Freemo - N Module help

[PiperguyUMD]

Hello All,

I've been working on several modules, with the intention of being able to set them up in a loop in the garage - see pic below. I know that the standard isn't intended to do this, primarily because of the accuracy needed to make them line up, but I think I may have figured out a way to make this work! I've been dabbling in woodworking for a while now, and I've built the faceplates for all of my modules. I'm quite confident they are consistent in their dimensions. My original plan was to laminate two pieces of 2" pink foam form the surface of each module, but despite my best and most careful efforts, the discrepancies in the shape of the foam was enough to throw off my plan...



So in discussing this with a friend at church, he mentioned another friend that had a sign shop - including a 5'x10' CNC table that he frequently uses to cut foam! To boot, the guy at the sign shop is a model railroader! Enter the new game plan - have the module surfaces CNC cut to perfection - meaning that if I'm careful when attaching the faceplates, I could in fact assemble the modules in a loop. Right!?

Here's where I need a hand if anyone has the chops - If I send someone sketchup files of the shapes below, could someone put them in some kind of vector file for me? Thanks!

[railnerd]

The CNC machine should help... I will be using one to help a friend build a helix for his home layout.

All that said, a tape measure and Norm's advice to measure twice and cut once should have been sufficient, right?

-Dave

P.S.: Be aware that foam also has a tendency to change shape over time as it releases trapped gasses within the material.

[railnerd]

If you would like a DXF— you should be able to export that from SketchUp, though, right?  Will you also CNC the plywood, too?

-Dave

[PiperguyUMD]

If you would like a DXF— you should be able to export that from SketchUp, though, right?  Will you also CNC the plywood, too?

-Dave

Thats what I thought, but I'm using the free version of sketchup, which apparently won't cooperate with that plug-in.

I thought about CNCing the plywood, but I think the big thing is getting the angles in the corner modules right. I plan on making jigs so that I can have some consistency when gluing the endplates to the foam.

[Bendtracker1]

So just a quick question?
Are you planning to have just the foam layers spanning between the end caps with no support below the foam?

[PiperguyUMD]

So just a quick question?
Are you planning to have just the foam layers spanning between the end caps with no support below the foam?

Yes - 4" of foam, and 1/8" fascia on each side should be plenty strong right?

[Bendtracker1]

From a cabinetmaker's point of view, no.
Even though you laminate them together, there is still no support.
In time the foam will sag and could change in shape as railnerd stated.  The 1/8" fascia won't add much.
Do yourself a favor, when you have the cabinet shop CNC your foam out, have them CNC a piece of 1/2" plywood the same size and then laminate the foam to the plywood.
Then you can glue it and screw it to your end caps.
At least this way, if anyone decides to lean on it, or if you lose your balance, or something falls against it the foam isn't going to snap.  Don't take a chance.

If you're going for light weight, then have them do a cutout in the plywood.

[PiperguyUMD]

From a cabinetmaker's point of view, no.
Even though you laminate them together, there is still no support.
In time the foam will sag and could change in shape as railnerd stated.  The 1/8" fascia won't add much.
Do yourself a favor, when you have the cabinet shop CNC your foam out, have them CNC a piece of 1/2" plywood the same size and then laminate the foam to the plywood.
Then you can glue it and screw it to your end caps.
At least this way, if anyone decides to lean on it, or if you lose your balance, or something falls against it the foam isn't going to snap.  Don't take a chance.

If you're going for light weight, then have them do a cutout in the plywood.

Good points. This actually gives me several ideas! Thank you for the feedback!

[Bendtracker1]

Yup, good luck.

[samusi01]

I use Adobe Illustrator for making my vector files. An alternative would be Inkscape. Not having any experience with it, I should imagine you can output to PDF or whatever is necessary for your CNC machine.

Having cut foam on a CNC machine, my recommendation is to pay close attention to tool speed: too fast means you'll not get a clean cut, but it'll melt the foam. Ask me how I know...

[railnerd]

Yes - 4" of foam, and 1/8" fascia on each side should be plenty strong right?

nope. 

[Steveruger45]

Like others have said the “foam alone” or almost alone will not be structurally strong enough for long enough.
I would recommend to use a box construction technique using 1/2” plywood 3” wide and suitably cross braced every 12 to 16 inches and mount/glue  the foam on top.  That will be plenty strong and light and give you some structure to mount legs in the corners. The box construction will give you underlayout space for the wiring too.
If you want to also hide/protect the foam edges, which is a good idea to do as well, then mount a 1/8” facia all around to a height to suit your terrain intentions and protect the butt together ends.

[SandyEggoJake]

Welcome to Free-moN.

+1 for some type of facia.  And warpage / shrinkage of foam is not the only issue.  It is understood you plan to use such in your garage.  But if & when you do need to move or store them, a rigid wood fascia will serve you better to protect all your hard work. 

If a goal is to save time in your build, you might consider making the legs out of EMT (see http://www.nlandpacific.com/Standards.html)

[Lemosteam]

@PiperguyUMD , can you export thecad file of each foam panel as a .stp file?  If yes I an make a drawing for you and export as a DXF or DWG (both vector files I believe) and email them back to you.

PM me if you can export the .stp files and I will share my contact info.

[samusi01]

@PiperguyUMD, two other things spring to mind regarding foam and CNC routers:

First, my experience is limited to 1/2" foam, not two inch foam as you are planning on using. The CNC router I use has a vacuum attachment and it tends to lift the foam (and 1/8" hardboard)off the machine bed if the material is not well secured to the bed.

Next, I've cut my subroadbed out of 1/2" MDF on the aforementioned router. One thing I do is have a first pass with a pointed tool (like a 60 deg point) and I scribe my centerlines on the material about 1/16" deep. I then switch tools and cut the subroadbed out of the material. I don't know how far along your plan is or if it'd work at all well with foam but I figured I'd throw it out there for you to consider if you haven't already. The attached image shows a recent job with the centerline grooves highlighted by pencil.

Sam