trackwork 2

I was looking through my collection of books and magazine articles I've collected over the years on laying track and I'd have to say that no matter how much I read, it doesn't help me near as much as actually doing it. The idea is that reading gives you knowledge, but experience is the teacher. This holds very true for me. I know how my code 70 ME track is supposed to look; straight, level, without deviation vertically or horizontally. My turnouts correctly aligned, the throwbar centered directly over the control wire hole and when the tortoise or blue point is connected an equal point swing in both directions as the point rail pushes up against the stock rail. My NMRA track gauge confirms what I see or think I see as the case maybe. Something working sometimes is just not as good as something working all the time. The occasional pick of a point by a 40' box rolling over a switch happens for 5  main reasons that I've experienced.

1. there's a problem with the box car
a. wheels - dirty, distance between wheels is wrong,
b. car - weight too light or shifted to one side causing the car to lean.
c. trucks - mounting screw too loose or tight against the mounting post or both trucks mounted too tight or too loose. One truck should be mounted slightly looser then the other providing a counter balance along the car as it rolls over the track.
d. everything else

2. there's problem with the turnout
a. controlling direction point rail not snug against the stock rail, or gap not correct on the open point rail, points not level and sitting above the stock rail.
b. dirt or debris in the frog or flanges, soldered frog wire is too high and interferes with car wheels as it rolls over these connection points
c. everything else

3. theres a problem with the switch control 
a. under the layout machine; blue point, tortoise, not mounted or aligned to turnout correctly.
b. control wire not centered equally on either side of the control wire hole, too light a gauge control wire.
c. everything else

4. couplers
a. coupler height maybe, but mostly the couple swing is restricted or not freely swinging
b. everything else.

5. operator error
a. panic throw of switch points under cars
b. partial or wimp throw of blue point
c. everything else.

Surely there are other reasons for the occasional derailment at the switch which is where they occur on the Placerville branch.  Outside the turnout itself, for example at incoming and outgoing switch connecting tracks not properly aligned. They should be no abrupt angles between adjoining track pieces. In fact no differing angles at all. Put a small hand mirror on top of the rails and look down the track through the mirror. It will  reveal any and all kinks that have developed.
All in all it isn't easy for me and other modelers to get this right. All of us have our own strengths that we bring to the table. Take your time and don't quit until you do get it right. This may take days or months, but keep plugging away at it. Zero derailments is the goal after all.