How to solder brass to aluminium ?

Are there any tricks to soldering brass to aluminium or should I just solder the same as brass to brass ? Some of the etched brass wagon kits I have on order have an aluminium roof and I intend to solder brass strips to the underside of the roof to act as spring clips to hold the roof in place.

As far as I know soldering to aluminium is impossible – you may be best to scratch the aluminium fairly deeply to provide a key where you want the brass strips to attach, and then epoxy them to it

You require special flux and special solder to work with aluminium and it is about as difficult as soldering gets. Not impossible.

What kit manufacturer is dumping that sort of kit on the market these days ? Id ask for a piece of brass sheet in compensation or condemn the kit to where it belongs.

One instance I would stick with glue

You require special flux and special solder to work with aluminium and it is about as difficult as soldering gets. Not impossible.

What kit manufacturer is dumping that sort of kit on the market these days ? Id ask for a piece of brass sheet in compensation or condemn the kit to where it belongs.

Comet & 247s coach kit all come with Aluminium roofs but there have a lip that gos in side the coach sides I glue these in to the body when i build there kits

Aluminium to aluminium or brass to aluminium

ordinary lead tin solder or pure tin solder.

part is knowing how to do it……….but it is not that hard to do at all…..

Aluminium fails to solder because the surface freely oxidises in seconds, and you cannot solder toAluminium oxide, but you can solder topure aluminium, and that is the clue to how to tin the aluminium. Once tinned, it is easy to solder to other metals and the joints are as tough and sound as any other soldered joints.

The key to it isVaseline grease, pure petroleum jelly BPC grade, which is applied to the surface and then the area is abraded with a stainless steel wire brush, making sure the Vaseline remains covering the metal keeping the air off the surface. The now dirty vaseline can be wiped off, and fresh applied, which will help stop any contact with air whilst heat is applied for the soldering.

The solder is applied with a hot tinned soldering iron and will flow quite easily as long as the cleaning was thorough.No further flux is needed at all,The now tinned aluminium can be joined to itself or other tinned metals as normal..

If the object is a larger casting, or thick sheet, then a Eutetic solder can be used which requires a gas flame, this goes on without any preparation, it removes the oxide as it tins the surface. It is used to weld aluminium and Zamak etc. or conventional solder can be used to give the join.

The joints are absolutely as good as usual with aluminium, failures are down to poor preparation, and not properly getting the solder to tin the metal.

There have been other solders made in the past for aluminium, using very active fluxes, but these were withdrawn from the general market as the fumes are very toxic from the strong acids used to strip the oxide surfaces as the solder was applied.

Modern pure tin solder works fine, but it requires a lot of heat, and aluminium conducts heat so well it makes getting it hot enough a bit more difficult, so conventional lead solder is much better.

Once the aluminium is tinned, low melt solder will work in the usual way to attach white metal castings.

Hope this helps clear up the issues,

I am fairly sure that the Comet aluminium is extruded. I do know that I very successfully soldered brass wire to a roof top filler that I had recently drilled through to accept the wire. the solder flowed in and the joint is permanent i think. Certainly it withstood quite a lot of abuse when I finished bending the wire.

Yes – Comet roofs are extruded aluminium or aluminiom alloy (cant remember the name of it).

Ive used solder paste with a gas torch to tin aluminium coach and wagon roofs.

Yes – It does take a lot of heat. I pre-heat the roofs in the oven until ready to solder.

The solution state reached as you heat up the solder paste mean that as you apply the flame to the aluminium there is no chance for the oxide to reform.

Once the aluminium is tinned then you can solder more or less anything to it and get a good strong joint.

Comet & 247s coach kit all come with Aluminium roofs but there have a lip that gos in side the coach sides I glue these in to the body when i build there kits

I try to avoid glueing roofs to wagons or coaches as you never know when you want to get at the inside again. All roofs should be removable if possible. It also makes painting easier.

One instance I would stick with glue

What kit manufacturer is dumping that sort of kit on the market these days ? Id ask for a piece of brass sheet in compensation or condemn the kit to where it belongs.

I like my roofs to be removable because it makes painting easier and you never know when you may want to access the inside of the wagon.

Dart Castings produce their GWR brake van kits with an aluminium roof or so I was told. I have not bought any kits from them yet. There is not a lot of choice if you want to build an AA3 brake van.

…There is not a lot of choice if you want to build an AA3 brake van.

We have always recommended gluing the roof to the sides/ends which then forms a stiff body. The body is retained on the underframe by screws and is thus easily removable for painting, access, etc.

While you can solder Aluminium (it is difficult but not impossible) I would advocate the use of glue as two dissimilar metal welded together will (after a time) fall apart – unless you passivate the joins – anyone old enough can remember the early Range Rovers where aluminium and steel parts where connected gently rotted away.

I have some BSL aluminium sided coaches which have been held together with evostick joints coated in epoxy – so I know that works.

