I’m a recent convert from HO to N, and am using foam on a hollow-core door as benchwork for the first time. Up til now, I’ve really been happy with the foam/door approach. I’ve used caulk to adhere my roadbed to the foam, and my track to the roadbed. It’s working great, but here’s a little stumbling block I’ve hit.
With nearly all my track in place, I’ve started adding Caboose ground throws to control my turnouts.I thought I would just be able to use caulk to hold the ground throws in place, but it ain’t working so well. Of the two ground throws I installed as a trial, they’ve come loose several times.
I use Trackbed for my mainline, and cork sheet for my passing tracks (to provide a lower profile). Industry tracks will be laid directly onto the foam.
The two ground throws I installed were on passing tracks, so I used small rectangles of cork to mount the ground throws on. I applied what I thought was a generous amount of caulk, then used T-pins to hold the ground throws in place for 12 to 24 hours. I remove the T-pins and flip the ground throws a few times, and they come loose from the cork.
Is there a better adhesive to use for the ground throws? Or do I just need to lay the caulk on thick? (Thicker, I should say; I’ve put down a pretty good amount already.)
Your advice would be greatly appreciated. Thanks in advance!
Let me preface this by saying i hate using extruded foam for mounting track and turnouts etc. but as I see it your best choice would be to use the same caulk that you used to secure your track to the roadbed. DAP3.0 is the best stuff to use. It sets up really fast and hold great. If you did want to remove the ground throw you could gently pry it up with a knife.
I use Caboose Industries ground throws (HO scale), and I mount them on Woodland Scenics Foam Track Bed to match the height of my track which is also laid on Woodland Scenics Foam Track Bed.
I nail the ground throw in place to secure it and then cover the base (and the nail heads) with a thin layer of ballast.
Surprisingly, ground throws may not even be necessary especially for low traffic branch lines and switching layouts. I just slip a sliver of styrene under the throw rod and flip the points with my fingers. The styrene gives just enough friction to hold the points in place. I’ve been doing it for years with no problems but keep in mind I run a light traffic, slow moving branch.
Cut a small square of masonite or other thin wood carve out the foam so the throw is level with the switch throw and mount the ground throw to the wood first and them glue it to the foam.
I keep seeing more and more posts of people attaching things with caulk only to have it easily pop loose - I gotta ask, just what exactly are you using? Because anything I’ve ever attached needs significant force to remove, it doesn’t just fall off. If plastic could not be reliably glued to cork with latex caulk, my curves would straighten out when I ran a 4-8-4 over them as it all let loose.
I would not expect the tiny mounting surface of a ground throw to stand up to a lot of use, there just isn’t enough surface area to glue to the cork - I assume you mean the ground throw came loose from the cork, not that the cork pulled off the foam. Track nails and making sure some caulk was int eh holes migth be sufficient unless someone really manhandled the ground throws. I installed a new turnout last night and I had previously pinned it down with no caulk to check the alignment. When I spread the caulk over my roadbed with a putty knife, it forced a bit in the holes. It was a mistake to use the same holes when I pinned it in place to wait for the caulk to dry - a little was forced in the hole with the pin and when it dried the pins were held in, not impossible to remove, but with more force than I expected - usually they just pull right out. This type of thig, done on purpose, in addiion to caulk on the botton of the ground throw, might be enough. The small square of wood or masonite is probably even better - scre the ground throw tot eh wood, caulk the wood to the foam. It shouldn’t come off unless you really make an effort to pry it up. If it does, maybe you’re using the wrong caulk.
I’ve even used caulk to attach Tortoise machines right to the bottom of the foam - no plywood or anything. It defintely was not going to fall off on its own.
In summary - I have successfully attached the following material combinations using latex caulk: extruded foam to extruded foam. foam roadbed to extrded foam. cork roadbed to extruded foam. plastic to extruded foam. plastic to cork.
