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Re: Model brake component size comparison to prototype
Dennis Storzek
On Sun, Apr 5, 2020 at 09:04 PM, Tony Thompson wrote:
Richard Hendrickson did the same to get some durable bracket-mount grabs. I still have a couple dozen of his parts, very nice brass. Don't know what reject rate occurred.Those may well be my parts, I intended to sell part of the run to recoup some of my cost, but when Richard heard about it, he bought all I wanted to sell. Dennis Storzek
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Re: [Non-DoD Source] Re: [RealSTMFC] Model brake component size comparison to prototype
Gatwood, Elden J SAD
Nice work, Paul!
Elden Gatwood
From: main@RealSTMFC.groups.io <main@RealSTMFC.groups.io>
On Behalf Of Paul Woods
Sent: Monday, April 6, 2020 7:43 AM To: main@RealSTMFC.groups.io Subject: [Non-DoD Source] Re: [RealSTMFC] Model brake component size comparison to prototype
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Re: Model brake component size comparison to prototype
Paul Woods <paul@...>
An example of the casting work I have done - O-scale freight truck with functioning equalisation - and genuine American black walnut bolster. I had expected to find some shrinkage in the axle-boxes because they are a big lump compared to the arch-bars but they were fine, all portions of the sideframes turned out at intended size. Regards Paul
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Re: Model brake component size comparison to prototype
Paul Woods <paul@...>
Tony
I am greatly insulted by your tone and it appears that you have not put any thought into your comment. Seriously? You are trying to tell us that ALL the metal in a casting cools to freezing point at exactly the same moment? You might know a lot about metallurgy but I know a bit about building things from metal. I hadn't bothered mentioning that the brass caster's tale matched my own experience gained building steel ships because it didn't seem important, but fine: the metal might eventually shrink equally, but not all at the same time because cooling happens from the outside in, and this can be used to our advantage. I have dealt with plenty of castings, such as A-frames for supporting ships' propeller shafts, with significant variations in section size. The orientation of the casting as it is poured is quite important, with the thicker part intentionally placed above the thinner part so that it acts as a reservoir keeping the thin section filled as it cools....as a metallurgist you should be aware of the high density of metals such as steel and brass, and thus the pressure that will be exerted that can keep pushing semi-molten metal down towards the bottom of a mould when it is cooled slowly enough - that is the key, achieving a slow enough rate of cooling. You can't tell me it doesn't work because I've already done it; yeah sure, the metal shrinks but if it's done right it is possible to control WHERE the shrinkage occurs. The column that lost-wax brass parts are stuck to when they are cast serves as one heck of a big reservoir of molten metal as the 'branches' are freezing so I don't have any reason to doubt what the caster said. Paul Woods retired mechanical engineer
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Re: Greg Martin
james murrie
Schuyler;
What is the best way to reach out and send our good wishes, or the name on the Facebook account they are using? Jim Murrie Durham, NC
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Re: Model brake component size comparison to prototype
Tony Thompson
Dennis Storzek wrote: I've only ever done one investment cast project; I wanted some bracket grabs that were more robust than the typical styrene parts, so back when Intermountain was still molding parts here in the US, I bought a hundred detail sprues from their PS-1, clipped the runner with the grabs out of them, and sent them out as investment masters. I was warned about the potential for ash to plug the long narrow cavity, and indeed, the reject rate was someplace around 20%, but the properly filled parts were nice. Richard Hendrickson did the same to get some durable bracket-mount grabs. I still have a couple dozen of his parts, very nice brass. Don't know what reject rate occurred. Tony Thompson
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Re: Model brake component size comparison to prototype
Dennis Storzek
Well, we certainly have agreement here, don't we? Over the years I heard anywhere from "don't worry about it" to 7% shrinkage from pattern to investment cast part, although I dismiss both ends of that range. It does point out that investment casting is still somewhat of a 'black art' as far as the short runs typical in our hobby.
