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On the subject of prototypical signaling, I do have a question for you @kc9jts if you'll indulge me:I was always under the impression that, under the approach lighting scheme used by the SP, if a train occupied either the siding or the main between two control points (let's use Walong as an example), that all four signals protecting both ends (2 for the siding, 2 for the main) would be lit. Recently that's been called into question, however, as I've seen two bits of evidence which seem to contradict this:- A cab ride video from the loaded cans in the early 90s where they went in and out at Walong due to Maintenance in the Way on the main. At the south (east) switch Walong, heading out of the siding, they had a clear on the dwarf and the mast guarding the main was dark.- A photo of an uphill train stopped at South/East Bealville, presumably waiting on a westbound headed down the mountain where, again, the dwarf governing the stopped train's movement was red but the mast signal on the main was dark.This seems a little contradictory to me because, in another cab ride video (headed down the mountain this time), the train went through Walong on clears and the signal governing movement off the siding on the signal bridge just before tunnel 9 was clearly red (of course the signal on the main was showing clear).Could you perhaps shed a little light on this? Am I correct to assume in light of my (very limited) evidence that all four signals at both ends of a siding would light if the main was occupied, but if only the siding was occupied, only the two signals (one protecting each end of the siding) would illuminate? I've seen photos with the siding signals unlit as well and the sidings weren't unbonded, so I have to assume the dwarves weren't constantly lit.Changing all of this is just a matter of modifying existing JMRI Logix tables, or setting up new ones, and I'd like to get it right - so thanks for any insight you might have!
... The SP liked to mix things up quite a bit with how each location worked and there could be a lot of variation between similar locations that are adjacent to each other...
I've also recently been playing around with the implementation of electric time locks which work pretty well, but will look a lot prettier once all the fascia hardware shows up:https://www.facebook.com/NScaleTehachapiPass/videos/966308530150964/ (can't embed this one as it's a FB video)
Neat device there Chris! But I have a question. Why was the prototype mandated to use a time lock? Why not rely on train detection and keep the switch locked until there was no longer any train between the approach signal and the switch? The logic apparently allowed the switch to be thrown when the approaching train had not yet reached the approach signal, but instead started the timer when it had. So the logic already "knew" where the train was, so to speak. To use a timer seems less safe, to me at least. There is propbably something I just fail to see here, but if so please enlighten me
First off let me offer a slight disclaimer and that is that most of what I know comes from looking at signal plans and not from "in-cab" experience (I may need to hide and change my name to avoid getting tarred and feathered but I had a hand in the replacement in a lot of the old stuff on Tehachapi). Second off, I will answer the next question that has not been asked yet: no, I cannot post the plans as even though a lot of the stuff is obsolete they are still considered proprietary. And now let me add a third disclaimer: The SP liked to mix things up quite a bit with how each location worked and there could be a lot of variation between similar locations that are adjacent to each other; so really each location would need to be addressed individually.To your specific question about approach lighting now.......North Walong has both the trailing signals lit off of the same relay (which combines the track relay for both tracks) so they should be lit together. The facing signals at North Walong are also lit off the same track relay but as has been previously discussed the bottom head would only light for a diverging move and that is because the lighting circuit for the bottom head had a relay that could check if the top head was better than red.South Walong was a little different. Both of the facing heads lit off of the same track relay and it does not appear that it had a provision for the bottom head to be dark for a train lined on the main. The trailing heads did not light in series with each other as each lit off of their individual track relay.Most of the track circuits were lit based on a "center-fed battery" that would be located roughly in the middle of the siding and feeding the track relays on both ends. If there was an engine or real short train on one end of the siding it is possible that only that relay would be shunted whereas the same relay at the other end of the siding would still be energized (the track circuits would have resistors to adjust the shunting sensitivity so in the scenario I just described it is possible that all would be lit or just one side, depending on the adjustments).East/South Bealville (CP SP340) functioned the same as South Walong where the lights on the main and siding each lit based off of track occupancy on only the track they governed movements from.Hope this helps
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Topic: SP Mountain District (Tehachapi Pass) - N scale (Read 19480 times)
