< Piston Valves >
The picture shows section of my piston-valve
cylinder. I designed it as simple as possible
so as to make the construction easier than
the original slide-valve cylinder.
1) The valve has no piston ring.
2) The steam chest liner is not press-fitted
but close-fitted with a sealant.
3) The valve is made from ground rod.
4) The valve bore is finished with a parallel
reamer.
The steam-chest liners are made from gunmetal
rod.
It is turned down to a close fit in the steam-chest
bore, and drilled slightly smaller than the
final inner diameter.
Grooves for steam-port are turned with a
parting tool.
The groove-to-groove distance is controlled
by lead screw of the lathe.
The upper and lower slots are cut with a
metal saw.
Width of the slots should be exactly the
same as the grooves.
The steam inlet and outlets are cut in the
same position as those of the cylinder block.
With a boring tool, the bore is opened out
to a shade undersize, and finally finished
with a parallel-reamer.
The piston valves are made of ground stainless
steel bar.
The center part is reduced with parting-tool
and roundnose-tool, while the both ends are
left as the ground diameter.
The valve is reversed and finished to a final
length in a home-made brass corret.
The bore is drilled slightly oversize of
the valve spindle.
The valve will be fixed onto the spindle
with E-rings.
The position of grooves for E-rings are determined
from actual job.
Finished liners and valves.
The liner is fit to the cylinder-block with
Loctite 510 (anaerobic sealant with heat
resistance) and secured with screws.
The sealant is immediately cured in the absence
of air, so the assembly should be completed
within a second. Overflow sealant in each
port is removed with cotton swab.
I did a steam test for the cylinders with
Aster's gauge 1 locomotive.
I boosted the power of this little engine
with an electric blower on her chimney. Once
the cylinder was warmed up and dried, the
piston moved smoothly according to the position
of the valve.
The side covers for the cylinder block are
made from brass sheet. The sheet is bent
to "U" shape and divided in two
covers. A pair of round bar and angle is
useful for such a bending work.
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