Silver Soldering

[Peter Miller]

Dural needs anealing to bend ot it will crack on sharp bends. Normally this is done in a salt bath. Depending on the grade, some will age harden back to normal hardness.

Going back to my airframe fitting days. We also used to soften those pruple rivets which work hardened as we closed them.Was it only 40 years ago that I was doing that?

[Myron Beaumont]

Peter
Guess so ! 'cos I remember them & still got some somewhere. Wasn't it a dye which soaked into the anodisation that made 'em pruple (as you put it)
Grumpy Myron,

[Peter Miller]

I think they were dyed for identification. I seem to remember that that they were "hiduminium" rivets but what that means I don't know.
The Dural that we used was normally L72 for aircraft work.

[Bob Cotsford]

Thanks for the suggestions, the bracket will connect the end of sprung oleo leg to the combined axle/control rod, so is mounted within 6mm or so of the wheel. It reverses the action of the full size, where the oleo carries the axle and the control arm stops it spinning and swinging - like a bottom wishbone on a car. It's from the Don Stothers plan, where he just flattens and drills the end of the sprung leg for the axle to pass through, I wanted to make something a little more 'engineered'. I take it tinmans solder is stronger than plumbers solder, or is it the same stuff?

[Peter Miller]

I would imagine that tinmans and plumber solder are very similar.

My Squires catalogue has stopped listing Tinmans or plumbers solder. I wonder why? Probably something to do with the cretins in Brussels.

You want a solder with a higher percentage of lead. They do list a Tin Copper solder which melts at 227C which is a lot higher than normal cored solder.

Ring Squires on 01243 842424 for a free 600 page catalogue of tools and masses of other goodies. Minimum order £7.50 and postage is free. Very fast delivery.

My only connection with this company is as a very satsified customer

[Steve biplane]

Peter, sometime back in 1920's Rolls-Royce set up a company called 'High Duty Alloys Ltd' to develop high strength aluminium alloys. They were particularly interested in were increasing the strength of alloys at temperature so they could be used for pistons and cylinder heads. They also developed alloys that didn't age harden at room temperature after heat treatment but had to be 'artificially aged' by heating to ~170 degC. They were given the designations like 'hiduminium RR56' taking bits out of the words HIgh DUty aluMINIUM. I didn't know these alloys were used for rivets though.
Steve

[Peter Miller]

I always wondered what Hiduminium meant.

The rivets were always called by that name, maybe it was wrong. I seem to remember it from trade training but it is a long time ago, Trade training was 52 years ago!!!

[Malcolm Fisher]

Tinman's and plumbers solders are very different alloys.
Re soft solder

Tinman's is more or less the same 60:40 lead:tin alloy as cored solder. I can't remember the analysis of plumbers' metal but the major difference is that it doesn't have a definite melting point.

Timan's melts and "freezes" at a given temperature while plumbers' metal has a stage where it is a sort of paste, i.e neither solid nor fully liquid, enabling it to be "wiped" as used to be done in making joints or mending bursts in lead pipes.

This skill is rapidly disappearing as it is now forbidden to use lead in solder for joining the copper pipes which replaced lead and are now in turn being replaced by a range of plastics.

[Peter Miller]

I told you it was the B****y EU. They even stopped Hassleblad from making one their cameras because the was lead in the solder of the circuit boards. I wonder when they will insit that all the lead is removed from church roofs.
I have a huge sheet of lead given to me by my local roofing contractor. I use it for balancing models. I suppose the thought police will be round to remove that before long.

[Peter Miller]

I told you it was the B****y EU. They even stopped Hassleblad from making one their cameras because the was lead in the solder of the circuit boards. I wonder when they will insit that all the lead is removed from church roofs.
I have a huge sheet of lead given to me by my local roofing contractor. I use it for balancing models. I suppose the thought police will be round to remove that before long.
I know that the higher the lead content the higher the melting point of the solder.

[Malcolm Fisher]

I still do the occasional plumbing job and, if it entails removing/replacing lead pipe, I save the lead for "noseweight" (very rarely tailweight).

Contrary to "regulations" I melt the stuff in an aluminium pan on a portable gas stove and pour it into suitable moulds.

I have even poured molten lead directly into holes in glider noseblocks - chars a bit, but never comes adrift when the cavity is greater than the access hole...

BTW, Peter, I have a lead covered bay window which will need recovering in the not too distant future and I propose to use the traditional lead sheet.

