#### Re: DCC Wiring - Can it cause a fire?

Flash Gordon

Steve,

I must admit I was also confused by your use of the term "fouling point" because I was thinking in model scale track laying. I am ashamed for not seeing your logic at first because I was also a real time switchman.

We always had to be sure spotted cars did not foul the main. The method was to stand over the rail with one foot on each side and stick out your arm to be sure it did not touch the car in question.

I have a feeling you were also a railroader do to your reference to the “beanery”. I worked on the “Snake” Southern Pacific in the San Francisco area in the 60’s; specifically the Alameda Belt line.

Thanks for your tip on model railroading and be sure to not walk on the “ball” of the rail.

Ed S

At 02:20 AM 1/23/2014, you wrote:

In response to my comment:

“  . . . keep those gaps inside the fouling point of your turnouts and equipment and it will reduce the number of problems due to shorts by reducing the possibility of shorts.”,

Bob inquired:

“Are you suggesting gaps closer to or farther from the frog?  Could you explain what you mean with a little more detail? Or point us to a diagram or discussion.>>

The Fouling point is the location where equipment on the diverging tracks of a turnout would sideswipe each other.  Trains & equipment need to be spotted beyond the fouling point so equipment can move into/out of the adjacent track without sideswiping each other.

Starting from the point end of a turn out, you have points, frog, fouling point.  Your gaps go between the frog and the fouling point.  These gaps should be as close to the frog as is reasonably possible given the track construction methods used.

The rationale is this – In theory, (most, there are always exceptions <>) operators will keep equipment beyond the fouling point so trains don’t snag on each other.  If they do that (as they should), and the gaps are between the frog and the fouling point, the metal wheels of stopped equipment are unlikely to span the gap, potentially creating a short if the turnout is thrown against the equipment spanning that gap.

We had an incident on a local layout where this actually occurred.  Track was hand laid, and one side of the frog extended about six inches down the yard track.  A train entered the track from the far end of the yard and pulled down to the far end, where it stopped with one of its front wheels spanning the frog gap.  As the engineer was moving slow, he was almost stopped when tht axle spanned that gap, and didn’t notice that he’d straddled the gap.  The turnout was against him, so the frog was one polarity and the rail under the train the opposite.   Additionally this was the last train of the session, so the short went completely un-noticed.  The layout was shut down and we went to beans.  Several work sessions passed where we had track power on for various reasons.  When we finally went to move the train for re-staging purposes, it wouldn’t move.  Inspection revealed that the gear on the front axle had gotten so hot that the plastic had flowed around the bearing block on that side of the axle, and had cooled around the bearing block effectively freezing the mechanism.  Layout owner, not realizing that any of this had happened, attempted to move the train by turning up speed on throttle.  Only thing that happened is track to decoder and decoder to motor wiring got hot and the insulation burned off.

All of this would have been avoided if the gaps had placed properly  (between the frog and the fouling point originally.

Best regards,

Steve Haas

Snoqualmie, WA

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