Cylinder Material

[brucevoelkerding]

I will be machining the Cylinders for my current 3-1/2" Gauge Locomotive from solid, continuous cast, Bar material. The easiest Material to obtain is CDA 932. Comparing the Specifications between CDA 932 and Gun Metal (CDA 905) -

                              CDA 905                       CDA 932
                              SAE 62, Gun Metal          SAE 660
                              as cast                           as cast
copper                      88                                 83
tin                            10                                   7
zinc                            2                                   3
lead                           0                                   7
ult strength               45 ksi                           35 ksi
yield strength            22 ksi                           20 ksi
hardness                   75 BHN                         65 BHN

CDA 932 is commonly used in the US as Bronze Bushing Stock. I am curious if anyone has experience using CDA 932 for a typical, low-superheat Steam Locomotive. I plan to use graphited string Packing. I will not be siler soldering anything to the Cylinders (cf high Lead content of CDA 932).

thanks for your Experiences,
Bruce

[simon6200]

In Australia the most readily available bronze is LG2. We silver solder it all the time, using it for boiler bushes and fittings and fabrications. I know of several sets of cylinders made with it for the bores. One was written up in AME but that probably doesn’t help you. It was also shown briefly in our newsletter:

www.slsls.asn.au/newsletters/SLSLS%20May%202017%20Newsletter.pdf

[brucevoelkerding]

Simon, thanks. Looking around the Internet I found the following Specifications for LG@. I have added them to my Table -

CDA 905 CDA 932 CDA 836
SAE 62, Gun Metal SAE 660
as cast as cast as cast
copper 88 83 84
tin 10 7 5
zinc 2 3 5
lead 0 7 5
nickel - - 1
ult strength 45 ksi 35 ksi 36 ksi
yield strength 22 ksi 20 ksi 19 ksi
hardness 75 BHN 65 BHN 60 BHN

note "as cast" refers to "continuously cast Bar Stock", not a Sand Casting. I think I will go with the CDA 932. The worst Case is if the Bore wears.

Here is a Cylinder Repair I designed at Work which worked out well. There was a Device which dispensed Adhesive into the metal Bases of Fluorescent Lamps. The Heart of the Device was an aluminum Block with qty 4 integral Air Cylinders (1.00" Bore) with a Cavity/Manifold to distribute the Adhesive. A Walking Beam transferred the Bases under the Device and 4 Bases were filled simultaneously. The Production Cycle was around 2 seconds (?) per qty 4 Bases. Since the Bases were in a single Row with a pitch of 1.25", that meant the Wall between the Cylinders was 0.25". One of these Devices had worn Air Cylinder Bores. How to re-bore and sleeve ? I decided to use the Material used by Bimba Air Cylinders to sleeve the Bores. They have an Air Cylinder with an 1-1/16" Bore x 1-1/8" OD stainless Steel Tube for the Cylinder Tube. Unfortunately that is a special Tube made specifically for Bimba. Bimba would not sell any of the special Tube Material to our Company. We purchased qty 4 Bimba Air Cylinders with an extra 2" of Stroke and cut the Cylinder Tubes out of the Air Cylinders (they are rolled into the Cylinder Heads). The Dispensing Head was rebored 1-1/8" (1/8" Wall between Cylinders now) and the stainless Steel Tubing was loctited in place. That Repair was still in Operation 5 years latter when the Production Line was shut down due to the LED Conversion of Lighting.

[oldnorton]

Looking at the specifications for bronzes I find interesting.

SAE660 is one of the phosphor bronzes commonly used by the UK hobby industry as a bearing material, the other being Colphos. The phosphorus makes it 'stiffer'. I can only guess that the lead helps its performance as a bearing, as well as making it easier to machine. Another phosphor bronze is PB102, used commonly for model boiler bushes, but this has no lead (IIRC) and is a pig to drill and tap without very sharp tools and lubricant.

LG2 also has lead in it (Leaded Gunmetal), developed many years ago by early gunsmiths to make the bronze machinable. In theory, the leaded bronzes should not be silver soldered to a copper boiler but LG2 has been used for years for the dome rings on small boilers. I know that SAE660, despite its higher lead content, can be silver soldered.

I cannot see why SAE660 cannot be used in place of LG2 for a cylinder block. My only question would be what would be best for the piston material. I would be cautious about using the same bronze since we are taught that only cast iron parts run well on themselves. To maintaining the corrosion free properties you could use stainless steel pistons. Because of differential expansion there would be a thou or two more slack when hot, but that is not necessarily a bad thing.

