Tehachapi Loop II

[GaryHinshaw]

The 10-second rule has worked very well for me and, since its implementation, I haven't noticed a single block drop occupancy. Best yet, it's incredibly easy to do with JMRI.

Good to know!  It is easy to implement, for sure.  Thanks Chris.

[jagged ben]

Yeah, this diagram is probably confusing when shown out of context.  (Sadly, I can't find the post where I first discussed it...)  In any case, this is supposed to show how I wire for current detection in a long block.  In the top half, "A rail, 3 track sections" indicates the A-side rail of 3 sections of track that comprise one block, each with their own feeders from the main bus.  I don't use rail joiners, so each track section needs its own feeder from the bus, as shown.   The bottom half shows how I run a sub-bus for each block, so that I can detect current in any track section in that block.  Each block gets its own sub-bus, while the main bus can make a much longer run.  The B-side bus does not need a sub-bus, so I didn't bother to show that.  Hope that clarifies it.

-gfh

P.S. Nice shots jb.  I'd like to get back to Richmond to visit some day.  My brother lives just a few miles from there.

It might be useful to distinguish between 'block', meaning what it means on the prototype, and 'detection section' meaning individually detected sections of track on a model (or even the prototype in some cases).  In other words, your diagram shows a single detection section which relies on a sub-bus rather than joiners to manage electrical connectivity to all its pieces of rail.  We do exactly the same thing on our club layout.  The difference may be that we will have up to four detection sections per railroad block, whereas you are mostly doing one detector per block.    (Another difference is that we switch blocks among multiple cabs, so our 'sub-buses' are really the only busses we have.  But that's a tangent.) 

To be clear, if you have multiple detection detection sections in a single railroad block, you program Logix in JMRI to have all detection sections trip a single internal sensor for the block, for signalling purposes.

Another big application for distinct detection sections besides automatic train running or locating of trains in staging would be grade crossings.  With gaps placed at appropriate distances from the crossing you can tolerably simulate prototypical timing on gates going down.  (Of course if you want the gates to stay down while the whole train is crossing, then you need either full implementation of detector wheelsets along with Chris' ten second debounce, or you need an optical sensor or two across the track.   But the approach timing generally relies on the locos and should work well.) 

Gary, thanks for the kind words and if you're ever going to be stopping by do PM me beforehand so I can try to be there.   

[ednadolski]

No, it's not the detection I don't have confidence in.  I lack confidence that my train will arrive at the end of the staging track in one piece with none of it on the floor.      In other words, I want to know to stop immediately if I see a derailment happening.

Aha, yes, the Heisenberg Trackwork Corollary: a train only stays on the track for as long as it is being observed.... ^[1]

FWIW, I notice that whenever there is any part of a moving train that I cannot see, I find myself almost reflexively listening more attentively than usual for the clattering sound of a dragging wheelset.   In my case the train room is quiet enough that I can hear that sort of thing, but I'd expect that in a club environment there is too much ambient noise for that to be of much use.

One thing that worries me sometimes is unplanned uncouplings that happen when a train is out of sight.  I recall one time where I had a string of autoracks at the end of a train.  On one trip up the Loop, I thought I was imagining that the train had somehow mysteriously gotten a bit shorter than on the previous lap.   On the next lap, I was surprised to see emerging from Tunnel 9 that the lead engines had some unexpected company:  they were pushing two of the (formerly trailing) autoracks!   They had uncoupled themselves from the tail of the train on the downhill staging track and had sat on the track unobserved, until the next time the train came around to push them forward again thru the tunnel.

I found out that this was because of the slinky, truck-mounted MT couplers:  the pogo slack action on a slow-moving downhill train can be enough to cause the couplers to let loose.   It was not a bug, the couplers were actually operating exactly as designed -- I just hit one of the conditions that triggers the uncoupling behavior.   (As it can happen rather consistently, it's just another motivation for me to convert to the LEZs, but I haven't done that yet with the autoracks because (a) it's not a trivial conversion, and (b) I can't run body-mounted couplers on long cars on my current layout due to the mainline curves being too sharp.)


Great layout pics, BTW... thanks for sharing! 

Ed

[1] ... and in the absence of guests, of course 

[jagged ben]

...
Great layout pics, BTW... thanks for sharing! 

Ed
...

Well, they're not great pics.  They're crappy pics of a great thing.     But thanks.

[John]

you guys seen this

[svedblen]

Yes, that is @ChrisKLAS's awesome layout 

[ednadolski]

I was just watching that to see what color the Approach Diverging uses at East Walong

@ChrisKLAS -- you know you've nailed it when other modellers are using your work as a proto reference!   


