K-27 Firebox Ring query

Hi
In part 15A of 'Live Steam & Outdoor Railroading' the drawing shows the firebox ring being outside dia of 52mm, in the following issue part 15B the backhead and firebox back sheet show the hole dimension of 53 and 54mm respectively, the comments state 'to be filed at assembly to fit firebox ring' for the backhead, in the firebox back (54mm) it says 'fit to firebox ring' which i see as being 52mm, so my question is why such a large discrepancy what am i missing please? in other words what am i not understanding with this?
cheers Malc

I don't have that copy of the LSOR article, but I do have both volumes of Kozo's K-27 books.  This happens to be in Volume 1.

When I look at the overall boiler drawings at the beginning of chapter 15 (which I assume would correspond to part 15A), I read the fire box ring as being 54mm OD.  The drawing shows a 50mm ID, with a wall thickness of 2mm.  The wall thickness would be included twice, so the OD of the ring is 54mm, though the OD dimension is not specifically shown.

Later in the chapter, section 15-5 (which I assume corresponds to part 15B in the magazine), it shows 53mm for the fire door ring in the backhead, and 54mm for the opening in the backsheet.  His directions have you solder the firebox ring into the baksheet first, then later, adding the backhead. And as you say, it does say to file the opening in the backhead to fit the firebox door ring.

So the only thing I think you might be missing is one wall thickness for the firebox door ring?  If the drawings in the magazine show the OD being 52mm, that would seem like a misprint to me, since the book shows otherwise.  And both the book and the magazine show the back sheet to have a 54mm opening, which would match that.

I'd vote for 54mm being the OD of the firebox door ring.

Kim

When I look at the overall boiler drawings at the beginning of chapter 15 (which I assume would correspond to part 15A), I read the fire box ring as being 54mm OD.  The drawing shows a 50mm ID, with a wall thickness of 2mm.  The wall thickness would be included twice, so the OD of the ring is 54mm, though the OD dimension is not specifically shown.

It just goes to show i need to slow down my enthusiasm and read more carefully, i am glad i am doing cad first becasue i can catch my errors, you are indeed right it is a 2m thickness giving 54 which now makes perfect sense.

Later in the chapter, section 15-5 (which I assume corresponds to part 15B in the magazine), it shows 53mm for the fire door ring in the backhead, and 54mm for the opening in the backsheet.  His directions have you solder the firebox ring into the baksheet first, then later, adding the backhead. And as you say, it does say to file the opening in the backhead to fit the firebox door ring.

Makes so much sense now to me


I'd vote for 54mm being the OD of the firebox door ring.

Me too :-)

Thank you so much for pointing that out that.......tempering excitement 
Malc