Are there any tricks to soldering brass to aluminium or should I just solder the same as brass to brass ? Some of the etched brass wagon kits I have on order have an aluminium roof and I intend to solder brass strips to the underside of the roof to act as spring clips to hold the roof in place.

Yup. Comet roof to model body (oh er misses) – Evo Stick every time.

Anyhow, recently on a brass van kit I have used some little shaped bits of pasticard glued to the underside of the brass roof as shown. Crude but effective with some flexibility and will work on almost anything you use for a roof.

Modern pure tin solder works fine, but it requires a lot of heat, and aluminium conducts heat so well it makes getting it hot enough a bit more difficult, so conventional lead solder is much better.

I always thought that there was a big problem in applying too much heat 400 deg to aluminium ? Doesnt it anneal at a much lower temperature than brass.

My suggestion earlier was not to glue the roof on, it was to glue the clips on the roof. I also do not like gluing roof of a van on permanently as I find it very difficult to glaze something once that route is taken and painting (if and when) is also made difficult.

But in preference, I would consign the aluminium to the scrap box and replace with a brass roof.

I am pretty sure that the Dart Castings kit AA3 roof was not aluminium but brass. I built one and certainly dont recall having an issue with the roof – I shall have to dig out my notes later now just to check.

Coaches – not something I often build – so cant comment other than to say as above I would seek to replace with brass or glue in the clips (as much as I find the use of glue on metal kits distasteful and heretical)

At last a definive method for soldering aluminium.

In the 70s I built some of the old BSL ali-sided coach kits. They all made up into some quite nice models. I hadnt looked at them for ten years or so, so imagine my horror when I opened the box to find that they had mostly fallen to bits. The epoxy had failed between the whitemetal ends and the aluminium sides, hence my wish to rebuild them (plus quite a few more in the bottom drawer) by doing a firm soldered joint between end and side.

To this end, what wattage/temperature iron would you recommend for the tinning of the aluminium? I use a soldering station with a maximum temperature range of up to 420 degC. Would I need to revert to an old large hot iron (80 watts?)?

I try to avoid glueing roofs to wagons or coaches as you never know when you want to get at the inside again. All roofs should be removable if possible. It also makes painting easier.

with comet kit the chassie is bolted to the body so you can get in when you want i also build 247s kits this was as well

I try to avoid glueing roofs to wagons or coaches as you never know when you want to get at the inside again. All roofs should be removable if possible. It also makes painting easier.

with comet kit the chassie is bolted to the body so you can get in when you want i also build 247s kits this was as well

Dart Castings produce their GWR brake van kits with an aluminium roof or so I was told. I have not bought any kits from them yet. There is not a lot of choice if you want to build an AA3 brake van.

Both the Dart Castings (Frogmore) and the Southwark Bridge kits for the AA3 toad come with brass roofs.

The heat level will affect the coach roofs, and may induce a warp as the metal relaxes, and soldering clasps or tabs to sheet or extruded aluminium may result in a small dished area around the soldering.

The expansion due to the heat locally stretches the metal, and as aluminium softens easily, a permanent dishing, or doming, occurs, although it can simply be pushed back, as the metal is soft.

However, on a coach roof any warping and ripples will show badly, and I would not risk a soldered aluminium roof on a full length coach.

Much better to use epoxy, and a good grade like Araldite, Loctite,(brand), which grips pretty well to aluminium and brass, given the correct preparation.

HANDS UPthose who wash the item in clean strong solvents, after abrading the surface and handle the item with clean disposable gloves before glueing…be honest

Most people dont, and get away with it, as the epoxy can stand a certain amount of oils on the surface and still grip. Some glues can stand a lot, Loctite make grades that resist oil by degrading it as the glue sets.

But for model useclean the item, abrade with a stainless steel wire brush, fine grade wire wool or plastic 3M pads, then wash with cellulose thinners, and dry, then glue ASAP, with handling by Latex gloves…….the joints will not then fail.

Epoxy gluesvary a lot, the five minute types are actually more sticky than the long set traditional types, they have fillers that allow a bit of give and flex. But long term they harden off and may fail sooner than a rigid version.

An alternative areGorillatype glues, expanding PVC foam glues, they work well with metal as well, and do not mind oils on the surface to an extent. They are not just wood glues, at which they excel, but are good for metal to metal, or metal to wood. They sand well, and take paint etc

The other glue for aluminium to brass is superglue, with clean joints, and activator, the joints are even better than epoxy. But the joint must be good to start with, the best is anassisted joint,mechanical aided by glue, or close contact, simply adding glue to a joint as a glob of glue over it is the worst way, but tends to be the method forced on modellers by the kit designers

On soldering aluminium the iron should be a larger high capacity type, with a large tip to store heat, as the aluminium conducts heat away quicker than brass.

Pre-heating the whole roof would help as mentioned, but the whole process of soldering a roof is a fraught process with soldering, let alone adding the problems of aluminium to the e glue, it is easier.

