Alternative to soldering

[Hogster]

Hi Guys,

When securing a brace to an undercarriage leg and wire wrapping the joint as you might do for soldering, would using epoxy adhesive be an adequate alternative to solder?

[PatMc]

No.

[Hogster]

Thanks for the quick reply Pat. Care to elaborate?

[crispin church]

going by planes in your photos not on that size

on smaller then depends on how good the wire and the wrapping and your epoxy is

a soldering iron is a good thing to have and you can pick up cheap you dont need anything big even asda or tesco one are ok

[Ernie]

Hi Hogster, No again. Don't be put off by soldering, There was a very good article about it a few months ago by WOO. A bound and soldered joint is what you need. Silver soldering is even stronger, but a wee bit more difficult, because it needs more heat.....................................................................................ernie

[PatMc]

Epoxy holding metal to metal won't stand the shock loads of landing. Even if it stuck to the metal it would loosen within a few landings.

[Hogster]

Thanks for the advice. Soldering it is then.

[Ernie]

Hi again Hogster, The soldering article is in the Jan 2013 issue........................................................ernie

[Erfolg]

There is little argument that soldering will produce a secure joint, particularly when compared to epoxy.

However there is a down side, that downside is that it is possible to loose many of the properties of piano wire has, as supplied. Putting the least amount of heat into the joint for the shortest time will alter the properties the least.

Due to the increased mass of the joint any issues of bending will not affect this area, it will be an increased tendency for the wire some distance from the joint, to take on a permanent set, if subject to bending forces, rather than springing back.

In many instances, such as cabane rigging, it is of little consequence.

To date I have seen little option other than to solder though.

I have seen the occasional mechanical joint. The trouble is there are no commercially available bits for the method. Also the one or two I have seen have either been bulky and probably heavier than soldering, or a crimped system I saw on a FF, seemed fraught with difficulty in achieving the necessary joint, without a seriously powerful crimping tool. I understood that the joint was made with a commercial wire conductor jointing kit/tool. At present this approach seems a non starter.

[Stevo]

Never had a problem soldering - the lead free solder melts at around 271 gegrees C, and music wire won't loose a temper at this low heat. Now, silver soldering... that's a different ball game... easy to do, but will take the temper out so careful where it;s used!

[Peter Miller]

You will make no difference to the wire with soldering irons, they only get up to about 700 degrees, not even tempering temperature. It isn't until you start silver soldering that you will start to make a difference

For soldering larger piano wires you do need a good sized soldeing iron. I have a big old (50 years old AT LEAST)Henly Solon 75 watt one with a 1" bit but good 40 Watt iron will do it, it just takes longer to heat the wire up.

Cleanliness is vital.

[Hogster]

Thanks for the info. I'm ok with soldering, in fact job is done. I was just curious as I thought epoxy would be plenty tough enough.

[Ben B]

As much as I'd just solder it, I think if you abraded the wire, stuck them firmly together and then wound CF (either CF rope or thin woven matt) round and effectively laminated a CF tube around the bonded wires it would be seriously strong. What's the tensile strength of plain solder? A quick search suggests 30,000 if the gap is moderate (0.5mm). Steel has a tensile strength of 100,000PSI and CF is 500,000 (approx). Therefore I see absolutely no reason why it wouldn't work. The only disadvantage of CF is its bulky (for a given strength) compared to metal and you'ld want to ensure it wasn't too rigid otherwise it would be fragile so you might need to carefully consider which epoxy to use.

Another way of doing it would be do put the wires inside a CF tube and pour a slushy epoxy / microballoon mix inside....

Soldering is quite a useful art to master though so I'd still just solder it.

I did some experiments a few years back on epoxying metals. I compared aliminium epoxied vs friction stick brazing. A 10mm surface area of epoxy failed at a tensile load of 12kg which is quite impressive!

[Erfolg]

I think the misnomer stems from the way that tempering was undertaken in the past at workshop level and particularly that in the early 60,s that metallurgy was more art based than science. From the mid-late 40's a transformation started, which by the 70's started to prove many of the suppositions of scientists, Transforming material technology into a science. It was now when the terms of energetically favourable started to be standard phraseology.

There was the concept that carbon steels would be heated to a certain point, and the formation of an oxide film would be observed on the cleaned and polished material. There upon the material would be cooled, by various methods.

This worked, certainly to the satisfaction of a tradesman. From the stand point of metallurgists, the results may not have a hardness value as wanted from a standardised production viewpoint, there being variation.