Ed

[ednadolski]

I've been doing some more research and thinking over the various approaches for block signalling and detection.  I am starting to think that for a layout with this kind of very basic operating scheme, that a DCC-based detection system with all the accoutrements may simply be overkill in terms of capability, complexity, and yes, cost.  In exploring possible alternatives, one idea that I find growing on me is to build a single control panel that is a simplified version of a classic Union Switch & Signal CTC machine.

This panel would be reminiscent of the CTC machine used to run Tehachapi "back in the day", which seems appropriate considering the long history of the prototype.  As I recall the actual Tehachapi US&S CTC panel is currently located at the La Mesa club in San Diego, but I am not sure if it is operational.   Being a hands-on kind of guy, I also like is the tangibility of a hardware control panel.  (I use computers, touchscreens, and trackpads every day, so there is a certain appeal to being able to get a break from all that.)  While this does preclude the opportunity for fully automated running,  I have always thought of that as more of a nice-to-have but not really essential.  Likewise, I don't see much need for the flexibility & expansion capacity of a full digital system.

I spent a little time developing a panel layout, and this is what I have so far:



This will probably be about 12" wide and make use of the US&S-style plates & knobs available thru Rix Products.  The rotary switches would be hard-wired to the turnout motors and signals on the layout. I will probably include some simple logic and optical detectors on the layout to force a clear signal to drop to red as a train enters a control point.

Since the panel operator can easily see the whole layout (except of course for the hidden helix), I am not sure whether it is really necessary to have occupancy detection on the layout.  The only purpose would be to drive the lamps on the schematic board.  I'm still planning to gap and wire the track so that a current detection scheme could be implemented in the future if desired. (Admittedly I still am not too keen on the idea of having to make scores of resistor wheelsets.)

There are of course no signals in the staging area.  I haven't shown anything on this panel for how the staging helix would be blocked & wired, but at minimum I expect to have some lamps corresponding to the 'stop block' locations discussed in previous posts.

Ed

[ChrisKLAS]

I was just watching that to see what color the Approach Diverging uses at East Walong

@ChrisKLAS -- you know you've nailed it when other modellers are using your work as a proto reference!   


Ed

Wow, so much has changed since then... I really should make a new one soon!

Regarding your signal inquiry, I think you mean what aspect is displayed for a train heading into the siding at Walong. If that's correct, 99 times out of a hundred the crew would see a red over yellow (diverging approach). There was also a facility by which the dispatcher could line a second train into an already occupied siding behind the first guy on a Red over Lunar (restricting) aspect. Since H2 searchlights only have 3 disc slots, it's important to note that SP's decision to include lunar on the lower head also means there's no green - so even if a train is lined in and right back out, the best signal it can get is red over yellow. If you have any Tehachapi signaling questions, don't hesitate to ask. I've spend the better part of a decade researching this.

[kc9jts]

Wow, so much has changed since then... I really should make a new one soon!

Regarding your signal inquiry, I think you mean what aspect is displayed for a train heading into the siding at Walong. If that's correct, 99 times out of a hundred the crew would see a red over yellow (diverging approach). There was also a facility by which the dispatcher could line a second train into an already occupied siding behind the first guy on a Red over Lunar (restricting) aspect. Since H2 searchlights only have 3 disc slots, it's important to note that SP's decision to include lunar on the lower head also means there's no green - so even if a train is lined in and right back out, the best signal it can get is red over yellow. If you have any Tehachapi signaling questions, don't hesitate to ask. I've spend the better part of a decade researching this.

Any plan on replicating some of the double-blocked yellows or double blocked reds?  Also as info if a northound heading towards Walong is lined into the siding it would have an approach diverging (yellow over yellow) at the intermediate at 352.57 and that would be followed by a yellow signal at the north end of Marcel heading northbound.  At North Walong itself the northbound signals could only show red or green (no yellow).  Due to grades, short spacing of signals, train braking, etc. Tehachapi Pass had all sorts of signal nuances, including the repeater signals in some of the sidings for downhill moves.

[ednadolski]

Wow, so much has changed since then... I really should make a new one soon!

Really looking forward to seeing that!   

Regarding your signal inquiry, I think you mean what aspect is displayed for a train heading into the siding at Walong. If that's correct, 99 times out of a hundred the crew would see a red over yellow (diverging approach). There was also a facility by which the dispatcher could line a second train into an already occupied siding behind the first guy on a Red over Lunar (restricting) aspect. Since H2 searchlights only have 3 disc slots, it's important to note that SP's decision to include lunar on the lower head also means there's no green - so even if a train is lined in and right back out, the best signal it can get is red over yellow. If you have any Tehachapi signaling questions, don't hesitate to ask. I've spend the better part of a decade researching this.

Interesting, I did not know that the SP's lower signal heads could not display a green.

