Steph Dale
Western Thunderer
In the past couple of months we've hit a minor snag at Finney7 towers, which was associated with the construction of belpaire fireboxes. The problem was that although they're relatively common things to have to make, they're complex shapes and as we went through the process of developing our new instructions we felt that we should offer more complete guidance on how to do it, just in case the builder was not familiar with the techniques.
So, I had a look around; there’s some stuff in a couple of old Model Railway News and books by Guy Williams and others; some go back to the fifties. Here then is the official Finney7 recipe for constructing a Belpaire firebox. This applies equally to those that were designed by Martin Finney and other designers such as Malcolm Mitchell or David Andrews; it's not even scale-specific as the components required can be selected on size for the kit and scale in question. I've also included a note further down the page on how to mark out a wrapper from scratch if you're not building a kit. The example given here is for a 7mm 47xx, from the Martin Finney/Finney7 stable:
The 47xx kit comes with double front firebox spacers and a single rear one, all out of the 0.7mm (28thou") nickel-silver fret and a wrapper, mostly half-etched from the 0.45mm (18thou") brass fret. This gives a good combination of surface detail and solidity; the double front thickness helping with forming the corners of the firebox. The spacers are provided with pairs of nominally 3.5mm holes, so a length of 4BA studding was purchased as well as both brass and stainless steel nuts; it has to be a good fit in any provided holes and with 4BA being specified as slightly larger than 3.5mm it's worked well:
First job is to work out how long the sections of studding need to be, the answer is 'a bit longer than the wrapper':
The front spacers are then laminated and all spacers cleaned of their cusps. The brass nuts are threaded on to the studs:
Using the small dimples provided on each part the centre lines are marked on the outside...:
...and the inside of each part:
With all the parts cleaned up and marked out, construction can commence by setting the two spacers on to the studs, retaining them with the stainless steel nuts and ensuring the length of the assembly matches that quoted in the instructions. In the case of the 47xx, that's given as 60.9mm. Always measure the distance from the bottom of the firebox; even using a steel rule and eyeglass you can get pretty close to this sort of dimension with care. Take your time, measure and check it a few times:
It's much easier to use a vernier or similar gauge as not only can you be sure the measurement is pretty precise, it will also be a good check that the spacers are parallel to each other. Assuming the nuts and studs have reasonably well-formed threads, they should be...:
I'll be along with part 2 shortly, I'm just going for a cuppa...
Steph
So, I had a look around; there’s some stuff in a couple of old Model Railway News and books by Guy Williams and others; some go back to the fifties. Here then is the official Finney7 recipe for constructing a Belpaire firebox. This applies equally to those that were designed by Martin Finney and other designers such as Malcolm Mitchell or David Andrews; it's not even scale-specific as the components required can be selected on size for the kit and scale in question. I've also included a note further down the page on how to mark out a wrapper from scratch if you're not building a kit. The example given here is for a 7mm 47xx, from the Martin Finney/Finney7 stable:
The 47xx kit comes with double front firebox spacers and a single rear one, all out of the 0.7mm (28thou") nickel-silver fret and a wrapper, mostly half-etched from the 0.45mm (18thou") brass fret. This gives a good combination of surface detail and solidity; the double front thickness helping with forming the corners of the firebox. The spacers are provided with pairs of nominally 3.5mm holes, so a length of 4BA studding was purchased as well as both brass and stainless steel nuts; it has to be a good fit in any provided holes and with 4BA being specified as slightly larger than 3.5mm it's worked well:
First job is to work out how long the sections of studding need to be, the answer is 'a bit longer than the wrapper':
The front spacers are then laminated and all spacers cleaned of their cusps. The brass nuts are threaded on to the studs:
Using the small dimples provided on each part the centre lines are marked on the outside...:
...and the inside of each part:
With all the parts cleaned up and marked out, construction can commence by setting the two spacers on to the studs, retaining them with the stainless steel nuts and ensuring the length of the assembly matches that quoted in the instructions. In the case of the 47xx, that's given as 60.9mm. Always measure the distance from the bottom of the firebox; even using a steel rule and eyeglass you can get pretty close to this sort of dimension with care. Take your time, measure and check it a few times:
It's much easier to use a vernier or similar gauge as not only can you be sure the measurement is pretty precise, it will also be a good check that the spacers are parallel to each other. Assuming the nuts and studs have reasonably well-formed threads, they should be...:
I'll be along with part 2 shortly, I'm just going for a cuppa...
Steph
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