I am pretty sure that the Dart Castings kit AA3 roof was not aluminium but brass. I built one and certainly dont recall having an issue with the roof – I shall have to dig out my notes later now just to check.

I really cant see why Comet and 247 should supply a kit with a aluminium roof – especially given all the issues it causes.

What are the advantages – if there are any at all – for a kit supplier to supply an aluminium roof instead of a brass one ?

Now, having checked, both the AA3 and the AA15 (probably all of them) ARE brass – so no problems with their kits.

I really cant see why Comet and 247 should supply a kit with a aluminium roof – especially given all the issues it causes.

What are the advantages – if there are any at all – for a kit supplier to supply an aluminium roof instead of a brass one ?

What issues? As Stephen has pointed out, it can be soldered or glued.

The extruded aluminium roof goes back some way. I think that PC Models were one of the first to use them in 4mm. For some complex roof profiles (High elliptical or multiple curve cove roofs) they provide a good solution, providing a more consistent shape and thickness than vacuum forming with an edge gutter and internal cantrail for stiffening the body sides. If made in brass the roof is usually too thin at the edge and has to be formed to shape. Brass is okay for a simple arc profile but not for anything more complicated.

I have used aluminium extruded roofs on a number of 4mm coaches, with nuts soldered to brass cross pieces glued between the inside of the cantrails to take fixing screws through the carriage floor. The oldest are still holding together after more than fifteen years.

Extruded ali roofs have been standard issue for some 40 years or more. A couple of us reversed kit makers instruction and build the coach around the floor instead. It was easier for the builder and involved a lot less masking up for the painter.

There is no earthly reason why roofs need to be soldered to coach bodies, well not if the sides are built around the floor and the roof lightly glued on after all the painting and glazing has been done.

What issues? As Stephen has pointed out, it can be soldered or glued.

I saw nothing in Stevens post to contradict my original answer that soldering to aluminium is NOT a piece of cake. Although he indicated that it could be done – I didnt say it couldnt, most of the post was explaining how it is

and then concluding the same as I suggested – use glue.

The issue, as stated, is that you end up using glue or have a difficult (but no one has said impossible) job of soldering.

The use of aluminium goes back a way but that does not justify its use in a new kit. Perhaps aluminium is considerably cheaper to the kit provider? But I cannot see why it should even be considered when a brass kit contains all brass parts that can be soldered and the roof can be as easily cut and rolled or etched and rolled from sheets of the same. Enabling the kit builder to continue using the same metal-to-metal joining techniques used in the rest of the kit construction.

So I still maintain that any kit that uses it should be seriously questioned, and if I were asked to build one the first thing would be sourcing brass sheet to replace the aluminium. Nothing to do with being able to solder brass to metal just that it is not worth the extra hassle.

Im yet to see any reason why aluminium has been used. Why has it become the norm among some coach kits?

I think the best way is to have the floor and bolsters solid, with a simple drop in false floor and interior, the coach ends secured to the base, and sides, and the roof secured to the top of the walls with long bolts through from the base floor. They can usually be hidden in partition walls, or in the corners of the vestibules, and coach corners.

This way does require a good solid top edge to the sides, I usually solder a square section brass rod or tube to the top edge, making it about 1/16 thick or thereabouts..

My own roofs are rarely anything but real wood, done in maritime style double diagonal planking over shaped formers for a plain arch, or end to end wood strip for more complex shapes or clerestory roofs. With double diagonal planking the wood is pre-softened in hot water first, to aid a smooth curve.

The oak planking is made from six inch long oak strip cut on a band saw from old parquet floor strips, hence the length. It is laid over formers shaped to the required profile, the strips about 1.5mm thick, over what is finally needed to allow for sanding. The planks are staggered to make sure joints are out of line.

It is glued on with superglue on the planks and PVA glue on the formers, the two glues react and bond almost instantly. Then the whole planked surface is sanded to shape, and any gaps filled with a PVA and sawdust mix wood filler..

If a super smooth surface is required, not to show any trace of planking, a layer of damp medium weight Japanese tissue is applied with shrinking dope to secure it. .Any cross strips or surface banding is added in cartridge paper, secured with pva glue

This is then given a couple of coats of dope based sanding sealer, and then undercoat in car cellulose paint, The underside, (interior), is fully doped as well to prevent moisture entering the wood and setting off warping.

The advantage of a wooden roof is the ease of construction and the ability to add rails at the edge on the underside to completely engage with the sides. It is easy to paint and also quite light weight.

The perceived disadvantage is warping, especially if doped, but this can be controlled by careful drying, and the roof is pulled to shape and snug fit by the retaining bolts, which always oppose the cupping warp.

Once the bolts are tight the roof is pulled against the ends and the strengthened sides and is dead flush with the sides.

The other main advantage of using wood is the very low cost, and the exact nature of a true custom fit to the body.

The pictures show a van roof being built on a false flat ceiling base, with shaped formers, and end to end oak planks, same method applies to coaches,

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