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Should I paint my Pratt Truss bridge before complete assembly or wait ?

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  • Member since
    September, 2019
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Should I paint my Pratt Truss bridge before complete assembly or wait ?
Posted by thanosazlin on Sunday, September 15, 2019 7:31 AM

Hi all, I'm new to model railroading and also air brushing. I was wondering what the recommendations are pros/cons for either painting my bridge you see in my pic now when it's about 75% complete or just put it all together and then paint it ? 

I was thinking I might have a more difficult time getting the small out of the way spaces if I waited to put it all together then paint... but, then i thought well if i paint it now as in my attached pic i am going to have glue spots or other issues  when i go to assemble it ??.. if i did paint it now i would take all the remaining individual pieces you see and remove from their modeling and paint them all individually before final assembly a bit of work but thought i would be worth it..

Just wanted input from those with years of experience :)

Link to my bridge pic

https://drive.google.com/open?id=1Fy2-nmU0wooidq4F6A9GekWQxR9eTyC2

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Posted by rrebell on Monday, September 16, 2019 11:28 AM

Paint when done. I did a much more complicated Central Valley kit and it worked out fine and with rattle cans even. Just need to be carefull and with an airbrush it should be even easier.

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Posted by thanosazlin on Monday, September 16, 2019 11:54 AM

great! thanks for the advice.. i have done my research on video examples for airbrushing. i'll test on some old plastic stuff lying around first until i get the hang of it.. take my time, quick fast strokes, light coats, maybe 2+ of the light airbrushing .. avoid stopping or holding the airbrush in places :( of course. I think i got it, was just wondering on the before or after bridge assembly, after sounds fine to me.

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Posted by jjdamnit on Monday, September 16, 2019 12:08 PM

Hello All,

I recall reading an article on building a steel smelting works, on another online source (due to the rules of this forum I cannot refer to the site).

The builder painted the sub-structures during assembly, then did a final coat of the finished structure.

Because this was an extremely complicated build the paint-as-you-go method was employed for maximum prototypical effect.

When you paint any part of a project remember that the paint will typically "seal" the bonding surfaces so cleaning the area will produce a superior bond.

This holds true for styrene and wood- -with some exceptions- -of course.

When I built a bridge out of wood I stained the individual members before assembly because the carpenters glue would inhibit the stain from reaching the wood and create unwanted masking at the joints. 

In the August, 2019, Model Railroader magazine; pg. 38-43, there is an article on a bridge build.

The modeler pre-painted some areas before final assembly and then "finished" painted the completed structure.

Please keep us apprised of your build and as always...

Hope this helps.

"Uhh...I didn’t know it was 'impossible' I just made it work...sorry"

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Posted by MisterBeasley on Monday, September 16, 2019 3:00 PM

I also built the Central Valley truss bridge.  I did all the assembly first, and then painted it with a rattle can.  It came out just the way I wanted it.

But, it was all a single color.  I also built an older Atlas chord bridge.  This had wood walkways and metallic handrails, so it got done in several steps before final assembly.

It takes an iron man to play with a toy iron horse. 

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Posted by snjroy on Monday, September 16, 2019 3:04 PM

There is more than one way to skin a cat they say... I like to wash all the parts on their sprues, let it dry, and paint the base coat using the airbrush without taking off the parts from the sprues. Now in the case of a bridge, the base can be a grimy black or green color (look at the pictures on the Web...). I painted mine a rust color, assembled it, and painted it black with the airbrush, but not totally, leaving in some tints of rust. In all cases, it's a lot easier to give it a base coat before assembly. You just need to scrape off the paint where the glue will be applied. You can do touch-ups after the assembly - which is why I don't weather the parts before assembly.

Simon

  20190127_171339 by on Flickr" alt="" />

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Posted by mobilman44 on Monday, September 16, 2019 3:43 PM

Hi, and welcome to the Forum!

