Help! - soldering tips

[Erfolg]

Myron

 

You are so correct. Processing history is important in the physical characteristics of piano wire.

 

As all engineers know, inputting energy/heat into the wire, even at relatively low temperatures, will initiate the release of strain energy and grain growth and re-forming of grains and grain boundaries, etc. More heat at longer times increases the extent.

 

But as a RR trained engineer you know all about these things.

 

As you suggest, once heated as in silver soldering, the characteristics of cold drawn wire are lost, heat treating will never regain the same characteristics. Yes you can harden the material, but the directional properties are gone.

[Boots]

I tried silver soldering and it made the piano wire soft, good joint but piano wire much like mild steel. I tried electrical solder but the flux is useless for steel. so I used plumbers active flux and electrical solder, you have to keep the heat on for a while whilst all this flux bubbles away but it ends up a good joint and the piano wire is still springy, I did bind it with copper wire and let it cool naturally

[Erfolg]

The words of Myron are spot on.

 

Piano wire obtains many of the characteristics from processing. The most significant are obtained by cold drawing, this process results in grains which are distorted, small grains and the impurities more widely distributed amongst the longer grain boundaries. The processing is commonly recognised as work hardening.

 

There are other process at work and without getting to much into the processes, revolves around the amount of carbon in the steel, and if it is in a FCC (Face Centred Cubic) or BCC (Body Centred Cubic), the important aspect of these structures is the density, which determines the hardness. The trouble with this bit is that it would take pages to explain the processes and the implications. But this is essentially the hardening and other associated processes.

 

Putting large quantities of energy/heat into the wire will as Myron has stated do two things, the first, the processing characteristics will be lost and secondly the structural characteristics will change due to these phase changes.

 

Putting less heat into wire as in soldering almost certainly have less profound changes. Yet changes will occur. The question is will we notice them in the real world. If you were making cable with armouring wires, the engineers will have come across the consequences from time to time of heating. Yet many modellers claim the wire is as strong as ever. From experience in industry and text books, commonly the Heat Affected Zone (HAZ), often results in a failure adjacent to the jointed area. But it is a case of less heat, the less the changes, possibly to the extent that modellers are not to obviously affected. So soldering has to be better.

 

A mechanical joint,should be better, in the 50's some modellers commonly used them. They are not obviously in favour now, so perhaps they are not as easy to make as other types.

[Peter Beeney]

I’ve always found too, that the blowtorch is a very good additional soldering tool. I have a 340 gram Primus propane bottle, you can hire these from builder’s merchants, Travis Perkins is the one I use. You buy the on/off valve and a selection of about 3 nozzles, but change the the bottle for a refilled number. This seems to be really inexpensive, and they are still easily available. Plumbers use these for copper pipe work, and they are also useful for heating other items, of course. Mine seems to last for ages.

To solder U/C legs for instance, what I’ve found works is cleaning the wire with something like course wet and dry paper or wire wool, nice and shiny, then bind, or whip, the overlap with copper wire. The whipping as in whipping the rings on a fishing rod, nice and neat, turns laid side by side. I would think that 15 amp fuse wire might be suitable. I use additional flux, Powerflow, for most soldering apart from printed circuit board and component work. Warm the wire with the flame, you can then run some flux in, you only need a smidgin, this prevents the metal oxidising as it gets hotter, show it some more flame, not too much, and then the solder will flow in and instantly run out, coating everything. Don’t over do it, otherwise any surplus will settle as blob at a low point. As soon as the solder sets, wipe any flux residue off with a piece of kitchen paper towel.

I’ve never had any problems with Plowerflow flux, and that also lasts a long time, too, my pot is still the original one I had. I use it on batteries, wires and connectors etc. I’ve also used silver loaded solder for quite a while on these items, it’s a bit different, it simply needs a bit of getting used to.

I also have a solder station, with an adjustable temperature iron. This is for the standard type soldering jobs. Also a selection of different gauge multi-core solders. I find that having the right size solder helps to make a better job. The thinnest size is almost like a thick cotton, it was used by the lads out in the fields doing some very delicate work on some fairly complicated printed circuit boards. I invariably tin the items to be soldered, and also the piece of damp sponge to keep the tip of the iron clean is invaluable.