So a train entering Walong siding from either direction should generally expect to see a red over yellow, did I understand that correctly?   And would the same apply to Woodford siding?

Chris, do you have any links to pics/info about the CTC panels that they used?  I'm thinking that it would be nice to assign the same switch & signal numbers as the proto, but the pics I found do not have enough detail.   One difference in my case, I've had to swap left & right on my panel so that the operator will see the trains moving in the same direction as indicated.   Some compromises are unavoidable...   


Thanks,
Ed

[ChrisKLAS]

Any plan on replicating some of the double-blocked yellows or double blocked reds?  Also as info if a northound heading towards Walong is lined into the siding it would have an approach diverging (yellow over yellow) at the intermediate at 352.57 and that would be followed by a yellow signal at the north end of Marcel heading northbound.  At North Walong itself the northbound signals could only show red or green (no yellow).  Due to grades, short spacing of signals, train braking, etc. Tehachapi Pass had all sorts of signal nuances, including the repeater signals in some of the sidings for downhill moves.

I don't want to take over Ed's thread, so I'll just say that a LOT has changed with the signal system since this video was made almost 3 years ago. Woodford, Cliff and Bealville have their repeaters working too.

[ChrisKLAS]

Really looking forward to seeing that!   

Interesting, I did not know that the SP's lower signal heads could not display a green.

So a train entering Walong siding from either direction should generally expect to see a red over yellow, did I understand that correctly?   And would the same apply to Woodford siding?

Chris, do you have any links to pics/info about the CTC panels that they used?  I'm thinking that it would be nice to assign the same switch & signal numbers as the proto, but the pics I found do not have enough detail.   One difference in my case, I've had to swap left & right on my panel so that the operator will see the trains moving in the same direction as indicated.   Some compromises are unavoidable...   


Thanks,
Ed

That's correct for a train taking any siding on Tehachapi. Red over yellow unless the siding is already occupied; then red over lunar. SP also liked to save bulb life (at the cost of relays) so they only lit the top signal head when they could get away with it. If you're sitting in tunnel 9 looking at a stop signal at the west switch at Walong, that signal will be red/red. However if it's showing a straight approach or clear, it'll be yellow or green over dark. Intermediates work the same way except that even on a stop indication, the bottom head stays out, so you just have red over dark. The only time the bottom head was ever lit on an intermediate was for the approach diverging (yellow/yellow) aspect.

I actually don't have much info on the CTC machine since that was in use well before my era. I did find out recently that the one down in San Diego, which I always thought was the real one too, is actually a replica. That was a little disappointing.

[ChrisKLAS]

That's correct for a train taking any siding on Tehachapi (edit: except Cliff. Cliff is a 10mph siding so trains would head in there on a lunar indication in all circumstances. Not enough coffee yet this morning  ). Red over yellow unless the siding is already occupied; then red over lunar. SP also liked to save bulb life (at the cost of relays) so they only lit the top signal head when they could get away with it. If you're sitting in tunnel 9 looking at a stop signal at the west switch at Walong, for example, that signal will be red/red. However if it's showing a straight approach or clear, it'll be yellow or green over dark. Intermediates work the same way except that even on a stop (restricting, at an intermediate) indication, the bottom head stays out, so you just have red over dark. The only time the bottom head was ever lit on an intermediate was for the approach diverging (yellow/yellow) aspect.

I actually don't have much info on the CTC machine since that was in use well before my era. I did find out recently that the one down in San Diego, which I always thought was the real one too, is actually a replica. That was a little disappointing.

And now I can't even edit a post correctly. I must REALLY need more coffee, lol.

[kc9jts]

That's correct for a train taking any siding on Tehachapi. Red over yellow unless the siding is already occupied; then red over lunar. SP also liked to save bulb life (at the cost of relays) so they only lit the top signal head when they could get away with it. If you're sitting in tunnel 9 looking at a stop signal at the west switch at Walong, that signal will be red/red. However if it's showing a straight approach or clear, it'll be yellow or green over dark. Intermediates work the same way except that even on a stop indication, the bottom head stays out, so you just have red over dark. The only time the bottom head was ever lit on an intermediate was for the approach diverging (yellow/yellow) aspect.

I actually don't have much info on the CTC machine since that was in use well before my era. I did find out recently that the one down in San Diego, which I always thought was the real one too, is actually a replica. That was a little disappointing.

Slight correction: Cliff still had a diverging approach (red over yellow) aspect and not a restricting as the aspect into the siding.

Signals and switches:
North Woodford: signals = 46, switch = 45
South Woodford: signals = 52, switch = 51
North Walong: signals = 54, switch = 53
South Walong: signals = 56, switch = 55

The signals are Left/Right