< Grate, Ashpan and Firedoor >
The original drawings show a simple ashpan
held by a supporting pin through the frames,
which can immediately remove the fire in
case of emergency. However it means we cannot
abandon the ash during the boiler is working.
So I designed the ashpan with a double door.
Both door hinge axles hold forked levers
in 45 degree which connected to an operating
block by flat bar arms. The operating pin
is screwed into the block with a coil spring
around it. The pin is supported by a square
bush under one of the stretchers.
As grate and ashpan are the hottest parts
in locomotive at working, they are best made
up from stainless steel. The bottom door
and the side walls are made from 1.5 mm stainless
steel sheet. The hinge axles are slotted
1.5mm width to hold the door plates and brazed.
The axles are hold in four phosphoric bronze
bushes in the front and rear walls. The remainder
was made from bright mild steel, and assembled
by the hardened steel pins and the E-rings.
My cast iron grate from a supplier doesn't
fit to the William's firebox. I tried to
cut out with a hacksaw, but the material
is too hard and brittle to do that. So I
ground out excess part with 'shaper'. Incidentally,
the cast grate should be placed backside
up to make the bottom end of the slits wider
than the top end. Moreover, you had better
make the grate sloppy in the firebox, because
a grate is often distorted by heat.
The spring was coiled in the lathe. Its force
was designed 0.5kgf at closing and 1.5kgf
at opening.
Some folks say Loctite is not enough reliable
to fix the driving and coupled wheels onto
the axles. Therefore I fixed them with set
screws as follows.
The wheels with the axle are aligned on the
lathe cross slider, tilting 45 degree toward
the headstock. Starting with a shallow guide
hole by an end mill, the job is drilled deeply
up to the axle, then screw tapped.
The firehole door is made from free-cutting
stainless steel. By reason of available material,
the door disc was parted off from a fat round
bar, but it is easier cutting from a sheet.
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