What’s the best way of fitting the chimney

[Michael CallaghanParticipant @michaelcallaghan68621]

Hi chaps, what’s the best way of fitting the chimney to the smoke box. This is for a 5 inch gauge B1. Thanks

[Michael CallaghanParticipant @michaelcallaghan68621]

[Nigel Graham 2Participant @nigelgraham2]

Not shown on the drawings?

I don't know the particular loco but the fastenings are often screws (small hex-headed) or round-headed rivets, spotted from the chimney base flange, and the tapping or clearance holes as appropriate drilled radially to the smokebox axis.

An alternative, shown in Martin Evans' book, is a two-part chimney, the visible part being a sleeve over an inner liner/petticoat-pipe with a flange inside the smokebox, secured by small countersunk screws. The outer chimney, apparently a push-fit, covers them.

Some designs might use the petticoat-pipe as a sort of "nut" though I have not personally seen examples of that.

Have a close look at what other builders have done, preferably on similar classes. Even better, what did the full-size B1s have?

'

The key point is not only is the finished chimney being properly radial and vertical to the smokebox, but the blast- nozzle being concentric with it. I have made a simple gauge consisting of thick, turned discs grub-screwed to a stout steel rod, for assembling my steam-wagon's equivalents.

[Simon CollierParticipant @simoncollier74340]

I did mine with 8 x 8 BA small hex head screws. I drilled 1.5 mm first with battery drill, trying to drill at a tangent to the flange in each position. Then drill 1.8 and tapped smokebox, which in my case is about 1/8 steel. Went well.

[Speedy Builder5Participant @speedybuilder5]

My 5" SPEEDY has a flared blast pipe silver soldered to the smokebox and a cast bronze chimney slipped over the blast pipe and riveted to the smokebox (stops onlookers pinching it !).

[GreensandsParticipant @greensands]

This a copy of the Don Young drawing which I have used building his 5" gauge Black Five and closely follows full size practice.

[Michael CallaghanParticipant @michaelcallaghan68621]

Thanks chaps. Sorted now.

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