< Steam Chest Cover 2 >
The picture shows section of a steam chest
gland. Full size steam chest is pressure-sealed
but my model's isn't. The steam chest cover
is centered toward the steam chest by the
gland. Also the glands push the piston liners
from both ends.
The glands are made from gunmetal round bar. After all of turning and boring operation, the work is parted off, reversed and finished to a desired length. At this point, the front glands are kept 0.2mm longer than final length. As the upper picture shows, the center hole is a little enlarged from bottom side because too long bush causes friction even with a small error.
Full size gland is sealed by diamond shaped flange. The diamond shape is milled with rotary table. Holes for dummy bolts are also opened here.
Dummy parting line between the flange and the gland is cut with a sanding wheel.
This is drilling jig for the covers, turned from a steel round bar blank. Cross lines for alignment are scribed on a face and the side.
The front cover has a horizontal groove in its bottom. One of secure bolts has to be in the groove. So I drilled larger hole for the bolt, then fixed the jig onto a cover with a bolt, and drilled other holes through the jig.
The back cover holes are simply drilled through the jig at a time.
The cylinder block is countersunk through the jig, drilled undersize and tapped. Probably clamping hides some holes of the jig. Firstly open two holes and fix the jig by screws, then open the rest of holes.
This is my method to tap holes. After drilling, keeping the position, replace the drill with a smaller drill-chuck with tap and handle. And then slightly slacken the larger chuck so as to let the smaller chuck move freely for tapping. Note a nut in the tap to indicate depth of the hole.
This is a gunmetal casting for back cover of the inner steam chest.
In order to chuck tapered bush truly, I prepared simple brass collet that has tapered bore and a side gap.
The back cover is bolted onto the cylinder block. Oil cup plug and bush end plug were screwed into the cover. Note a vent hole of the bush end plug.
Here the 0.2mm longer front glands are finished as follows. All of parts except the front cover are assembled to the cylinder block. Height difference between the front gland and the cylinder block bolting face is measured by height gauge. Finally, each front gland is finished as the difference becomes 0.05mm. This value holds the liner firmly in the steam chest with a minimum distortion of the cylinder block.
The cover and the gland have to be connected by an oil pipe. I extended oil cup plug to imitate the oil pipe. This long bolt also prevents the gland from rotating.
All of the steam chest parts are assembled. Each valve spindle should rotate freely. Any tightness shows centering error of the glands.