Outside cylinder GA
Cylinder Parts 1
Cylinder Parts 2
The marked out cylinder end plates are set up for drilling
Drilling the reference holes through four 1/8" thick plates
Setting up the end plates for boring the cylinder opening using the wobbler
Drilling the end plates for the cylinder
Boring the cylinder opening in progress
Boring the end plates for the valve chest. A second set of four plates then followed for the other engine.
The next operation was to make the cylinder backplates. These were made from 1/4" thick brass plate to give plenty of machining allowance as I wasn't sure how much distortion I might get during the silver soldering process. Four plates were cut and mounted in the milling vice for machining the edges to form accurate rectangles. - Preparing brass plate for cylinder backplates
Drilling the backplates. Multiple clamps were needed to allow for moving them as the drilling progressed. After spotting the four plates were through drilled undersized for 7BA.
Next the large rectangular hole was milled out in the backplates.
Then the profiling of the outer edges of the plates again using co-ordinate location of the milling cutter
Profiling the backplates 2
Profiling the backplates 3
Profiling the backplates 4
Drawing showing the path of the milling cutter dimensioned in 10 thou intervals for profiling the backplates
Cutting the exhaust passages through the backplates
Squaring the corners of the holes
Close up of a profiled corner
Close up of a profiled corner after finishing with the Dremel
Set up for making the locating slots for the front back and internal plates
Locating slots completed
The end plates were returned to the mill to form the projections that locate them in the backplate
First trial assembly of the back and end plates
The next operation was to make the cylinder barrels. I had checked the LG2 material chosen could be silver soldered and I was fairly sure that provided the material was unstressed during heating that there would be little distortion, so I was confident proceeding with this material. I bought continuously cast thick walled tube and cut it into suitable lengths for machining. - Bronze tube marked for cutting
Cylinder barrel external machining
Internal boring
A Cylinder barrel ready for final machining
At this stage the barrels (six of them) were machined close to finished size. The ends of the bores were opened up and a tapered transition to the bore size made to facilitate easy entry of the ringed pistons. I failed to photograph this work. Following this the cylinders were then set up again for the rebate to be machined on the ends of the outside of the barrels so they would fit into the end plates - Setting up the barrel in the four jaw for rebating the outside ends. Note the internal ends had already been opened up and chamfered
Machining the rebate
A similar machining process was done for the valve chests and once these were machined all over to the near finished dimensions, final machining of the external surfaces could proceed. To achieve this a mandrel was made so the valve chest could be mounted between centres - Valve chest mounted between centres
Profiling the exterior of the valve chest
Profiling almost complete
Valve chest in cylinder frame
Likewise the cylinder barrel was mounted on a mandrel between centres for external profiling - Finish profiling of the cylinder barrel.
Cutting the ports in the barrel
View of ports and location flat
Cutting the ports in the valve chest
As the cylinders and valve chest ODs intersect it was necessary to machine a flats on the cylinder at each end, on the internal ribs and along the length of the valve chest. These also located the components so they have the correct angular relationship to orientate the ports correctly. - Machining the location flats
Drilling the frames from the cylinder backplates
Not the most elegant set up for the drilling machine but it sufficed
Once done, the embryo cylinders could be temporarily bolted to the frames, one of those moments in the construction that gives a much needed morale boost. - Cylinder fitted to the H4 at last
The H4 at the 2014 Harrogate Exhibition between Jim Scott's magnificent Terrier and Ian Spencer's B1