Randall / GGMRC Model Train Layout

Presentation

2017-12

This document gives a short overview of the model train layout. The layout was built by the GGMRC (Golden Gate Model Railroad Club) started in 1961. It is located in the basement of the Randall Museum in San Francisco, CA.

1- Layout Design

2- Layout Design Impact

3- DC, DCC and DCM

4- Electrical Design

5- Power Supplies

Older Power Supplies

Lights Power Supplies

Critical Power Supplies

DCC Power

6- DCC Bus Wiring

7- Mainline Turnouts

8- Branchline

8.1- Reverse Loop

8.2- Branchline Main Panel

8.3- Smith Flat Panel

8.4- YouBet Panel

1- Layout Design

The design of this layout may look peculiar and confusing to first time observersers. From a model train perspective, trains randomly go into tunnels and emerge somewhere else in the opposite direction. The layout itself looks quite confusing to the casual observer at first.

Here’s what visitors see when they enter the room:

And here is the track plan, which shows the multi-level mainline looping over itself repeatedly:

The track forms a mainline, which is sometimes single track and sometimes double track. There is a branch line and several yards. As it was common in this era, the layout is controlled by two main control "towers" -- the Valley Tower and the Mountain Tower. These panels concentrate all the blocks and turnouts controls for the corresponding sections of the layout. Each yard has its dedicated block and turnout control panel.

Operators are usually very confused at first. Here’s what one of the two main control panels looks like:

The Mountain Tower panels (block control and turnout control)

Although it all seems confusing, there is some definite logic and rationale in the layout plan and the control panels.

There are two major power districts (valley or mountain) which can be operated using two different throttles (power supplies at different levels). Each "tower" (mountain or valley) is actually composed of three sub panels, as pictured above: one turnout panel and two block control panels (Valley 1 vs 2, Mountain 1 vs 2) which duplicate each block control, thus allowing a specific block to be powered either by throttles from side 1 or side 2 or turned off. At some points mainline blocks also had occupancy lights.

The yards have their independent throttles and tracks leads in and out of yard have a power selector to dictate which throttle is powering an engine entering or leaving a yard. Later radio-controlled DC boosters and MRC power supplies were added.

This always seems confusing to the non-initiated so I’d like to introduce a bit of background on why the layout was built that way.

Layout design has naturally evolved over the years. This layout is built using what was the “state of the art” back in the 60s. The natural tendencies for layouts back then was to try to cram the most track in a given space. A longer mainline makes people who like to run happy. The easiest way to achieve that is to have multiple levels, with the track looping on itself.

On the pictures above, the “mountain” area and the “devil gate loop” are good examples of that. On the mountain side the track goes up through three levels, on the other side it goes down through two loops. This looks visually confusing as trains enter a tunnel at the middle of the mountain at one level and go out of the mountain at another elevation in the reverse direction.  As an anecdote, it is worth noting that this design style fell out of favor in the 80s in favor of more linear layouts with elevation being taken care of using helixes behind the scene -- which has brought different design issues.

One interesting design consideration is that when I joined the GGMRC in 2014, everyone was running the mainline clockwise, that is starting from the Stockton Yard towards the Stockton Station then to the Mountain/Summit then going down through the “devil’s gate” loop (which is obviously build to look like the well-known Tehachapi Loop in California). However I was told the layout was originally designed to run counter-clockwise and the reason they choose to run clockwise is that the mountain is a 1.1% grade going up followed by the loop with a 1.75% grade going down, which is much easier than the reverse. Personally from an operational perspective I see the layout as being able to run both directions at once with clear sidings for meets and potential for helper units being added and removed for the long grades.

Let’s consider the electrical and control aspect. The layout obviously started as DC (non digital) control. One bit of background explanation is useful here: on a DC layout, the trains are powered by the voltage applied to the track. Typically one transformer is connected to the track and varying the voltage controls the trains speed -- all trains powered by the same transformer all go at the same speed at the same time, they cannot be individually controlled. This is clearly an issue on a large layout like this where they would be multiple trains, possibly in reverse direction.

