66 66 66 66 66 66 a On the 30th of November "which I expect will stand it."* he says," I saw the tilt go admirably from 16 to 24 strokes "per minute, and it could have gone much faster, but our "men could not work the iron under it. Joseph said that "yesterday they made it go 28 strokes per minute, which is "much more than the engine should do by my calculations; "but in the midst of our glory, the hammer helve broke: it appears to have been rotten. The steel camms answer very well, and the whole will answer better when made to have less lift and more strokes, as it will then answer for a "common tilt for steel; at present the blow is so strong, that "we dare not attempt to hack a piece of iron under 1 inch square, otherwise it knocks it to pieces. By the help of some more weight on the outer end of the beam, it goes so regular that you cannot tell when the engine is going out " or when coming in." On the 12th of December,-" I went "out to Soho yesterday forenoon, hoping the engine would "be ready for trial, but it was not. In the evening they "wrought it 2 hours, 240 blows per minute, rise of hammer " 8 inches." On the 13th,-" We have tried our little tilting"forge hammer at Soho, with success. The following are "some of the particulars:-cylinder 15 inches diameter, 4 "feet stroke, strokes per minute 20. The hammer-head, "120 lbs. weight, rises 8 inches, strikes 240 blows per minute. "The machine goes quite regular, and can be managed as "easily as a water-mill. It requires a very small quantity "of steam, not above half the contents of the cylinder per "stroke. The power employed is not more than of what "would be required to raise the quantity of water which "would enable a water-wheel to work the same hammer with "the same velocity." Next month, they were "making an"other to work a hammer of 700 lbs., which will soon be at "work." This was for Mr. John Wilkinson at Bradley, and, on the 27th of April, 1783, Mr. Watt writes, "We have had a "trial of our new forge-engine at Bradley; cylinder 42 inches "diameter, 6 feet stroke. Makes from 15 to 50 (even 60 *To Mr. Boulton, 28 November, 1782. 66 "strokes per minute) at pleasure, works a hammer of 71⁄2 cwt. "raised 2 feet high, which makes 6 strokes per stroke of the engine, and has struck 300 blows per minute; we are, how"ever, going to make it strike only 4 blows per stroke of "the engine, because we want the latter to go 20 strokes per "minute, and they want only 90 blows of the hammer in "that time; but will increase the weight of the hammer to "10 cwt. N.B. The engine is to work two hammers, but is "capable of working four hammers, of 7 cwt. each." 66 In a letter written on the previous day, he had said, with excusable pride, "I believe it is a thing never done before, "to make a hammer of that weight make 300 blows per “minute; and, in fact, it is more a matter to brag of than "for any other use, as the rate wanted is from 90 to 100 "blows, being as quick as the workmen can manage the iron "under it." This most valuable application of steam-power was, accordingly, reserved for insertion in yet another patent, which Mr. Watt took out on the 28th of April, 1784. The relative specification, enrolled on the 25th of August in that year, may probably be viewed as second in importance to none of those prepared by Mr. Watt subsequent to that of the Separate Condenser in 1769; as, besides many improvements now of minor consequence, such as steam-wheels, balancing of pumprods, communication of motion from the same engine to two separate primary axes, and apparatus for opening the regulating valves with rapidity, it contains various methods of converting a circular or angular motion into a perpendicular or rectilineal motion,-one of those methods being the wellknown and much-admired Parallel Motion;-a method of working a tilt-hammer for forging iron, making steel, &c., by steam;-and the application of the steam-engine to give motion to wheel carriages for carrying persons or goods. Of the last-mentioned invention, and of its inventor's views of the subject of locomotion by steam, in general, we shall presently treat. Of the invention of the Parallel Motion,-a beautiful mechanical puzzle which different philosophers have attempted to explain in various ways, but which has uni 66 66 66 66 66 "which I expect will stand it."