Would you like some of the old stuff? - you would have to collect...

[Peter Miller]

Thanks Malcolm but I have still got masses of the stuff. Most of my designs do actually need tailweight. I prefer that as it takes a lot less to move the CG back a given amount that it does to move it forward.
Done a bit of lead casting too. For those who haven't, just make sure that the mould is completely dry or it spits out.

[Steve biplane]

If you are going to cast lead then please make sure you do it in a well ventilated space (preferably outside) and don't breath in the fumes. Leather gloves and a pair of goggles are also sensible precautions.

Health and safety legislation gets a lot of stick in the media but it is there to protect people working in factories who otherwise, in this case, would be exposed to lead fumes from industrial scale soldering. The same can be said for cadmium or solvents or any number of nasty substances just waiting to overload our bodies with heavy metals or cancer producing agents. Is the legislation worth having? Well if you retired from a lifetime in industry in the 50's or 60's you would probably die before you got to 70, these days you will probably reach 80. I think some of that increase has got to be down to healthier environments in the factories, and the houses surrounding them.
As long as we take sensible precautions when we very occasionally use things producing lead or cadmium fumes we should be ok.
Steve

[Peter Miller]

Yes, agreed but some of the rules do get a bit over the top. They are going to ban celullose dopes, now the body excretes celullose but the two part equivelants are cumulative and more toxic.
Then we have the guards on some machines, they are so restrictive that you can't actually see what you are doing, eg a mill at a school where I worked.
The latest one where scaffolding MUST be used, it means that even window cleaners should put up towers or scaffolding.
I am waiting for the day when they specify that models must have a steel cage round the propellers. Don't laugh, they are stupid enough to bring that in.

[Steve biplane]

I know what you mean about the guards around machines in schools. A couple of years ago I went to a local school's open day and watched a kid on a drilling machine. I don't think he could see a thing through (a) his ordinary glasses (b) his safety goggles (c) the plastic swarf guard on the drill. It looked more like a game of pin the tail on the donkey than engineering!

[Malcolm Fisher]

Like you, Peter, I would prefer to have to add weight at the tail but this rarely happens. I also don't seem to have needed much lead at the front with the last few models I've built - none at all on the latest :-))

As for guards on machines, IME, operators can usually get round these - I worked in a foundry where one chap using a sand mixing mill worked out where the microswitch was and mangaed to keep the mill running with the guard raised. He also managed to lose a finger by trying to clean it out by hand while it was running in that state...

...needless to say the Company was held to be liable for his injury.

Sorry folks - forgive the thread drift.

[Peter Miller]

Yes, you will always get the clever blighter who overides the safety systems. Anyone that stupid deserves all that he gets.

My trouble is that I design the tail end as light as possible with medium tail moment arms and longer than needed nose moments. I often need a coupel of ounces of lead in the tail. My last scale model needed 5 1/2 ounces of lead in the tail, that did grieve me considerably.

[Malcolm Fisher]

Wow! I would be worried if I needed that much in the front end :-)))

[Steve Hargreaves - Moderator]

Check out the Hangar 9 Camel then.....according to a review I read in RC Model Flyer it needed 1.2KG yes thats one point two kilograms or 2lb 10oz of lead to balance properly...this in addition to a Saito 80 four stroke. Apparently there is a special box built into the front to take a cast ingot & the US supplied kits come c/w a 15oz ingot cast for that very purpose!!!!

Thats a whole lot of lead to carry around....methinks the tailplane must be made out of some of Peters Church roof!!!!

Just on the subject og lead in solder this has been banned under EU wide RoHS (Retriction of Hazardous Substances) legislation although leaded solder is still allowed for military/aerospace use & in medical & safety critical equipment....what does that tell us about lead free solder?? I'll leave you to make up your own mind!!!

Just picking up on Steves point about keeping nasty substances away from people he is right up to a point but sadly vested interests can still come into play. The company I work for make electrical connectors for the military...in the military world bright & shiny things tend to get shot at so we plate them in a dark olive green. The compound we use as a dye is called hexavalent chrome & is also banned, which is fair enough as it's nasty stuff. When we heard it was on the list we asked our chemical suppliers for an alternative & they said "...if you find one let us know cos we've been looking for 15 years & haven't found anything...."!!!!

