The Crossley was purchased second hand from a Picture Palace in Kingston-upon-Thames where it had remained unused since its purchase from Crossley's in 1914. It was intended to use the engine for the generation of electric power for the Picture Palace, hence the unusually large flywheel.
Thomas Boughton transferred the gas engine to Tring using a steam traction engine. The Crossley engine was installed at Grace's Mill in the winter of 1921/22 and remained in daily service until the severe frosts of 1963/64 burst the big cooling tanks. While new tanks were being acquired the line shafting to the Mill was being operated by a tractor and it was found that the running costs were about half that of the Crossley gas engine, even when operated from the 'Producer Gas Plant' which in itself was considerably cheaper than using town gas.
Running the engine on Natural Gas was also considered, although in the end the engine was retired and replaced by a four cylinder Dorman Diesel engine.
The Gas Engine provided all the motive power to the Mill from line shafting, which in turn drove twin pairs of 'four foot' mill stones together with Oat Crushers, Oat Clippers, Mixers and all other equipment used at the Mill. Also driven from the line shafting was the Dynamo that provided all the electrical power to the Mill. The electrical power plant consisted of a bank of accumulators that were charged by a Dynamo to maintain a voltage of 110v DC. The original Dynamo and Control panel are now back in operation on the engine. Unfortunately the accumulators were scrapped when the engine was moved from the Mill and we now have only a token number of replacement accumulators connected up for demonstration purposes.
The engine was started by hand using 'Town Gas' and then switched over to 'Producer Gas' after a few minutes running. It originally required two men to start the engine but the last owner, Bob Grace, had developed a method of starting the engine by himself, after the acquisition of a petrol primer/starter, a cord and a lever were rigged up to trip the Magneto at the appropriate time as the flywheel was rotated.
The Producer Gas Plant now resides alongside the engine and was the last of many used with the engine as they tended to corrode away very rapidly. This last one was made by Hornsby Stockport in 1913. The gas was produced by passing steam though red hot 'pea sized' anthracite, where the steam reacted to produce various combustible products. In the 1920's when times were hard, the anthracite was purchased direct from the South Wales collieries and collected from Tring Railway station by horse and cart. A wagon load cost £8.00 and undercut the local coal merchants, much to their annoyance. The Gas Plant was called a 'Suction Gas Producer Plant' as it was the suction of the engine that drew the steam and the air over the anthracite. The greater the suction of the engine, the more gas was produced. When starting up, a blower was used instead, until the gas produced a clean blue flame from a test cock on the expansion tank near the engine (no longer fitted). The gas from the anthracite was hot and dirty with bitumen products. Before use in the engine it was passed though a washing tower containing running water and coke, mounted alongside the anthracite burner, prior to passing into the expansion tank near the engine. The furnace containing the anthracite was water-cooled, the cooling water in turn producing the steam for feeding through the anthracite to produce the gas. Although the gas plant is beyond restoration we have brought it inside the engine house, alongside the engine, to show the complete plant.
The engine had laid dismantled at Pitstone for some 20 years, when the Beds & Bucks Stationary Engine Club undertook the restoration of the engine and creating an engine room from part of an open barn. Work started in 1992 and the engine was running within 2 years. The engine club still maintains the engine and runs it on the Family Fun & Craft Days.