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mageus

DIY viaduct?

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mageus

Has anyone here scratchbuilt viaduct?  I'm going to try to make some for Kato track.

I did some measurements with a digital caliper.  From the top of a pier (not including the s-joiner or gap) to the track bed is 12mm, which happens to be how thick "1/2" inch MDF is.  I was going to cut curves using a router and circle jig.  15"-16.3/8" double track roadway is 58mm wide.  With catenary bases it's 73mm wide.  I was going to make a 75 mm wide viaduct base.

I'll use 1/8" MDF for the sides of the viaduct.  I was going to kerf it to allow it to bend (cut slits along the height).  I have a conical bit for my dremel tool that can cut fine triangular lines.  I'll space the cuts the same as the panel markings on the Kato viaduct.
Since the base is 1/2" I'm hoping glue will be enough to hold the sides in place.

For piers I'll take a 2x4, round the edges, and cut it to various heights.  I can cut the top at a slope to match the grade I need (about 4%).  The base can be wider than the viaduct, with a slot cut in the top that the the viaduct will sit in.

I'll drill holes in the top of the piers.  I could either screw the viaduct down, or just use pins to hold it in place.  The track would just rest on top of the viaduct.

Couple questions:

- Can someone tell me the height of double track viaduct in mm?  Total height, from the bottom of the viaduct base to to top of the walls.

- Can someone tell me the width of the 'panels' molded into the side of the double viaduct walls?

- I was originally going to make one or two long viaduct pieces to hold several track segments.  I then thought of making viaduct for each piece of track to allow flexibility in the future.  Should I line the viaduct up with the track ends, or should I overlap track and viaduct by 50% to give stability to the track joint?  The pier would sit under the track joint in either case.

 

Any other thoughts?

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macdon

I did.

 

I had a lot of spare curves, so I started building my Byodo-in 360 layout with cardboard viaducts and laminated foamboard piers. I eventually replaced all the diy cardboard viaducts with kato viaducts but my piers remained foamboard as the kato piers didnt have the exact height increments I needed.

 

post-1282-0-27732800-1387584181_thumb.jpg

 

My 3' x 7' freight layout still has diy viaducts - plywood flooring and laminated card sides for kato 20-150 curves. Since it was typically a constant height, I just bought the kato single piers and glued them under the plywood viaduct floors.

 

post-1282-0-84707700-1387584200_thumb.jpgpost-1282-0-80915400-1387584220_thumb.jpg

 

My 4' x 10' shinkansen layout also has a diy viaduct - but just for the double crossover

 

post-1282-0-97709200-1387584243_thumb.jpg

 

Not entirely diy, but I did modify a kato double track straight for a kato turnout also in my shinkansen layout

 

post-1282-0-05096900-1387584160_thumb.jpg post-1282-0-89839400-1387585185_thumb.jpg

 

Mardon 

Edited by macdon
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cteno4

I was just thinking about this this afternoon when knoodling on my btrain shorty layout design. I want single viaduct at less than r249, so will need to make them. Should be simple as Mardon has done, ply, mdf or foamcore then 040 styrene sides.

 

I can measure up he viaduct for you. Sides are about 040 - 060 styrene. The vertical lines in the side could just be scored with a matte knife or plex scorer. Score a larger sheet and then cut the strips off. Dremel with a router plate and sharp tip along a straight edge would work well too.

 

The piers are closer to 1x2 stock for the concrete Y piers. You can easily cut them out of 3/4" stock in the Y pier shape and round the edges with the router.

 

Might be easier to just cut the bases on a band saw than router with the circle jig. Spindle sander then makes short work of smoothing it all out if you have access to one.

 

1/2" is plenty of surface to attach the walls to.

 

Router will work well to put the small rabit notch just below the wall.

 

I think either way would with track sized sections or long stretches of viaduct. If you do short sections then you will need supports at the joints and a small base plate under each joint may be necessary. Could do a little biscuit joint between pieces to line them up. Viaduct pieces rely on the unijoiners and up to 3 S joiner pieces per joint to hold them firmly together.

 

Cheers

 

Jeff

Edited by cteno4

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mageus

I finished the bases.  I used a a circle jig with the router (long board with an adjustable pin at one end) since I was cutting 2' boards.  This gives 90degrees of the 15/16" double track.  I have enough for a full circle.  No need to finish it since the router cuts perfectly.  This method makes it easy to cut tons of bases of the same radius at once.

 

The reason to score the sides is to kerf it.  1/8 MDF won't bend to a 17" radius curve by itself.  I'm going to try the tiny pilot tip of a forstner bit to score 1/32" lines.  I can use the fence to easily stagger the lines.  I'll score a whole board at a time, and then just cut strips out of it.  This should (theoretically) be the easiest part of the project.  However, if it doesn't work, I'll try 0.04" styrene.  If I have time I'll rabbet the lower edge to match the Kato part.

 

I'm using 2x4" because I was originally going to have the piers wider than the viaduct and slot the tops so the viaduct is cradled.  I'd tape the piers to my layout.  The viaduct would be loose but supported well.  However, now I'm planning to use #4 wood screws to secure the viaduct to the piers.  Hopefully my drill press is accurate enough to place reproducibly spaced holes.

