After fitting the brakes I decided to return to the loco body to move that forward.
That started out as a one forward one back because I had to re-solder the boiler section as for some reason the soldered seam had failed. Still better that it failed now than when the loco is finished. That little job done I looked in the box and sighted the chimney casting so decided to tackle that.
There was quite a bit of discussion about the David Andrews Chimney, or to be more accurate about all the chimneys in the kit's that are/have been available for a Princess Royal with the consensus being that none of them were accurate. Mike Hopkins was commissioned to draw up and have cast an accurate replacement (by David Hill at Gladiator I think). Noting that I was building a Princess Mike dropped me an email and asked if I would like a replacement for the kit provided casting and I took him up on it.
Now I have to confess, having used one of Mike's chimney castings on the Class 5A, that I am not wild about the way that Mike designs the flare/inner chimney. I understand that being 3D printed the chimney needs to be supported and that those supports have to be cleaned up so adding them at the bottom makes sense I much prefer to remove the usual screw thread/stub from the bottom of the chimney, drill it out and them use the smoke box wrapped in wet and dry to smooth out the flare to make it sit on the smoke box properly.
Although I forgot to take a photo of the Princess chimney before I started I had a J63 chimney in stock (for when I get around to swapping the lopsided one off my J63). The Princess chimney was similar to the photo above in that it had the remains of the casting sprue attached to one edge of the hole and the remains of the supports around the bottom of the inner chimney and the flare.
I started by cutting off the casting sprue and then had made a start on the laborious job of filing out the rest when I thought that I could pop it in the lathe and use a tiny 3mm boring bar to remove the remains of the sprue from inside the chimney. To stop the rim getting marked I wrapped it in a strip taken from an aluminium drinks can (I have a few cut down cans in the workshop for just such tasks). Suitably protected I put the chimney in a collet and centred it as best I could (it still had a slight wobble). Then working steadily taking 0.1mm cuts I bored out the remains of the sprue. I also shortened the inner chimney by approximately 2mm which took care of the stubs of the supports.
That done I used a diamond coated mini drill attachment to grind of the remains of the stubs on the base of the flare.
At this point the hole in the smokebox is only about 1mm in diameter and I was wonder about the best way to enlarge it as the inner chimney is just over 10mm in diameter. I decided to use the practice smokebox that I ad created to ensure that I could successfully roll the thick material of the smokebox.
As luck would have it I have a 5mm centre drill which up to now has been too big for anything that I might have needed. It was perfect to drill a hole and then use the countersink part of the bit to slowly open out the hole in the smokebox until the chimney would fit.
This confirmed that the chimney would sit flush on the smokebox so now I just need to open out the hole in the proper smokebox to suit.
