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Volume 5 (2012)

The Design of Bull’s Direct Action Steam Pumping Engine



Bull’s Pumping-Engine, 1798.
Click to enlarge the photo.

The most successful of those competitors of Watt who endeavored to devise a peculiar form of pumping-engine, which should have the efficiency of that of Boulton & Watt, and the necessary advantage in first cost, were WILLIAM BULL and RICHARD TREVITHICK. The accompanying illustration shows the design, which was then known as the 'Bull Cornish Engine.'

The steam-cylinder a, is carried on wooden beams b, extending across the engine-house directly over the pump-well. The piston-rod c, is secured to the pump-rods d d , the cylinder being inverted, and the pumps e, in the shaft f, are thus operated without the intervention of the beam invariably seen in Watt’s engines. A connecting-rod g, attached to the pump-rod and to the end of a balance-beam h, operates the latter, and is counterbalanced by a weight i. The rod j, serves both as a plug-rod and as an air-pump connecting-rod. A snifting-valve k, opens when the engine is blown through, and relieves the condenser and air-pump l, of all air. The rod m, operates a solid air-pump piston, the valves of the pump being placed on either side at the base, instead of in the pump-bucket, as in Watt’s engines. The condensing-water cistern was a wooden tank n. A jet 'pipe-condenser' o, was used instead of a jet condenser of the form adopted by other makers, and was supplied with water through the cock p. The plug-rod q, as it rises and falls with the pump-rods and balance-beam, operates the 'gear-handles' r r, and opens and closes the valves s s, at the required points in the stroke. The attendant works these valves by hand, in starting, from the floor t. The operation of the engine is similar to that of a Watt engine. It is still in use, with a few modifications and improvements, and is a very economical and durable machine. It has not been as generally adopted, however, as it would probably have been had not the legal proscription of Watt’s patents so seriously interfered with its introduction. Its simplicity and lightness are decided advantages, and its designers are entitled to great credit for their boldness and ingenuity, as displayed in their application of the minor devices which distinguish the engine. The design is probably to be credited to Bull originally; but Trevithick built some of these engines, and is supposed to have greatly improved them while working with Edward Bull, the son of the inventor, William Bull. One of these engines was erected by them at the Herland Mine, Cornwall, in 1798, which had a steam-cylinder 60 inches in diameter, and was built on the plan just described.

Reference

'A History of the Growth of the Steam Engine' by Robert H. Thurston seen on The Project Gutenberg EBook.



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