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| Installing new crown brass on steam https://www.rypn.org/forums/viewtopic.php?f=1&t=26320 |
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| Author: | Tim Gautreaux [ Tue Oct 14, 2008 9:48 am ] |
| Post subject: | Installing new crown brass on steam |
Can anyone share his knowledge about installing new crown brasses in new driver boxes? Specifically, should they be pressed in snug or is any clearance allowed/necessary? Are there any big "don'ts" in the installation process? Tim Gautreaux |
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| Author: | Dave [ Tue Oct 14, 2008 1:53 pm ] |
| Post subject: | Re: Installing new crown brass on steam |
Hi Tim - Baldwin spec is: 1.5 tons per inch of outside brass diameter with a .030 allowance on each toe in a cast iron box. 2.5 tons per inch with a .045 allowance for cast steel boxes. Hope this is what you need. dave |
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| Author: | Tim Gautreaux [ Tue Oct 14, 2008 11:49 pm ] |
| Post subject: | Re: Installing new crown brass on steam |
Thanks, Dave. Is there a minimum clearance? Tim |
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| Author: | Dave [ Wed Oct 15, 2008 11:25 am ] |
| Post subject: | Re: Installing new crown brass on steam |
Not sure what you are asking for. Main journals are bored out .017 larger than journal diameter. Others 1/32" oversized for grease, 1/64" for oil. (Baldwin spec. 4-8H). Distance between bottom edges of brass 1/4" larger than journal diameter. Chamfer bottoms of brasses. Is your answer somewhere in here? dave |
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| Author: | Tim Gautreaux [ Wed Oct 15, 2008 5:12 pm ] |
| Post subject: | Re: Installing new crown brass on steam |
Thanks for the interesting and helpful information, but it doesn't answer the original question about how tightly new crown brasses should be machined to fit in driving boxes. Tim |
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| Author: | Loco112 [ Wed Oct 15, 2008 11:26 pm ] |
| Post subject: | Re: Installing new crown brass on steam |
Richard, where did you find that particular bit of comprehensive driver box info? I might could find bits and pieces of it, but not all of what you posted in any one volume, so I'm really interested to know what text it came from. Whatever it is I know I need to find a copy! |
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| Author: | Dave [ Thu Oct 16, 2008 8:10 am ] |
| Post subject: | Re: Installing new crown brass on steam |
Baldwin standards books. They were reprinted some years back, but copies are a bit hard to come by. The tons of pressure referenced will, when combined with your Machinists Reference, provide you with the oversize you need to machine them according to the diameters. Make them big enough to take that pressure in the press to install. So, yes, oversized. Given they will be pressed in with several tons of stress, they are likely to somewhat diminish in ID, so might want to rough machine the ID before installation, then finish ID after in boxes. Having closed my business and packed up most of my old books, I can't provide you with the oversizes for varying diameters. You will have to ferret them out on your own. Lots of old specs refer to tons of pressure for such information - it is a bit unlike today's versions, but probably a machinist apprenticing in 1915 would have learned this stuff as a matter of course. dave |
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| Author: | Tim Gautreaux [ Thu Oct 16, 2008 9:19 pm ] |
| Post subject: | Re: Installing new crown brass on steam |
Thanks, Dave and Jeff. Your answer tells me what I need to know. Tim |
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| Author: | Bruce_Mowbray [ Fri Oct 17, 2008 12:32 pm ] |
| Post subject: | Re: Installing new crown brass on steam |
Tim, Be careful making the brasses too big. A crown brass can easily spread the box too far at the cellar space. I made the brasses "on size" with the opening in the box and allowed the excess on the toes to provide the pressure to make it tight. Did you receive my PM? |
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