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Short circuits at frogs

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Short circuits at frogs
Posted by moranjlcc on Sunday, October 24, 2010 10:30 PM

I'm perplexed about this one.  I have a locomotive, a Broadway Limited AC 6000, that will frequently short circuit when it hits an insulated frog.  This does not happen every time on every turnout, but frequently enough to take it off the layout.  Other locos travel around the layout ok, although occasionally other locos will stall at the frogs.  I'm using Walther "DCC ready" turnouts.  The other thing to note is that this same loco worked fine at the RR club yesterday.  Any ideas?? 

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Posted by rrinker on Sunday, October 24, 2010 10:46 PM

 Get an NMRA gauge and check that all the wheels are in gauge.

                          --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

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Posted by larak on Sunday, October 24, 2010 10:53 PM

Perhaps a dumb question on my part , but does it SHORT or STALL at the frogs. It makes a difference in where I would look for the problem. I know that you said it shorts but later you mention that sometimes other locos stall. I just want to be clear about your symptoms.

The mind is like a parachute. It works better when it's open.  www.stremy.net

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Posted by locoworks on Monday, October 25, 2010 2:56 AM

the problem is likely to be that the loco tyre tread is wide enough to bridge the small bit of insulation in the frog between the two polarities right next to the 'pointy' part of the frog.   if you used electrofrogs it would cure the issue, OR, wire the point/switch as if it was electrofrog and use insul joiners on the inner rails and feed them as a pair with a switch that moves with the tiebar.

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Posted by Hamltnblue on Monday, October 25, 2010 5:30 AM

I had the problem with one of my AC6000's and an SD60i

The problem was with the turnout. I had to file this gap a little larger.

Springfield PA

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Posted by moranjlcc on Monday, October 25, 2010 8:28 AM

yes, I did that and the wheels are all in guage

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Posted by moranjlcc on Monday, October 25, 2010 8:29 AM

Thanks, it shorts the system out when it hits the insulated frog on the turnout(s)

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Posted by moranjlcc on Monday, October 25, 2010 8:31 AM

Thanks, this is very helpful and I'll give it a try.  Is it also unique to these big locos?

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Posted by DigitalGriffin on Monday, October 25, 2010 10:52 AM

First off:

Walther's DCC friendly turnouts are NOT insulated frogs.  They are metal and therefore live frogs.  BUT you have to wire the frog to a relay (switch machine) for this to be true.

Second:

Walthers sold some "DCC friendly" turnouts that were not DCC friendly.  The problem was the throwbar points were being held together by a single piece of metal.  This means both point rails shared a common or the same polarity.  As a long wheelbase loco went around the curve it had the potential to touch the opposite polarity rail causing a short.  When Walthers realized the problem, they recalled said turnouts to be fixed.

Pictured below is the way the Walthers DCC SHOULD look (points are not connected).  If it has one piece of metal between the two points at the throw point, then it needs to be fixed.

Third:

Make sure the frog is properly isolated from the inner legs.  To do this you need to turn off layout power, and get a volt meter that has continuity testing or resistance measurements.  Put one probe on the frog (point 1), and the other probe on the four points listed in the picture below (points 2, 3, 4, 5).  If it beeps (continuity testing) or reads near 0 Ohms (resistance measurement) then you have a short between the legs and frog.

Don - Specializing in layout DC->DCC conversions

Modeling C&O transition era and steel industries There's Nothing Like Big Steam!

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Posted by soller on Monday, October 25, 2010 12:40 PM

I have a loco that stall at the frogs. What´s the problem?

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Posted by DigitalGriffin on Monday, October 25, 2010 2:13 PM

soller

I have a loco that stall at the frogs. What´s the problem?

Most likely your frog is not powered.

Don - Specializing in layout DC->DCC conversions

Modeling C&O transition era and steel industries There's Nothing Like Big Steam!

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Posted by Hamltnblue on Monday, October 25, 2010 2:23 PM

What make and model of loco is stalling at the Frogs?

Springfield PA

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Posted by rrinker on Monday, October 25, 2010 2:24 PM

 However, if it's a big loco like an AC6000 and it shorts on a dead frog, unless you are using a huge turnout (ie something larger than the commonly available #4, 5, 6, or 8) then you may have an issue with the locomotive, as there's no way all the pickup wheels could be on the dead frog at the same time. This is usually a problem with very small locos and in particular ones that only pick up from 2 wheels on each side. The BLIs and other 'modern' models pick up on 8 or more wheels, both sides of each truck, and should have no stallign issues over a dead frog.

                         --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

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Posted by Hamltnblue on Monday, October 25, 2010 2:31 PM

On mine it's not the frog that was shorting but the spot I pointed to in the earlier post.  It was the Atlas number 4's that I had the most problem with.  A quick hit with the dremel fixed the problem.

Springfield PA

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Posted by soller on Monday, October 25, 2010 4:47 PM

OK. The frog is not powered. But what about if I use a manual turnout. What can I do?

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Posted by selector on Tuesday, October 26, 2010 8:00 AM

A dead frog should affect only the tiniest of switchers, say with only two axles set within about 1.5" of each other.  The heavy majority of locomotives of any description produced since 2000 should have enough wipers that the cross dead frogs.  Every one of my roster of engines, diesel and steamer, large and small, crosses every turnout of mine, commercial and hand-laid, and every single frog is deader'n a doornail.

You may have an issue with a turnout frog that lifts your engine enough that it breaks contact with the one remaining axle and the rails  Or, your points rails are not getting power due to slop in the pivot and no wipers under them as many turnouts have.  If your points really only get power when they lie tightly against their adjacent stock rail, then sloppy positioning could make them dead.

A multimeter test would help.

Crandell

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Posted by soller on Tuesday, October 26, 2010 9:44 AM

My loco has only 4 axles. The back axle has traction wheels and when this loco goes forwards it stall at the frogs.

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Posted by DigitalGriffin on Tuesday, October 26, 2010 1:06 PM

soller

My loco has only 4 axles. The back axle has traction wheels and when this loco goes forwards it stall at the frogs.

Is the frog metal at all?  If so, and you want manual throws, then you'll want to use one of these:

http://www.cabooseind.com/index2.php?page=GroundThrows  (The one pictured on the upper right)  Connect the middle leg to the frog and the two side legs to each rail.

 

 

Don - Specializing in layout DC->DCC conversions

Modeling C&O transition era and steel industries There's Nothing Like Big Steam!

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Posted by soller on Tuesday, October 26, 2010 2:35 PM

It´s a Roco turnout, I think it´s insulfrog.

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Posted by moranjlcc on Wednesday, October 27, 2010 9:14 PM

Thanks Crandell,

I think I have a problem with the frog lifting the engine as you described; what did or would you do about this?  

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