Bachmann Steel Turnout Shorting

[jviss]

This is weird and unexpected.

I finally finished my first DCC conversion, a BBH 4-6-0 Anniversary model.  This is also the very first time I have run a DCC anything!

I have a layout on the floor, all Bachmann steel alloy track.  I have several turnouts.  When I run the locomotive very slowly over a left turnout, from the entry point to the left turnout side, the loco stops, with a short circuit indication and alarm from the booster.

Upon closer examination and some experimentation I found that the loco wheels, both the pilot truck wheels and the drivers, have a tendency to short the two rails that meet at the frog.

I changed out that turnout and experienced the same thing with a new one.

I had never noticed anything awry when running DC.  I also don't notice an issue with any of the other switches, of which there are currently three more; one more I'm traversing in the same way with no issue so far.

What to do?  Any ideas?

Thanks,

jv

Turnout is: MANUAL TURNOUT - LEFT Item No. 94351

[Joe Satnik]

jviss,

Is the curved point rail being shorted to the straight point rail by the wheels, or

is the divergent frog rail being shorted to the mainline frog rail?

Does the short occur on both routes and in both directions?

Joe

[Joe Satnik]

Another check....

Nothing on the track, DCC running,

can you cause a short by just pushing down on the frog or rails around it with your finger?

Joe Satnik

[jviss]

jviss,

Is the curved point rail being shorted to the straight point rail by the wheels, or

is the divergent frog rail being shorted to the mainline frog rail?

Does the short occur on both routes and in both directions?

Joe

Hi Joe,

It's the latter, I think: the divergent frog rail being shorted to the mainline frog rail.  Please excuse me if my use of the terminology is faulty.  I'm attaching a pic with the shorting area circled.

[jviss]

Another check....

Nothing on the track, DCC running,

can you cause a short by just pushing down on the frog or rails around it with your finger?

Joe Satnik

Thanks for the debug advice, I'm at the office, I'll try this when I get home tonight.

[jviss]

Getting back to this, thanks Joe - but no, the short isn't caused that way.  I found that one side of the frog is slightly higher than the other; but I don' think that's the problem.  The problem, I am pretty sure, is that the lead truck wheels are too wide!  Mine measure 4.8mm across the tread, i.e., from the corner where the flange and tread meet to the outside edge of the wheel.  The Bachmann metal passenger coach wheels don't short the frog.  They are 4.53mm.  

With a regular DC setup I don't think you could crawl the engine slow enough to detect the short - it would be for a very short duration.  However, with DCC, you can crawl really slowly, and the fast short-circuit detection and protection on the Digitrax Super Chief will shut it down, stopping the engine on the spot.  

I measured bogies on three Bachmann 4-6-0's so far and and all the bogies have this same dimension.

This is also exacerbated by the fact that the piece of the frog that is shorting is slightly proud, i.e., slightly higher that the other.

So, the choices to fix this that I can think of are to:

• modify all of my bogies so the effective tread width is less;
• or insulate just a little bit of the frog so it doesn't short;
• or even disassemble the switch and grind the frog a bit (it's cast stainless steel).
  

.     

I'm open to suggestions.

Thanks,

jv

[Joe Zullo]

"...or even disassemble the switch and grind the frog a bit (it's cast stainless steel)...."

The frog on those switches are plastic.

[jviss]

Then it isn't the frog I'm referring to, it's the rightmost of the two, small, metal pieces of rail in the top of the pic I posted. 

[Joe Zullo]

Oh, that's  just what they are...stub rails.  

First make sure it is tight. There is a screw underneath it to attach it to the ties. I would not grind it from the top. It is nickel plated and you will quickly grind through it to a copper plating. If you must grind it to lower it I suggest removing it and grinding the bottom to lower it.