 

I've decided to match the viaduct lengths to the track segments.  That makes it easy to move things around since this is absolutely not a permanent setup.

 

- Jeff, how tall is the double viaduct (from underside to top of the sides)?

 

- Mardon, how much gap do you have between your viaduct sections?

 

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cteno4

Magnus,

 

yeah once you get the router template set up you can whip out a bunch!

 

sorry i missed you were going to use 1/8" mdf for the side walls. thats probaby way too thick for visual reason as well as the practical ones you mention. I would look at 040 - 080 styrene. so much easier to work with on something like this. if you go to a big plastics shop or sign making shop you can pick up a 4x8 sheet of 020-060 styrene for like $8-20 and you will have enough to do lots of stuff! very handy and super cheap like this. You can just roll a sheet up to fit in your car! side wall thickness 050" on the actual viauduct. the grooves are 1.21" on center with about 040 gaps so the panels are about 1.17" long. 8 total evenly spaced and gap between two viaducts makes a similar space to make it all even. there is a little 060 wide bump out behind each seam that is maybe 020 high.

 

here are the full dimension. i did them in mm as its a lot faster and easier with the calipers. also some picts.

 

cheers

 

jeff

post-24-0-67169100-1387654694_thumb.jpg

post-24-0-64181200-1387654709_thumb.jpg

post-24-0-00506100-1387654728_thumb.jpg

post-24-0-26058600-1387654740_thumb.jpg

post-24-0-53249900-1387654762_thumb.jpg

Edited by cteno4

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mageus

Jeff, thanx a ton for the info.

Attached are pics of my progress so far.  The width is slightly smaller than stock (by mistake), just barely enough to fit catenary bases.  The 5mm pier was a challenge.  (Blade guard?  What blade guard?)  Now I just need to make a jig to drill the piers at the requisite 2.3 degree angle.

I scored the MDF with the router, using 1" spacing.  It worked well, but MDF is pretty stiff.  I originally wanted to stagger the inside and outside lines by 1/2", but mistakenly made them overlap.  Even with a cut on both sides, it took a worrisome bit of pressure to bend the MDF.

Yes, styrene is much easier to work with than MDF.  Guess I just needed an excuse to pull the table saw out again.  Question is:


- How does one glue styrene to MDF?  PVA? CA? Gorilla?

post-1971-0-44972500-1387820684_thumb.jpg

post-1971-0-43290200-1387820687_thumb.jpg

post-1971-0-24143300-1387820690_thumb.jpg

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cteno4

Mageus,

 

you are most welcome. looking good. the catenary bases on the viaduct actually just fit inside the walls, so just right there!

 

yeah curving mdf like that is tough. might try wetting it a bit to see if that will help it bend smoother. my worry with the mdf and the grooves is that it will want to bend more on the grooves than the rest and the individual segments wont bend as well.

 

if you rough the styrene pva might work ok. CA will seep into the wood too much to do well (gel helps, but still can be hard to get enough surface area bonded). some folks will impregnate the wood ends with pva or other primers and then sand flat then use CA on that smoother surface. gorilla sticks pretty well to styrene, but use sparingly as once out of the joints its a mess to clean up.

 

make a little zero clearance insert for your table saw (usually can just cut one out of ply and pop in) to cut the styrene. cuts much cleaner with a zero clearance, less chipping. 

 

great work, fun watching the progress!

 

jeff

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mageus

I ditched the MDF idea.  It does bend in segments.

 

I always use a zero-clearance throat plate unless I'm cutting a bevel.  I've heard you shouldn't cut plastic with a wood blade since it melts into the blade and is hard to clean.

 

I ended up cutting 1.5mm strips out of scrap pine.  It bends and follows a 17" curve great without any gaps.  2mm bent OK, but is a little thicker in terms of looks.  It will be easy to glue to the MDF bases, and I can still rabbet the lower outside edges of the viaduct to match the stock parts.  It won't be as durable as styrene, but neither is the catenary.

 

I won't score the strips since they are pretty thin.  I'll probably line them after painting and before clear coating.  I use mechanical pencils to panel-line my plastic models.  Faster than doing a wash and lighter than a pen.  Wonder if that will look good here.

 

I don't think I'll scew things together.  The curved bases ended up being just a little too short.  24" is barely too short to fit 90degree of 17" curve.  I'll end up with 1-2mm gap between bases.  I'll try to compensate by overhanging the sides.  However, it would be a pain to get all of the screw holes to line up properly.  I'm thinking double-sided tape, that rubbery grey 3M stuff with the red backing.  Sticks firm but comes off easy.  That stuff is basically the precursor to 3M Command tape, and much cheaper.

 

As always, this project grew to way more than I expected.  Shoulda just layed out for the Kato stuff.  But where's the fun in that?

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cteno4

hey sounds like a good solution. i was going to say veneer as well as you can get it in 7/8" rolls cheaply at varying thicknesses.

 

yeah i thinks screwing may be too much. another idea would be to just put a couple 1/8" dowels sticking down at each end of a viaduct piece like 1/4" or so and then make a 3/16" holes in the pier tops for them to go into. would give you enough hold to keep things in place but give you a little wiggle if needed.

