Burrell Smokebox Door Curvature

Burrell Smokebox door curvature or no curvature? This miniature traction engine sits on my desk in various stages of design and build. Sometimes loving it and sometimes tormenting me. At the moment the smokebox door is staring at me with it’s flatness. It really does need to have some curvature.

However, what is the curvature? Some quick searching online and I found this Burrell build as a reference: Burrell Single Crank Compound Traction Engines – 4″ Scale. Andrew gives the radius as 18.75″ for this 4″ engine. By the way, this is a lovely build and well worth looking at if you’re thinking of building a traction engine.

4″ scale is 1/3 and so 18.75 x 3 / 20 = 2.8125″ => 71.4mm

Now I just need to work out how I’m going to machine that radius onto a smokebox door blank. Hmm, I could do this in steps and then just smooth it. Or I bite the bullet and finally make a radius turning attachment for the milling machine. There has to be a number of ways of machining a curvature onto a piece of metal. Or even forming a curvature onto a piece of metal.

Another one to add to my task list as this smokebox door is going to nag at me until I get it right.

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