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| Brake Rigging Rod Alloy https://www.rypn.org/forums/viewtopic.php?f=1&t=47469 |
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| Author: | jayrod [ Sat Jul 01, 2023 4:07 pm ] |
| Post subject: | Brake Rigging Rod Alloy |
Another brake question. It never ends…. But at least I’m learning as I go. The Pullman I’ve been working on broke a brake rigging rod. Apparently cracked sometime and finally broke. Is there a specific alloy for the round bar? Rod is slightly bent so weld-on splice likely won’t do, at least in my book. |
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| Author: | Kelly Anderson [ Sat Jul 01, 2023 4:50 pm ] |
| Post subject: | Re: Brake Rigging Rod Alloy |
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| Author: | softwerkslex [ Sat Jul 01, 2023 5:25 pm ] |
| Post subject: | Re: Brake Rigging Rod Alloy |
jayrod wrote: Another brake question. It never ends…. But at least I’m learning as I go. The Pullman I’ve been working on broke a brake rigging rod. Apparently cracked sometime and finally broke. Is there a specific alloy for the round bar? Rod is slightly bent so weld-on splice likely won’t do, at least in my book. Well, we had an old brake rod in our scrap pile, and I cut a slice of it off for what I don't remember. I put it in the lathe, and started turning it, and found a hidden fissure right through the middle! So I wouldn't put too much confidence in the quality of brake rod material. |
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| Author: | QJdriver [ Sat Jul 01, 2023 5:30 pm ] |
| Post subject: | Re: Brake Rigging Rod Alloy |
In my infinite wisdom, I suggest 4140 heat treated... |
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| Author: | jayrod [ Sat Jul 01, 2023 9:37 pm ] |
| Post subject: | Re: Brake Rigging Rod Alloy |
Quote: Well, we had an old brake rod in our scrap pile, and I cut a slice of it off for what I don't remember. I put it in the lathe, and started turning it, and found a hidden fissure right through the middle! So I wouldn't put too much confidence in the quality of brake rod material. This rod looked like it had a longitudinal crack that corroded into some kind of occlusion in the middle. The break didn’t look like a normal break you’d see when steel fractures like that under tension. It was kind of lumpy, almost crystalline. Acquiring a bend in that area didn’t help much, either. So yeah, not a quality piece. It’s a 1921 vintage car. Don’t know the vintage of the rod. |
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| Author: | David Johnston [ Sun Jul 02, 2023 2:03 am ] |
| Post subject: | Re: Brake Rigging Rod Alloy |
The design requirements assume the material will be A-33, wrought iron. The yield strength used in design is 10,000 psi, giving a safety factor of about three. But actual construction these days uses A-36. |
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| Author: | jayrod [ Sun Jul 02, 2023 7:01 am ] |
| Post subject: | Re: Brake Rigging Rod Alloy |
David Johnston wrote: The design requirements assume the material will be A-33, wrought iron. The yield strength used in design is 10,000 psi, giving a safety factor of about three. But actual construction these days uses A-36. That explains the look of the broken ends. My brain didn’t even think “wrought iron”. If I recall somewhat correctly, it doesn’t like getting bent so that could ultimately explain the failure. |
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| Author: | PCook [ Sun Jul 02, 2023 10:51 am ] |
| Post subject: | Re: Brake Rigging Rod Alloy |
Expanding on Sammy's post, a major locomotive builder also listed 4140H as being a suitable material for this type of application. PC |
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| Author: | Kelly Anderson [ Sun Jul 02, 2023 11:37 am ] |
| Post subject: | Re: Brake Rigging Rod Alloy |
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| Author: | jayrod [ Sun Jul 02, 2023 2:01 pm ] |
| Post subject: | Re: Brake Rigging Rod Alloy |
After looking up the properties, I’m going to agree with David and Kelly. A36 is common, easy to work with and with the size of these rods - they’re huge compared to freight cars - I don’t see breaking it again unless the welds on the jaws are poor. Thanks for your responses. |
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