Overview: This winter I will be undertaking building three new modules for the club I belong to. They will be 2 4’ modules and 1 six foot module. Each module will have three tracks, (numbering 1 thru 3, where track 1 is the closest to the audience) the two 4’ modules will only be the approachs to the 6’ module. The 6’ module will have a Walthers pivot bridge and (If I can find it) an AHM rolling lift bridge. For right now I am assuming I will not be able to find the AHM kit and will have to gantlet tracks 2 and 3.
Known answers to the operation: I know I will need optical occupancy detectors for both tracks 1- 3, motor and decoder for the bridge. I will need to isolate the bridge section from the rest of the track and isolate at least 3 feet on either side of bridge to stop the trains if the bridge is open or if a train is on track 2 or 3 and approaching the bridge at the same time.
Questions.
1.) How do I rig the system so that if the bridge is open that it stops all traffic somewhere before the bridge on the 4’ modules?
2.) How do I rig tracks 2 & 3 so that if a train from either track 2 or 3 is moving onto the bridge, that it kills the power to the approach for whichever track the train isn’t on (ie., if the train is on track 3 it kills power on track 2 somewhere back of gantlet.)?
3.) What type of signals would approprate for 1940’s ish. Bullet, or semiphore. And how many would be needed? (I assume six. 3 for each approach.) How do I link the above to the signals?
Well, if it were my project I’d just use toggle switches and skip all the electronics. Leave it up to the operators to pay attention to what track(s) are occupied and whether the bridge is open or closed.
Have everything dead track until an operator actually needs to go over the module with the bridge(s).
Number 1 is simple: If the bridge is open all power is off. It is a simple electricl interlock, but since it is at 110 volts (even with a relay) you knead to know what ewe are dewing.
You gap all four approaching tracks. Only the track that gets the signal will also get power. This is not handled by train detectors, but by a switch lever in the tower. It is a home signal and needs to be controlled by the tower operator, not by track circuits. Those are used to protect the train that you are following.
The type of signal used is dependent on the type of interlocking machine used in the tower. The levers, the signals, and the switch motors were all built as a single unit by a single company. Most common in this country are Union Switch and Signal (US&S) and General Railroad Supply (GRS). So if you are following a prototype the kind of interlocking machine that they used at that location will tell you what kind of signals to use. Older machines were semiphores because the whole thing was mechanical and depended on the tower operator’s bowl of Wheaties for its power. Powered US&S machines used air pressure to move signals and semiphores. GRS systems used electricity, but were mostly semiphore type signals since it depended on the weight of the signal to move to a fail-safe (STOP) indication in the
I’m gonna assume that you’re part of a N-Trak / Freemo style club. On all the sections, wire the power bus according to the rules, however, DO NOT connect it to the tracks in any way. From here on out, I’m assuming one (1) bridge.
Wire in a secondary bus on all three modules, which DOES connect to the track feeders. Use a different (non-standard) power connector for this bus, so that someone setting it up can’t connect it to the main power bus of the layout).
On the 4’ modules - add a jumper (via DPST or 2x SPST switches) from the main bus to the sub bus. This will allow the 4’ modules to work even without the 6’ module. Add indicator lights also (i.e. you turn it on, and red lights).
On the 6’ module wire jumpers to micro-switches (or contact plates) under the bridge, such that when the bridge is up, power is cut to the SUB BUS (powering the 2 4’ sections, and the 6’ section). When lowered, the switches are closed, restoring power.
I’d use a detector controlling a normally-closed relay. When the detector fires (and energizes the relay), the other track loses power.
I would look for optical sesor units that controlled relays.
Use one each on any bridge that lifts and shut power off to the approach tracks at both ends.
If trains are running bi-directional on each track, then you will need four sensor sets. One for each approach track at each end of the bridge. When the sensor on the north track bridge at either end goes active, it shuts down the power to the rails at both approach track ends on the south track bridge. (And vice-versa.)
Signals could be any type depending on the railroad you want to follow modeling wise. Do some research. However, now the sensors that you choose will need some aux outputs for the signals.
Here is one place you can start looking for circuits:
I have a grade crossing module from rpaisley, and thinking about how it works, it could be used as the detector for tracks 2 & 3. You would need one board for each track. The tortoise output could be wired to a tortoise and then use one aux contact set of t
I would try to avoid the gantlet track if at all possible. It will be an operational headache and will require to people operating the trains to be throwing switches and having to stop their trains every orbit, or you will have to shut down one main for hands free operation. Very cumbersome.
If all you have are the home signals for the bridge then you really don’t need to worry about the yellow signals being active, there really isn’t a signal indication that will need them. Yellow signals convey information about other signals, since you don’t have any other signals beyond the bridge the only indications you will have will be either stop or clear, yes/no, go/no go.
Not to worried about gantleting two and three as track two and one are continuous orbit with right of way going in numeric order. So whomever is playing on track 3 will have to keep an eye out for two.
Track 3 is the play track for the club at shows. Not all modules have track three, and it’s very likely that track three could end up being an island of three tracks in a see of two.
Doesn’t really matter, yellow signals give information on how to proceed approaching the next signal (except for restricting). If you read any of the indications for signals with yellow in it they all say something to the effect of reduce speed and prepare for the next signal. With the number of signals described there is no “next signal”.
If you are thinking the yellow will slow trains down going over the bridge, that’s not what the home signals would do, the speed restriction in the timetable would do that.
To actually use yellow signals and fully interlock the bridge you would need between 11 and 19 signals (depending on how it was configured) spread out over all three modules.
[#oops] You’re right - I was crossing the ‘approach …’ and the ‘proceed [limited|medium|slow]’ aspects - although, for tracks 2 & 3, they would make sense to have “approach” apsects if a secondary signal was locked with the gantlet section.