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Bridge Piers

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Bridge Piers
Posted by carl425 on Sunday, October 11, 2015 11:19 AM

I just set my chop saw to 5° and cut a couple piers out of a 2X4.  Cut the short sides first, then screwed the base to a scrap piece of 1X3 to cut one long side, turned it around and cut the other.  I'm sure I re-invented the wheel, but I'm happy with the results.

I'm going to put a skim coat of spackle on them so they look like concrete.  These piers are probably close to 100 years old and built with forms made from boards rather than plywood.  I need to cut grooves into something that I can press against the wet spackle to make the lines where the edges of the boards were.

Two questions:

What material would be best to press the grooves into the spackle so that it would stick to the pier and not to the form?

On a pier this old, what size lumber was probably used as the forms?

Here's the one I'm trying to represent:

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Posted by rrebell on Sunday, October 11, 2015 12:09 PM

May be the wrong approch, I made a mold for plaster for mine out of groved styrene, worked great and you can use just one mold for different hights as you can cut down the finished post.

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Posted by 7j43k on Sunday, October 11, 2015 12:31 PM

Looks to me that the spacing is 8".

I would be wary of using a solid piece of wood.  Cracks and splits can occur over time.  I wouldn't take the chance.

Like Rich, I would make styrene forms, and do a pour.  Seems like more fun.  I think Hydrocal would likely work.  You want something that won't shrink (much).  You could arrange a void, if you think it would be nice.  DO NOT put a non-removable "thing" in the middle.  Like wood.  Or foam.  I s'pose I would/will make an inside form out of styrene.  Since it's mostly hollow, I could leave it.

If you use "scribed siding", as Rich did, you can scrape down the seepage as necessary, if you think it too prominent.  The abutments I will be working on were formed with plywood (I think).  So I will likely use 4x8 sheets of styrene.  And teeny tiny little nails.  No, not really!

 

 

Ed

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Posted by doctorwayne on Sunday, October 11, 2015 12:38 PM

I also made moulds using sheet styrene, with scribed-in board detail, and used Durabond-90 patching plaster for the piers.  It hardens in about 90 minutes, with no shrinking and, once cured, is extremely hard.

I did a thread on this here:

bigbluetrains.com/forum/viewtopic=casting+piers

...but noticed when I checked just now that the photos are gone.  Bang Head

If you can wait about a half-hour or so, I'll restore them, as they pretty-well cover what you need.

EDIT:  Photos have been restored.

I also forgot to mention that if you pursue the plaster-on-wooden-block idea, use a paper towel to wipe some vegetable oil on the material you're using to impart the board detail, then press it into the wet spackle.  I use it as a mould release in the linked thread, and it doesn't seem to affect the plaster at all, as the hardened piers readily accept a thinned, water-based paint stain.

Wayne

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Posted by cowman on Sunday, October 11, 2015 1:34 PM

You could use your method of cutting the piers, but use foam for the material.  The Connecticut Valley Model RR Club brings a modular layout to shows.  They made their piers out of pink or blue foam.  Theirs were done as stone piers, so they scribed in the lines for large stones.  There are photos of their Crawford Notch layout at their website.  For scribing board lines I'd try pressing a piece of board and batten into your spackle.  Textured paint might work instead of spackle, but pressing the lines in before painting.  Also, that long ago they probably used rough cut lumber of random widths.

Good luck,

Richard

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Posted by carl425 on Friday, October 16, 2015 10:22 AM

Here's my first try.  Not sure why, but the yellow and the texture is greatly exaggerated in this picture.  It is actually much more subdued.

In any case, it's nice to be working with Testors rather than Dewalt for a change. 

I bought styrene and hydrocal to try casting them.  I just have to decide if this is "good enough".  I only need two piers of this shape so I'm not sure the ROI is high enough to make a mold.

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Posted by rrebell on Friday, October 16, 2015 1:53 PM

Do the investment, you cut too many corners and it starts to tell plus the mold is still good and you may find a use in future or sell it on e-bay.

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Posted by doctorwayne on Friday, October 16, 2015 5:08 PM

carl425
I bought styrene and hydrocal to try casting them. I just have to decide if this is "good enough". I only need two piers of this shape so I'm not sure the ROI is high enough to make a mold.

I, too, needed some piers for a particular situation, but in the link I posted earlier, it shows how you can make a multi-use mould - the style and details, especially on the top, suit certain bridge types, but the mould is designed so that it can be any height within the range of its size. For example, a bunch of identical 2" high ones for a low-level crossing of a river, or a bunch of short-to-tall-and-back-to-short ones for crossing a valley.  The same mould works for all of them, depending on how much plaster is used for each. 

