Talk to your boiler inspector ! If you deviate from the published or recognised design then you will have to show all calculations and materials specs ! There are numerous books on the matter of boiler design, K.N. Harris, Martin Evans, Tubal Cain, Etc. Do the calculations and show them to the inspector, he or she will advise on the way forward ! Bear in mind that it will not always be a case of increaseing dimentions by a simple factor, some will need to be considered on the square. Ask anyone who has made a 3" minnie ! Good luck. Noel.

Pressed wrong button

Edited By duncan webster on 19/12/2021 21:49:38

Before you just multiply the (non -boiler) parts by 1.5 check whether the scale of the bodywork is actually the same as the scale of the wheel space relative to full size. 5in models are often scaled as 1in = 1 ft but obviously the wheels aren't.

You may also want to look at the Reeves RV6 boiler, good build thread here with a GA so you can see sizes. Might have to register to see the many images as they are posted as attachments.

I wonder if scaling up that boiler will be able to supply enough steam, it is a fairly basic design with a smallish heating area. First thing that jumps out at me is the top flange will end up about 1.5" wide and may well need stays as it's usual to have approx 1" between supports or stays to avoid excess thickness of the plates.

Edited By JasonB on 20/12/2021 07:43:32

[This posting has been removed]

Is there a chimney and associated draughting on the 5" boiler – if not then i seriously doubt (infact am certain) that it wont make steam. Scaling it up would just make it worse. No fire tubes, water tubes or cross tubes? I must be missing something – but to answer your original question yes its a simple scale up. As JB has said you might need to look at the flat areas but increasing the thickness will sort that. Ive made lots of 5" and 6" dia verticals and they dont require any stays – but I do work everything out in cad first to ensure I comply with the build codes and safety margins. If you follow the ozzy codes you will comply with the rest of the world. UK codes are fine for UK but lack detail.

Looks a very interesting project Steve.

I took over a set of Paddington plans that someone had started to convert down to make a more to scale Speedy.In the end I just drew out masses of bits starting with the frames. Frames being 5/16" slimmer which gives her a more squat apperance. Every so often some more bits get snapped up when they come up for sale.

I have also jumped into 7 1/4" tank loco lovely size.

David.