To solve that issue, the mainline is cut into blocks that can be independently turned on or off. One additional complexity added here is that they have not one but four independent power sources -- two power districts (the two Towers) which each two “cab throttles”. On the Mountain Tower picture above, the “Panel 1” on the right and the “Panel 2” on the left can be used to decide if a given block is powered by the throttle 1 or the throttle 2 or neither.

Yards have their own control panels with their own separate “cab throttle” power supply. A switch is used to decide whether the yards are powered from throttle 1 or 2 (to enter and leave the yard) or by the yard throttle (when inside the yard).

Thus two operators could run trains on the Mountain area, with two different operators on the Valley area, then each yard could have its own operator.

The Stockton Yard panel (apologizes for the low quality stitching)

To understand the nature of the confusion in operating this, let’s look at this picture:

This part of the layout is actually controlled by 4 distinct control panels, each located at different places. Here’s the same image with indications of where the control panels are and which area they operate:

The mainline is on the very right, controlled by a “valley tower” control panel in the middle behind that mountain on the side of the layout (dark blue); the main Stockton yard is composed of two sections controlled by two separate panels (light blue and red) and the Stockton Industrial yard is controlled by another panel (green). One needs to crawl under the layout to reach the two yard panels denoted in green and red below.

Another issue worth pointing out is that the “Valley Tower” control panel, denoted in dark blue above, also controls mainline turnouts which are located on the very opposite side of the layout, out of visual range.

The following schema represents the track from the picture above (seen from the left). It shows which track is controlled by which yard panel:

One leading confusion is that the panels are old and quite frankly poorly documented. The schema above is one I made to understand the logic behind it and especially to understand what happens at the boundaries.

It is worth noting that although the panels have blocks numbers, these have no matching visible indication on the layout. Similarly, turnout toggles offer no way for one to directly match a specific button to a turnout on the layout. The only link is the track plan on the panel, which some people find obvious and others find cryptic.

2- Layout Design Impact

It’s worth noting that from an engineer and operational perspective, this is quite a good scheme. There is both logic and complexity. For example taking a train from the mainline to the passenger yard next to the roundhouse involves no less than 3 panels, located at different places. The downside is that it involves quite a bit of crawling under the layout to reach some of these panels. I did observe that most club members did not care for that complexity, which means few would look for such operations or be extremely reluctant (and annoyed) at it.

The same goes for running in opposite directions on the mainline. On the prototype (“real”) railroad, it involved careful coordination to have trains that can meet and stop at sidings. The same would be needed here, with operators coordinating with each other and using the sidings available via the Mountain Tower control panel or the Valley Tower control panel. The lack of labelling and the lack of easily identifying which turnout toggle controls which physical turnout means that a lot of operators would just randomly flip a toggle to see if they actually triggered the turnout they wanted. I have seen every operator make mistakes when switching, including seasoned operators. This is not a sound operating principle.

Consequently what most members did was just stick their trains on the mainline and run it as a unidirectional loop with no operation variety whatsoever. Everybody running long trains one following each other.

Another issue is that this layout was also an “exhibit” for the museum hosting it. Every Saturday, visitors would come in and expect to see trains running, most visitors being kids who want to see trains running around, which works well on this complex looping layout design. This compounds the issue as operations are not something exciting to look at and falls in disfavor of simply running trains on the mainline as a continuous loop. On the plus side, since the layout loops over itself, even multiple trains all running in the same “logical” direction look like they are going in different directions visually so it does give a greater sense of variety than there actually is.

Historical anecdote: this kind of layout is well designed to have one manned dispatcher in each control tower. Two operators can run on the mainline in reverse of each other and coordinate meets with the tower dispatcher. Since each operator would use the wired “throttle” connected to the tower, they would be next to each other and be aware of the area in control. Eventually starting in the 70s/80s, this layout design started to fall in favor of “walk around” cab designs in which small control panels are scattered on the fascia of the layout, directly facing the turnouts they control. This makes it trivial to understand which toggle controls which turnout. Plug-in throttle or wireless systems mean an operator can literally walk around the layout following its train, instead of relying on a central dispatcher. A walk-around design also greatly simplifies electrical wiring as there is no longer a need to run long cables from a central tower to remote parts of the layout.