The entire connector industry, worldwide uses, we reckon, about 5kg & as Steve says it makes sense to ban 'orrible compounds where possible......the French, German & Italian "White Goods" manufacturers use it as a passivate & it means they don't have to prime the metal first. They use around 20 tons of the stuff a week(!!) & guess what?? They can still use it........it depends how hard you lobby the EU I suppose!!!

Sorry to go Off Thread...back to silver soldering!!!

[Peter Miller]

Heck! You don't expect the French, Germans or Italians to obey any EU rule that doesn't suit them do you. Only stupid countries with civil servants who have had their brains removed obey the EU rules and then they actually add to them.

[Alistair Taylor]

Ahem

speaking as a civil servant....apparently with no brain and a fixation for EU law....

I've used aluminium welding rods with success on model engine silencers and on a car cyclinder head. The only challenge with a bigger job is getting it up to temperature. May I recommend the Russell Hobs fan oven, which does the job quite well, managing to acommodate the head sideways and heat it to 230 degrees c in short order, the final heating being accomplished with two £10 blowtorches from off the market, and a VERY understanding and cooperative missus.

Oh yeah - make sure you've got something heatproof on the lino BEFORE you attempt to lift it out of the oven (e.g. paving stones), and some REALLY thick gloves (I used leather motorcycle gloves inside gardening gauntlets).

The smell of engine oil can be "encouraged" away most effectively with garlic bread....if you can stand continental ciusine.

The challenge with model-sized items is not transforming the item being heated into a molten blob with heavy-handed application of the blowtorch.

If a brainless civil servant like myself can accomlish it without falling foul of EU regulations, I'm sure a skilled septagenarian (adept octogenarian?) like yourself Peter will find it dead simple :)

AlistairT

[Peter Miller]

OOPS! Hi Alasdair. I am sure that Civil Servants are completely intelligent when away from their desks and engaged in normal pastimes even if my local farmers and ground landlords (and full size aviators) might consider me rather gullible if they read this.

And I am not a Septagenarian yet...got a few months to go!!

[Erfolg]

Returning to your original thread on winding springs. Some of the statements made were right (at least in the distant past). The large conglomerate where I trained as an Engineer (the practical bit), wound some of its own springs. These ranged from small instrument springs to large springs for control valves on steam turbines.

What is interesting (well maybe) is that small springs were wound on mandrels etc. and that was the end of their manufacturing treatment. In the case of large springs they would be wound, ground (ends) and heat treated.

I was told that in the case of small springs the most satisfactory way was

a) Buy die drawn wire, where the processing history and base materials produced a wire, with very directional properties due to the work hardening from drawing, drawing also have produced lamella in the grain (and elongated grains) structure due to the drawing, further increasing the directional properties. The subsequent winding process further stressed the spring, which preffentially returned to its formed position because that required the least energy.

This method could only be used where the springs were small, to large and the outer or inner surfaces would exceed the UTS and fail (crack). The other limitation is that the stressed position has to be less than the UTS. Small springs of this type will often fail due fatigue as the stress level is above the indefinite cycling stress level.

Any heat treatment would, (such as annealing) would destroy the benefits from the processing. The longer you anneal the larger the grain growth, large grains produce a weaker material.

b) Large springs were wound from the “normalised condition” as the winding would introduce directional stresses that were high and the forces required to wind wer also high.

After winding any grinding would be done prior to heat treatment, as the grinding could adversely effect the structure locally (heating).

When wound, the springs would be heated to above the upper critical limit (the red heat ) just sufficient to get the outer layer to temperature and the core to a lower temperature. The springs would then be rapidly cooled to prevent a phase change (it’s the compact atomic structure at temp that produces a harder material). The cooling velocity being dependant on the composition of the steel, some requiring water if a very hard outer shell is required, often oil (lower cooling rate). After this they would often be heat treated to reduce the stress level.

I have had to leave an awful lot out because there are many issues regarding the effects of alloying, processing.

I personally think you should try to bend your springs cold, forget about heat treatment.

With Aluminium alloys I could write many pages. The bottom line these days most commercial alloys tend to be the Silica types (cheap), the precipitation hardening etc. being for high strength applications Aircraft, Bicycles (7000 series) etc.

Regards

Erfolg

[Malcolm Fisher]

At risk of going further off topic and with more reference to EU legislation, we discovered some years ago while in Ulster that it was no longer possible to ret flax for the production of linen in Ireland.

All linen spun and woven in Ireland at that time came from flax retted in Belgium...

[Peter Miller]

Now that sounds totally logical...to EU bureauprats