I have used 3/16" square spruce sticks(from your LHS or even Hobby Lobby). I glue them down with PL300(foam safe) glue. They are the exact match for the cork roadbed and provide a ‘solid’ base to spike the ground throws to. Our club used small squares of 3/16" plywood with a ‘kerf’ cut down the center for the throwbar. Again a ‘solid’ base that can be glued down and the grond throw can be spiked to.
We also attach Tortoise machines to that 3/16" plywood and glue the ‘pad’ to the bottom of the foam as needed. Never trust the foam for nailing/spiking/screwing…
I pour little pads of concrete around the layout, just like CP does.
Actually it is plastic molding. It is the same thickness as the cork roadbed. It comes in a 8’ length for about $1.00 a length. I cut about an inch off and paint it gray. Caulk it to the foam and caulk the groundthrow to that. Never had one come loose yet.
For track mounted directly to foam, I just cut out a little square in the foam an set my little pad of concrete into the foam. Just like Canadian Pacific does when they mount their track to the foam.[:)]
I cut little squares of plywood the same height as the cork I use under the track and glue them in place with caulk, then I use micro screws to hold the ground throw, talk about rock solid.
Gotta agree with Randy. You mention using caulk but don’t say which brand/kind. I’ve used the DAP Alex Plus Acrylic Latex caulk ($2/tube at HD) and have never had a problem with things pulling up.
My last few layouts have been cork roadbed over pink foam. I’ve used the cork to build up the rectangular area to raise it to the same level as the roadbed. I use N scale Caboose Hobbies sprung ground throws with a dab of Walther’s goo under it and two 1 inch brads put through the cork into the underlying foam. The brads I insert and about a 30 degree angle towards each other. Using that technique I have not had any come loose. Works fine. I used Goo because I had a tube lying around. - Nevin
I use the same method that I used for mounting servos and belcranks on RC model plane foam wings, and they had to take a lot of punishment.
Cut a square piece of plywood that your ground throw will mount to with small screws. About one inch by one inch. Carve out the foam so the top of the plywood is level with the roadbed. Next glue the plywood to the foam with epoxy. I use the five-minute type. Fill in around the plywood with caulking to smooth things out. Paint the plywood, then mount the ground throw.
Hey everybody, thanks for all your responses. Sorry I haven’t checked in sooner, but I’ve got this pesky job thingy …
A few have asked what caulk I’m using. The answer: DAP Alex Plus acrylic latex caulk plus silicone. As I mentioned earlier, it worked like gangbusters for holding the roadbed and track down. The only problem I’ve had is with the ground throws, which I figured was due to the minimal surface area or perhaps the smooth plastic bottoms (or both).
I only had a chance to speed-read through the thread, so I’ll have to check it out again. But I think I’m going to give one more try to what I’ve been doing; but this time instead of inserting the T-pins into the holes in the ground throw’s base plate, I’ll just run the T-pins in alongside the baseplate to hold it down. That should allow some of the caulk to well up the spike holes in the baseplate and perhaps provide a better grip.
If that doesn’t work, I’ll likely do what several of you have suggested: mount the ground throws to a piece of wood and “bury” the wood in the foam. Makes a lot of sense, even though it sounds just a bit more time-consuming than I hoped for.
Thanks again, everyone, for responding. I’ll let you now how it turns out. And if anybody has any other bright ideas, please share!
I keep seeing more and more posts of people attaching things with caulk only to have it easily pop loose - I gotta ask, just what exactly are you using? Because anything I’ve ever attached needs significant force to remove, it doesn’t just fall off. If plastic could not be reliably glued to cork with latex caulk, my curves would straighten out when I ran a 4-8-4 over them as it all let loose.
I would not expect the tiny mounting surface of a ground throw to stand up to a lot of use, there just isn’t enough surface area to glue to the cork - I assume you mean the ground throw came loose from the cork, not that the cork pulled off the foam. Track nails and making sure some caulk was int eh holes migth be sufficient unless someone really manhandled the ground throws. I installed a new turnout last night and I had previously pinned it down with no caulk to check the alignment. When I spread the caulk over my roadbed with a putty knife, it forced a bit in the holes. It was a mistake to use the same holes when I pinned it in place to wait for the caulk to dry - a little was forced in the hole with the pin and when it dried the pins were held in, not impossible to remove, but with more force than I expected - usually they just pull right out. This type of thig, done on purpose, in addiion to caulk on the botton of the ground throw, might be enough. The small square of wood or masonite is probably even better - scre the ground throw tot eh wood, caulk the wood to the foam. It shouldn’t come off unless you really make an effort to pry it up. If it does, maybe you’re using the wrong caulk.
