In the Kalmbach book on Benchwork, it shows the method that Bill Darnaby uses of simple 1x2 supports out from the wall every 16" with nothing else but 2" foam as the benchwork. A beautifully simple system for railroads with no elevation changes. Well, I need a grade of up to 4% and I was wondering if 2" thick rigid foam would deflect enough to make that work?
The majority of the shelf would be at a fixed height on risers while a trackwidth of foam at the front would be on a downgrade of 2% or 4%. Would the foam snap instead of bending smoothly? Or should I actually break the foam and use plaster/sculptimold/etc to patch the transition? Sanding down flat foam to a grade does not seem to be a great way to get a smooth grade, nor does cutting the grade out of the foam. What are your thoughts?
A long enough piece of 2" foam would bend – after all, a 1 foot piece of prototype rail would not bend, but a 39’ lenth of rail will bend; likewise a 1 foot piece of 1x4 lumber won’t bend, but an 8 foot length will – but I am not sure you’d get the bend you want in the distance you want it to bend in.
An extremely lengthy 4% grade might be possible, and indeed the rigidity of the foam would give you very nice natural easement curves at the ends of the bends, but you do not say what your distance is for the beginning and end point for this grade. In most cases of home layouts I suspect the distance is too short to get the bend you want with the lengths of 2" foam available.
I have 2" foam on my entire layout as the subroadbed, and while I have the same benchwork book to which you are referring, you would have to have at least a full 8+ foot long piece of the foamboard in order to really get the kind of elevation change you are looking for.
So if you are going to make a loooong run you might be able to cut along the long edge of the foam and gently lift it while shimming up the underside somehow.
[I wouldn’t even attempt this if you aren’t going to have a plywood base underneath the foam. I believe Bill (and Lou Sassi in his scenery book) just built a simple 1x3 or 1x4 open grid bench and glued the foam to the top of it; this will definitely make it harder to shim up the foam riser section.]
Yes, even steel reenforced concrete bends when it is long enough.
For our model railroading purposes, I would say 2 inch foam does not bend. We made lots of very rigid cosplay props from it over the years, like this staff.
First of all [#welcome] to the forum. You initial posts will get hung up by moderation.
4% is on the steep side for grades. Are you sure the engines you have and the rolling stock you want to use will make it? You may want to test first.
Somewhere on Youtube, Ken Patterson has a video (the are impossible to search by key words) where he made a grade using 2" layers of foam, and a laser light level. He uses pruning saws and electric chain saws. He made it work.
I glued 1" on top of 2" and with a sureform and sanding made a 2% grade. It was hard to make it an even slope. I am satisfied but I will never do that again.
Besides it’s inherent stiffness, how would you even get 2" foam to bend? Maybe you could screw it down with fender washers and then elevate the upper end, but I think the washers would rip through the foam.
Go to your local Lowes or HD and see how well 1" rigid foam bends. Should bend a bit better than the 2". Then just sandwich it to make the 2" to match your base foam. Stagger the joints in the foam ‘cause you need 8’ length of run for a 4" rise @ 4%
The only way you could possibly do it would be to secure the foam to a plywood base with the proper adhesive - except for the thin strip you want to elevate, which you would leave unglued. In any case, foam this thick doesn’t “bend” in the way the OP might be hoping.
I’ve made a couple of smooth grades from foam by cutting the foam into a long wedge. It works better if you cut the underside and leave the top smooth. You do have to deal with transitions from level to grade and back to level at the ends.
Technically, any material deflects under load. Material cannot support a load unless it deflects. That’s why bridges and house floors are way overbuilt for the loads they carry. Deflection to any significant degree is unacceptable. Post tension cable bridge decks rely on transfer of deflection loads to steel cable anchor points, vertical loads become horizontal tension loads. Your car will still move up and down as other vehicles drive by you.
Extruded foam is pretty rigid. 2" foam is pretty much overkill for the loads imposed by HO scale model railroads. Heavy locomotives weigh maybe 500g (around a pound).
Rather than worry about sufficient flexibility I’d be more concerned about supporting the deflected sub roadbed in its bent and sloped configuration. If you think about the supports you need under the inclined 2" foam then using 1/2" foam sheet on top of whatever supports you elect to use makes more sense. 1/2" foam is pretty rigid over spans of less than a foot. You only need to use 1/2" foam at the transitions from horizontal to sloped and back again. The 2" foam inclined ramp itself wouldn’t need to be bent for a constant grade.
Carving a consistent grade into layered 2" foam seems unnecessarily laborious. Getting a smooth top surface would take skill and time. However, on reflection, only the transition needs to be “bent”.
Add it all together and Woodland Scenics Riser System starts to look very attractive. Gives a flat surface for your track underlay, comes pre moulded in 2%,3% and 4% inclines AND starter ramps. Easily curved and almost as easily cut. By combining 2% and 3% inclines and ramps you can build a 1% grade by reversing the 2% on top of the 3%. Other combinations are feasible. It isn’t cheap but then it is very good stuff. For long grades using 2" foam you could just get a package of 2% ramps, use one to start the incline and another to end it, makes fairing in the transit
You can get a bit less than 2% by streching the inclines a bit on WS stuff. Also this kind of thing helps with the easements. Keep in mind that even a 2% incline man not be liked by your engines under load. My last layout was flat as far as the accual track excenpt for a small run of 4% plus on a side run up to a yard less than 2’, all worked great. New layout 2% grades, major issues on long trains as the 2% is about 14’ long. Luckily layout was intended for 7 car trains only but I was just playing around.
Incidentally, kerfing or relieving the back side of this foam works analogously to how it does in wood. You can bond a straight piece of flexible stock to the ‘back side’ once you have the curve jigged, if you want it to ‘hold alignment’ for installation – just shim that layer. Use expanding foam or perhaps ‘foaming glue’ injection if you’re concerned with any sub grade ‘voids’.
(This is for closed-cell elastomer foams, not beaded ‘Styrofoam’ or its like – but we all know that instinctively already)
But as mentioned above, seems like a lot of unnecessary labor when you can just get the WS risers and use foam tack or hot glue. To each his own I guess [:)]
And when did I EVER eschew sesquipedalian technological overkill? [:-^]
But it is one of the best ways to get precise roadbed line and surface if that’s perceived as valuable… for example setting up for superelevation, transition spiraling, and vertical curvature all at once … to be negotiated by Proto 2K PA trucks…
One issue with kerfing foam sheets is the snap effect. Any cut line is highly likely to snap right through the sheet (the cut line focuses tension forces to far higher levels than affect the uncut surface because the material is brittle).
Kerfing works with wood, plywood, mdf and hardboard because all of those products are fibre matrix structures and inherently flexible (trees by evolution for easily observed reasons) . Extruded foam really isn’t any form of matrix. There’s no continuous fibre despite being “extruded”. It is also very inconsistent internally with weak spots and lumps everywhere if you cut into it.
Styrofoam sheet isn’t made with bending in mind. You mould it or mill it if you want it shaped.
Edit: just working on kerfing and bending my 1/8 hardboard fascia onto my foam layout. Kerfing the inside of the bend would work for foam sheet. Basically you’re cutting out the compression side so should not develop any snapping force. For wood, you tend to kerf the “back side” so as to preserve the face finish. So kerfing the track side of the bottom of the grade and the underneath at the top should work. The bottom will need fairing with foam putty or drywall mud but the top should stay smooth. You want a very gradual horizontal transition anyway. At both ends.