And some firms ARE using styrene as the burn-out material, although it typically isn't very hard and doesn't contain much colorant. Injection molded styrene also has a shrinkage factor, appx. 1/2%, which has to be added to the metal shrink factor. I've only ever done one investment cast project; I wanted some bracket grabs that were more robust than the typical styrene parts, so back when Intermountain was still molding parts here in the US, I bought a hundred detail sprues from their PS-1, clipped the runner with the grabs out of them, and sent them out as investment masters. I was warned about the potential for ash to plug the long narrow cavity, and indeed, the reject rate was someplace around 20%, but the properly filled parts were nice. Of course, the nicely molded acetal parts from Kadee have made that no longer worth doing. Dennis Storzek
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Re: Model brake component size comparison to prototype
Tony Thompson
Paul Woods wrote: My casting supplier tells me the shrinkage occurs in the rubber mould, not the metal casting because the column of molten brass in the cast keeps pressure on the mould as it cools, helping reduce shrinkage. Sorry, this is nonsense. The entire volume of the metal is shrinking as it solidifies and cools, and nothing in ordinary life can constrain it. The molten column AND the part are all shrinking equally. Tony Thompson retired metallurgist
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Re: Model brake component size comparison to prototype
spsalso
Paul,
I will disagree with your statement that shrinkage does not occur in the metal casting process. If we assume the mold is filled out with molten brass, and the brass cools down to its phase change temperature of 920 degrees C., thermal contraction will occur as the solid cools from just under 920 degrees to 25 degrees C. The piece will pull away from the walls of the mold. The "column of molten brass", if it even still remains liquid, will be trying to compress a solid. That solid will not compress significantly. As I said, the shrinkage during the casting process for brass is 1.7%. Roughly. Ed Edward Sutorik
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Southwest Scale Productions Boxcar Doors
Following on on some
previously posted material, attached are two formats of a document describing
the post WWII boxcar doors produced by Southwest Scale Productions, with photos
of both the prototype and model for each one.
I am unable to load
them to the files area, but hopefully they will find a home
there.
Steve
Hile
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Re: Illinois Central 40' ss boxcar information
Chuck Cover
Thanks Tim. Nice photo.
Chuck Cover Santa Fe, NM
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Re: Model brake component size comparison to prototype
Paul Woods <paul@...>
Hi Folks
For the benefit of anyone not familiar with the brass investment casting process: I do CAD design work for cast brass model railroad parts, along with other methods (laser, photoetch); the 3D-printed master is made 2% oversize and a rubber mould is made from it. Today the rubber is transparent, and the mould is poured as one block then cut in half with a scalpel. I always do my 3D-printed patterns with sprue gates but sometimes an area won't fill with metal properly, and any additional sprue gate can simply be carved out of the mould to correct the problem. A special hard wax is then injected into the mould, making as many wax copies as required. These waxes are then 'treed up', that is, stuck on a wax cylinder so that they look like branches on a tree, then the whole lot is dipped in high-temp plaster repeatedly to build up sufficient thickness. The plaster mould is heated to run the wax out (hence the term 'lost wax'), so that molten brass, bronze or whatever can be poured into the resulting cavity. My casting supplier tells me the shrinkage occurs in the rubber mould, not the metal casting because the column of molten brass in the cast keeps pressure on the mould as it cools, helping reduce shrinkage. I usually see shrinkage i.e. low spots where the surface should be flat, where a large cavity is filled through a smaller sprue gate and so the metal in the sprue gate can freeze before the metal in the cavity, preventing more metal from flowing in. Uneven cooling is the sworn enemy of metal casting of any kind, so large thick sections should be avoided; it will usually give a better result if a large part is either hollowed out or assembled from smaller parts. It can be an expensive waste of time trying to burn styrene parts out of plaster moulds because styrenes can include fillers to make them harder, and these are not always combustible. The ash can get pushed into the smaller nooks of the mould by inflowing metal, preventing the fine details from filling. To the best of my knowledge, wax masters cannot be used for spin-casting pewter, because the type of rubber compound used (at least, by my local supplier) to make the mould produces heat as it sets, sufficient to soften or even melt styrene, so wax doesn't stand a chance. This similarly rules out the use of 3D-printed resin masters, so if metal masters cannot be made by hand then the process has to be plastic master - brass casting - pewter casting. This can still be worthwhile but you have to require huge numbers of something, such as tieplates, to justify the effort. The tricky part is judging the amount of shrinkage to allow for because the brass casting process involves shrinkage and then so does the pewter casting process, so one multiplies the other. I would love to find a spin-caster who can use wax patterns because that would reduce the costs quite a lot. Regards Paul Woods Whangarei, NZ NYCSHS #7172
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Re: Reboxx 1.035 wheels
Schleigh Mike
How many sets do you need, Brian? Mike Schleigh in Grove City, Penna.
