Peter,
Cheers, that's a fair assessment
I also asked around about micro flames and like all recommendations is highly subjective and personal; some people can model with a bent nail and smoldering stick, I can't. Expensive tools don't always make a better job, but I've yet to find one that didn't make it easier and thus, more importantly, enjoyable.
So I started out with this.
It's a micro flame, it has a flame that is controllable and self ignites, so does what it says on the tin, but it's crap. Primarily the flame is way too long on even the lowest setting and unless it's more than 70° to the vertical cuts out. Being a south paw the flame control on the left is a right pain, especially if the right hand is holding a delicate part in place ready for soldering. It has been relegated to lighting the wood burner to save burnt fingers from matches and for that it is truly an exceptional tool!
Having struggled for months with the above I gave in a opted for what is probably the most expensive hobby micro flame around.
I simply love it, well balanced, well engineered, ambidextrous flame control and when near full will solder at all angles, even upside down, without cutting out. The flame on the lowest setting is very small and compact, about 25-30mm to the tip of the cone, though that gets longer as the gas level drops as you need to ramp it up a bit to maintain the smallest flame.
Other peoples mileage may vary of course.
So onto flame soldering and here's how I do it, or have been doing it.
This is a small part and probably about as hard as it gets I'd imagine, there are no half etch guides or slots and tabs to help location and squareness, a simple free standing butt joint.
The first step is to tin the joint edge of the web.
I've also marked on the top of the tender side with a black marker and scribe line my initial fixing point, it's opposite the other already fixed in place web, it's hard to see but it is there.
The hardest job with a web like this is getting it square in two planes, vertical and transverse across the tender, so to help this I tack it at the very tip near the top and to do that I use the big ESRA set to 400°C and on the 'outside' of the tender.
Make sure the inside of the tender is well fluxed and you'll just see the solder at the top turn shiny, that's the clue to take the iron away, we only want a few mm soldered at this point.
It also helps if the iron is 'wet' with solder, this will leave a solder mark on the outside but it's way easier to clean it off that big flat surface than from the inside once the web is in place.
You can see the mark on the left outside from the previous web fitting and yet to be cleaned.
Once the part is held we can tweak it to make it nice and square and then do the final solder with the micro flame.
At this stage the web will support it's self so the clip above is a photo prop.
Cut a very small sliver of solder, remember the edge is already tinned and if it's all square and clean should be more than enough, but I prefer a bit more mechanical grip. The larger the blob of solder the more you have to clean so gauging the exact size is personal preference. Place the sliver of solder in the heel of the joint and flux well and set the flame to the lowest setting.
Now the hard part, getting the heat where you need it and not unsoldering your tack joint....or anything else in the vicinity! This is where you need to take stock of your heat loads, small heats very fast, large very slowly, yes I know, the bleedin obvious....but frequently overlooked.
I know that underneath my tank well deck along the side is a large support strip so that is going to be my largest heat load. The well deck is thin but a large expanse so the heat will take time to travel out to anything important. My lowest heat load is my tack joint at the top tip of the web so I want that heated last if possible.
In the end I centred the flame at roughly where the sliver of solder has been placed in the above photo, for the actual joint the solder sliver would be right in the corner, the heel of the joint.
As you heat the area the flux will spit and sizzle and that has it's own issues, sometimes the spit will be right under your sliver and it'll ping off at hypersonic speed, in which case I stop, remove all the old pre heated flux, clean and start again....keeping the original tack in place though. The safety flux I use is a kind of one shot deal, if the joint doesn't take first time then next time the heated flux seems to form a barrier and much swearing will evolve.
You'll soon see when the joint makes as the solder should flash along all the joints and it should end up looking like this.
You can see it has formed a nice fillet weld along all the edges, you can also see that my heat source was well away from my lowest heat load, this is visualized by the solder fillet between the deck and side which has run toward the rear of the tender by a good 10 mm or so, my flame centre was near that brown dot on the deck.
All that's needed now is to clean up, there will be a larger blob in the heel and depending on the finish you want will depend on which tool you use.
For a nice clean cut square no fillet joint you need one of these, a stabby sharp pointed thingy.
This will remove all of the fillet, the only problem there is that the more fillet you remove the weaker the joint, on the tank side it's not important as there's a massive fillet and support strip underneath, but for the web then it might be a touch too much. Besides the real thing is welded so for that I use the tip of a pair of needle tweezers.
Here we're not removing much material, just smoothing it really, perfect for leaving a small fillet and simulating a welded joint. I've also got some old screw drivers and often use old needle files with damaged tips to scrape away as well, whatever you can get your hands on really and works best for you.
If your sliver of solder was just the right size then you won't need to take much off at all
Right one down, four more to go
MD