Looking for Max Shim Thickness for Peco 100 Guard Rails

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Well-Known Member
Bending Experiments

Over the past few days I've been looking at this 'bending the guard rail' idea, and thus far I am not that enamored with the idea. Certainly it would save a lot of time, but I've run into a few problems.

Spacer Piece:
First off I though it would be wise to find a good solid piece (metal) to place between the track and the guard rail such that I didn't over-bend the guard rail. I found in my closest approximation that the stock gap is about .050". I happen to have a nice piece of tough steel plate that measures about .030" thick. Using this plate thickness would leave me with a .030" gap which II felt was just right considering that I had done previous experiment with .010" and .020" shims into that .050" gap,....equals .040" or .030" gap on finished turnout.

I had a number of different sets of pliers, including several sets of line-man pliers, and I had an older screwed up turnout to experiment on. I started off squeezing the guard rail with one face of the pliers and the metal rail itself with the other. First off I needed to lightly round off the very sharp edges of one squeezing face of the pliers as they would dig into the relatively soft plastic of the guide rail. Sgueezing directly against the metal rail did NOT appear to be any problem with dislodging the rail, nor marring it up. But even with the smooth face (no 'teeth' in that direct gripping area of my pliers), I still marred up the plastic guard rail (admittedly it was the outer surface of my flangeway), but is still was a little unsightly.

i subsequently discovered that I was NOT getting my flangeway slot down to the dimension of my spacer piece (.030"), but rather to only about .040". What might be the problem? I thought perhaps like a lot of bending exercises it need to be over-bent slightly to end up with my desired slot dimension. I subsequently inserted a slightly thinner piece of metal and achieved that goal,...but it was not a nice smooth looking guard rail any longer, and it had actually peaked up in a few spots that would need filing down.

I was (am) getting discouraged with this ideal and went back looking at the metal shim idea. While this looks really slick, it not as easy as it looks to get a good firm (non-glued) fit.
..and the metal shim is not readily 'trimmable' like the plastic shims.

I believe I may return to some plastic shim experiments,...wish Evergreen made black plastic strips.


New Member
Thank you for bringing this problem to light. I have some peco curved switches and have always considered the track jumping caused by weight or wheels. Never looked closely at the switch itself. I understand that your main concept is to shim the guard rail.
I'm just thinking out loud here.....
What if you could remove the guard rail, smooth down the ties and replace it with a newer (longer) section of rail. Shimming the newer rail higher could also be done as suggested somewhere. Not sure what adhesive you could use. I've not tried this so forgive me if I'm pushing this over the edge. Just a random thought....


Well-Known Member
Shim Experiments

2) Styrene strips:
I had some .015” thick strips but they were 1/4” tall, but then I found some Evergreen ladder strips, and some particular ones that were .020 x .040. I tried gluing these in to the flangeway of that Sm Peco (figured that if I could make the Smaller radii Peco work that would prove the effectiveness of this approach).

It did work, for all of the steamers except the 2-10-4. And the .020” thickness seemed to work also.

I had a problem getting the styrene strip to fully glue to the guard rail. You can probably see that its not fully bonded in its center portion. Need more careful gluing, and perhaps some better glue than the styrene bonding agent I used. I'm sure my old Tenax 7 would have done a better job. It was also tough to get the bonding solution on JUST the face between the guard rail and the styrene strip,...invariable some solution would end up on the outer side disrupting that nice smooth side.

NOTE !! I did discover something about the height of this shimming piece. When I first glued it in I paid particular attention to NOT let it be any higher that the other tops of the rails. As it turns out that was a little too low. When I popped it off and reglued it higher, it worked even better. I am now convinced this shim piece needs to be a bit taller than the adjacent rail, particularly for our very smalled flanged wheels on modern American equipment. Plus, this will not negatively affect matters as there are no portions of our locos or cars that project down this far directly adjacent to the inside rim of their wheels.

I think I am going back and rerun my experiments with the plastic shims, both with .011" & .020" thick ones I have on hand. Plus I believe I now know how to properly glue them with superglue. To me it seems to make a little longer, smooth slot. And I want to keep them flush (not proud) of the surrounding track, so those track cleaner cars/devices can run over them cleanly.


Well-Known Member
I was (am) getting discouraged with this idea of bending the guard rails, and I went back looking at the metal shim idea. While this looks really slick, it not as easy as it looks to get a good firm (non-glued) fit.
..and the metal shim is not readily 'trimmable' like the plastic shims.
I believe I may return to some plastic shim experiments,.
I'm going to run some new experiments with the plastic shims. To me they seem to offer the longest, smoothest slot transition.

I want to reaffirm the minimum thicknesses that are acceptable, best steps in applying them, and which types of turnouts are to be considered ???

I'm trying to set up the most challenging, while simple track plan into which to place each of the different turnouts under question. Here is what I've come up with,...

The locos will come down a relatively straight section that then turns left thru a 24" radius section of track. It then must immediately enter the turnout in question (short Y shown here) and go off in either of 2 directions,...diverge off onto the right hand track/siding, or enter the curved track to the left which is a challenging 22" radius curve.

This reversal of curves should put the loco to the challenge of negotiating the turnout while challenging the turnout to steer the loco thru without picking-the-frog, and/or derailing in some other manner.

(I'm already surprised at a few initial trials without any shims)

I started out with the short 'Y' turnout type as I have utilized quite a few on my layout plan,...and I figured its relatively tight curves might make it a challenge, particularly where I have several in a row right after one another.

(I also have a Roco brand Y in there to test, as I have a few of those on my plan)


Well-Known Member
the test Loco lineup:

1) 4-8-2, IHC, C&O Mountain (made in Solvenia). Has a very very mild case of cookie cutter wheels.
I have quite a number of these locos as they run very well, they were relatively cheap, etc

2) 4-8-2, Bachmann, C&O Mountain. Has modern small flange wheels.

3) 4-8-4, Bachmann, Northern Santa Fe, I have 3 of these but was not able to get them operational for this test

4) 4-8-4, Broadway Ltd, Northern Santa Fe,

5) 2-10-4 BLI ,T-10, C&O Blueline model

6) 2-10-4 BLI, T-10, C&O paragon 3 model

7) Number of long articulated locos, but did not test these as they likely wouldn't have problems because of their articulation.


Well-Known Member
As I had mentioned above, "I'm already surprised at a few initial trials without any shims".

Peco Short Y turnout (no shims)
The first test I made was with the Peco short Y. My initial thoughts were that this turnout would give me more problems than it did, primarily because of its relatively tight radi. Turns out it give me some sporadic problems with 2 of the engines.

Naturally the 2-10-4 locos did derail most of the time, but surprisingly ONLY on the diverging route that bears off on the opposite direction from the curve leading into the Y. ( I term it counter-turning). If the loco continues in the already curving direction, there was no derailments, even when continuing on in a 22" radius curve.

The Backmann 4-8-2 mountain loco was another problem. It also derailed when 'counter turning', but did not when continuous turning. I suppose this was due to its very fine wheel flanges? I definitely need these to work well as I have at least 3 of these locos (I really like these flying pump, vandy tender, C&O mountains).

Another welcome surprise was the BLI 4-8-4 that did not show any signs of derailing on this turnout, nor many yet to be reported,...even with its fine wheel flanges.

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