spindle, DD, at C. Any required pressure is obtained, according to the number of weight rings, W W, put on. The water passes to the machines through outlet, E. Suitable valves are fitted, not only to prevent accidents from too much water being pumped in, but also to automatically stop the pumps, whether driven by belting or separate engines, when the accumulator is filled. Other ordinary forms of accumulators, similar to those used for cranes (see p. 4) can be used when a complete shop is fitted up on the hydraulic system, or for working flanging machinery, etc.

There is little reason to doubt, from the results obtained in practice, that, in a complete hydraulic workshop, only aboutto of the boiler power would be required as compared with that necessary where ordinary steam or geared machinery is used, and even better results when compared with the system of separate steam cylinders attached to each machine. The loss of useful effect between the pressure pumps and the accumulator has been shown by experiment not to exceed 31 to 43 per cent.

The loss by friction in the accumulator is only 1 per cent., and taking the friction at the machines themselves, which does not exceed 1 per cent. also, we have only 2 per cent. total loss from friction in the machines.

The Power absorbed by shafting has been shown by experiments in a length of 1200 feet of, say, 23 inches in diameter, with all the straps off, to be about one horse-power indicated for every 100 feet of shafting. If to this is added the friction of the belts and the gearing of the various machines, it will be seen the loss of power is much greater by shafting and gearing than in the direct application of hydraulic power transmitted from a distance through mains. Another interesting fact is that, in consequence of the motion of the hydraulic machine being least when giving off the greatest pressure, the speed of the water in the main is at its slowest, and therefore the friction is least.

In addition to the above considerations, the hydraulic system must be credited with all the economy obtained by the saving it effects in expensive roofs and walls, required not so much for shelter as for carrying shafting and pulleys; the

RIVETTING MACHINES.

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absence of all foundations; and also the saving in head room, and the consequent greater facility of working cranes, etc., owing to clear headway. There is again a great saving in shop floor room, and in boiler and ship yards where much rivetting is done, the portable riveters, by enabling the work to be quickly turned out, make a small ground area as productive as a large one not so fitted.

RIVETTING MACHINES, STATIONARY.

In these machines the closing pressure upon the rivets is capable of adjustment, according to the requirements of the work. The pressure brought to bear on the rivet combines the effect of a blow and also a steady squeeze or pressure, which pressure can be retained as long as desired. This property is also taken advantage of to lay the plates together before rivetting, thus saving much heating and risk of burning the plates. From 10 to 15 rivets per minute can be closed in boiler work, and for girder work a considerably greater speed can be obtained.

The force used varies from 25 tons to 50 tons closing pressure upon the rivet-heads. In practice it is found that 40 tons can do any work up to 11-inch rivets in 11-inch plates.

The latest form of this machine is shown at Drawing No. 57. As will be seen, the cupping die is flush with the top of the cylinder, thus enabling the rivets in flanges and angle irons on flat surfaces, and the throats of locomotive fire boxes to be readily reached. In this case the cylinder and gear are all above ground, and the action is directa great point, if it can be managed. As a rule, the hob, or dolly, should be of steel or wrought iron, to allow of small flues being got over it for rivetting. The stroke of the dies is such that if the rivet is too short, the full pressure is given to close it; if too long, no harm comes to the machine, and different numbers of thicknesses of plate can also be rivetted without any special adjustment.

PORTABLE RIVETTING MACHINES.

These machines will close, say, 300 rivets from 1 inch to 11 inch in diameter per hour; they are very useful in a workshop, and can either be suspended from special cranes or can be hung temporarily from ordinary cranes over the work to be rivetted.

Drawing No. 58 shows the type of machine first patented by Mr. Tweddell, but with several recent additions in details. It will be seen that it has two levers. The rivet is closed by causing the cupping dies attached to the levers to be brought together. Either end of the lever may be used for rivetting, the other end, of course, acting as the fulcrum. In this way two gaps are available-one, a short one, capable of closing large rivets; the other doing proportionately smaller rivets at a greater gap. The pressure water is brought through the curved tube by which the machine is suspended. This combination of suspending gear and pipe is used in several forms; it simplifies the tackle about the machine, and allows it to assume various positions without breaking any joints. This last is a recent addition, and it may here be observed that Mr. Tweddell has frequently acknowledged the valuable assistance he has received in designing new machines on his system (especially for rivetting purposes) from Mr. James Platt and Mr. John Fielding, and indeed many of the machines about to be described are jointly patented.

Work done.-In bridge work, about 2000 rivets per day can. be put in on straight girders; as many as 5000 rivets have, however, been put in by one machine in ten hours.