Like Kozmyk, I spent a bit of time soldering. From abrasive soldering, tinning things like six or twelve by half inch aluminium bus-bars down to making servos; also live mains soldered connections, that was accepted practise back then, I’m not sure that it would be today though. We did quite a bit of live working, both on low and medium voltages. Good practise for playing with electric models at the patch!

I’d have thought that the soft soldering temperature, below about 400 C, would be insufficient to cause any softening? Maybe it would need at least twice that? I’ve never noticed that soldering piano wire has ever had any adverse effects.

Incidentally, I noticed in HobbyCraft this morning that they had at least 10 250 gram spools of 60/40 Tin/Lead solder; and it's a fairly reasonably small gauge. A bit expensive at £17 a roll, HobbyCraft seems a bit like that, but one roll would probably last a whole model club a long time. I think the rule is that you can still sell it, buy it and use it, but not start any new jobs with it. But then again, that might just depend on which hymn sheet you are singing from…...

PB

[Ian Jones]

Re steel hardening by rapid cooling - thanks to all that contributed in answering that question.

 

I've pondered over that before and now I will ponder no longer.

[Biggles' Elder Brother - Moderator]

Peter,

 

It is still legal to sell and use leaded solder as a private individual. The restrictions on its use apply only to businesses and comercial manufacturers as far as I know.

 

The best place for solder I've found is Carrs - big with the model railway boys.

 

BEB

[Peter Beeney]

BEB,

I mentioned the solder because I think there is a school of thought that considers that leaded solder is banned entirely. I don’t think this is helped by the fact that I think it can be a bit difficult to obtain; and this may be a little clue as to where to buy it. For instance, I’ve not been able to find it on Maplins website, so presumably they think it’s banned, too. As I read it, anyone can repair anything that was made with leaded solder, but it’s not used on new work. All the time it’s available I guess it would be difficult to regulate in any case. I don’t know if this is a worldwide situation, or if it only applies to Europe and America. Or even how it applies to plumbing applications. Is this using up exiting stock, or is it still being produced?

Fortunately I only use solder in relatively small amounts, so I probably have sufficient for a few more years, by which time I shall be seriously losing interest anyway.

I’ll also correct my deliberate mistake in my previous post, the line ‘below about 400 C’ should have have read ‘below 400 ℉’. At 400 ℃ I reckon you might be silver soldering and brazing. These sort of temperatures may affect the hardness of piano wire, perhaps.

This seems to be the same sort of situation as with nicads, confusion reigns everywhere!

PB

[Kozmyk]

RS, Farnell, Rapid, Screwfix. ToolShop, Toolstation etc etc are all still selling 60/40 solder.

 

The EU RoHS directives are rolling in but so are the exemptions on product longevity testing grounds.

Lead soldering is prohibited for food cans and plumbing.

 

There are various applications where leaded solder is the right stuff for the job and the alternatives give inferior performance.

 

Lot's of people thought that a total ban was coming in 2010 but it hasn't happened yet.

[John Tee]

Re leaded/unleaded solder, in plumbing it can't be used for pipes carrying drinking water, but i think it can be used for things like lead flashing.

john

[Erfolg]

Peter

 

With reference to the issue of altering the properties and problem of soldering drawn wire/piano.

 

There are a number of ways of considering the issue. In my opinion it is a mistake to consider the issue in terms of Annealing or Normalising and the common heat treatment applied to carbon and alloy steel, as used in production etc .

 

We should consider the material in terms of the fact that most piano wires will be  an alloy steel where a lot of the properties arise from the strain energy/process history, as  Myrons comments.

 

even for pure definitions of heat treatment where martensitic structures and grain boundary modification is sought, it is considered to start at 150C. Lead free solder has often a eutectic (lowest melting point) of 217-227C, dependant on Tin, Silver, Cu, composition. The potential is certainly there, even by these mechanisms.

 

From experience from armoured cable (bundled steel wire armouring) at BICC (some 35 years ago) that the strain energy is released if heated to high for to long. Very similar to aging of castings etc, in effect. In this case some of the directional qualities and strength is lost.