 

gap sounds fine, its hard to get things much lower on tolerances doing stuff like this unless you have really good gear and take a lot of time being ultra careful. doing a tiny overlap at one end with the side walls can get rid of it as well and just sand down to where its perfect. you wont notice the slight gap inside on the floor.

 

carbide blades have not melted styrene for me or plex, but they will tend to chip them some even with a zero clearance. the good plex baldes hae every other tooth beveled off a tiny bit to i guess clear the plastic and get a smoother cut and it seems a less chipping.

 

ive cut thin styrene with a cheap plywood blade as well. you tend to get a little melting and burring along the cut edges which you can just rub off. ive never had any big melts onto the blade, but this is only going thru like 080 stock at most. im lazy all the time with the good wood carbide combo blade (80 tooth) and will rip 1/8" plex all the time. not the smoothest edge, but i just take it on the oscillating belt sander to clean it up. blade shows no bits of melted plastic on it.

 

lines sound like that should work fine. just hit with some dull coat afterwards to fix them. visually from any distance the depth is not going to be seen and it just looks like a line. they also have a faint raised line horizontally half way up the panels as well (you can see it in the picts above).

 

hey you are having fun with this! and if you ever want to do non standard radius stuff you have to do this sort of thing! You have helped me think thru how ill do mine for my btrain shorty single track shinkansen viaduct where ill be using tight radiuses.

 

cheers

 

jeff

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mageus

Yes, I decided to overcut the sides and them cut them to length after gluing them to the bases.  I have a flush-cut saw that works perfectly.  I'm  actually surprised at how accurate things came out.  At 17" radius there was <1mm error in the 45 degree circumference.

 

The dowels have the same alignment issue.  However, I thought of routing a slot under the viaduct and using either dowels or screwheads in the piers to sit in the slots.  It's easier to guarantee alignment in only one axis.  Routing a curve using the table is tricky but doable.  You can't use a straight guide.  I'm thinking of opening the router fence mouth so some of the curve rests in it, and then 'spin' the part in the opening.  Otherwise, I'll have to route from above using an edge guide cut to the same radius.

 

I'll prime the pieces, and may just leave them like that for a while if I get lazy or busy.  The single track viaduct is grey anyways.  Unless I want to whip out the airbrush, spray can is an easy job.  Not too hard to stack them all up and line them after painting.

 

Yeah, although it's a lot of work it's tons of fun.  It forced me to add some parts to the table saw and tune things up.  I took some days off for the holidays, so I've been able to work on this.  Definitely need to custom it for anything other than 15/16" in double track.

 

 

 

 

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tdconep

Thanks all for this thread. I have been looking for ideas to cut some costs on my next project. I love Kato track and especially their turnouts, but the cost sure mounts! I think I favour the styrene option for the sides. MDF just doesn't bend to the curves as well and I have difficulty getting a good painted surface because the MDF just sucks in the paint!

 

We also lie in the sub-tropics (Brisbane Australia) the climate is much like Florida and I worry about MDF swelling. Has anybody who has used MDF in this sort of project had any problems with swelling in high humidity?

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kvp

If you fully paint an MDF board with water tight acrylics, then once dry, it could not absorb water at all. Styrene also needs a good coat of UV resistant acrylic or other paint to avoid UV damage and yellowing. I'm planning to go on the plywood with styrene sides way too for a ttrak module as putting a length of 10 mm plywood across an upside down ttrak module is easier than hacking Kato viaducts or station plates to be level with the sides and this way it seems easier to build on top, then just wrap the visible edges with 1mm styrene and paint everything.

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gavino200

I did.

 

I had a lot of spare curves, so I started building my Byodo-in 360 layout with cardboard viaducts and laminated foamboard piers. I eventually replaced all the diy cardboard viaducts with kato viaducts but my piers remained foamboard as the kato piers didnt have the exact height increments I needed.

 

attachicon.gifIMG_1221.jpg

 

My 3' x 7' freight layout still has diy viaducts - plywood flooring and laminated card sides for kato 20-150 curves. Since it was typically a constant height, I just bought the kato single piers and glued them under the plywood viaduct floors.

 

attachicon.gifIMG_1315.jpgattachicon.gifIMG_1316.jpg

 

My 4' x 10' shinkansen layout also has a diy viaduct - but just for the double crossover

 

attachicon.gifIMG_1451.jpg

 

Not entirely diy, but I did modify a kato double track straight for a kato turnout also in my shinkansen layout

 

attachicon.gifIMG_1189.jpg attachicon.gifIMG_1190.jpg

 

Mardon 

 

 

That turnout is amazing. I thought it was factory. I actually saw it a few weeks ago while doing google image searches for layout ideas. I've looking out for it in stores. I figured it was a Japanese market special or something. 

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medusa

That turnout is amazing. I thought it was factory. I actually saw it a few weeks ago while doing google image searches for layout ideas. I've looking out for it in stores. I figured it was a Japanese market special or something. 

 

Same here. I just was starting to ask you which Kato order number this is... ;)

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