You might consider spraying the pieces - even if still on the sprues - beforehand,  which will cover most of the surface area.  Upon completion of the model, you can touch up the base color, and then do whatever weathering you like.

I've found that using a rattle can of good model paint - which the same color available in bottles - makes painting the finished model much easier. 

 

ENJOY  !

 

Mobilman44

 

Living in southeast Texas, modeling the "postwar" Santa Fe and Illinois Central 

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Posted by selector on Monday, September 16, 2019 6:01 PM

I suppose the adhesion of whichever glue you intend to use could be a factor.  Will styrene glues work well when the mating surfaces have acrylic or oil-based paints on them?  Dunno.  How 'bout 'as well'?

If a person knows there could be a reduction in efficacy with painted surfaces, one could possibly scrape or roughen some of the surfaces to be bonded?  Extra work, and it might ruin more of the painted surface than you intended.

Handling the parts and gluing them means you could leave hand oils and acids on the surfaces that you later will want to paint.  That can't be good.  However, one more chore would be cleaning it all somehow, and not breaking fine details while doing it.  And thence to paint.

Decisions...decisions.

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Posted by BATMAN on Monday, September 16, 2019 7:55 PM

Some parts need to be painted before assembly as they are too difficult to paint in place either with a brush or airbrush. Just take time and make sure you don't paint the bits that need to have glue on them, it can make for aDunce moment. I have spent time with file in hand removing paint where it shouldn't have been.

Brent

It's not the age honey, it's the mileage.

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Posted by doctorwayne on Monday, September 16, 2019 10:54 PM

Welcome to the Model Railroader Forums, thanosazlin!  

Painting the parts before assembly will make it difficult to get a good glue bond, unless you scrape-off the paint where the solvent-type cement will be applied.  Some folks opt to paint first, then assemble the parts using ca, but a joint made with solvent cement is a much stronger (and neater) bond.           

Each of the bridges shown below was built as a single assembly, and then painted using Floquil paints and an airbrush.  All were too large for my paint booth, so were painted outdoors.  All bridges shown are removeable as one-piece units.

The tall bridge in the rear is all Micro Engineering parts, while the one in the foreground used two Atlas deck-type truss bridges, and Atlas through girder cut apart and modified into a deck-type, along with some Micro Engineering deck girders...

...this one is mostly Micro Engineering parts, along with two Atlas deck trusses...

This one used two Atlas deck trusses, plus a Micro Engineering short deck girder, hidden by the trees in this photo...

...but visible here...

The first photo, below, is the west end of the Maitland River bridge, with a 30' deck girder at the far end, followed by a 50' deck girder (both from Micro Engineering), and another Atlas through girder, converted into a deck-type (the LHS had a bunch of them, used, for a couple bucks each, so I bought 'em all.  One of them ended up as a turntable).

Here's the main span, from Central Valley...

...and the east end of the bridge, another converted Atlas through girder...

....and my favourite photo of the bridge...

Wayne

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Posted by SeeYou190 on Tuesday, September 17, 2019 6:18 AM

My procedure for through truss bridges is to paint them black prior to assembly, then paint them the final color once fully assembled.

.

If the final color is black, I use a mixture of four parts black, one part white, and one part red to get a color that looks like black under indoor lighting.

.

The Central Valley bridge is molded in black, so the step can be skipped.

.

Any part left in the black preliminary coat in the final paint will look like shadows in the layout room.

.

-Kevin

.

Wink Happily modeling my STRATTON & GILLETTE RAILROAD. A Class A line located in a personal fantasy world of semi-plausible nonsense on Tuesday, August 3rd, 1954.

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Posted by Medina1128 on Thursday, September 19, 2019 10:09 AM

selector

Handling the parts and gluing them means you could leave hand oils and acids on the surfaces that you later will want to paint.  That can't be good.  However, one more chore would be cleaning it all somehow, and not breaking fine details while doing it.  And thence to paint.

Decisions...decisions.

 

This is exactly why I keep a box of latex gloves on hand.

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