Sweet Pea Firebox support brackets

[280vs]

Could I ask for some help from Sweet Pea builders, owners or boiler inspectors?
I've just acquired a Sweet Pea of which I know little history.
Probably built in the mid '90s, it has run but has been partially disassembled and repairs started - the most obvious issue being pitted piston rods (they look like mild steel), so new stainless rods and CI pistons have been made (in the box of bits).

The boiler is stamped up to identify it as being from Bishop Ellis - not tested it yet but I believe it to be water-tight (I will be testing it in the next few days).
However, there is an issue with the 'Z' shaped support brackets on the firebox.
The original drawings in the EIM construction series called for 2 studs each side and indicated a fillet braze between the firebox outer shell and the bracket faces.
One of those bracket faces is still attached, but the rest of the bracket is missing (looks like it has been filed off smooth where it was bent). None of the other bracket remains but there is a patch of silver solder where it would have been - the solder was patchy so it didn't look as though there was full penetration and adhesion across the surfaces, which seems odd given the maker. No sign of any studs.

The original spec for the brackets was 16swg brass. Given the differential thermal expansion between copper and brass, thermal cycling of the brackets and potential fatigue on the bends (especially if an unsuitable grade was used and maybe they were strained when clamped in place?), I can imagine that they might have cracked through.

My questions are:
1) Has anyone come across a similar issue with these support brackets?
2) Has the bracket mounting changed between the original articles in EIM, what's in the book and on the drawings? (I only have the EIM articles so far)

I note that some commercial builders now use blind tapped bushes for the support brackets - as here

I'd welcome your experiences and suggestions before I take it to discuss with our club boiler inspector.

Thanks,
Andy

[millman]

I have a couple of Sweet Peas on the go at the moment, actually being honest they have been on the go for twenty plus years, don’t ask why I am doing two, the reasons have been forgotten many years ago. My boilers were commercially made and have blind tapped bushes but no matter how hard I try I cannot bend up the Z shaped brackets and make them fit. It is my intention to make a cradle something like a smokebox saddle to fit between the frames and just let the boiler lay on it. The boiler mounting is the only thing that has given problems in an otherwise enjoyable build. Early new year resolution is to finish one at least next year, only cab to put together and saddle tank to make.

[280vs]

Thanks Millman.
May I trouble you for the size of the bushes - thread & depth?

[millman]

Bushes are 5/8” diameter with a 2BA tapped hole. Flange thickness is 3/32 and tapped hole is 5/16 deep. I had no say in what was done, I quite expected the four studs as per the book but I was told bushes are the better way, possibly because they don’t get bent in transit to the customer. With hindsight, a wonderful thing, I would make the bushes with about 3/8” dia body and head about 1/2” diameter and the head as thin as possible as I had problems, if I had not made the smokebox and saddle I could have raised ice whole boiler / smokebox assembly up by about 3/32” and saved a whole load of grief. Hope this helps.

[280vs]

That's really helpful - thanks again.
My loco has a fabricated saddle - I'll check out the clearances with some temporary props under the boiler to see what there is space for.