Model Railroading > Undertable switch repaired ... now another issue

I have one switch in my small classification yard that is presenting an issue that I can't grasp.

When operating in DCC, most (but not all) engines stumble as they cross the frog. Now, here's the catch .... only when the switch operates straight thru rather than using the turn out. In the turn out ALL the engines cruise right on through without a stumble. Now if I come thru at the speed of heat, then the locomotive passes right on thru without a stumble. Go slow and, in both directions, the locomotive will either stumble or outright die on the frog. I've cleaned it until the shine is visible from outer space, so that base is covered. In the video you can see when it stalls, just a 3/8" push off the frog and it starts back up again.

I don't understand why it only stumbles when the switch is set up for straight thru and not when it's set for the turnout.

Ideas?

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A lot of track power and signal problems are, if the symptoms are read correctly, trying to tell us what is wrong.
It become a kind of fun exercise in logic to troubleshoot them.
In this case my first suspicion is, after seeing that your frog has insulation on all four rails, that what ever is controlling the power to the frog works only in the reverse position.
If you have a switch machine or point actuator with a set of SPDT contacts to route the power to the frog, either the contact or the wire from the turnout side track power to the frog is not making a good connection.
Try some checks with a volt meter.  Using your AC volt setting, see whether the power between the rails is good (16-17 VAC) then move through the turnout in both the straight and reverse settings, testing the track power on each section of rail: points, closure rails, stock rails, and the frog.
Somewhere you will find zero volts, which should tell you where the circuit is open.
I have had to do this a few times on a 20+ year old layout as old solder joints corrode or otherwise fail.  (Hint: run a feeder to each rail, don't rely on rail joiners, even if you solder them.)
Good luck, you are now doing the work of a prototype signal maintainer.

Perhaps your electrical source is dead when the switch is straight thru. I assume you have a method of switching polarity. You could also use a frog juicer to fix

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The design of that switch is to have two small metal strips that are spot welded to the underside of the rail to connect the same polarity to the isolated section of rail, I forget which exact section. If you could turn the switch over you should see them on the underside of the plastic ties. I've noticed that occasionally the spot weld comes loose.

Suggest putting a voltmeter on it and looking for an intermittant or simply zero voltage.

+ Or, as mentioned above, the source of the voltage may be an issue. the voltmeter will help find that as well. These days a decent digital voltmeter can be found at Auto supply stores for about 20 dollars...before the Tarriffs started anyways.

++ another possible fix is to have feeders on all sections rail, so the diverging rails would have feeders off-picture so to speak. The cuts in the rail around the frog, which are filled in with epoxy, would prevent short circuits when the points are moved.



Edited 2 time(s). Last edit at 05/16/19 22:14 by TCnR.

Your problem might actually be the point itself. If you set an engine with one truck sitting on the frog, chances the wheels will be inside the insulation with the other truck sitting on the point.  If it doesn't move with power on, take a small screwdriver and push the point harder against the stock rail. If it takes off, there's your problem. Now you can use fine emery paper  to clean the backside of the point and inside of the stock rail. I've had a few do this and it's always been the point causing the stall.

The points are not making proper contact with the rail when thrown in the direction
that the engine stalls.  The above post suggesting cleaning the inside of the points is a
good possible solution. You could add keep-alives to your engines so they keep running
over  the dead spots, or replace the switch with a new one with a more DCC friendly
switch rather than a power routed switch.

I help keep the HO railroads running at both train museums in Tyler and Palestine, so i
am quite familiar with these problems.

This is where you need a multi-meter to see where you are getting power and where you are not. You also want to make sure the frog is not reverse polarity too!

Ted Curphey
Ontario, OR

I would also check the locomotive as it amy only be picking up on one truck on one side.  I have had that happen

Darin Umlauf
A WC, SOO and GBW fan in Slinger, WI

I have scrubbed the point rails on all the switches and still have issues.
Some locomotives are more susceptible than others. Keep alives are a good fix but I literally have over 100 DCC locomotives I probably wouldn't live long enough to do all the work and would also likely run out of money before I run out of time.

At this point, I'm think frog juicers as a more reasonable method. I'm essentially illiterate when it comes to anything electrical, so I'm wondering if I have the knowledge or the skill to accomplish it without professional help.

And speaking of professional help, I am looking for somebody in the Central Texas area to give me a hand installling signals, etc. at the Olsen Rail Museum in Clifton, TX. Probably a day or two at the maximum. We are funding limited but could cover reasonable travel costs. Contact me via private message if you are interested.

THANKS !!!