Carbon steel (0.6-0.99)

Further investigations quickly established a relationship with both the alloying materials (if present), temperature and time at temperature.

As can be seen from the above graph, there will typically be some impact on raising the material into the 300C range, particularly if allowed to soak. This is the equivalent of

The big question will you notice it? I would argue prolonged soaking would be the equivalent of stress relieving, particularly given the processing history of drawn carbon steel. Again processing history, another buzz phrase from the 70's, not much used before.

[Peter Miller]

Erfolg, The question is just how much difference will soldering at 700 degress make to the strength, springyness and stuffness of 8 SWG piano wire?

Then we have the different types pf piano wire. The wire that I buy from SLEC is great, really strong although a heavy landing will bend it. The stuff sold under the K&S label is nearer to wet spaghetti and bends far too easily.

[Erfolg]

Peter

In many cases I see know alternative to soldering.

My main concern has been the lack of understanding as to potential consequences. In the case of undercarriages, I do think that careful thought should be given to the issues, particularly if silver soldering or brazing is envisaged. In principle I personally would advocate the use of lead tin solder over lead free, the difference in temperature may seem modest, but say 100C would be a large difference with respect to the final results.

A major difference that the oxide film method of heat treatment as used in workshops, was the usual practise of water quenching. The significance in our case, that the growth of grains was halted.

In the case of soldering UC, some may be tempted to air cool, which would allow grain reorientation to continue.

I think our education has a lot to do with our preoccupations and understanding of what is of importance in the real world. We all will remember the preoccupation with the formation of Martinsitic structures, phase changes, and all the structures formed when cooling at various rates etc. It was the same with aluminium, a preoccupation with solution hardening types, with a total disregard, well almost, of silicon types, which are far more commonly made, being cheaper. The reason being that there is a lot of academic areas to discuss and analysis, in many cases with these topics.

My thrust has been, be careful how much energy/heat you put into your piano wire and get rid of it as quickly as possible. In some cases, changes take place, not due to a temperature dependant phase change, being more akin to weathering processes, or stress relieving techniques, in some instances.

[Peter Miller]

I would never suggest using anything but soft solder on undercarriages.

I know a pupil at the school I worked at was building a model and the teacher brazed his undercarriage for him before I could stop him, ruined it of course.

As a modeller I would say that any changes in piano wire due to soft soldering would not make a noticeable difference to the strength of the undercarriage. True, a landing three pounds heavier might distort the undercarriage a fraction more but who is going to measure the force of the impact and the amount of distortion.

So, while they make a possible measurable difference under laboratory conditions the average modeller is going to heave the leg straight and carry on.

In other words, while it is nice to know enough about metallurgy to say that this or that might happen we, the average modeller, don't know and so long as the undercarriage works we don't really care.

Now I remember having to get rivets annealed in salt baths when working on aircraft and knowing that they would age harden if not used in a given time but that was for a specific purpose and we knew what had to be done and why and we could see the results.

Oh, and I should add that even slightly softened due to soldering, that undercarriage will be a lot stronger than is assmebled with epoxy.

Edited By Peter Miller on 29/04/2013 12:22:11

[Frank Skilbeck]

I've got some of this, but never tried it for undercarriages, might be better than regular epoxy. But as with soldering the final joint strength will be determined by the preparation of the surfaces to be joined, with solder it just doesn't take if the surface preparation is poor, whereas epoxy wouldn't look any different but would just be a very poor bond.

Friend is welding the undercarriage on a scale plane that I'm currently building, we'll see if that make the piano wire lose its structure.

[Ben B]

JB weld is seriously strong stuff. The PSI I seem to recall is about 5000 which is the tensile strength of some of the lower strength lead+tin solders. Welding is great if you've got the gear- I wouldn't take the weld too near the edge of the fuselage due to concerns about making the wire brittle, certainly after welding I would expect a fair proportion of the wire near the weld to be glowing red hot.

[Erfolg]

Ben

I certainly would run a mile from a welded joint, however done, if the properties of piano wire is to be preserved. The process takes the parent metal right up to the temperature range the many have alluded to, that is molten, totally changing the prossessing structures forever. Even controlled cooling will only recover some of the properties, if achievable at a practical level, over the longer range.

