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More New Nastiness in 3D Resin Printing
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Bill Welch
This link takes you to MMC Design on the Model Shapeways site. The
items are 1/35th scale for Sherman tanks. I think the Periscope guards are particularly interesting in terms of what is possible. http://www.shapeways.com/shops/MMCDesign Bill Welch 2225 Nursery Road; #20-104 Clearwater, FL 33764-7622 727.470.9930 fgexbill@... |
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Sort of... I am more interested in a photo of the actual part,
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and not a drawing of what it would ideally look like. Tim O'Connor This link takes you to MMC Design on the Model Shapeways site. The |
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I recently worked up some HO concrete railings (appropriate for steam era layouts) and described them on my blog:
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www.bobsworkbench.com Photos of the models are included there. Bob Sterner St. Paul, MN --- In STMFC@..., Tim O'Connor wrote:
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Very impressive! Bob can you describe the under-structure of that
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road bridge? I'm amazed by the shallow depth of the prototype bridge seen from the side. Of course in 1910 they didn't have to worry about 80,000 lb trucks. Tim O'Connor I recently worked up some HO concrete railings (appropriate for steam era layouts) and described them on my blog: |
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Hi Tim,
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I had the same thought as you when I was looking at the prototype bridge. It's not the only one (now gone) in that part of town that seems very thin to my eyes. It could be my model accentuates the effect because for reasons probably nobody but me cares about I had to lengthen the model bridge about 25% compared to the prototype. The person who designed the prototype bridge -- C. Turner -- was a big shot in the early 20th century in concrete construction techniques. He was pushing a design approach he called the "mushroom system", which I don't know much about. If you're referring to the understructure of the model, I built it up with Luan, then I added the trolley tracks via handlaid rails to that. I then used Durham's water putty to make the road surface. Steam Era freight cars run underneath! Bob Sterner St. Paul, MN --- In STMFC@..., Tim O'Connor wrote:
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Read http://skyscraper.org/EXHIBITIONS/VERTICAL_URBAN_FACTORY/concrete.php
for more about Turner and his mushroom system. Basically he discovered that if you flare out the top of a concrete column, ie put on a mushroom cap, the column will support a greater amount of weight and allow for thinner floors without the need for reinforced beams. Essentially a post and beam construction without the beams. The prototype bridge in Bob's modeling looks to have columns with a flared top, ie the mushroom system, allowing for a thin road deck. But I would caution about lengthening the span when modeling, as it won't "look right". Engineering statics and dynamics are precise science, especially when it comes to bridges. A certain span will require a certain depth in beam or floor thickness. The greater the span the thicker the structure. But everything has a limit. Doug Harding www.iowacentralrr.org |
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soolinehistory <destorzek@...>
--- In STMFC@..., "Bob Sterner" wrote:
The "mushroom system" Bob mentions incorporated a funnel shaped top on each concrete column, so that thin deck actually has much more support than is evident from the view looking down. The Same general construction was used on the Soo Line Chicago freight terminal built about 1913, IIRC. The entire four city block terminal yard area was built on a concrete deck to match the height of the grade separated approach tracks, this freeing the space under the yard for commercial rental. One track dropped down a ramp to give the ground level tenants rail service, too. It was a successful design, the terminal, though much underutilized in recent decades, was only torn down in the last ten years. David Lieder had an article about the construction of the freight terminal about five years ago in The SOO, the magazine of the Soo Line Historical & Technical Society that had a lot of period photos of the construction. Dennis |
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Anthony Thompson <thompson@...>
Doug Harding wrote:
The prototype bridge in Bob's modeling looks to have columns with a flared top, ie the mushroom system, allowing for a thin road deck. But I would caution about lengthening the span when modeling, as it won't "look right". Engineering statics and dynamics are precise science, especially when it comes to bridges. A certain span will require a certain depth in beam or floor thickness. The greater the span the thicker the structure. But everything has a limit.Well said, Doug. Girder bridges in particular have length to depth proportions which depend on loading, for obvious reasons. Paul Mallery's bridge book (Carstens) lays all this out quite clearly. Modelers who start with, say, an Atlas girder bridge and simply shorten or lengthen it, are playing with fire if the change is much more than 10 percent in either direction. But if you start with Mallery, you can get it right. Tony Thompson Editor, Signature Press, Berkeley, CA 2906 Forest Ave., Berkeley, CA 94705 www.signaturepress.com (510) 540-6538; fax, (510) 540-1937; e-mail, thompson@... Publishers of books on railroad history |
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