Wayne

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Posted by carl425 on Friday, October 16, 2015 6:36 PM

doctorwayne

 

I, too, needed some piers for a particular situation, but in the link I posted earlier, it shows how you can make a multi-use mould - the style and details, especially on the top, suit certain bridge types, but the mould is designed so that it can be any height within the range of its size. For example, a bunch of identical 2" high ones for a low-level crossing of a river, or a bunch of short-to-tall-and-back-to-short ones for crossing a valley.  The same mould works for all of them, depending on how much plaster is used for each. 

Wayne

 

I actually read your thread a few months ago (thanks for posting it) then read it again before starting this test.  I only have plans for two bridges on the layout that will require piers and the other has points on the upstream side so a mold would only be useful for 2 piers.  I'm not really happy with this one, so I'll probably start cutting styrene tomorrow.  I can at least use the chunk of wood that I cut out as a template to cut the styrene pieces.

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Posted by NP01 on Friday, October 16, 2015 11:59 PM

carl425

I just have to decide if this is "good enough".  I only need two piers of this shape so I'm not sure the ROI is high enough to make a mold.

 

I would do what you did. This feels pretty fast and is a good result. you could replace later on ... For me it's important to get the pike running so I would sweat the details later. 
 
I am not sure I have seen a lot of cracked/split 2x4s over time ... maybe I don't know something. 
 
NP. 
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Posted by rrebell on Saturday, October 17, 2015 7:46 AM

You have not ever been in the trades then, when you get to smaller lengths, they split all the time, let alone when they dry out.

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Posted by farrellaa on Saturday, October 17, 2015 9:19 AM

I needed 2 piers that were about 6-7" high and made them from clear pine (well seasoned wood) and then covered them with styrene cut stone sheets. I used Walther's Goo and then made the styrene overlap at all corners and solvent cemented them to each other. I carved the corners so you didn't see the edges of the styrene. This way they won't peel at the edges. They have been on the layout for a couple of years now with no signs of cracking, splitting or peeling. I thought of doing the plaster casting method but wanted something I could screw the 3 bridge sections to. Everything worked out OK for me.

   -Bob

Life is what happens while you are making other plans!

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Posted by 7j43k on Saturday, October 17, 2015 10:14 AM

For me, the number of piers and abutments I will need is quite low--right now, only two of the latter, but ya never know.  I plan on building the forms from styrene, just as has been discussed.  But instead of making a mold for re-use, I plan on "stripping the forms", just like the real ones.

This is partly driven by the fact that I "only" need abutments.  And those tend to be custom designed for the site.

But it's mostly just for fun.

I believe the abutments I will be modeling used plywood forms.  Which strikes me as odd, as the bridge resting thereon is REALLY old.  Older than me, even.  But since plywood was used for WWI airplane propellers, I s'pose......

 

 

Ed

 

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Posted by 7j43k on Saturday, October 17, 2015 10:37 AM

cowman

Also, that long ago they probably used rough cut lumber of random widths.

 

 

 

Rough cut?  Absolutely.

Random?  I suppose it could happen.  But generally, I don't.  When the form builder is setting up the job, he will order his wood, either used from company stock, or new.  And he will specify the quantity and dimensions.  I do not think he will say "Just drop off whatever is lying around."

If the job uses standardized planking, it is easier to design.  It is easier to order the wood.  It is easier for the jolly workers to unload from a flat and stack at the job.  It is easier to decide which piece of wood to take off the stack--they're all the same.  It is easier to handle--they're all the same.

While it is true that random width planking would work, I think it would only be used on a bargain-basement job by a Laurel and Hardy crew.  If that level of quality is appropriate for a particular railroad, then I s'pose........

 

 

Ed

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Posted by carl425 on Saturday, October 17, 2015 5:35 PM

NP01
For me it's important to get the pike running so I would sweat the details later.

That fits with my usual philosophy of not redoing anything until I've done everything, but in this case it's nice to take a break from all the carpentry, track laying and electrical to do something more like building a model.

 

I haven't seen a lot of split 2X4's either. The one that these piers were cut from was salvaged from the closet wall I took out to expand the layout space.  The house was built in 1982, so this one is probably as dried out as it's ever going to get.

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Posted by wabash2800 on Saturday, October 17, 2015 10:08 PM

I would recommend gluing strip wood together (stacked) and using that as your imprint tool.  When you think about it, that's how the forms would be in real life. Perhaps you could built it in an "L" shape so the board imprints will line up all around?

I built my molds out of pine strip wood and poured the HydroCal in. The stripwood pieces were glued together but the molds were held together with track nails until the plaster set. I used a little PAM cooking oil in a spray can for mold release and stained my abutments with diluted soy sauce in little packets from the local Chineese restaraunt. (If you do it right, it gives the color a very slight yellow tint. I also weathered a little with diluted India Ink and rust colored chaulk for rust streaks. To me this is most realistic looking concrete you can get.

Victor A. Baird

Fort Wayne, Indiana

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