New undercarriage for my Ripmax SE5a

[Ian Jones]

I made a test piece and it worked out as intended:

So I made up the parts for the real thing. I cleaned all the metal with meths then gave it a good scrubbing with wire wool. I applied flux for lead free solder, heated it all up with a blow torch applied the lead free solder and...

... the solder wouldn't flow. It was hot enough I'm certain of that but why the solder wouldn't flow I don't know.

Now I'm stuck and don't know what to do

Help!

[Alan Cantwell]

could be a few problems

,one of the parts was not at the right heat,

solder was in the torch flame, and melted before the surfaces where at heat,

material not compatable,

soldering with a blow torch is not the way to go, you can silver solder with a blow torch, but then, i use a propane torch, not a butane, butane burns dirty, but the only way to convetional solder is with a heavy duty iron, and clean emery cloth, a cleaner is not neccasary. get yourself a heavy duty electric iron, as big as possible, mines an animal, weedy ones are no good, one of the metrials is obviously piano wire, but whats the sheet plate? looks galvanised

[Chris Bott - Moderator]

It does look like the sheet metal has enough mass to wick away the heat such that it never gets to temperature. The metals need to be hot enough to melt the solder as you feed it in but not so hot that it tarnishes.

What is the sheet metal Ian? Can you use a small offcut to see if it is compatible with the solder?

I think I'd try "tinning" the components too before assembly. That way theres a thin skin of solder properly wetted out and stuck to the surfaces. This will also keep any contaminants off the surface.

[fly boy3]

Just my thinking. As others have said ,tin the local area only where the copper wire will be positioned with a soldering iron. Use 60amp old fashioned fuse wire instead of the copper wire, as this is already tinned. Apply soldering iron together with cored solder to the wires only. Cheers

[Biggles' Elder Brother - Moderator]

As you know Ian - there can only be two reasons -

1. not enough heat or

2. not clean enough.

The whole thing doesn't look very clean to me TBH - no insult intended there - you know what I mean, it looks heaviely oxidised!

If you're sure that you are getting the heat in to the job - then I would suggest investing in a fibreglass pencil and then abrade the areas you intend to solder until they are bright. Avoid touching them.. Then use a good strong acid flux and a powerful iron/gas torch - that should "do the job"!

BEB

[Eamonn Fahey]

Posted by Biggles' Elder Brother - Moderator on 10/04/2012 19:28:52

The whole thing doesn't look very clean to me TBH - no insult intended there - you know what I mean, it looks heaviely oxidised!

BEB

I think the problem is too much heat. Soft solder, electrical fluxes and blow torches do not go well together. Use a big Iron, at least 60W, and tin everything. Wrap with fuse wire before sweating everything together.

[Biggles' Elder Brother - Moderator]

Yes I was wondering if it looked a bit "overheated"!

I'd agree with that. For most undercarriage work personally I use fuse wire because its effectively pre-tinned.

You could clean up the areas on the plate as I suggested and then tin them. Then all you have to do is sweat them together as Eamonn suggests.

BEB

[John Olsen 1]

What is that sheet metal? Anyway, you can solder with a propane torch, I have done it. But you don't need to get the job very hot, just enough to melt the solder, which means going easy with the torch. However for this sort of job, as has been mentioned you don't really want electrical cored solder. Being an old reprobate I am not very convinced about the idea of lead free solder. Some 60-40 or 50 50 tin lead would be OK for this Apart from the choice of solder, I would use some stuff called "Duzall" for this, I'm not sure if that is a global or local brand but it is based on zinc chloride or "killed spirits" as the old timers used to call it. They used to make their won, you just drop slivers of zinc (old dry cell casing) into hydrochloric acid until it stops fizzing. Old techniques aside, a decent hardware store ought to have something suitable, and a big heavy soldering iron, something round 100 Watts or more, would be good to have.

Incidently if you do get hold of some suitable flux, kep it well away from any metal objects that you value, like lathes, milling machines, model aircraft engines, your car, and so on. The fumes that come off the flux when you solder will cause instant rust on any steel that is nearby, and probably are not all that wonderful for your lungs either.

