itzow wrote:Thanks for the answers, but I need it a bit more exactly. Are there some special typs of crossover switches or does they need a special center track distance?
but you might see trains gap in yards
Can you explain this more in detail?
around large curves
I hear this the first time, is there a special radius necessary?
In general, the third rail on the straight side of a switch crosses to the side of the track opposites the turnout. There is a short gap near the switch points to allow the third rail shoe on a car entering the straight rail to pick up power. On the crossing track a piece of third rail occupies the space between the running rails between the tracks. Since there are four pickups on each car, this insures thatmost of the crossover is powered. Only when all four shoes are out of touch, does the car lose power. Scissors crossovers have less third rail, so gaps are more likely. Double Slip Switches are even worse due to all of the moves possible.
Basically, the only good way to approach third rail is by way of the ramped end. Any other way the shoe comes in contact either tears off the shoe or tears up the third rail.
A more noticeable third rail gap occurs at a section break, the point where two third rails, fed by different isolation switches or substations meet. Here, there is a gap which must exceed the dimension between truck centers on the largest car in use by about two feet. This insures that if a car accidentally enters a section which is shut off, it doesn't energize that section with possibly fatal results.
Finally, on modern cars, the lights are powered from the low voltage (battery) circuit. This is usually fed from the 600 via a motor-generator set or DC-DC Converter. When the 600 is lost, the batteries take over. As they discharge, sensors in the lamps turn some circuits off. Thus for a normal third rail gap or section break, the lights stay on. If you happen to ride the "Train of Many Colors", the R-33MLs have the newer type lights. The older cars, and R-33WFs have the older variety, and they will flash going through gaps.
The next stop is Washington. Change for Forest Hills Trains on the Winter St. Platform, and Everett Trains on the Summer St. Platform. This is an Ashmont train, change for Braintree at Columbia.