Casting Deck plate bridges

[unittrain]

I need to scratch build several deck plate bridges based on prototypes I have measured and drawn up in CAD obviously scratchbuilding these by fabricating the whole thing would take way too long! What I was wondering is would it be possible to fabricate say one section of a girder using styrene and archer rivet decals to make a mold to cast copies in order to complete a full span? For some of the spans I was able to use the walthers through plate girder by splicing together various panel sections but some of these bridges I think would be easier to accomplish via molding since the stiffener spacings vary along the girder span, but I'm not sure as I have never tried casting parts. Thanks for any information.

[superturbine]

Yes it can be done.... I've seen examples of bridges done with castings from a single master.

[LV LOU]

Yes,it can be done.The big deal is,though,that a bridge girder is a two sided piece.Not so easy to make a mold,especially with no experience.[If ya gotta ask,you're probably in over your head already,LOL!] Also,to get a really nice quality casting on something with rivets,deep reliefs,ETC,you really need to have a pressure pot and a vacuum chamber to make good molds and castings,which require a vacuum pump and a compressor,oh yeah,and a scale..Not necessarily a cheap proposition.Now,you can get away without all the toys,but you won't get REALLY nice castings.Now,one other option...If you do a really nice job on the masters,you may get a goofball like me to do them for you if I think I can make a few bucks selling them,LOL!!

[nkalanaga]

True, a girder is two-sided, but if the girder is hidden under bridge track, and the underside isn't easily seen, there's no need to detail the inside.  In that case, you have a casting as thick as the top and bottom, with detail less than halfway through on one side, very easy to cast.

[SkipGear]

I looked into casting for the bridge below.....





I had gone as far as building a master to cast. After holding it in hand. I realized how thin the cross section was going to be and how hard it was going to be to keep it a uniform thickness, fill in all the girder details, and not warp in the process. I decided it would be cheaper and faster to use Micro Engineering bridge parts to create the girders the length I need. It turns out the panel size was very close to what was used on the bridge I was modeling, I just needed them in longer sections. I got out the chopper one evening and made a bulk of uniform parts and spent another couple nights building.



The result turned out very nice. I had considered Archer rivets to finish out the cap strips on the girders but realized I would have close to $100 in decals to finish it out. Two double rows of rivets per side, roughly 30" each was going to eat up 5-6 sheets of riviets.



For a ballasted deck bridge, you probably have a lot less detail to worry about.

[Philip H]

Tony,
Both of those bridges are pretty HAWT!  Any chance they appeared somewhere else on TRW with a build thread?

[unittrain]

I looked into casting for the bridge below.....





I had gone as far as building a master to cast. After holding it in hand. I realized how thin the cross section was going to be and how hard it was going to be to keep it a uniform thickness, fill in all the girder details, and not warp in the process. I decided it would be cheaper and faster to use Micro Engineering bridge parts to create the girders the length I need. It turns out the panel size was very close to what was used on the bridge I was modeling, I just needed them in longer sections. I got out the chopper one evening and made a bulk of uniform parts and spent another couple nights building.



The result turned out very nice. I had considered Archer rivets to finish out the cap strips on the girders but realized I would have close to $100 in decals to finish it out. Two double rows of rivets per side, roughly 30" each was going to eat up 5-6 sheets of riviets.



For a ballasted deck bridge, you probably have a lot less detail to worry about.

I cut up the walthers bridge and made several spans out of I think 6 kits I just cut them at the panel points and spliced sections together and they came out really nice. It would be nice if someone would come out with brass strips with etched rivet detail for scratchbuilding, a box girder is a simple scratchbuild if it weren't for the rivet detail.

[Scottl]

I've been thinking about that issue.  Could you use a model with rivets as a template and rub the rivets into very thin metal stock?  Like 0.005" brass?  I have not tried it, but I'm facing the same issues with rivets and the Archer decals will be expensive for a large project.

[Hornwrecker]

The old school way I remember seeing in MR & RMC was to use a watch gear of suitable size, and make a little pizza cutter device to run over the brass which was placed on a surface with some give.  You'd have to use annealed brass for this to work (well?).  No idea how well it works.  Maybe using it on that copper foil tape used  to make stained glass windows would be better than brass for long strips in N scale.

[DKS]

You might think about just making a few panels. Cast them, assemble the panel castings into a complete plate, then cast the plate.

[LV LOU]

The old school way I remember seeing in MR & RMC was to use a watch gear of suitable size, and make a little pizza cutter device to run over the brass which was placed on a surface with some give.  You'd have to use annealed brass for this to work (well?).  No idea how well it works.  Maybe using it on that copper foil tape used  to make stained glass windows would be better than brass for long strips in N scale.

If you want to go that route,Micro Mark sells Pounce wheels for just that purpose..

[nkalanaga]

I've used both, and they do work.  The Micro-Mark wheels make sharper rivets than the watch gear, but spacing is a little wide for many N scale models.

When I posted my comment about casting I was thinking of DECK girder bridges.  Obviously, if one wants a through girder, it has to have details on both sides!  Even the mention of Walthers through girder bridges didn't tip me off, as the last through girder I bought was chopped and bashed into a deck girder...   

[robert3985]

I'm using Micro Mark HO scale rivets for my N-scale bridge rivets and bolt-heads on my kit-bashed twin Warren truss bridges on my Taggarts module.  They're a lot cheaper than Archer and I find them easier to apply since the decal base is not so super-thin.

I've also built several short bridges using Micro Engineering parts and kits, as well as the new Atlas C55 thru-plate-girder bridge, using Micro Marks rivet decals added to fabricated Styrene pieces.

[unittrain]

You might think about just making a few panels. Cast them, assemble the panel castings into a complete plate, then cast the plate.

This is what I think would be best, I could make a really detailed short section and cast copies. One question though would I have to pressure cast the parts?

[SkipGear]

Tony,
Both of those bridges are pretty HAWT!  Any chance they appeared somewhere else on TRW with a build thread?

Thanks, I never did a start to finish on it. Just various pics here and there as it came together. The biggest issue was making a plate girder and truss bridge that were the same length. The truss bridges are Kato bridges with section cut out, then the girder bridge had to match.  The bridge started with two truss bridges in the early 1900's, then in the 30's one of the truss bridges came down and was replaced with the girder bridge. As it is now, only the girder bridge remains.