bronze, aluminum, materials in general, appropriate use?

[dorin]

Just curious if anybody can make a quick comment on appropriate uses of different metals.

I see for example, wheels are iron or steel?

Sometimes you see bronze cylinders? bronze bushings on boilers.

I understand you could use aluminum but probably use steel tires?

Would you ever use aluminum on valve gear? or bronze valve gear?

How about aluminum or bronze for truck frames?

No project ideas, just trying to educate myself on what materials are appropriate where.

Thank you,
Mike

[Bill Shields]

Aluminum has very little place on a steamer, except in places where ease of casting is important for decorative stuff...like a decorative steam dome ring or cover plate or some such.

After all aluminum adds little weight and if you have ever tried it, is a bear to paint and get to stick.

Brass has no place on a boiler, nor does aluminum. Always use bronze.

Aluminum in valve gear? Shudder.....

OK, MAYBE as a steam chest cover plate, but even that is a stretch in my book.

YES, I have seen aluminum parts like connecting rods used, and yes they will work, but my preference is not.

NOW - if you are talking aluminum / bronze alloys, it is a horse of a different color.

[dorin]

Thank you Bill, by the way. I like the "Tom Thumb" article..

Since you brought up alloys, I am reminded of my posting about ZA-12 probably 6 years ago.

Did I see some bronze castings of couplers?

Thanks!

[Bill Shields]

T Thumb series is a lot of fun....can do that on a smaller loco - just have fun and don't worry what people think.

'Bronze castings of couplers' ? Don't understand.

[dorin]

Should have put it this way.
Can you make couplers out of bronze, or will they not hold up?

[kenrinc]

I have a pair of bronze couplers on my loco now and never had an issue. They are certainly strong enough.

I agree with Bill, that for the most part, aluminum has little value on a Live Steamer. Probably the biggest issue with using aluminum is just it's coefficient of expansion. You may be able to cast drivers from aluminum and sleeve them with steel tires but my guess is those tires wouldn't stay on very long. Aluminum is excellent for pouring test castings of any patterns you've made. I've seen the following cast in aluminum:

Trailing Trucks
Frame Rear Cradle
Frame Pilot Beam and crosstie
Cast Cabs

I've also seen stack bases and smokebox fronts made from aluminum, melt! For other things like running gear, "aircraft" alloys like the 7000 series have been used. I've seen very nicely made gear using all aircraft grade alloys that have been running for years. Everything is typically sleeved with bronze or non friction bearings.

A lot these days comes down to cost and circumstances. On a smaller loco I would think that you would want to gain as much weight as possbile on the drivers so aluminum doesn't really make any sense.

Grey iron is typically cheaper in comparision to the copper based alloys (brass & bronzes). Iron does rust but when kept "wet" with steam oil it's fine and works well. Iron is typically coated with paint for external parts so they work fine there. I believe Machinery's Handbook has good info on bearing surface selection. Nelson's book (so you really want to build a LS loco) also has a chart of what metal works with the other (in a bearing situation).

Silicon Bronze has been used since the early days of Live Steam. It's a great alloy for pouring your own castings at home! These days it's a bit more expensive hence the use of grey iron for most locomotive core assemblies. Iron is heavy, cheap and machines well. If the iron doesn't work for a bearing surface you can sleeve it with bronze. The general outlook these days is no brass around the boiler, even though all the locomotives I've seen have brass in everything from the exhaust stand to the turret.

Ken-

[Soot n' Cinders]

Brass has no place on a boiler, nor does aluminum. Always use bronze.

Bill, what is the reasoning behind this out of curiosity? I've seen many steamers with brass turrets and plumbing along with brass throttle valves. Also, would red brass work instead of standard yellow brass. And what allow bronze would you suggest over brass for use on our steamers?

[David Powell]

I use Aluminium ( usually T 60 61 ) to make connecting rods for fast revving engines. I have a 4 3/4" gauge vertical boilered engine. It uses a Stuart Launch engine cylinder block 15 / 16 bore 1" stroke if I remember . It is geared down 2.5 to ! with 2.75 dia wheels . I have seen 12 mph and more on riding cars with speedometers. Rough Math 9" per rev of wheels ,12mph = 1050 feet per minute 750 wheel revs,1875 engine revs. I think my choice of Aluminium connecting rods is justified. Incidentally low gear is 6.1 and she really revs in that one. Regards David Powell.

[rudd]

Soot, curious where you are in Ga..

To answer your question -
"Conditions favoring dezincification are contact with slightly acid or alkaline water. Not highly aerated, low rates of flow of the circulating liquid, relatively high tube-wall temperatures and permeable deposits or coatings over the tube surface. "

Sounds much like a boiler, doesn't it?

"Dezincification selectively removes zinc from the alloy, leaving behind a porous, copper-rich structure that has little mechanical strength. "

http://events.nace.org/library/corrosio ... dezinc.asp

[RONALD]

Here are some castings I made awhile back that have yet to be finished.
The tender waterbed is aluminum as are the tender trucks (A356).
The delta trailing truck, and front truck are red brass (C83600).
The driving wheels are cast iron, as are all the rest of the wheels not shown.
I'm getting ready to pour some frame parts, and they will be in C99700 Manganese Brass.
All of those castings were done in Lost Foam.

[Soot n' Cinders]

Soot, curious where you are in Ga..

I'm north of Atlanta and about 40 minutes from the Canton, St. Paul, and Pacific Railway.

To answer your question -
"Conditions favoring dezincification are contact with slightly acid or alkaline water. Not highly aerated, low rates of flow of the circulating liquid, relatively high tube-wall temperatures and permeable deposits or coatings over the tube surface. "

Sounds much like a boiler, doesn't it?

"Dezincification selectively removes zinc from the alloy, leaving behind a porous, copper-rich structure that has little mechanical strength. "

http://events.nace.org/library/corrosio ... dezinc.asp

Sounds like brass is bad inside the boiler, especially for a throttle valve. Also sounds ok for the turret and fine for tubing.
So, ideal parts would be either solid bronze or copper and save the brass for decorative bits where they won't be in contact with steam.

[Bill Shields]

long term, brass disintegrates in boiler environments. The zinc cooks out and the stuff becomes a piece of brittle Swiss cheese...which is one good reason why you never brass weld a copper boiler together - always use silver.

I also have brass on my boilers, but NEVER as the first 'anything' connected to the pressure that cannot be shut off quickly if / when it fails.

I have a brass turret, but behind a bronze shut-off valve....and the turret is VERY thick.

I don't use brass 'nipples' or any type of fitting unless it has a bronze shut-off first off the boiler..

2 years ago, at PVLS, a young fellow who had just purchased an old steamer (3/4" with copper boiler), and hydro tested it, had the blow down valve just disintegrate and blow off, INSTANTLY dumping all the water..

OS Live steam (Japan), if you look at their www site, has a warning about long-term use of brass blow-downs, complete with pictures of some of their failures.

It isn't worth it...just be careful and informed.