the water pump is not only pumping water - the main use for these engines - but the water also serves to pump the cooling water around the cylinder before exiting to its final destination.

Looking at photos of full size and the Patent the 1:4 scale drawings were not quite right externally so I drew mine to hopefully be a bit closer to the original. The most noticeable feature that I added was the flange where the bottom of the pump mounts to the main body, though mine is a dummy.

I started by facing and then milling two flats along the length of some 1in. brass bar so that I had some ref faces to work with and then drilled, reamed and tapped the long holes using the 4-jaw. Then over to the CNC firstly with an adaptive path to rough out from one side.

Then a couple of finishing paths though; the majority was done with a scallop using a 3mm dia ball nose cutter stepping over 0.2mm per pass. After that it was flipped over and the other side cut.

The bottom flange was also machined on the CNC before being ‘parted off’ with a slitting saw

The flange and a piece of flat material were then silver soldered to the body; the flat material milled to final size, and thickness then drilled along with a few other cross passages. The remaining parts were just turning and a bit of milling to form the hexagons.

All seemed to move as it should once assembled. Just got to make the pivot pin to replace the 3mm machine reamer I am using in the photo.

The last thing to make was a wooden sled to mount the engine on as it needed to be raised up to clear the camping gas burner body. The CNC makes quite a neat job of mortice and tenon joints.

Then a coat of paint, the bed plate and furnace were done in a stove paint. The pumpkin orange and dull red flywheel are close to original colours and I gave them a coat of clear matt as it did not want the orange to look too flashy.

Part 1 here   part 2 here part 3 here  Part 4 here  Part 5  Part 6  Part 7

Part 8  Part 9