 

To some extent this is dislocation theory, which was sometimes disputed by older metallurgists. Today with electron scanning microscopes, the mechanism has been observed, so is now considered a fact by most.

 

Just as with welding it will be the material adjacent to the joint which will be more prone to bending under extreme conditions, for broadly similar reasons.

 

Do we as modellers notice any changes? Many say not. I suspect that it happens. Yet localised bending which occurs during an incident, may not be recognised as partially  due soldering, conversely could have happened any way due to the forces involved. Then the argument comes down to if it matters. My real point is that more heat and soaking, is more likely to make soldering matter, in stressed areas.

 

I accept that soldering may be the only convenient practical solution to some problems.

Edited By Erfolg on 27/02/2011 18:55:59

[Peter Beeney]

Erfolg,
Thanks very much for your reply. I accept that you are correct on this issue. I have little or no knowledge of metallurgy, and in fact I had to check on words such as martensitic to at least have some some small chance of understanding a little of what you are saying. I’m afraid my experiences of metal working are limited to some trainee blacksmithing, as in a forge,with a little furnace fire, when I was at school, two days a week for two years, and quite a lot of welding, gas and electric, literally in the field, or at least on site, things such as constructing bespoke exhaust systems from three and four inch water barrel, (we always called steel water pipe barrel - as you do!) for medium to larger size diesel generators. I enjoyed all of that.

Back at the undercarriage soldering, I’ve done a bit of this, for me and others, and I can’t say that I’ve ever had any particular problems. So maybe it’s not that critical. The undercart itself would always be ok but if the fixing to the model, of whatever type, was slightly suspect, then this would soon become apparent. I’ve seen the nose-leg that breaks after much service, or perhaps fracture is a better word, just at the point where it tends to get bent on the edge of the fuselage, I think this may be due to work hardening, or just getting fed up maybe, but nothing to do with heating.

One issue there may be nowadays is simply the quality of the metal that come with some ARTF’s. One way of describing it might be drawing a comparison between it and and an item made from a mixture of wet cardboard and tired plasticine! With the metal coming as second choice! (I’m sure Wallace and Gromit approve!). Although having said said that, whilst they are frequently subjected to the beginner’s rather slightly heavier type of landings, and thus require many little ‘resets’ , usually involving a bit of brute force and guess work, they never seem to want to give in and break. So what am I complaining about...?


So, whilst I’m probably not very often Normalised, I might sometimes said to be Annealing. I used to kneel on the ground but now I use a kneeler. My club mates think I’m starting the engine but I think the more astute amongst them have a suspicion this is a cover for a small prayer for heavenly, or at least airborne, radio control guidance………

Happy Landings!

PB

[Myron Beaumont]

Talking of undercarriage legs (well someone mentioned them ) ,Have you all noticed that nose legs always bend at the point of entry to the underside of the fuselage ,even with the useless couple of turns in the wire half way down said leg ? Answer ! More coils on thinner real piano wire .How many suspension units on cars have only 2 or3 coils ?

Tip of the day on the wrong thread .Sorry

[Erfolg]

I had not Myron, but then again most of my models have no undercarriage, flying as I do from a rough grass field.

 

I guess a number of issues, could be at play, again, I think you will be aware of them.

 

As you emphasised, processing history is important, in many of the properties of a material, possibly more important than heat treatment in many instances.

 

I think most engineers are aware that work hardening, is very important in many bending operations. Take a Stainless steel tube, if the material being bent did not work harden whilst being bent, the wall would thin unacceptably in the outside surface, yet work hardening ensures that a consistent (more or less) wall thickness occurs, rather than local thinning leading to rupture.

 

Yet taken to the extreme, work hardening or fatigue, results in breakage. Our dislocation theory again, where the slip planes become blocked, after movement of many dislocations, to form a tangle.

 

I guess a major factor leading to bending, is straight forward, bending moments, and local stresses developed, relative to the yield point (although in the real world of alloyed steel etc, there is no clear point as with Mild Steel). I guess that if all your landings were good ones, the bending takes place slowly, becoming noticeable only when I land a model as a single event.

 

My God, this is taking me back some 40 years, but maybe I remember what i do, as a consequence of using the principals subconsciously during my working life, as I suspect all engineers do.