Metric Minnie

Can anyone advise I am starting a build of Minnie using a combination of the metric plans available and LC Mason's book. The plans say use m4 bronze with a stainless steel spacer. Could I use stainless all thread ?

No, use bronze as it will be easier to solder and I would also use bronze for the spacer if using that method. Most boiler inspectors would not approve of stainless stays in a copper boiler.

The more commonly used construction meyhod these days would be to use 1/8" rivits for 5 of the stays and the 4 corner ones solid lengths of 3/8" (10mm) bronze that can then be drilled and tapped for a stud and nuts.

Talk the boiler through with whoever is going to test and certify it before you start buying and cutting metal.

Also don't drill the 3.5mm holes shown in the top of the boiler barrel and thickening plates for the cylinder and motion bracket as show on Julius' drawings the cylinder can't be fitted with bolts FROM INSIDE THE BOILER

Edited By JasonB on 21/09/2016 13:25:01

Thank you for that information. I have located my nearest / easy to attend ME club and will discuss with there boiler tester. Instead on the 3.5mm holes what do you recommend instead ?

As per the book and original LC Mason drawings. The thickening plates should be soldered to the inside of the boiler and can be retained in position with a single 1/8" copper rivit in the middle while soldering. The boiler can then be hydralically tested without having to try and block all those 3.5mm holes.

Drill the cylinder saddle and use that to locate the position of the holes on the boiler,

You should use 6BA fixings or as you are doing a metric engine then M3 would be the closest. You will have to make bronze bolts as they are not easily available. These bolts can ge inserted from the outside.

J

Thanks again Jason I have had another thumb through the book and seen now the reference to soldering the plates in. I have realised after a search that finding hens teeth may well be easy compered to bronze bolts ! Your guidance is appreciated as this is my first big steam project and first boiler build.

Mark