High Beeches Hot Air Engine Part 4

With Dave Carpenter back and the team again at full strength we have made some good progress. A few lengths of iron water pipe acquired at a local scrapyard and a box of iron fittings acquired at Cranleigh classic car show have been used to plumb the cooling water tank to the engine to complete the water circuit. We intend to siphon water from the top pond down to a fitting outside of the building to fill the tank when required.

A visit to another scrapyard turned up enough flue pipe to connect the engine firebox to the outside of the building. This is now all in place but requires a stay to support it above the engine. The furnace was originally lined with fireclay to protect it from the effects of the fire which can embrittle iron. Looking on the internet, I found that 1 part fireclay with 2 parts of sand produces a refractory lining suitable for home pizza ovens or metal melting furnaces. It should be perfect to line the interior of a hot air engine furnace then!

A 25 Kg bag of fireclay was sourced on the web, mixed with sand and applied to the interior of the furnace. This was a messy job done in two layers with chicken mesh reinforcing  to give it added strength. This lining is now in place and drying so we will see how it holds up on the first firing of the furnace.

The crankshaft has been sleeved to provide two good bearing surfaces of slightly larger diameter than  original.  This enabled  the white metal  main bearings  which were in  a poor state to  be scraped larger to fit thereby improving the condition of these. This took some time to get right as the two bearings had to be scraped ‘in line’ by hand but the result is excellent. As the top bearing caps could be removed, these were taken home and machined to the right diameter to fit the crankshaft  and a set of shims  (as required by the larger crankshaft)  made up  to set clearances.

We expect the cold piston to be back from welding very soon so we can then re-assemble the flywheel to crankshaft, install the re-furbished connecting rods and  it will look like a hot air engine again. Next and almost final job is to form the leather seals to make the engine airtight.

Richard Amos