My thanks to Mr. Zander of Z-Stuff for Trains for supplying info about DZ2500 operation.
A lot of us are used to the Lionel O gauge switches that have derailment prevention built in - they use isolated rails and lightening fast switch machines such that we can run trains full throttle into one of these switches and and derailment is avoided.
However, other switch/switch machine combinations do not have lightening fast response. For example, Ross Custom Switch with Z-Stuff DZ2500 switch machine. The derailment prevention capability of the DZ2500 is triggered by isolated rails like Lionel, but the DZ2500 takes 0.2 to 0.4 seconds to throw the switch. So the question arises - what distance from the switch to the anti-derail isolated rail start/location? To find the answer, we need the max speed our train will approach the switch, and how long the switch machine takes to move the points. So in FWIW-MED #1 I introduced my train calculator program that can calculate MPH, Time, and Distance. In this case, we can use the Distance calculation.
I want to know how many inches of track will my train traverse in the time it takes the DZ2500 derail prevention to throw the switch. I want to cause the DZ2500 to start throwing the switch so that the switch is thrown before the train gets to the switch. The below diagram shows the switch in the "Out" position, but the approaching train wants the switch to be in the "Thru" position. The train will encounter the Isolated Rail, and the distance Isolated Rail is from switch points will determine if derailment will be prevented.
In the screenshot below, I chose O gauge, Distance Calculation, a time of 0.2 seconds (fastest DZ2500 time), and a scale speed of 100 MPH. I did the calculation a second time using the 0.4 seconds (slowest DZ2500 time).
The calculator comes up with 7+ inches and 14+ inches traversed at scale speed of 100 MPH, i.e., the isolated rail needs to start/be located about 8 inches or 15 inches from the switch to prevent derailment. You have to decide where you want to start/locate the isolated rail for derailment prevention, using the calculations as a guide.
Of course, this same calculation can be made for any scale and any switch/switch machine combination, but you will either have to measure, guess, or as the Manufacture as to how long the switch throw operation takes.