Peter

I know that the change in structure is more than theoretical. I first became aware of the issue when working for BICC, where some unexpected issues had arisen with the braiding on armoured cable (drawn wire). The issue I guess comes down to, is the UC strong enough/resilient enough under normal duties. A particularly heavy arrival, could result in a permanent set. What we would not know, if this is a result, in the material yielding under forces lower than specifications suggest or we have just exceeded the permanent yield of the as processed material.

I think we both agree, often there is no practical alternative to a soldered joint. I would urge resisting the temptation to put more than just enough energy to cause the solder to run.

Frank

I know it is tempting not to take any benefit from a bound joint when comparing a soldered joint. In this case although difficult to quantify, with any accuracy, I think you must make an allowance from this benefit. It could well double the joint strength (the binding), although I do not actually know, I feel it is of significant benefit.

[Bob Cotsford]

Someone used to sell wire undercarts that looked to be resistance welded, I may well have one knocking around at home which was used a on a few 4-5lb cabin models without folding up.

[Erfolg]

Yep resitance welder should do the trick, in that the heat is very localised.

Many sheet metal welding shops will have a resistance welder as part of the standard workshop tooling. It may worth a try.

When I came to think about it, I am pretty certain I have in the distant past seen commercial items produced by spot welding. I do not recollect any in resent years.

I had, had thoughts of some one with a stick arc welder, or worse still oxy acetylene. I never thought of spot welding

[..]

Posted by Hogster on 27/04/2013 10:22:09:

Hi Guys,

When securing a brace to an undercarriage leg and wire wrapping the joint as you might do for soldering, would using epoxy adhesive be an adequate alternative to solder?

I know its not much help directly but I TIG weld all mine . Luckily I have a £12000 set at my disposal and I do it for a living but you wont get a better result. If you live near me I am partial to beer If not and its a special project why not see if someone local likes beer too.

J..

[Chuck Plains]

Back in the day, (I'm 60 now and was 15 then) I joined a slot car racing club where virtually everyone built their own chassis from sheet brass or stainless steel and piano wire. And although I haven't built any undercarriage for a plane yet, I would definitely say no to the epoxy route.

Let me also say that MOST SOLDER JOINTS FAIL IF THE METAL WASN'T CLEAN!!! Degrease, dry and clean the area to be soldered!!! Music wire is supplied with an oily coating to prevent rust. Use hot soapy water if you have nothing else. Dry it quickly. Then use wire wool, abrasive paper, a file or whatever you can to make the steel bright (NOT POLISH!!) Steel is a 'white metal', so make it look like it and your soldering has the best chance of working. If you clean a piece of steel but leave it over night, clean it again before soldering. If you clean a piece of brass but leave it for an hour, clean it again before soldering. Copper: clean it immediately before soldering.

I reckon that an average landing might produce the same sort of stresses that go through a slot car chassis in a racing environment.

I used to use the good old Weller soldering gun that my parents bought me (140w if I recall though my newest one is 100w) for most of this work. I also used the cheapest solder as I was reliant on my pocket money. Many of the older (earning) guys at the club used silver solder and their chassis were noticeably more durable.

These images are from slotcartalk.com as I don't have any stuff left from that time.

The central 'drop arm' (blue arrow) that holds the slot guide at the front is actually sprung from near the motor, helping to reduce chatter where the braids touch the contacts on the track. I've also marked (white arrow) the 'z bend' of the side plate mount.

 

The flat side plates on this design are 'sprung' on the central frame and have thin tubes soldered to them for pin mounting the body shell. This allows a slight amount of movement of the body and side plates which has a damping effect when the chassis tries to skip around. It works moderately well without being too complex. Heh, yes, I know that whole thing looks blimmin complex, even to me. So I'll confess here and now that my most successful cars often had chassis purchased from other club members who built to order.

The only time we used epoxy was if the main 'crown' gear on the back axle was a solid steel one. We would smear epoxy on the axle before sliding the gear into position, tighten the grub screw, then bake it for a while. But this was merely a way of reducing any vibes from affecting the grub screw.

Edited By Chuck Plains on 30/11/2013 12:00:36

[Peter Miller]

Looks like the old Airfix motor to me. We used model locomotive motors but we used to convert Scalextric to use the Airfix steering. THat worked really well.

We had a very keen luchtime club at RAF Stradishall, not really into high performance cars but I did build a few scratch built ones.

Well, there wasn't a model aircraft club on camp!

AS to using epoxy for undercarriages. You might as well wrap the joins with sellotape for all the good it will do

Edited By Peter Miller on 30/11/2013 11:40:01