Norm

[brucevoelkerding]

Norm,
you bring up a good Point regarding using different Materials in rubbing mating Surfaces. I am curious, when gunmetal Cylinder Casting Set from one of the Trade Suppliers is used, what Material is the Slide Valve Casting made from ? My Locomotive will have Slide, i.e. D, Valves.

[oldnorton]

Sept 13, 2024 17:56:58 GMT brucevoelkerding said:

Norm,
you bring up a good Point regarding using different Materials in rubbing mating Surfaces. I am curious, when gunmetal Cylinder Casting Set from one of the Trade Suppliers is used, what Material is the Slide Valve Casting made from ? My Locomotive will have Slide, i.e. D, Valves.

Sorry Bruce, I don't know. But my 5" 0-6-0 slide valve loco has brass rubbing faces soldered onto the bronze slides.

[John Baguley]

If you buy a cylinder casting set then the valves are almost certainly going to be the same material as the cylinders. The piston blanks will probably be the same material as well.

The cylinders on my Helen Long were fabricated from SAE660 silver soldered together. I did use some aluminium bronze for the pistons though as I had some the right size. I always use PTFE rings on pistons so in theory they touch the bore rather than the piston.

John

[brucevoelkerding]

John, thank you for your Input re SAE 660 Bronze. I will use that Material.

Norm, I was thinking about using ordinary Brass (C360) for the Slide Valve (this is a 3-1/2" Gauge LBSC Netta built to look like a Q6). C360 is a free-cutting, leaded (2%) Brass here in the US. Is that the sort of Brass you used ?

[oldnorton]

Sept 16, 2024 12:37:49 GMT brucevoelkerding said:

John, thank you for your Input re SAE 660 Bronze. I will use that Material.

Norm, I was thinking about using ordinary Brass (C360) for the Slide Valve (this is a 3-1/2" Gauge LBSC Netta built to look like a Q6). C360 is a free-cutting, leaded (2%) Brass here in the US. Is that the sort of Brass you used ?

it was a second hand engine so I don't know what the builder used.

But, when my lubricator failed, and the engine was working hard with lots of priming, one of the brass faces was heavily scarred due to washed off oil and the pressure on the valve face. Not a problem as I could skim several thou off the face of the slide. The brass suffered much more than the bronze of the cylinder block top face.

Norm

[tenor]

Sept 13, 2024 17:56:58 GMT brucevoelkerding said:

Norm,
you bring up a good Point regarding using different Materials in rubbing mating Surfaces. I am curious, when gunmetal Cylinder Casting Set from one of the Trade Suppliers is used, what Material is the Slide Valve Casting made from ? My Locomotive will have Slide, i.e. D, Valves.

Soooooo.....  do we all think the trade suppliers are really going to cast the piston and valve from different material?  No, it will all be patterned on one board, moulded in one flask and all from the same alloy.  For model engine use it won't be a problem until you clock up a few thousand running hours.  So how many Sunday afternoons is that?

Martin

[oldnorton]

A conversation regarding whether bronze pistons, running in same material bronze cylinders, would be advisable, is welcome. I have no idea. If they are lubricated then I assume there is no problem.

The only definite we know is that cast iron piston rings in cast iron bores is a good idea - hence the entire automotive industry.

Suppliers of ME castings will not have thought this through. If they are well lubricated it will not matter.

My only experience is that stainless in stainless is a bad idea.

Norm.

[johan]

Did any of the 1:1 locomotives used bronze on bronze? If not, then why?

[chris vine]

I don’t know if they did.
But cast iron on cast iron works so well and is very cheap by comparison with bronze!!
Most industrial machines are used all the time so any problems of rusting up don’t really occur.
Chris

[Roger]

I opted for SAE660 for my Cylinders, primarily to avoid any issues with rust when laid up. I haven't steamed it yet though. It's cheap enough if you shop around. I bought mine from Leeds Bronze, and they were significantly cheaper than anyone else.

[brucevoelkerding]

after searching the States, I found a 3" dia solid continuous cast x 9-1/2" long Drop of CDA 905 (i.e. Gunmetal) at a Bronze Supplier in Houston, Texas (I live near Cleveland, Ohio). I never would have found it without the InterNet. Being a Drop, there was no Cutting Charge or Minimum Invoice Amount. But of all things, it was sitting in a Warehouse just 16 miles from my House !

Due to the Design of my Q6, I could not use the Cylinders for LBSC's Netta. I will use regular Brass (CDA 360) for Items with no Wear Surfaces (Front cylinder Covers, Steam Chest Covers, perhaps Steam Chest with separate Bronze Stuffing Boxes).

I am thinking of using CDA 932 (SAE 660) for the Slide Valves.