derailment at the frog

Model Railroader General Discussion (Model Railroader)
1

I keep getting derailed at the frog (throat?) The wheel diameter is small enough to drop between the rails at that place which is enough to make it come off the track. Anyone have any suggestions?,

the switches are #4 Atlas HO snap switches. The train and cars are from a Walthers train set a couple of years old. The wheels off one of the cars measure .368". If someone has an email address I can send the pics

thanks

2

A couple of questions:

  • Are the switches Atlas Customline #4 or are they Atlas Snap-Switches? The Snap-Switches have a continuous 18" radius curve through them and have plastic frogs. The Customline turnouts curve to the frog, then are straight through the frog and beyond.
  • Your wheel diameter measurement sounds like a typical 33" diameter wheelset.

First look at the frog area; is the frog worn down? the switch may need to be replaced. Next, consider putting some plastic shims in the open area of the frog so that the flanges ride across the shims and the wheels do not drop.

The next big item is the actual wheels. The plastic wheels are many times out of gauge. Get an NMRA gauge from you LHS and check them. Replacing them with metal wheelsets does wonders.

Jim

3

Is this only one loco or one car? Or many?

Is it at only one turnout? If so, do you have other, similar ones that are ok?

That will help narrow-down the problem.

Also, do you have an NMRA track gauge? No modeller should be without one. That will quickly tell you whether wheels or track are out of gauge (too close or too far apart), or other clearances aren’t right. They’re available at most hobby shops and online retailers, such as Walthers http://www.walthers.com/exec/productinfo/98-1, or 1stPlaceHobbies http://www.1stplacehobbies.com/cgi-bin/prod.asp?pn=98-1&x=0&y=0.

I’m not familiar with those turnouts (the term many model railroaders use for track switches, to avoid confusion with electrical switches), but it sounds like the guard rail (adjacent to the frog, just inside the outer rail) might be too far from the outer rail. It’s supposed to hold the outer wheel close to the outer rail so the inner wheel, that goes through the frog, won’t “wander” and cause a derailment.

If that’s the case, you should be able to shim the guard rail with a small piece of styrene (plastic).

4

First, the Atlas switches are notorious for having a wide flangeway across from the frog. Get some Evergreen strip styrene .010 by .060 inches and glue a section of this on the guardrail across from the frog. Measure this with your NMRA check gauge, the no-go point should not drop into the flangeway. You can see the NMRA standards and recommended practices:

http://www.nmra.org/standards/consist.html#standards

Second, the critical dimension in this case is the wheel width, not diameter, which will allow it to fall into the gap. In some cases the flangeway through the frog is too deep and can be shimmed in the same manner as the guardrails.

5

Tim Warris did a great video discussing the alignment pf the frog, wing rails, and guard rails and now they work together to keep the train where it should be. He discussed in the forum here.

I learned a lot from it.

Hope that helps.

6

SIMPLY PUT the wheels and rails are not in agreement.

Is it the wheels, or the rail? To be determined.

Most probable: check the wheel spacing with an NMRA gage. Go from there.

Most expensive: replace the car and switch.