3- DC, DCC and DCM

As stated above, the layout did start as a DC layout. Also called “analog”, in “direct current” mode trains are powered via the track and the voltage applied to the track directly dictates how fast the train motors go. Any engine placed on the same piece of track receives the power and thus runs.

Over the last 10-20 years, trains layouts have started switching or being built exclusively for DCC, “digital command control”. In this scheme, model trains are still powered by the track and the track is always at full voltage. However each engine is equipped with a microcontroller (called a “decoder”). Each engine is given a number and the microcontroller listens for digital commands send via the track and only accepts the ones for that specific number. Users operate the trains by using wired or wireless remotes (called “cab throttles”) which send run commands to a specific engine number.

A few years ago the layout was converted from DC to DCC. I did not find any specific documentation on the technical implementation of such, so the following is entirely based on my own discussions, observations and understanding -- and many times lack thereof.

The layout was not just “converted to DCC”, it was made to be able to work either in DC, DCC or “DCM”: each control tower has a large switch to dictate which electrical mode can be used.

DCM is short for “DCMaster”, an obsolete vendor-specific technology from Broadway Limited to address sound engines running on DC analog track.

From what I gathered, there was a rationale to keep the layout operating in both DC and DCC modes. First current members probably had a lot of DC engines which were not DCC compatible. There also seems there was a split in the group between those in favor or against this evolution. Finally the “Junior Engineering Day” event (in which the club invites all museum visitors to run the trains) was only setup to work in DC as the engines used were not compatible with DCC.

I must say the conversion was cleverly done and really well executed. Yet it does result in panels which end up more complicated than needed. The procedure to change the layout between DC and DCC mode was quite complex and error prone, involving changing toggles on both control tower panels and switching a number of power supplies. The procedure was not written down anywhere that I knew and only a couple members really knew what to do.

Ironically, multiple people told me they wish the existing control panels stay as-is, because of the nostalgia and historical significance. The problem is that this complexity has a cost. There has been a lot of iterative work on this layout over its fifty years of existence. There is a lot of obsolete wiring under the layout, it’s extremely hard to figure if a given thing is actually used or not. The panels have the same issue. They have seen multiple iterations, with empty holes that used to host toggles doing who knows what. There are a lot of lights and wires for a former block occupancy system that is nowhere to be found. There has been additions hastily crammed in a corner in order to not change the rest of the panels. The list goes on.

4- Electrical Design

“It seems to run on some form of electricity”.

There is a lot of wiring under that layout. I mean a lot of it.

Some of that wiring obviously dates from the original DC design, for which there are plans however I have no idea how relevant they are. The current wiring is a mixed bag. In some places it’s very clean and logical, on others it’s frankly just a big mess, with some remnants of wiring that goes unused. Then on top of that was layered all the DCC work, which although clean and logical adds one more layer of complexity.

Let’s start with the power supplies, of which there are many.

5- Power Supplies

Under the layout are located many power supplies. Some have proven to be obsolete and not used anymore, and a few are critical. There is no obvious record of which so this section will try to explain what matters.

Older Power Supplies

In several parts of the layout are located large power supplies attached to the benchwork's support beams. These are totally unconnected. They are part of the original DC throttle equipment dating from the 60s. They are custom made and the schematics are available in the paper archives electrical cabinet. These are permanently mounted to the layout beams. At this point they are of purely historical interest as they show excellent craftsmanship.

There were several modern MRC power supplies under the layout -- one under each tower and yard, which were connected to the remaining DC throttles.

Lights Power Supplies

Under the Valley panel behind the TV is an old-style power supply. It is actually used and delivers ?? V DC to the building lights.

