Advice needed on soldering brass

[Anonymous]

Hi,

I was just trying to make some modifications to my unpainted old brass locomotive. Although I use flux, the solder does not adhere to the locomotive, only to my add-on parts. Is there any particularly reason? Is a special flux needed? I also cleaned/washed the parts to be soldered. But it did not help.

Best regards,
Confused modeller

[GN-Rick]

I have some experience with updating brass models. Without knowing what
soldering tool you are using, I will hazard a guess that you are using a typical
soldering pencil (iron). Normally these don't put enough heat into the large
area of a brass model to achieve solder adhesion-the model will act as a heat
sink and the heat will spread out through the model and not concentrate where
needed. The detail parts, on the other hand, are small enough that they will
get hot enough to retain solder adhesion. The tool you really need is a resistance
soldering outfit-(Micro-Mark has 'em). They concentrate heat at the point of contact.

[CPPedler]

Hi,
You say that you washed the brass but you don't say with what, if you washed it with warm soapy water then it probably is not clean enough. It may have some sort of varnish applied and would need to be cleaned with some type of stripper , living in U.K. I'm not sure what you guys have over there but here I would use celloluse thinners ... nasty to use but very effective just make sure that there are no plastic parts attached because they would be severely damaged and use with plenty of ventilation, don't breathe in the fumes!!!!!
If you have cleaned it with something stronger the soapy water then as GN-Rick has suggested use a resistance soldering kit.. they really are the best for detailed work. CPPedler

[Anonymous]

I was worried about messing up my brass engines so when I wanted to add some parts I used CA, it worked wonders. The engine does need to be cleaned very well where the glue is going to go.

Bob

[SPFan]

In addition to a clean surface and adequite heat I'd suggest an active flux . Most if not all of the fluxes used for electronic work are not active enough. I use a liquid flux called Stay Clean made with zinc chloride. You want to heat the local area as fast as possible by using a tip that is as large as possible, otherwise you risk having other parts fall off as heat is spread through the model. A resistence unit is desirable but I have detailed an number of brass models without one. One trick is to use solders of decreasing melt temperature when two parts are located close together. TIX makes a low temperature solder that is very strong that is very easy to use.

Pete

[lonewoof]

After a few abortive efforts, I learned:
That 40-watt iron that does wonders soldering wiring & cricuit boards WON'T HACK IT on a brass locomotive body. I use a 250 watt soldering GUN, a 300 w. tinsmith iron, (sometimes) {shudder} a propane torch. The trick, as others have pointed out, is to get the joint HOT, QUICK!
Get some SWIF solder PASTE (hardware store, plumbung supply). I like the "95-5" variety. Good active flux, melts easily.
If these are other detail parts near where you are soldering, mush some paper towels in water and use to keep these parts cool, (so they don't fall off while you attach something else.
When possible, do your soldering from INSIDE the model. Most detail parts have a pin or lug that goes in a hole (in the boiler, or whatever). Put your heat & solder on the inside; you can get good heat transfer an not as much mess to clean up when you're done.
Other tips as others have suggested.
Luck!

[Anonymous]

Hi,

Many thanks for all the pointers. Any suggestion where I can get a good resistance soldering iron, apart from the offering at mirco-mark?

Best regards.

[CPPedler]

There are several manufacturers in U.K. if you can get hold of a copy of the Railway Modeller in Hong Kong , you should be able to . Resistance Soldering Units retail at around £100 sterling Good Luck . CPPedler