Looking for Max Shim Thickness for Peco 100 Guard Rails

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I bring this up as an individual subject as I am sure there are LOTS of Peco Code 100 turnout users out there. And there are likely LOTS of those users that have experienced some derailing problems in some situations

There is a relatively simple modification that will improve their performance. It involves the guard rail 'slot' across from the frog area. I'm almost surprised that Peco themselves have not offered some sort of 'fix kit'

The flangeway across from the frog is just a bit too large for the needs of most modern American train models. This excessive width allows the axles to shift away from that outer rail and over towards the frog slot. The wheel(s) may then encounter the tip of the frog and ride up over the tip of the frog, resulting in a derail.

There have been a significant number of folks who have shimmed up this flangeway in the guard rail to help prevent this problem. I've seen some folks that report the use of shims of .010".

I'm searching for what might be other suggestions/experiences for a maximum thickness that might be used??
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Well-Known Member
Fine Tuning Peco Code 100 Curved Switch Check Rails

Using brass shim on guard rail,..pretty clean installation.

Interesting observation about backing thru the turnout verses forward picking of the frog.


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from another forum,...

When you bought Peco turnouts that were supplied with paperwork in the box they themselves said to glue .010 thou shims to the guard rails if you ran scale type wheels sets. I have shims in mine .010 thou in the older ones. These newer ones with out the adjustable spring tensioner have up to .020 thou. I also now make the guard rail longer so that the end is not almost opposite the tip of the frog. I found once I had the wheel set further over I wasn't getting the short problem as much from the two merging rails at the frog of insulfrog type turnouts.

Hope this helps Les


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I have a number of curved PECO turnouts, and don't recall having this problem with them. However, it is good to know about it, and how to fix the problem, if it occurs! Thanks! :)


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Shim Experiments

One of the reasons I brought this subject up at this time is that I had been doing some testing on a custom double crossover arrangement that had one leg going off via a curved (dbl-curve I term it) Peco turnout. Upon exiting that curved turnout I sought for the track to enter a rt-hand turnout that would eventually feed a container port facility. I decided to experiment around to determine what size turnout this might be. Here are the 3 Peco options I was considering,..

1) Lg size Peco:
All of my locos would go thru this turnout, including the 2-10-4 Broadway T-1

2) Med size Peco:
The 2-10-4 would not go thru this without consistently derailing its first driver on the point of the frog. Several of my 4 driver axle driver steam locos also had problems here. The IHC 4-8-2 Mountain did NOT have a problem here ( I surmise that is probably due to its slight cookie-cutter flanged wheels).

3) Sm size Peco:
All steamers but the IHC mountain had problems here.

NOTE: None of the diesels had any problems with all 3 sizes, including the very small flanged 6 axle ones.

At first I was wondering if it was the 'S' curve coming off the curved Peco that might be the problem. But I had also been aware that some shimming of Peco guard rails had been tried successfully in the past,...might this solve a portion of my problem? Good time to experiment while I had this test bed set up.

I looked around for some plastic or metal strips I might utilize to conduct a few experiments. I found VERY limited materials either in my storage trailer, nor in the local stores. Remember I am looking for something probably .010” to .020” thick, by .040” to .060” tall.
1) Metal faced tape:
Why not multiple layers of metal-faced duckwork tape,...total failure

(metal tape on upper guide rail in photo, metal shim on lower guide rail )

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.

3) Metal strips:
Looking back at that video I posted early on I began to give more serious consideration to the metal shim idea. I had a .010” thick sheet of steel. Could I cut it into thin strips? I gave it a try with big thin snips, then had to reshape that little thin strip into a presentable shape,

I'm pretty much convinced that I want to go the metal shim route. But I was not finding a ready made strip of metal at first. Finally I have found two candidates from K&S
815020 & 815021

Both of these are 1/64” thick (.015”),...nice compromise between .010” & .020'.
One is 1/16” (.0625”) tall which would make it slight proud if its bottom edge were sitting on the tie plates. The other is 3/32” (.093”) tall which I figure would be sitting on a slight slot cut into the plastic ties/tie plates with a hand held cut-off wheel rubbed back and forth.


Well-Known Member
I have a number of curved PECO turnouts, and don't recall having this problem with them. However, it is good to know about it, and how to fix the problem, if it occurs! Thanks! :)
Me and my big mouth! I have a kitbashed 2-10-4 that I store on a siding which branches off a curve, but with the siding coming off on the straight side of the Peco turnout. Haven't used the siding much. Today, when I tried backing the locomotive onto the siding, the 4-wheel trailing truck derailed...several tries! I cut a piece of .010" brass sheet so it projects above the guardrail and the stock rail. It works, even though I didn't cement it in yet. Probably will use some CA. OTOH, if I can find a short Shinohara turnout, I may substitute that instead. Funny thing is that trains proceeding into the curved portion of the turnout from the point of the frog, do NOT derail? Go figure. :confused:

Well, I finally got a Round Tuit and cemented the shim in place with gap-filling CA. Ran the locomotive back and forth several times and NO PROBLEM! :D Thanks for the suggestion, folks! BTW, I checked at my LHS (Caboose in Lakewood, CO, and they haven't seen hide nor hair of a U.S. speced PECO turnouts, yet! Also checked with several other dealers at a model railroad show who carry PECO turnouts. No joy their either! I looked at replacing the PECO turnout with a modified Shinohara, but that wouldn't fit in. So, looks like the problem is solved!
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