I am getting ready to make crown brasses for a 1/8-scale steam locomotive. The only information I have been able to find on the web is the following for the Pennsylvania Railroad Company:

The specifications for phosphor-bronze bearing metal call for a homogeneous alloy of copper, tin, lead, phosphorus, as free as possible from every other substance, and of the following composition:
Copper 79.7 percent, tin 10 percent, lead 9.5 percent, phosphorus 0.8 percent. The rejection limits are as follows: Lots will not be accepted if the analysis as above described gives results outside the following limits: Tin, below 9 percent, or over 10 percent, lead, below 8 percent, or over 10 percent; phosphorus, below 0.7 or over 1 percent; nor if the metal contains a sum-total of any other substances than copper, tin, lead and phosphorus in greater quantity than 0.50 percent.

This is no longer a standard alloy, what is being used for crown and rod brass?

Thanks

Tim

Try 932 Alloy Bronze, also known as SAE 660. It's available in bar form from McMaster-Carr.

Hi Chris

660 is the standard bearing bronze. But I do not think that is always the best choice. I found some old posts showing problems with 660. I am thinking that C54400 Leaded phosphor bronze would work better.

Tim

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In a not entirely unrelated discussion.....concerning a 1/1 scale locomotive, a crown brass with a babbit liner and oil lubrication is being considered, based on favorable reports of a locomotive with many in-service, highly loaded, track speed miles being run on her using that system now. Have you thought about a babbit lined bearing?

Why limit your confusion to a narrow perspective? There's a whole range of other things out there that you can further be indecisive about. Many modern bearing materials have been developed since then.

I'm very pleased to see a substantive technical discussion here....

dave

Hi Kelly

I was looking at C936 do to its high lead content. The one thing I do not like in C544 is the amount of zinc in it.

One report I read: "The phosphorus was added for its supposed beneficial influence in the foundry. Phosphorus is a deoxidizing agent and has the property of rendering the metal exceedingly fluid."

So it has nothing to do with the bearing serviceably just in the making.

Both C936 and C544 have a Machinability of 80 %


Hi Dave

Yes, I have looked at adding Babbit to the bearings. I am still looking.

Has anyone tried Magnolia #120 High Lead?

Thank you for the input.

Tim

When the 1702 received new crown brass in 2003, the 936 was used due to the higher lead content. We also duplicated the oil channel found in the boxes removed from 611 ( the one with the Franklin Poppet valve gear, formerly at TVRM), except we did it on both the front and the rear of the bearing (10 and 2). We lubricated the bearing with Journal Tex, with a 6x11 friction pad. We also protected for a forced oil feed to those same oil channels, but never needed them. The first run out with the new brass we ran 5-10 degrees above ambient. (no load, 15mph). The next day we loaded her with one of the GP9's in full dynamic, 15mph for about 10 miles. 5-10 degrees above ambient. After that it was pretty much ambient unless we got water contamination in the cellar. Towards the end of that season both sides of #4 started to run warmer than the rest, but only by 5-10 degrees. I'm not so sure it wasn't really the lateral that was making the heat, rather than the crown. I was pretty happy with the situation. Was looking forward to putting her back in the gorge the following season, but was not to be. . . .

Ryan

Hi Ryan

I am thinking that 936 is a good choose, there are other alloys with a higher lead content:
C93800 High-Leaded Tin Bronze (SAE 67) (78-7-15)
C93900 High-Leaded Tin Bronze (SAE 67) (78-6-16)

But the 1928 study http://archive.org/details/jresv1n3p343 shows that there is little advantage in going above 12% lead. One other advantage with 936 is that it is easy to purchase in small quantities.

Thank you for your input.

Tim