Fire Grate Past Frustrations
Owners of Polly V locomotives suffer the frustration of juggling the original bar grate into the firebox opening and then getting the ash pan to seat correctly before inserting the retaining pin. With the old bar grate I had mounted some reference blocks on the ash pan floor to keep the fire grate roughly, but still lose, while the ash pan was juggled into the correct position and the retaining rod inserted. On a cold frosty morning at the track, when keen to get steam up, this was always a pain to do. I resolved to fix or at least ease this problem on the new Rosebud Grate.
I have a ball bearing rolling road that fits on my B&D Workmate stand and this allows easier access to the underside of the engine.
I mounted the new Rosebud Grate in place in the bottom of the firebox and threaded some 16 SWG wire through the firebox door and into a pair of the holes in the centre of the new Rosebud Grate. I could now pull the grate upwards and hold it in place in the firebox floor opening. I did a dry fit of the ash pan and inserted the retaining rod. Looking back down into the ash pan from the rear of the engine I could see that with the grate pulled up tightly into the firebox opening (using the wire) there was about 3mm of clearance between the ends of the new grate supporting pillars and the ash pan floor.
Leaving the grate securely in place, held with the wire, I dropped the ash pan out of the engine and cut a piece of card to exactly fit inside the ash pan bottom surface. I painted Engineers Blue on the ends of the Rosebud Grate mounting pillars. Very carefully I offered and fitted the ash pan in place and inserted the retaining rod. I then released the retaining wire on the grate and let the grate drop so that the grate pillar ends contacted the card and left blue witness marks. I tightened the restraining wire again to lift the grate and then dropped the ash pan. I had four usable blue marks on the card showing where the pillars were located relative to the ash pan base.
I drilled out just the two best marked diagonals pairs with 5.5mm holes and then dropped the grate out of the engine and mounted it on the ash pan. I cut the length of the two M5 mounting screws such as to be tight into the pillar holes while not quite gripping the ash pan floor. This gives a degree of movement (aka slop) when offering the assembly into place on the locomotive.
Now only a single integrated lump (grate + ash pan) needs to be juggled in place on those frosty mornings.
This afternoon I ran the Polly up on the rolling road with the new Rosebud grate fitted. After lighting with white spirit soaked kindling, the safety valves were blowing after 17 minutes. The fire looked bright and even on the blower and on no-load running. It is not a true test but certainly looks promising. Following the rain over the weekend, we have been given permission to run steam once again at the Club so maybe an outing is called for on Sunday to get a real feel for the changes.
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