On Sunday, April 5, 2020, 05:37:17 PM EDT, Brian Carlson via groups.io <prrk41361@...> wrote:
Does anyone know where any Reboxx 1.035 33“ wheels might exist on a hobby shop shelf or workbench someplace never to be used. I am looking for some for a project, either single or double insulated. I miss reboxx wheels. Brian J. Carlson
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Re: Reboxx 1.035 wheels
Dave Parker
I found the same website last week, They only seem to offer 0.110" wheels. Reboxx were all 0.088" IIRC.
I really miss Reboxx. -- Dave Parker Swall Meadows, CA
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Re: Reboxx 1.035 wheels
James Brewer
Brian,
I don't have any Reboxx wheels in my stash; but I've noticed an ad in the last few issues of RMC for "JB Wheelsets" that says "slightly different name...same great product!" There is a web site listed www.jbwheelsets.com Other than noticing the ad I have no connection with this vendor. Good luck on your search. Jim Brewer
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Reboxx 1.035 wheels
Does anyone know where any Reboxx 1.035 33“ wheels might exist on a hobby shop shelf or workbench someplace never to be used. I am looking for some for a project, either single or double insulated.
I miss reboxx wheels. Brian J. Carlson
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Re: circa 1946 freight car images
BRIAN PAUL EHNI
A color photo of these two has made the rounds before.
Thanks!
From: <main@RealSTMFC.groups.io> on behalf of Eric Hansmann <eric@...>
The second handhold on the left end of the car sides became a practice in the early 1930s.
I model 1926 and I need to remove the second handhold detail from many resin and plastic models.
Eric Hansmann Murfreesboro, TN
From: main@RealSTMFC.groups.io <main@RealSTMFC.groups.io> On Behalf Of Tim O'Connor
Sent: Sunday, April 5, 2020 1:25 PM To: main@RealSTMFC.groups.io Subject: Re: [RealSTMFC] circa 1946 freight car images
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Re: Illinois Central 40' ss boxcar information
Eric Hansmann
Thanks, Ray!
Eric Hansmann Murfreesboro, TN
From: main@RealSTMFC.groups.io <main@RealSTMFC.groups.io> On Behalf Of Ray Breyer via groups.io
Sent: Sunday, April 5, 2020 2:55 PM To: main@realstmfc.groups.io; main@RealSTMFC.groups.io Subject: Re: [RealSTMFC] Illinois Central 40' ss boxcar information
1941-1942, not 1934. Most of the IC's single sheathed cars were rebuilt during the war years, and it does appear that all of them with wood doors (40' and 50'') got the rienforcing plate at the bottom of the doors.
Ray Breyer
On Sunday, April 5, 2020, 02:42:56 PM CDT, Chuck Cover <chuck.cover@...> wrote:
Hi Eric,
In the Ted Culotta article in RMC that was referred to in Ben Hom’s response to me states that all of the car doors received steel reinforcing plates at the bottom of the doors during the 1934 rebuilding project.
Chuck Cover Santa Fe, NM
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Re: Illinois Central 40' ss boxcar information
Eric Hansmann
Thanks, Chuck. I also have this kit. I think I’ll cut the current door out of the side casting and remove all the door hardware. A Tichy replacement will be installed with companion half-door to reflect the as-built prototypes.
Then I’ll need new decal artwork….
Eric Hansmann Murfreesboro, TN
From: main@RealSTMFC.groups.io <main@RealSTMFC.groups.io> On Behalf Of Chuck Cover
Sent: Sunday, April 5, 2020 2:43 PM To: main@RealSTMFC.groups.io Subject: Re: [RealSTMFC] Illinois Central 40' ss boxcar information
Hi Eric,
In the Ted Culotta article in RMC that was referred to in Ben Hom’s response to me states that all of the car doors received steel reinforcing plates at the bottom of the doors during the 1934 rebuilding project.
Chuck Cover Santa Fe, NM
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Re: Illinois Central 40' ss boxcar information
Ray Breyer
1941-1942, not 1934. Most of the IC's single sheathed cars were rebuilt during the war years, and it does appear that all of them with wood doors (40' and 50'') got the rienforcing plate at the bottom of the doors. Ray Breyer Elgin, IL
On Sunday, April 5, 2020, 02:42:56 PM CDT, Chuck Cover <chuck.cover@...> wrote:
Hi Eric,
In the Ted Culotta article in RMC that was referred to in Ben Hom’s response to me states that all of the car doors received steel reinforcing plates at the bottom of the doors during the 1934 rebuilding project.
Chuck Cover Santa Fe, NM
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