Class A sheathed smokebox

[NW Mailing List]

From another guessing bozo, the aesthetic point is likely related to paint. My understanding is that the smokebox, while at the “cold” end of the boiler, was too hot to hold paint. The gasses in the smokebox could still be 600+ degrees F. The extended jacketing and underlying insulation might have been to provide a surface cool enough for the paint to survive on (less rust as the graphite baked off!) - as well as providing a smoother look. 

Matt Goodman
Columbus, Ohio, US


> On Feb 6, 2023, at 9:21 AM, NW Mailing List <nw-mailing-list at nwhs.org> wrote:
> 
> Two very small points from a bozo who wishes to add his simpleton's conjecture to the mix:
> 
> 1.  It may be better to refer to what is here being called "sheathing," by its proper name, "lagging."  (Lagging was asbestos insulation, pressed into large slabs perhaps 4 inches thick, and perhaps a foot high and about 24 inches long, stacked along the outer shell of the boiler or the firebox wrapper sheet, all held in place by an outer sheet steel wrapper.)
> 
> 2.  What was the value of applying lagging/sheathing that far forward on the boiler?  By the time the hot gasses were that far forward, the preponderance of the heat had already been extracted in the flues and tubes, and the gasses were ready to be blow up the stack.  Did the application of lagging/sheathing to the smokebox really effect the final transfer of thermic values to the superheater tubes?  
> 
> A farmer's guess is that extending the lagging/sheathing forward to cover the smoke box was purely a matter of aesthetics.  But what do I know ... ?  I am only a guesser, like everyone else at this point.
> 
> -- abram burnett, 
> Turnip Oil: the Alternative Fuel to Save the Planet
>  
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