Soldering or Welding Brass


D&J RailRoad

D&J RailRoad

Professor of HO
I am planning on building a bridge. It will be a scale replica of the Diablo Canyon Bridge which is in AZ, east of Flagstaff on the BNSF mainline.
I have been investigating what material I need to use. Turns out I will have to use solid brass stock, 1/2"x 3/8" for the main arch and cross members and 3/8" square tubing for the uprights. The rest of the structure can be built with plastic prefab material, i.e. walkways, hand rails and tie rods.
The brass components will be joined together with thin brass sheet material at the joints as seen in the associated picture below.
I haven't worked brass and I'm not sure what kind of equipment I need to do the job right.
Can anybody provide some advice?


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Years ago I did a bit of work on brass locomotives and used a mini butane torch with acid core solder. Good luck with the project Ken.
 
My experience with brass soldering is confined to the industrial/manufacturing level where it was either silver solder (also called hard soldering) accomplished with an oxy-acetylene torch, or soldering using "killed spirits" liquid flux and a gas heated large soldering iron. My observation of the most favored method in modelling with very light gage brass is by resistance soldering as mentioned by Jerry, because of it's heat concentration, restricting heat spread and resultant distortion to the rest of the brass. Soldering irons would need to be of the butane heated type using acid flux. An electric iron wouldn't last long in that environment.
 
Can I just add, that's a mighty task you are taking on there Ken, might say almost, if not as great in size, as the prototype you are copying. Great courage comes to mind, but don't let that deter you. It has, as you know, been done in N scale.
 
As I would be joining the thin sheet brass to the square tubing brass and the solid stock brass, a heavy duty soldering iron wouldn't work?
Remember, the solid stock brass is only 1/2" x 3/8" and the square tubing will be 3/8" with .016" thick wall.
 
You may also want to consider differing solder mixes, as they do vary for actual melt temperature ...use high melt or silver type for initial components and work down in temperature ..
that way there is less of a tendancy for previous components to come loose
 
D&J RailRoad said:
As I would be joining the thin sheet brass to the square tubing brass and the solid stock brass, a heavy duty soldering iron wouldn't work?
Remember, the solid stock brass is only 1/2" x 3/8" and the square tubing will be 3/8" with .016" thick wall.
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It'll work OK, but an acid flux will be hard on the tips (should've specified that rather than the effect on the body of the iron). Where the difficulty comes in with any method of soldering or welding of thin to more substantial metal, is that the majority of the heat has to be applied to the thicker material to melt the solder. Brass, being very conductive of heat, it will spread along a solid stock further away from the point being soldered, before it reaches sufficient temperature at that point, whereas the thin metal will get very hot quickly. Where you may be joining two or more of the solid stock and particularly in this case, using the thin plate as the joining medium. it would be best to use a jig or clamps to position and hold all the pieces together so all in the joint can be soldered simultaneously. This may be difficult in as complex and variably angled structure as this. It'll be a new learning curve if you've only been used to soldering wiring contacts, but that experience will help with the adjustment in technique.
 
Ken , have you considered gluing together using JB weld ? I have used it several times on different types of metal and it has always worked well for me . The only drawback might be it takes time to dry were the solder does not have that issue , don't know though that might be a plus , give you time to fix any mis-alignment you might have.
 
jim81147 said:
Ken , have you considered gluing together using JB weld ? I have used it several times on different types of metal and it has always worked well for me . The only drawback might be it takes time to dry were the solder does not have that issue , don't know though that might be a plus , give you time to fix any mis-alignment you might have.
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That could be a good alternative if you can lay out a full scale plan on a flat area (maybe homasote?) of each side (if they differ) and pin on each side of the bits to hold them as you add others on.
 
My experience with JB weld is complete failure every time. As far as I'm concerned, it might be ok for pasting paper together in kids projects, but for anything else it doesn't hold up as they claim it will.
 
I would just get a couple of sample pieces and give it a shot. As Toot said, the thickness of your main beams may be the biggest challenge. I would pick up a bad a## iron for stained glass that recovers quickly because that thick stock is gonna suck the heat up.
 
Solid bar stock of that size will need a lot of heat ..
If you haven't bought it yet, you may want to consider hollow tubing there as well,
 
I have to go with the solid stock on the 1/2" x 3/8" part because it's not available in hollow tubing in that size.
 
Heat sinks will help to stop heat travelling along the bar, but don't reduce it 'cause they're sucking it up instead. The disadvantage of a gas torch is it'll burn up any jig or pattern you're using to locate the pieces, unless it's metal too. Not very practical for this exercise unfortunately. A decent wattage iron with a large tip is the best bet and getting a close fit of the cuts on the main pieces will reduce the amount of solder required. Pre-tinning will help too, probably more than anything. Maybe leave the light gage gussets till after and glue them on with CA.
 
Further thought, pre-tin the ends (thinly as possible) where the joints are with acid flux and do the actual joining with rosin core.
 
It would seem to me that you might want to consider match-drilling holes and inserting at least one pin in the major joints where there is a large discrepancy between the thickness of the parts. The pins could be escutcheon pins or an appropriate size round-head nail, such as a #17 copper-clad steel nail. The pin can be cut off and peened on the side opposite the head. Before pinning, a good soldering paste could be placed between the mating surfaces, and then a propane or even a butane torch used. I've also used Devcon Plastic Steel to join metal pieces such as zamak locomotive frames.
 
I need 1/2" x 3/8" rectangular tubing for this, not round tubing.
I have some square tubing to test my welding skills with. I'll have to figure out the jig system first then determine the heat source. I really don't think an iron will work with this according to several other experienced sources.
 
I would suggest if you intend to use a torch, that the jig/former have holes in it, to allow the flame to pass around the joint and through the jig. The accuracy of whatever you provide on the jig to locate the pieces is going to determine how well the total shape turns out. Low temp silver solder and an oxy-acetylene torch will provide greater and much quicker brazing of the joints. True welding of brass (actually melting the brass together) is not practical, or maybe even possible. I've never seen it done in my metalworking experience. I have seen copper welded using an Oxy/Acet torch, a very skilled process, 1 overlapping tack at a time. I have welded aluminium with the same and a special flux and filler wire, probably one, if not the most difficult metals to weld in that way.
 
I guess your saying the best proceedure is to solder the brass together instead of welding.
It would seem that a jig would need to be non-flamable and not absorb heat.
Not sure what the best source of heat would be though.
 
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