I’ve even used caulk to attach Tortoise machines right to the bottom of the foam - no plywood or anything. It defintely was not going to fall off on its own.
In summary - I have successfully attached the following material combinations using latex caulk: extruded foam to extruded foam. foam roadbed to extrded foam. cork roadbed to extruded foam. plastic to
Caboose Industries manufactures its ground throws with a type of plastic called Delrin.
While Delrin has great stability qualities making it a good choice for otherwise delicate moving parts subject to wear it tear, it does have its disadvantages. It is difficult to bond to itself so when you put together its high level switch stand, for example, you have to use CA glue. It is also difficult to paint the targets because of the glossy surface.
I did some quick research to determine how to bond Delrin to dissimilar materials. Here is what I found.
Delrin is an acetal homopolymer (polyoxymethylene, or POM) resin manufactured by DuPont.
Acetal is lightweight and has excellent dimensional stability, machinability and high mechanical strength and stiffness due to its high degree of crystallinity.
One of the properties of POM that makes it difficult to bond to is its low surface energy. Acetal can be bonded to itself as well as dissimilar materials using Bondit brand adhesives manufactured by RELTEK LLC.
Industry producers of acetal generally report it cannot be bonded without special surface conditioning, due to the high degree of polymer chain alignment and hydrogen pairing on the surface.
I don;t see some fancy expensive caulk, I use Polyseamseal brand clear latex caulk. This is the second layout I’ve built this way, and no, the other one did NOT fall apart. It USED to be the cheapest brand at Home Depot but now it’s up to the same price as the DAP stuff - certainly not $6 a tube though, more like $3. All of my successful adhesion results I mentioned were using this brand of caulk, not DAP or Liquid Nails, and at no time did I use silicon or the ‘blended’ types of caulk which are mostly latex but contain some silicon. When workign on my old layout I somehow ended up with a tube of silicon caulk, which I prompmtly used to seal around the basement window. It also kept me out of the basement for 2 days because of the stink. Do NOT use silicon caulk for model railroad purposes, other than soem of those waterfall effects I’ve seen using caulk and fishing line. In any large quantity you’ll need a fan to ventilate the room.
I’m not going to dispute the importance of proper ventilation under many circumstances. But I just wanted to point out the DAP product I’m using (with silicone) has little or possibly no odor. I’ve been using it in a one-stall garage, and have not noticed an odor at all. And I don’t recall the price, but it was certainly less than $6 a tube. And even if it was $12 a tube, it would be a minor expense compared to what we spend on other stuff for our railroads.
Looks more than a little “quick research,” Rich. Thanks!
I was guessing at least part of the problem had to do with that smooth, shiny surface. I thought about sanding it before trying to caulk these first two in place, but decided I’d try without doing so first.
BTW, anyone notice that the Caboose Industries packages say the product contains a material known by the state of California to cause cancer, or something like that? Wow. Reminded me of that old George Carlin bit, playing the newscaster: “This just in: Scientists have discovered that saliva causes cancer. But only if swallowed in small amounts over a long period of time.”
Anyway, I re-adhered my ground throws last night using copious amounts of caulk (enough to well up through the spike holes). I also used a needle to spread a bit of caulk around (and over) the edges of the base. Can’t wait to see the results after work.
Hey, that’s great to know. I was within seconds of buying a low-temp glue gun just the other day (costs less than $5), then backed off because I was afraid even the low-temp glue may wreak havoc on the ground throw. I’ve never used a glue gun before, but isn’t even the low-temp at 400 degrees or something like that?
Anyway, this will likely be my second option if I’m not satisfied with the extra caulk approach.
