< 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.