Tramway signals, good for any single track with passing loops

[tramcar trev]

Just discovered this.... Brings back memories and I would only have seen one of these open on a few occasions...

http://www.cotma.net.au/library/overhead/Forest City Automatic Tramway Signals.pdf

The real thing bears a striking resemblance don't you think?​

 

[Madman]

Wow, circuitry you can actually follow! Now days, all that stuff would fit into a cigarette lighter.

 

[Dtsteam]

Excellent, Trev. It shows that your version is spot on.
I never realised that they had counters, I always assumed it was one in/one out. Even looking at the piccy and the circuit diagram I can't work out which bit is which - particularly how the counter counts down.

 

[tramcar trev]

Wow, circuitry you can actually follow! Now days, all that stuff would fit into a cigarette lighter.

Now you have given me an idea.... The circuitry is so simple really its pre transistor and no valves or equivalent it simply relies on a circuit being opened or closed using the trolley wheel passing thru a pair of brushes to act as a STMC switch... Using SMT I reckon you could make these things small enough to actually fit inside the little cast resin boxes as per the full sized ones... replace the overhead contactors with a reed switch and magnet or such....
That would make a neat auto signalling system for any railway...

 

[tramcar trev]

Just seen this set of posts. Heck Trev, those PCB's are ace work.......

Thank you Ross, I'm chuffed that you're chuffed....

 

[UKSGR]

Where do you get the cast holders from?

 

[tramcar trev]

Where do you get the cast holders from?

Not sure what you actually are refering to.... The green boxes with the leds in them? If so I make those and I'm about to make a new lot but this time I will use the same shape as the original. If you want any let me know.

 

[tramcar trev]

Excellent, Trev. It shows that your version is spot on.
I never realised that they had counters, I always assumed it was one in/one out. Even looking at the piccy and the circuit diagram I can't work out which bit is which - particularly how the counter counts down.

No I didn't realise that either, I always assumed it was as you say 1 in 1 out..... Though I seem to remember at Bendigo they used to have a Cavalcade of trams to Eaglehawk and it used to cause big problems with the signalling.... Strewth my memeory is being exercised now, and I seem to recall that to over come this each tram had a white disk placed on its rear except the last tram. Now how exactly that prevented meeting head on I don't know. The golden rule was that you could follow the tram ahead of you into single track sections if you were no further than 100 yds behind, if you were further than that you had to stop and wait to get a green light...
There must also have been some indication to motormen too so that they would know how many trams were in the section..... There were other types of signals too I think Adelaide had a single light system and Sydney had some single light systems too where rather than change the actual globes from red to green an elecromagnetic device pulled a coloured glass back and forth in front of the single globe, I only know of 1 of these in a museum....

 

[gregh]

(this is related to the topic on Power buffers in DCC forum)

I think Trev is stopping his trams by removing 12V power from a section of track. This will result in an instant stop. As he has a fixed polarity on the rails (ie one direction only), he could try a big capacitor like this cct:

The diode is to protect the cap from reverse connections of the power supply.
I tested a single capacitor supplying a motor ? I had a 47000uF, 5V cap and used it to supply a motor with its wheels in the air, taking 140mA. The voltage decay when supply was removed was more exponential in shape and the motor took about twice as long to stop as theory predicts.
The calculated value in this case is:
C (Farad) = motor current (A) x time to maintain supply (sec)
acceptable voltage drop in this time

But testing shows the capacitor probably only needs to be ½ the calculated value.
You could probably incorporate this in each of your circuit boards. Unfortunately it only gives a soft stop not a soft start.

Here's the CRO trace of the test above.

 

[tramcar trev]

Ok, looks even better... Several stupid questions;
1) my supply is 12 V so I assume I need a capacitor double that. I have hidden away some where some 20V 1 farad Yes that's F not uF caps (actually they are spares to fit a Melbourne Z class tram) - suitable?
2) the larger the capacitor the softer the stop?
3) The power to the track is switched off whether there is a tram in the section or not, I assume this change makes no difference?
4) If I used the Dimmers suitably modified and the power goes off to the receiver/dimmer then an instantaneous start at whatever speed was set before the "blackout"would occur as soon as the power is switched back on... If I go with RC it will take a few seconds for the Rx to find the Tx and in that time I've shut the throttle down so a soft start would be gained then as you feed the power in via the ESC?

