Steel v. Brass

[dampfmann]

Kozo primarily uses brass in the construction of the A3. What are the pros and cons of using each material. The most obvious con for brass is its price. Is it possible to use a mix of materials? For example, machine the arch bars from brass and the bolsters from mild steel. Lastly, is it possible to silver solder brass and steel together when/if the situation arises.

Thanks for sharing your thoughts,

Martin

[Ed Hume]

Martin,

The obvious con of steel is rusting, but it has the pros of being easily painted with etching primers. I think silver soldering brass to steel can be iffy - you would probably want to use a more aggressive black flux. The solder would want to spread well on the brass before wetting the steel. Plus you have a mismatch of thermal expansion. My advice is to try it out with some scrap pieces.

A brief acid dip in sulphuric acid that has been used to clean copper scale and is blue (has copper sulfate in it) prepares the steel by plating copper on it which helps silver solder wet it. Try this out as part of your preparation, or for rework.

Let us know what you find.

Regards,
Ed

[kvom]

IMO there is no real need to use brass for anything structural as long as your equipment is sufficient for machining steel.

[pkastagehand]

Well, I'm a couple days behind this question, but I chose to build using steel and and cast iron except for water tank on the tender and for fittings and tubing of course. Far cheaper (especially since much of it is scrap on hand), mostly not much more difficult to machine although a tad slower due to cutting speeds and feed rates. I have not had to silver solder any brass to steel that I can remember. And since I welded the frame for the tender using a jig to hold everything I avoided a certain amount of drilling and tapping which I hate. I even did a welded steel boiler.

Mine is being done in 3/4" scale.

[daveb1]

Kozo callls for silver soldering the brass wheels to the ss pins on the blower valve and sight glass. I'm in the process of doing that very soon. I'll let you no how it turns out.