Chimney saddle, how to machine

[Scrat]

Hi,

I am restoring my Foden Lorry. The Chimney was completely rusted to bits so a new one was made.
The old brass end cap also fits the new one.
The big problem comes at the bottom end.
How do I machine a chimney base to fit the radius of the smokebox top?

Chimney OD at bottom: 43 mm
Smokebox OD: 177mm

The smokebox top has four screws to hold the Chimney base.
These form a square with 53mm between hole centres.

Can anyone help?

[Chip1e]

Hi I would try using a verticle slide in a lathe and cut the radius with a boring head. Or in a mill with a boring head. I have machined all my chimney saddles using this method but on a smaller scale only 16mm steam Loco's.
Regards
Paul.

[Old Man Aaron]

Aye, lots of ways you could fly-cut it.

[Scrat]

With my small MD65 lathe and the matching BFE65 mill I do not have much capacity.
The idea now is to make a dosk with a hole in the middle, bend it to suit the smokebox top, weld in a bit of pipe and then weld the tapered portion on top of it.
Looks ok on trial assemply.

Pics to follow.

[Boustrophedon]

The radius under to fit the smoke box can be machined or failing that can be filed and then worked up on an appropriately radiused dowel covered in wet and dry. The radius from chimney to the top of the smokebox I turned on the lathe which fits front and back but not down the sides. The achieve the rest I blended it with files by hand. Yes it's just a Mamod but I think it demonstrates the principle.

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