In wagon work, rivetting the frames of wagon bodies at works in Scotland, 2100 rivets have been closed per day by one portable rivetter.

Drawing No. 59 shows a machine designed for rivetting locomotive fire doors, angle iron rings for marine and land boiler fronts, furnace rings and lattice girders. The rivetter proper, R, is free to revolve inside a sleeve or strap, A, and when the holder up end, R, is placed inside a locomotive fire box, the man has nothing to do, when the fire hole door is circular, but turn it round on its centre, thus closing the rivets in its circumference consecutively, and, if oval or square, it can do them also with a very slight adjustment of the lifting tackle. This machine, being direct-acting, can be made very powerful for small gaps, and can close large rivets.

In locomotive shops, as many as ten rivets per minute have been put in foundation rings by these portable riveters, the rivets being inch in diameter and through a total thickness of copper and steel of 33 inches.

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Drawing No. 60 shows another form of portable rivetter, suitable for boiler flues, bridge work, girders, tender tanks, and work where a long gap is desirable. Most of these machines range from 3 feet to 4 feet 6 inches gap, and are specially designed for lightness; otherwise their principle of working is the same as older types of fixed rivetters.

These machines can be suspended from overhead travellers, or a fixed crane, as shown at Drawing No. 61. The suspending gear is so arranged that they can hang with their levers either in a vertical (as illustrated) or a horizontal position.

The cupping dies of these machines can also, when necessary, be made flush with the top of the cylinder (see Drawing No. 61, showing one suspended to a crane), in which case, as shown at Drawing No. 60, the cupping dies, A B, can rivet angles, etc., on flat surfaces, without the outer radius of the cylinder, C, coming in the way.

Drawing No. 62 shows a form of portable rivetter, which enables the cylinder to be removed altogether from the ends of the levers carrying the cupping dies. This, of course, enables more work still to be reached.

It is true that in Mr. Tweddell's first patent (see Drawing No. 58), the cylinder is out of the way also, but when the gaps come to be considerable, this form of machine, owing to its having two powers (and in consequence two gaps), becomes too bulky, and without sufficient compensating advantages. It is, then, better to dispense with this double action, and, by adopting another order of levers, sacrifice the use of the other end of the levers for rivetting, and place the cylinder there.

The most recent arrangement is shown on Drawing No. 62; great simplicity and stiffness have been obtained by adopting the radial cylinder and ram, as shown in the drawings. This type of machine has been used successfully for ship's stringers, floors, and similar work, and proved perfectly rigid and stiff up to 4 feet 6 inches gap, and while only weighing from 25 to 30 hundredweight; is capable of closing rivets 1 inch in diameter.

The cylinder, it will be seen, has its longitudinal axis coincident with a radius struck from the centre of oscillation of the levers. All connecting rods, etc., are thus dispensed with, and since the rams on the one lever, and the cylinder on the others, practically form part of their respective levers,

the whole machine is perfectly rigid-a very important consideration towards securing fair and sound work.

There are many other different kinds of rivetting machines made under Mr. Tweddell's system, but it is unnecessary to particularize them, their number and variety only proving the applicability of hydraulic pressure to this class of machine tools.

The application of portable machines, however, would be comparatively limited were there not also sufficient means of taking or applying the machines to their work, so as to do away with manual labour in this work also. For this purpose hydraulic power is, perhaps, in its best field, and by the use of hydraulic lifts (which not only do the lifting and lowering, but also serve to conduct the pressure to the tool), two purposes are served-first, the size and consequently the capacity for work of the machine is no longer limited by the weight which men can handle, and all pipes hanging about in the way are avoided.

HYDRAULIC (FIXED) CRANE AND LIFT.

Drawing No. 61 shows one of the numerous types of these cranes. A vertical lift of from 4 feet to 6 feet is obtained by means of the hydraulic lift, A, placed between the rivetter and the travelling carriage, B. The carriage travels the whole length of the jib, C, and the rivetting machine, D, can be racked in and out, without disconnecting the pipe joints. A crane fixed in the wall, and having 28-feet rake, can rivet any work placed within an area of 1200 square feet.

Very large and heavy machines can, on this plan, be used as portable tools, since all the raising and lowering is done by hydraulic power. In many cases these lifts are simply suspended from the end of an ordinary travelling crane chain, and in other cases hydraulic travellers are used, each case having to be treated on its own merits.

When no lifts are used, small copper pipes are employed to conduct the pressure water. These pipes are coiled in a spiral form. A spring-like action is thus secured, which allows the rivetter to vary its position within considerable limits; and in practice, the copper piping is found to answer perfectly, and it is not subject to the damage inseparable from the use of indiarubber hose.