Large Model Association Forum

hi all,

im after some advice and guidance on silver soldering. it something that ive never had a requirement to learn, but that has changed. i need to make and undercarriage for my 1/3 BUSA pup. the model came to me part built with a set of floats and no u/c. the BUSA plans call for a wire u/c but i would prefer to make it more scale like using the mick reeves plans.

so, i know the principles of silver soldering and brazing but im looking for any tips and advice. what solder do you use? is the 455 that cup alloys recommend the best stuff to use? also what sort of heat source? ive got a gas blow torch which will give a good general heating but would i be better with something with a smaller flame for more controlled heating? the u/c has quite a few joints close together so would i jig the whole thing up and make all the joints in one 'heating'??

thanks in advance

nick

Try and find the silver solder from welding suppliers, it has a pink coating which is the flux. Make sure all parts are shiny clean and if they are close together do them all together. If you are trying to use piano wire, the heat will take the spring out of it, not to be recommended.Solly

do you happen to have any more details of the 'pink rods' ?? also when you say 'if the joints are close together do them in one go', how close is close?? without looking at the plans i would guess some of the joints are within a couple of inches of eachother. im planning on using mild steel tubing for the main structure but with piano wire sections at the top to make it easier to fit to the existing mounting points that are already built into the airframe.

the other question i have is where do people do the silver soldering? for example do you have a dedicated area? is it a special surface?

cheers
nick

Nick, no details on the pink rods, I just get them fro a welding supplier. If the joints are a couple of inches apart, do them individually as long as you have a pencil flame. Obviously a heat proof surface such as a plumbers mat.

Rods are available from such as B&Q where they are confusingly called brazing rods, the correct name for silver soldering being silver brazing.
At work we use products from Johnson Matthey http://www.jm-metaljoining.com/

Mix it yourself powder is more controllable than ready mixed paste and does not set like a brick if it drys out on the shelf (we use non coated rods).

The heat source needs to suit the job, I use anything from a small blowlamp up to a 3 phase induction heater that requires a fork lift to move

Nick,

I never had much success with B&Q (and similar) soldering rods.

I'd suggest going to Macc Models (engineers supplies) and get some 1mm silver solder rod and powered flux. It's not so cheap but does a really good job and is easy.

Clean your parts, apply flux (as per instructions) and heat with a blow torch until the flux goes to a clear liquid - you're at the correct temp. Apply the tip of the rod and you should see the solder flow as if it were water.

I hope that helps.