| Description | Engine Designs by James Watt, Edward Bull and Jonathan Hornblower’s Engines, Dutch Windmill etc. (49 items).
1341. Equalizing Beams, Rotative Motions etc. Aug., Sep., Nov. 1781, Jan., Aug. 1782, Mar., Apr. 1783, Apr. 1784. 49 items.
Equalizing beams, rotative motions, graphs for valve working, toothed wheels and racks, working gear etc.
Also "double expansive" (compound) engine, with two 15 inch cylinders, 4 foot strokes.
Equalizing Machinery:
Equalizing machinery for expansive engine, Aug. 1781, equalizing machinery for 4 inch cylinder with 18 inch stroke, Sep. 1781, equalizing beam for Soho Engine, Nov. 1781 - original and reverse drawings; "equalizing machinery to work an ecliptic mill from a secondary cylinder" - drawing marked "imperfect"; equalizing machinery for exhaustion regulator and for opening the top regulator of a 63 inch cylinder (reverse drawing) - 2 drawings on 1 sheet, with unmarked reverse copy of the machinery for the exhaustion regulator; equalizing machinery to open the exhaustion regulator of a 63 or 60 inch cylinder - reverse drawing; sketch of equalizing machinery marked "Best Feb. 19th". These drawings all show equalizing machinery employing two wheels mounted in a spring beam, as described in James Watt's patent of 1782.
Equalizing Beams:
Sketch of equalizing beams; coloured drawing of equalizing beams; drawing showing equalizing beam [?] with an arch head, system of pullies etc. - partially shaded drawing. These drawings show equalizing beams as described in James Watt's patent of 1782.
Rotative Motions:
5 drawings of rotative motions (1 partially shaded) similar to the drawings of the 2nd to 5th methods of rotative motion described in James Watt's patent of 1781; "excentric for Soho, Jan. 1782" - drawing of a rotative motion similar to the drawing for the second part of the second method of rotative motion described in James Watt's patent of 1781; unmarked drawing of sun & planet wheels [?]; 2 small unmarked sketches for types of rotative motion.
Graphs for the Working of Valves:
Projection of the lever & curve of a 63 inch cylinder; projection of the lever & curve of a plain valve opening 3 inches with a 2 foot lever; untitled coloured graph showing "angles of loggerhead corresponding to equal opening of valve"; unmarked diagram for valve working [?].
Also 5 drawings showing toothed wheels (or possibly arms or sectors) working in vertical racks; 4 drawings of nozzles and working gear; 5 untitled miscellaneous drawings.
"Double Expansive" or Compound Engine:
Side view and ground plan of the engine and cylinders and equalising machinery, with notes by Watt on the working of the engine and a drawing of a chain link stuck to the sheet, Sep. 1781.
Sketch of engine marked "Front view of both cylinders" (not dated but from Sep. 1781).
Link of chain for "Soho Engine", Nov. 1781.
Side views of the upper and lower working gear for "up and down 15 inch engine at Soho", Mar. 1783 - reverse drawing.
"Drawing for Soho Small Engine Tilt", 8 Aug. 1781 [actually 1782? - this drawing is assumed to show the compound engine applied to working a tilt hammer and a pump, the uses ascribed to it in the List of Engines made at Soho; Dickinson & Jenkins (p. 161) suggest that this drawing is mis-dated and actually dates from 1782).
Loggerhead driver for 15 inch cylinder, Apr. 1783.
Piston for the 15 inch cylinder, Apr. 1784.
Coloured front and side view of pump [the pump worked by this engine?].
Original Portfolio or 'Book' No. 272. Catalogue of Old Engines p. 338.
John Southern opened Book No. 27 in 1782 and divided it into two parts, noting in his List of Books that the first part contained drawings for "Self-moving rotative Motions etc." and the second part, numbered as 272, contained drawings of "Equalizing Beams, Rotative Motions." In the two parts were placed drawings for the various designs and schemes that Watt was working on or had worked in the previous year, particularly in connection with his patents. They contained drawings of designs for rotative engines which appear to be more advanced than the type described in the 1782 patent, the "reciprocating semi-rotative engine" described in the 1782 patent, the various types of equalizing machinery developed by Watt for expansive working and used on engines at Soho and also described in the 1782 patent, drawings of the various types of rotative motion described in the 1781 patent, a "chain and bucket engine", various drawings of valves, working gear etc, and drawings of the experimental "double expansive" compound engine erected at Soho, whose construction and operation was included in the 1782 patent.
Henry Hazleton numbered the first part of Book 27 as Portfolio 1343 and the second part as Portfolio 1341.
Published references: Dickinson & Jenkins p. 124, 125, 161, plates XXIII & XXIV - side view and ground plan of the "double expansive engine", XXXIII - "Soho Small Engine Tilt".
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