| Description | These agreements between Boulton & Watt and their customers are for engines that employed a crank mechanism to turn the reciprocating motion of the engine beam into rotative motion to power textile mills, grindstones, tilt hammers, rolling mills etc. The crank was the subject of a patent taken out by James Pickard, dated 23 Aug. 1780. Although Boulton & Watt saw this patent as contentious for various reasons, they did not contest it or blatantly infringe it. Instead Watt sought ways to avoid it, and developed the sun and planet gear as an alternative means of creating rotative motion. They employed the sun and planet gear on most of their rotative engines in the 1780s and 1790s (see MS 3147/2/11, Agreements for Sun & Planet Engines). Pickard’s patent expired in 1794. Boulton & Watt had already used the crank on a few engines, and they employed it increasingly from then on.
The agreements are on parchment and are signed, sealed and witnessed by both parties unless otherwise noted. From the early 1790s basic lists of the metal materials of the engine were attached, and from June 1797 these lists were incorporated into the parchment.
From evidence in the List of Contents of the Watt Room (10/14), it is clear that in the 1890s Henry Hazleton arranged the parchment agreements to mirror the arrangement of the drawings in the "Catalogue of Old Engines". He divided the agreements by type of engine corresponding to the sections in the "Catalogue" – sun & planet, crank etc. Crank engines are listed in Section B of the "Catalogue" He referred to the agreements in the "Catalogue", calling them "parchments" and transcribing details of the partners, payment etc. for each engine.
Hazleton’s arrangement was lost after the collection left Soho Foundry, and the agreements for the various different types of engine got mixed together. All the crank engine agreements have been re-united and listed chronologically, in order to reflect the arrangement of the portfolios of drawings as closely as possible. Cross-references to the portfolios of drawings have been made where the engine can be positively identified. |