JD_Reith posted:...
I purchased the timer relay you referenced in your drawing from what I can tell. Here is the link timer relay. On the relay it shows the same labeling as what you drew, looking at the relay left side being where the 12V +/- enters, right side top is NC, middle is COM, right side bottom is NO. So when you give 12V power to this relay, it switches the relay and you get continuity between COM and NO (center and bottom) for the set time, then it returns to NC. From your description this would be delay off that is expected correct?
Right. That's behaving as a DELAY OFF relay which is NOT what we want. Looks like I gave you a bum steer. Sorry about that. 
Kind of annoying though since the listing specifically says DELAY TURN-ON:
In "researching" this more on eBay with other delay relay modules, it appears the wording of this Feature list is copied freely between different relay modules of different behaviors.
The chattering behavior you describe with both "trolleys" parked on their trigger sections is to be expected if a DELAY OFF relay is used (even if you used COM & NC terminals in an attempt to "reverse" the behavior). The DELAY OFF relay has a fraction of a second delay when you first apply power on the left-hand terminals before it turns on the relay. The relay then runs its 10 sec delay and turns off. The problem is the fraction of a second turn on time is long enough for the parked trolley to trigger and power up the other siding. The other siding does the same thing. And they just pass-the-baton back and forth as fast as the relays can turn on and off.
In any case a DELAY ON relay is absolutely required for what I drew. I thought a bit about it and it would be ugly to modify the circuit requiring some resistors and capacitors and some fussing to get the timing right. Not recommended.
The good news though is I actually have one of those lower-cost 10 sec DELAY ON modules I referenced earlier and I can confirm that it indeed behaves as a DELAY ON module. I just tested it and it runs up to 14 seconds max delay though it's a sample of 1. In any event, if 10 seconds is long enough for your trolley to power up, go to the bumper, reverse, and pass over the trigger section (on its way to the mainline), I recommend just getting a pair of these lower cost modules. I just looked and 99 cent free-shipping is not available just now but several sellers have them for just over a buck free-shipping.
If you need longer delays and want to find another off-the-shelf module, I'd want independent confirmation (maybe someone on youtube showing it in action) that delay-on is indeed delay-on. Unfortunately we've had this problem before with various low-cost eBay modules from Asia with descriptions that are misleading or simply incorrect. I should know better by now...
