High Beeches Hot Air Engine Part 3

Ian and I have been continuing the restoration but without Dave Carpenter, who is thankfully out of hospital and on the mend but under strict orders to take it easy!

We have installed the repaired cold cylinder and furnace cylinders with the steel plates made by Michael Brown put in their rightful places. The cold cylinder and engine base plate have been painted with red oxide for protection as the engine house is a little damp. The regenerator has been repacked using the old cast iron plates (after cleaning).

As some of these plates were broken on removal, stainless steel plates made by Michael Brown were fitted to complete the packing. We have re-hung the firebox after bringing together the many broken pieces. The joints and screws have been concealed with a heat resistant ‘fireclay’ so they will be less visible when eventually ‘blackened’. The new steel plate installed at the top of the firebox provides the correct location for the firebox hinge pin so the firebox now swings open and shut nicely. It also appears there was little distortion from stitching together all the firebox pieces. As the main crankshaft bearings were severely pitted, we had to remove the crank webs and the flywheel in order to re-machine the bearing surfaces.

To remove the webs, we drilled and tapped the key and used a high tensile M8 allen screw to jack the keys out. These crank webs are fitted to a shallow taper on the end of the crankshaft so Ian’s puller was pressed into service after we had removed the keys. Removing the flywheel key was more difficult and a long drill and steady hand was required to drill right through this to weaken the fit. After a lot of hammering and one broken club hammer handle, the key moved and we could separate the flywheel from the crankshaft.

I’m quite relieved to have the engine completely apart without damage but now we have to repair the bearings and make three new keys.  The wrist pins down in the two pistons were severely pitted so these have been machined down and the bronze conrod bearings white metalled to the new smaller size. The crank pins in the webs, also badly pitted, were machined down and sleeved slightly oversize so the original but worn bronze bearings on the conrods could be scraped to fit. A lot of rust has been removed from the two conrods to make them presentable.

We have installed a suitable cooling tank in the building (but have yet to plumb this up) and made a start clearing the vegetation from the roof of the building. This had grown in over many years and was a tangled mess.

The pictures show one of the two conrods before and after repair.

Richard Amos