Newbie question about materials

[Dkhartloff]

I have built 3 steam engine run on air using steel, alum., and brass. I want to build a live steam g scale Nina. After research I realize brass wond do I need bronze. So we're can I get phosphor bronze the least expensive. Also could I use stainless steel for piston and cylinder. Thank you.

[Bill Shields]

Stay away from stainless and aluminum.

Prices are all over the map. Nothing is cheap anymore.

Speedy metals, on line metals....Morgan bronze -> just look. It is a crap shoot..

[Greg_Lewis]

For small amounts I sometimes use Ebay. You do have to be sure of what you are buying, but I've had good experiences for years.

[Dkhartloff]

Why not use stainless

[Glenn Brooks]

Bronze or cast iron is preferred for cylinders because these materials don’t seize up when subjected to heat and pressure, also, they have ideal expansion coefficients under steam. Remember steam offers the worst conditions for two metals in contact with each other - heat and water.

Stainless also does not do well under these conditions - in fact, in an anaerobic environment stainless corrodes and fails with surprising rapidity.

Glenn

[gwrdriver]

If your other locomotives have been G-scale, then you probably know most of this already, but if not . . .

For "G" scale cylinders, brass is OK, if nothing else is available. Cast iron is also OK as long as good layup care (preservative lubrication) is taken, but a common bronze (like C260) is preferred. Phos-bronze (C510) is also OK but would be overkill. Either way a bronze slide valve is OK, and with proper lubrication bronze on bronze will outlast you. Stainless or Monel for piston and valve rods, bronze or brass for pistons with O-rings. No aluminum, anywhere.

A couple of things to consider, if you have concerns about these metal combinations. The mechanical forces in a Ga1 locomotive are a tiny fraction of larger scale live steam locomotives and are so tiny as to bear little resemblance to those in full size engines. Also running time is typically a fraction of that of the typical live steam engine (much less full size), so while there will be cylinder and valve wear over time it's so small as to be inconsequential, at least for many years. Many thousands of Ga1 locomotives with these material combinations have run for decades with only renewed O-rings and gland packing.

Wear which will eventually require your attention will take place, but in other locations such as valve gear linkages, axle bearings, and wheel flanges. Also, a running gear (chassis) mustn't be built too tightly because systemic friction can completely consume what little power small cylinders will generate. That being the case, running-in is an important part of building a Ga1 chassis and that's usually done with a couple of well-lubricated hours running up on blocks, equal time running in forward and back.

[FKreider]

303 Stainless is good for piston and valve rods and also good for valve stems on globe valves.

[B&OBob]

I have had excellent service from OnLine Metals for both large and small sections of cut-to-size stock in a variety of metals and plastics. If you use that company, buy as much of what you need at one time to save shipping cost, possibly even duplicating some actual requirements to allow for the inevitable machining foul-up. Building a Ga1 locomotive as you intend is so much cheaper than buying a finished model or kit, you can afford to order genrously and thereby build up a "scrap box" with the surplus for future needs.

GWRDriver's comments are right on target in my experience with Ga1. What is used for a passenger-hauling locomotive does not translate directly to Ga1, so stick to what works for the size locomotive you are building.

B&OBob

[hoppercar]

I go to my local machine shop down the road.....after showing the owner, some of my model projects ...he lets me pick thru there scrap material pile. I usually get pieces for pennies on the dollar....or no cost at all.......if you have machine shops in your area....check with them, about scrounging thru there scrap cut offs...you don't always have to go to the high priced suppliers