Soft Soldering

I'm trying to solder up some platework for this shunter. I'm used to lovely silver solder, where you get it all nice and hot, touch the work and it runs down the joint like a good un'.

Trying to to do the same with soft solder is horrible/impossible. Sop far I've attached three brass sheets out of four to the brass angle skeletons of the running boards. I'm using frys powerflow flux, muliticore solder and a miniature blowtorch. The drill is to heat up a few inches at a time, until the solder flows and then squeeze the sheet into place and hold while it sets. At the same time all nearby joints must be clamped shut. This is very slow and messy and dirty. Because of the localised heat, the sheet buckles and bends away, the flux catches fire(!) and smells.

I don't have a huge lump of copper to make an old-fashioned iron. have any of you old hands got advice as at the moment I'm in dread of the much bigger job of soldering up the bodywork in 20-gauge sheet, angle and various strengthening bits and pieces.

Neil

Hi Neil

You could try making a soldering iron bit that attaches to your gas torch. A piece of copper rod that has its back end held in the flame by a bracket, with the other "business" end filed into the shape of the soldering iron bit. One of my gas torches came with an attachement like that. The trick is to get the angle of the bracket right so you dont get flaring of the torch flame while at the same time directing the flame away from the sheet that your trying to solder. If you haven't got a piece of copper rod (about half inch diameter would seem about right) then a piece of brass or even steel might be worth a shot, The heat conduction down the rod won't be as good but it should still be sufficient.

Keith

Hi Neil,

Have a look it ebay items 170801605484 and 150776567817. The first one is one I remember seeing recently that looks big enough but I also found the second one tonight while searching for the first one

Les.

Hi Neil,

Fasten it all together with small brass screws before you try soldering it. You can then file off any protruding heads etc afterwards.

John

Edited By John Baguley on 15/03/2012 00:27:36

What we used to and still do is tin both parts then put together with a gentle heat also at this point can put in a filet of solder. am prepared to explain the teqnique in detail if anyone is interested.

bob

Bob has it, pre-tin all the parts where they will be covered. then you clamp up lightly and heat and run more solder into joints.

Preperation before tinning is important by scratching the surface and maybe chemical cleaning if you have big areas and follow through with the tinning straightaway.

Bare in mind a blow torch heat is very localized and a copper bit is much better for controlling the run of heat and solder.

I would not use multicore solder, use killed spirits (Bakers Fluid) you do not need a black mess floating around and if its catching fire/smoking you are too hot!

Clive

Edited By Clive Hartland on 15/03/2012 08:02:15

Bob and Clive are right, use plumbers solder, and flux, some COTTON cloth is handy to use as a wiper to wipe off excess solder. A good even heat over the whole area. You can use the multicore if you need a little touch on the edge to form a fillit. Ian S C

Neil,

You didn't say how big this item is. For O gauge modelling, the standard is to use a lead-bearing solder of decent pedigree, and phosphoric acid flux. Even for larger items I would avoid like the plague the use of plumber's solder of unknown composition, and fluxes of archaic recipe. Some of the latter are the devil to get rid of and are likely to cause corrosion years after the item is finished; the plumber's solders may well have very high melting points and this may be the cause of the distortion you are experiencing. And definitely save the multicore solder for electronic work and don't try using it here.

Carrs/C&L Finescale (http://www.finescale.org.uk/index.php?option=com_virtuemart&Itemid=56) sell an excellent range of solders with a range of melting points. If this is the only soldering to be done, I would use the 145 degree solder, it melts (as its name suggests) at a low temperature, is quite strong, and it flows and wets the brass well. If you have more bits to attach, start with a higher temperature solder and then move down the range. If you click on the above link, then on the "click here for datasheet..." you will get a very much more comprehensive guide than I can give you here.

The best soldering irons are the temperature controlled soldering stations, but be aware that for larger work even a 50 watt one may not have enough grunt; if you are likely to do a lot, look for an 80 watt or even 100 watt one. Another technique I use a lot is resistance soldering, which is rather like the juvenile equivalent of spot welding; however, since these units cost £150+, you are unlikely to be interested unless you plan to do a lot. (If you are interested, please ask).

David

Edited By David Littlewood on 15/03/2012 12:07:40

As far as electric iron go, a 175 watt iron is what I use, or I have three old iron weighing between 2 and 3 lb, these are the ones I learned to solder with when I was 10 yrs old, maybe less. Big iron and heat it up quickly, your wee torch could help preheating the metal. Ian S C

The application of heat for soldering large areas is a tricky one, as a torch heats locally but a big copper iron will spread the heat evenly and you can travel it slowly along the job.

Clive

Edited By Clive Hartland on 15/03/2012 14:13:55

If distortion is a problem you could always try clamping it up with solder paste in the joints and heating it gently in a domestic oven. The tin/lead solder melts at 183 °C so is well within the range of the oven. Solder paste is expensive but you'll end up using much less. If you set the oven to about 220 °C the flux won't burn and will wash off easily.

Best to try it when the boss is out shopping though!

Russell.

Thanks for the ideas

I have solder paste for surface mount components. Even at ebay prices it would bankrupt me to use it for this job! The larger part of the 'running board' is 1 3/8" by 10 1/2" long.

My dad has a big 100+ watt iron, but it's in South Wales - I don't have a big enough lump of copper to make an iron.

I think tinning is going to be the way; that will solve the problem of getting the solder into the joint.

I'll see if I can find some small brass screws or copper rivets a well.

Neil

Hi Neil

If you want a blow by blow description of how to do tinning please PM me and I will take time to send it.

Bob

Hi folks,

And the prize goes to... most of you!

Despite one dire warning I just tried some plumber's solder I found lurking behind the nasty modern lead-free stuff. The long melting range allowed me to tin the brass plate really easily, just wiping the end of the solder on the fluxed sheet and leaving behind a smear of solder. The few blobs were easily remelted and spread out.

The higher melting point made no obvious difference, but it seemed to go together much easier. I had been using toolmaker's clamps as I went along the joint, but for the final side I used - wooden clothes pegs! My big pliers held a long section of joint until it 'set' and the clothes pegs were sufficient to hold the sheet to the angle even if it remelted (I had annealed the sheet so it had no spring in it).

Still a messy job, but the Fry's flux doesn't go the same way as the multicore flux, so I think I can just about bear doing the bodywork with it. Som,e distortion isn't the end of the world - take a look at the prototype!

Wow! I managed to embed a picture!

Neil

(Either I'm a lousy typist or someone is eating my letters!)

Edited By Stub Mandrel on 16/03/2012 21:27:13