Don't bother trying to solder either aluminium or stainless steel.

regards

John

[Ian Jones]

Well thanks very much chaps I have read and noted the details of every reply, time to review what we have:

• The sheet metal is plain steel the wire is piano wire
• I used "powerflow" flux for lead free solder so next time maybe I will try leaded solder
• The wire wrap I used on the actual undercarriage in the 2nd photo above was new (what's old fashioned?) 15 amp fuse wire drawn through wire wool to clean it before use
• I cleaned the entire surfaces with meths and wire wool and next time will give the actual contact areas even more cleaning with a fibre glass pencil
• The biggest cause of my problem has been overheating
• The next biggest problem has been the butane/propane mix blow torch and using the wrong part of the flame
• I used a butane/propane mix blow torch because I thought that would be right for the size of the job, and getting heat into all areas of the joint - looks like a heavyweight soldering will be invested in very soon.
• The 1st photo above was the test piece, it wasn't a total success when I soldered it but the solder did flow in one of the joints so I thought I just had to make sure I got enough heat into the real thing - as I now know that was probably exactly wrong
• Another big contributory issue has been not tinning the job first. I'm a bit disappointed with myself on this one because I am good at electrical soldering, the secret of my success - tinning first!

As I said above I am very familiar with tinning electrical joints with electrical flux core solder but how would I go about it for this sort of job - heat the surface just enough to melt the solder which has been dipped in flux?

[Biggles' Elder Brother - Moderator]

Hi Ian,

I use a liquid acid flux - not popular I know, but it works for me! First as you already do get everything mechanically clean - wirewool and glass fibre pencil. Next I use an old modelling paint brush to slosh the flux about the general area!

Apply heat to the job - flash the flux off - lots of sizzling (if you copy me and use acid flux wear face mask - its not good to breath this vapour in!). Get the job hot enough so that when you touch the solder to the job it melts and flows over the cleaned area.

Then bring everything together and apply heat to the job again. Job heats up, solder tinning melts, joint forms - remove heat! You can optionally add more solder once the tinning melts - but remember only ever apply the solder to the job - not the flame/iron.

Personally I don't get on with torches - I always use an iron. I know where I am with a soldering iron!

Final point - I wouldn't touch lead-free solder with barge pole. Industry has to use it - we don't. I'll stick with me Carrs leaded solder thanks very much!

BEB

PS Oh, one thing I forgot. If you do want to use a liquid acid flux then about 9% conc Phosporic acid is about right and remember to wash the joint under running cold water afterwards to make absolutely sure you have rinsed all the acid away - or your undercarriage will turn green and drop off - oh er missus!

Edited By Biggles' Elder Brother - Moderator on 11/04/2012 10:50:19

[Ian Jones]

Hey, I'll give the acid a miss man .

Taken the rest on board and will post the result soon after I've bought myself a nice new soldering iron.

[Ian Jones]

From this:

to this:

Thanks for all your suggestions, those together with some help from clubmates has resulted in the above. It certainly feels solid, so as long as the joints are good and I've been succesful with the cleaning then it should be just the job.

I'm considering coating it in rust converter before painting, anyone any thoughts on that?

[Ian Jones]

And finally it looks like this:

Not as neat as I had hoped for but since it survived it's proving flights today then I'll stick with it. Only minor issue is that I need to place a washer at each end of the wooden axle cover to prevent it catching on the wire windings of the axle mounts.

Thanks for all your helpful suggestions and advice - what did the job in the end was 60/40 solder, bakers flux and a 100w soldering iron.

[Big Bandit]

Nice Job Ian .

Chris.

[Ian Jones]

Thanks Chris.

It could be neater but I'm happy with it as a first attempt in 45 years at mechanical soldering.

It looks like I may still have a problem though. The O rings do not seem to like being stretched and twice I've found one has snapped without even taking the aeroplane to the field. I got that idea from somewhere on this forum so if anyone has any experience with using O rings like this I'd be interested in their comments.

Why did I use O rings? Well they are easy to get, easy to fit and (provided they don't snap) give a nice firm damping on the axle. The tests I did with rubber bands had them giving too easily and not actually absorbing some of the energy of a less than perfect landing.

[Ian Jones]

A quick update.

I can confirm the O rings turned out to be useless, however I recently had to renew an inner tube in a pedal cycle tyre and now I have no end of suitable rubber bands that do the job brilliantly.

First day out with the SE5a for ages yesterday and it worked just as intended. Still firm enough not to bounce but shock absorbing enough for a heavier than intended landing.

Dead chuffed .

[John Olsen 1]

O rings are pretty good for sealing but I think don't have the strength to make them useful for rubber bands. They were provided with my Hangar 9 Fokker but are not up to the job. Apart from the cycle tube idea, you can get bungee cord in quite small sizes, or you can get hair ties which are kind of like a very small bungee rubber joined into a loop with a small crimp connector. It can also be worth trying the haberdashery department to see what sizes they have elastic in.

John