* On the 30th of November he says," I saw the tilt go admirably from 16 to 24 strokes per minute, and it could have gone much faster, but our men could not work the iron under it. Joseph said that yesterday they made it go 28 strokes per minute, which is "much more than the engine should do by my calculations; "but in the midst of our glory, the hammer helve broke: it appears to have been rotten. The steel camms answer very "well, and the whole will answer better when made to have 66 a less lift and more strokes, as it will then answer for a "common tilt for steel; at present the blow is so strong, that "we dare not attempt to hack a piece of iron under 13 inch "square, otherwise it knocks it to pieces. By the help of some more weight on the outer end of the beam, it goes so regular that you cannot tell when the engine is going out or when coming in." On the 12th of December,—“ I went "out to Soho yesterday forenoon, hoping the engine would "be ready for trial, but it was not. In the evening they "wrought it 2 hours, 240 blows per minute, rise of hammer "8 inches." On.the 13th,-"We have tried our little tilting"forge hammer at Soho, with success. The following are "some of the particulars:-cylinder 15 inches diameter, 4 "feet stroke, strokes per minute 20. The hammer-head, "120 lbs. weight, rises 8 inches, strikes 240 blows per minute. "The machine goes quite regular, and can be managed as easily as a water-mill. It requires a very small quantity "of steam, not above half the contents of the cylinder per "stroke. The power employed is not more than of what "would be required to raise the quantity of water which "would enable a water-wheel to work the same hammer with "the same velocity." Next month, they were "making an"other to work a hammer of 700 lbs., which will soon be at "work." This was for Mr. John Wilkinson at Bradley, and, on the 27th of April, 1783, Mr. Watt writes, "We have had a "trial of our new forge-engine at Bradley; cylinder 42 inches " diameter, 6 feet stroke. Makes from 15 to 50 (even 60 66 *To Mr. Boulton, 28 November, 1782. 66 "strokes per minute) at pleasure, works a hammer of 7 cwt. "raised 2 feet high, which makes 6 strokes per stroke of the engine, and has struck 300 blows per minute; we are, how"ever, going to make it strike only 4 blows per stroke of "the engine, because we want the latter to go 20 strokes per 66 minute, and they want only 90 blows of the hammer in "that time; but will increase the weight of the hammer to "10 cwt. N.B. The engine is to work two hammers, but is capable of working four hammers, of 7 cwt. each." 66 In a letter written on the previous day, he had said, with excusable pride, "I believe it is a thing never done before, "to make a hammer of that weight make 300 blows per "minute; and, in fact, it is more a matter to brag of than 66 for any other use, as the rate wanted is from 90 to 100 "blows, being as quick as the workmen can manage the iron "under it." This most valuable application of steam-power was, accordingly, reserved for insertion in yet another patent, which Mr. Watt took out on the 28th of April, 1784. The relative specification, enrolled on the 25th of August in that year, may probably be viewed as second in importance to none of those prepared by Mr. Watt subsequent to that of the Separate Condenser in 1769; as, besides many improvements now of minor consequence, such as steam-wheels, balancing of pumprods, communication of motion from the same engine to two separate primary axes, and apparatus for opening the regulating valves with rapidity, it contains various methods of converting a circular or angular motion into a perpendicular or rectilineal motion,-one of those methods being the wellknown and much-admired Parallel Motion;-a method of working a tilt-hammer for forging iron, making steel, &c., by steam;-and the application of the steam-engine to give motion to wheel carriages for carrying persons or goods. Of the last-mentioned invention, and of its inventor's views of the subject of locomotion by steam, in general, we shall presently treat. Of the invention of the Parallel Motion,—a beautiful mechanical puzzle which different philosophers have attempted to explain in various ways, but which has uni formly commanded the admiration of all who either comprehend the principles on which it acts, or behold the smoothness, orderly power, and "sweet simplicity" of its movements, -we find the following account in a letter from Mr. Watt to his son, already cited:* 66 "The idea originated in this manner. On finding double "chains, or racks and sectors, very inconvenient for communicating the motion of the piston-rod to the angular motion "of the working-beam, I set to work to try if I could not ❝ contrive some means of performing the same from motions "turning upon centres, and after some time it occurred to "me that AB, CD, being two equal radii revolving on the "centres B and C, and connected together by a rod AD, in "moving through arches of certain lengths, the variations "from the straight line would be nearly equal and opposite, "and that the point E would describe a line nearly straight, "and that if for convenience the radius CD was only half of "AB, by moving the point E nearer to D, the same would "take place; and from this the construction, afterwards called "the parallel motion, was derived. Though I am not "over anxious after fame, yet I am more proud of the parallel "motion than of any other mechanical invention I have ever "made." * In Mr. Watt's Appendix to 'Robison on Steam and Steam'engines,' he mentions that "the invention was made in the "latter end of 1783." The manner in which we find the contrivance of this admirable piece of mechanism first recorded in his correspond * Mr. Watt to Mr. James Watt, 10th November, 1808. |