Under the Mountain panel, there are two small power packs. One powers the motel neon sign. Another one used to power the grade crossing signal at block 120 before it was removed by a former member with little consideration.

Under the roundhouse, there are 3 small power packs. They power the hotel sign in the town and the building in fire next to it.

Critical Power Supplies

Right behind the DCC Command Station are located 3 critical power supplies:

  • A small regulated variable voltage power supply (with 2 knobs and 2 analog meters) is dedicated to the slow-motion turnouts. It's labeled with a "11 V MAX" label.
  • Next to it, I added a similar looking regulated variable voltage power supply for the new DCC-controlled turnouts.
  • On the other side of the DCC Power Pro is a large gray power supply with 3 outputs:
    • 24 V DC for the DC / DCC relays.
    • 12 V AC for … ??
    • 6 V AC for … (definitely some lights but what else??)

DCC Power

The layout uses an NCE Power Pro and three NCE 5-amps boosters which are then split in 10 power districts.

The NCE Power Pro (left) and 3 boosters

Each power district has its own NCE EB1 electronic circuit-breaker for protection against shorts.

The circuit-breakers for the 10 DCC power districts

Map of DCC boosters to power districts to blocks:

Booster 1

P1 V1 (Valley1)

P1 STKYD

Booster 2

P2 V2 (Valley2)

P2 NAPA

P2 TOWN LODI

Booster 3

P3 MTN

P3 BRN RCH-2

Booster 4

P4 MTN-2

P4 BRPORT

P4 SIA RND

Both control towers (Mountain and Valley) are are powered by 2 boosters. Here’s the split for the Mountain panel:

The DCC conversion made use of the block system and kept it intact. Since each block has two possible power sources, the DCC actually acts as one of the power sources. For example on the Mountain tower, there are Panel 1 and Panel 2 for block control, half of the block toggles on one panel toggle it to DCC whereas the other half is located on the other panel. These DCC toggles are denoted by a yellow handle.

Since each block has two power supplies in parallel (DC vs DCC), when operating it is important that one block toggle be up whilst the corresponding block toggle on the other panel be down, otherwise it can create shorts in the whole power district.

The rule when operating in DCC, as is the case here, is that all "yellow" DCC block toggles must be up and all the silver DC ones must be down. There is no written indication on the panels that they work that way.

6- DCC Bus Wiring

Pairs with one orange cable, one purple cable, and one dual white cable: the orange/purple are fairly large AWG, maybe 12 or 14, stranded. The white one is regular power cord cable.

The orange/purple cables are the output of the DCC circuit breakers and they bring power to each DCC power district. The white cables are connected to the 24 V DC panel and trigger the DC / DCC relays once the DCC main switch is turned on.

This can be seen next the DCC Command Station where the circuit-breakers are:

Under each tower panel (one per block panel), there's a relay with the other side of the orange/purple cable.

The relay acts as a dual 1PDT that toggles between the DCC or the DC input:

This double-relay scheme means that some DCC-only equipment can be powered only when the DCC is up (see branchline chapter below for an example).

The output are the two large black and red wires.

The black wire goes directly to the DCC power bus. The red wire is split and then fed to the smaller red wires for each block toggle.

The output of each block toggle connects to a switch board under the layout using red wires. For each block, the switch board takes two red wires from Panel 1 or Panel 2 of the mountain or valley panel, and outputs one red wire towards the track block. The red wire then joins the black wire and form the DCC power bus for that block, on which feeders are connected to the track.

To understand what’s going on, let’s look at the control panel of the Mountain tower, for example:

There are two panels, “Panel 1” and “Panel 2” which are replicas and have the same track layout with the same block toggles. Each block has a number and they are equally present on each panel. However on Panel 1 only the half toggles from the top are connected to DCC whereas on the Panel 2 only the ones from the bottom are connected to the DCC. The output of each block of the same number is connected together via a switch board under the layout, thus merging both sides.