This is very good, if the cap is large enough the tram may move forward sufficiently before it stops to allow the one following into the same dead section of track, that's a big ask I guess it would have to provide enough power for the tram to run half a metre...

 

[gregh]

Ok, looks even better... Several stupid questions;
1) my supply is 12 V so I assume I need a capacitor double that. I have hidden away some where some 20V 1 farad Yes that's F not uF caps (actually they are spares to fit a Melbourne Z class tram) - suitable?
2) the larger the capacitor the softer the stop?
3) The power to the track is switched off whether there is a tram in the section or not, I assume this change makes no difference?
4) If I used the Dimmers suitably modified and the power goes off to the receiver/dimmer then an instantaneous start at whatever speed was set before the "blackout"would occur as soon as the power is switched back on... If I go with RC it will take a few seconds for the Rx to find the Tx and in that time I've shut the throttle down so a soft start would be gained then as you feed the power in via the ESC?

This is very good, if the cap is large enough the tram may move forward sufficiently before it stops to allow the one following into the same dead section of track, that's a big ask I guess it would have to provide enough power for the tram to run half a metre...

Q1 - no you only need a cap voltage rating just above your supply volts (not double). But measurre your voltas at no load - usually it's higher than the rated volts
Q2. yes - bigger C means longer time to stop.
Q3. No problem - the cap will hold it's charge for many minutes/hours with no train in the section. If that's not enough just put a large resistor (10k, 100k ??) across the switch contacts to 'top it up'.
Q4. Sounds like a solution to a problem I hadn't considered !
Q5. I think a 1F cap would be much too big - the tram might go for metres !!!!

 

[tramcar trev]

Another idea occurred to me whilst languishing in the hot springs; put the huge cap on the tram with a diode to prevent the diode discharging back into the line and the tram lighting when it hits a dead section. I have some 10000uF x 16v caps somewhere that may just fit under the floor... Trial and error; they may not have enough capacity... They would have to be on the supply before the PWM of course....

 

[UKSGR]

Where do you get the cast holders from?

Not sure what you actually are refering to.... The green boxes with the leds in them? If so I make those and I'm about to make a new lot but this time I will use the same shape as the original. If you want any let me know.

Hi Trev

Yes, I would be interested in buying some of these from you. Any idea of a price? And how do you make them?

 

[tramcar trev]

They are cast in precoloured resin in silicone rubber moulds. The leds are encapsulated and are wired to work with the PCB circuits I use. I could make them with a common cathode just as easily giving 3 wires red, green and black for you to wire into your own system. The new ones would be the same shape as the one pictured, the genuine Forrest City ones.
As to the price it would depend on the quantity... But as an idea each one has around $7 worth of materials and takes around 30 mins to make. So I guess about $20 ea would be a sensible asking price. If you wanted complete signal units ie 1 control board, 1 signal box and 2 encapsulated reed switches I would have to work out a price...
There has been some discussion; http://www.gscalecentral.net/tm?m=127131&high=colour+light+staff

 

[tramcar trev]

As I previously waffled on about...
I have made up some masters for the "New" Forest City signals. The car counting type ( the longer one) is by necessity slightly over scale as dictated by the minimum size I could make the circuit board. It can only count to 5 cars too.... the smaller one which is simply 1 car at a time in a section is simpler and can integrate with the counters but will still only allow one car at a time on single track...
The holes at the bottom will allow for a short length of 3mm Silicone rubber tubing to hide the wiring and it can be bent and poked into a hollow traction pole or if need be can be mounted on its own pole... The position of the green and red leds has also had to be moved from the prototype for reasons of internal practicalities. These I will make in epoxy rather than polyester resin as the weatherability of the epoxy is far superior and though I will have plenty of spares I really don't want to have to replace them....

​

 

[trammayo]

They look the bees knees!