To summarize all this in one schema:

Each panel hosts about a dozen DCC blocks. There is a similar setup for the Valley panels.

7- Mainline Turnouts

Turnouts control represents another interesting topic.

The layout uses 3 kinds of turnouts: twin-coils, Fulgurex and Tortoise. It seems that twin-coils are used in the yards and the original mainline was apparently using Fulgurex turnouts. Later, some of the mainline and yard were changed to more modern Tortoises.

Turnout panels use rotary switches for Tortoise and Fulgurex turnouts (mainline) and push-buttons for the twin-coils (all yards).

The existing turnout panels all use non-momentary rotary toggle switches.

Power is provided by a regulated variable DC power supply located next to the DCC Command Station as indicated above.

Each rotary toggle switch is a 6PDT with only 2 poles used, so it ends up being the typical DPDT wired in a cross-over configuration. Turning the toggle effectively inverts the input polarity.

Input is the DC turnout power (red wire is negative, white wire is positive). Inside the panel, all red wires are connected together using a terminal block where all terminals are connected together with a bare wire.

Output of each DPDT is 2 wires, white and green. The whites ones travel directly to the corresponding turnout. The green ones are connected to another 1-to-1 terminal block inside the panel.

Schematics of the original wiring:

8- Branchline

8.1- Reverse Loop

The DC/DCC relay for the Branchline feeds a Lenz Digital Plus LK100. This is a “Reverse Loop” polarity inverter.

This is one case where the “double relay” scheme for the DC / DCC makes sense: the LK100 is powered by the DCC only when the relay is active.

An engine that goes from the mainline (block 321) to the branchline will eventually return at the Rodgers Jct  and can rejoin the mainline in the reverse direction. The full branchline is thus essentially a long reverse loop.

8.2- Branchline Main Panel

The branchline panel is hosted in a sliding drawer. Here’s the top of the control panel:

Under the panel is a terminal block connected to the various toggles:

This in turn connects to another terminal block on the frame of the layout, which comes with a clear label for each terminal position, as seen on the right.

Not all positions on the terminal are used.  Some have wires which have been cut or lead to nothing.

Each number corresponds to one toggle, as depicted below:


Usage on Panel

Wire color to drawer

Wire color on layout

1

Rotary Toggles with

  • Left to Throttle 2 (#9)
  • Right to Throttle 1 (#8)

On #4, the right side wire to Throttle 1 is broken.

White

Orange + Blue/White

2

Gray

Green (Sensor BL2)

3

Faded Orange

Red

4

Drab Brown

White/Blue

5

Not connected to push button
(I think it was for a former uncoupler)

Faded Orange

X

6

--

NC

NC

7

--

NC

NC

8

Throttle 1

Faded Green

Red (block power)

9

Throttle 2

White

Red (block power)

10

--

NC

NC

11

Rotary toggle, wired like #1-4

X (broken)

X

12

Not connected to panel

Blue

X (see note)

13

--

NC

NC

14

SPDTs using power from #18 (14 V AC) via 2 diodes to control Tortoise motors.

Drab Brown

Brown

15

Black

Gray

16

Black

Black

17

Faded Blue

Green

18

Label “14 V AC” (actually 12 V AC)

Faded Yellow

Yellow (AC power)

19

SPDTs for sidings power.

Gray

Gray (Sensor BL1)

20

Black

Brown

21

Faded Green

Green

X = there is a lead in the terminal screw that is broken.

NC = the terminal screw is not used at all.

Notes:

  • Position 11 is obsolete and not used; power from this siding is controlled by the Mountain Panel block 322.
  • Position 12 on the terminal block on the layout is used to connect a red wire to a red wire from a completely different circuit that has nothing to with the branchline drawer. Under the drawer, the wire is cut.
  • Position 18 connects to a “14 V AC” bus (which measured 12 V AC). For each turnout toggle, an SPDT selects one polarity of the AC power using a diode. This matches the “Tortoise wiring using AC with Steering Diodes” (PDF here):

  • The Tortoise AC power bus likely comes from the 6/12/24 V power supply behind the NCE command station.

8.3- Smith Flat Panel

This panel controls the section of Branchline between both tunnels. The two main blocks are “Smith Flat Block” and “Bear River Block”. One spur serves the “Gravel Pit” and the “Red Dog Mine”.

Front

Back

The panel connects to not one but two terminal blocks.
One just above the panel on the wall, which in turns feeds another connected to the layout.

Some of the wires delivering power are not on the second terminal, there come directly to the first terminal.

Terminal #1 from panel:


Terminal #2 to layout:

Here is the panel annotated with the terminal positions (from left to right):

To Terminal 1

To Terminal 2

To Layout

Usage

1

White

White

NC

Power to N/P turnouts, comes directly from somewhere else

2

Blue

Blue

Blue + Wh/Blue

Turnout N (normal)

3

White/Blue

White/Blue

Blue + Wh/Blue

Turnout P (divergent)

4

Yellow

Orange

Orange + Red

Toggle to power for Gravel Pit (feed by #7)

5

Yellow

Yellow

Orange

Toggle to power for Red Dog Mine (feed by #7)

6

Orange

Orange

Yellow

Output of the Bear River Block cab selector.
Rerouted via position 11 to go through the BD20 for Branchline Automation (aka the “tunnel block”)

7

Red

Red

Orange

Output of the Smith Flat Block cab selector.

8

Yellow direct to Red

NC

Orange + Gray

Source Power for Cab 2, used by #6 and #7. The Red wire from the Mountain Tower comes directly to the terminal 1.

9

Orange

NC

Orange x 2

Source Power for Cab 1, used by #6 and #7. There an Orange wire on the terminal 1 that comes from somewhere else.

10

Gray

NC

NC

Connected to main DC bus ground wire, for lights.

Notes:

  • Positions 2 & 3 connect directly to two twin-coils for the spur turnout. On terminal 2, there are 2 wires for one twin-coil motor and 2 wires (inverted colors) for the other twin-coil.
  • The rod for the Turnout N is not connected.
  • Either twin-coils do not work with the current power -- it’s the same issue as the Industrial City section, when tortoises were added, the power bus was changed to DC to work with the tortoises and does not adequately power the twin-coils anymore (these require AC IIRC).
  • Disconnecting #7 (the Smith Flat Block cab selector) removes power to the whole front of the Branchline, up to the station and the sidings!

Updates:

  • The panel has been disconnected from the layout as part of the renovation.
  • Positions #6 and #7 are feed by #9 (cab 1).

8.4- YouBet Panel

This panel controls the section of Branchline after the small YouBet town in the back of the mountain.

In this part, the narrow gauge forks and connects back on the dual-gage branchline as an unfinished reverse loop.

Front

Back

Now we have a name and a date for the panel.

This one connects to a 20-position terminal… using wires all of the exact same color :-/

Here is the panel annotated with the terminal positions (from 1 left to 20 right):

To Layout

Usage

1

Orange

Power from Cab 1

2

Yellow

Power from Cab 2

3

Blue

Common / Ground for lights

4

White

Power for turnouts 6 / 7

5

Not Used

6

White/Blue

Output of turnout divergent to narrow RR

7

Blue

Output of turnout normal to branchline

8-11

Not Used

12

NC

Wire from panel is connected to terminal but not used. Can’t tell what it does on panel either.

13

Blue + White/Blue

Output from Yellow polarity inverter.

One of the inputs comes from the output of the Greenhorn Logging RR cab selector.

14

White

15

Orange

Output from Coleman Block cab selector ⇒ Source for toggle 18

16

Not Used

17

NC

Output from YouBet cab selector

18

Orange

19

Yellow

Output of orange push button / turnout divergent towards logging RR

20

Green

Output of green push button / turnout normal

Updates:

  • The panel has been disconnected from the layout as part of the renovation.
  • Position #1 (cab 1) has been connected to #15 (Colemans Block)

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