Alternatives for point/turnout operation

bobg

bobg

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Hmmmm! :thinking: Having a minor point operation problem I'm considering powering them and then automatically switching them when a train is detected in the appropriate place. The point at the top of the picture is operated by the point at being 'trailed' in one direction (by the linkage), so that it alternates. The linkage works fine, if kept well fettled, but doesn't like being left idle for a time.

05936d5a78aa4c0a951e8691b9171108.jpg


I don't have, or intend to have, track power, and all stock has insulated wheels. What options are there for 'train in section' detection.

Distance switching is also a possiblity but not the prefered one.
 
I seem to remember from a previous post that these points feed into a return baloon loop, with a passing siding.


The LGB system of magnets, reeds and EPL point motors could be the way to go. Magnets under each loco, strategically placed reeds ( maybe need a bit of diode logic here ), a feed of 16 volts ac for the point motors. No power is fed to the track.

No need to use the expensive LGB magnets or reeds, alternatives are available....just need two LGB EPL point motors. As a by product, if the point motors had the auxilliary switches, they could operate signals.

See what others have to say...

Malcolm
 
I use reeds and magnets and would say that's the way to go too. My reeds operate relays that in turn operate the point motors.
 
MRail said:
The magnet system could have implications for visiting locos.
Click to expand...
Blue tac and spare magnets.
 
Yes I thought about magnets but came to MRail's conclusion that it was more difficult for visitors. Is there another reliable way?

Further thought/assessment has revealed that I only really need to power the top point (that diverts from the passing loop to the main loop, up or down trains. Malcolm's memory is correct). The bottom point can be left sprung to the up-line of the passing loop. A sensor is required on the main loop approach to the top point (up trains), and another sensor on the down-line of the passing loop to switch the point back again (down trains). In fact it matters not which direction the train passes the main loop sensor as if the point is already correct it will just re-pulse the motor. The down-line loop sensor will only be triggered by down trains. The down loop entry-point can also be left sprung.
 
MRail said:
nicebutdim said:
MRail said:
The magnet system could have implications for visiting locos.
Click to expand...
Blue tac and spare magnets.
Click to expand...
I was thinking of my own intended vist, of course.
Not sure about Blu-tac mixing with the steam oil goo under the locos?
Click to expand...
Very true. At the best it would lose it 'stickyness', at worst it could become very gooey and get to places not wanted.
Another method that would produce a pulse is to cut a running rail in 3 places in say a 1 inch length of track, then connect a wire to each of the two sections that are then disconnected. When the wheel passes over the middle cut it would bridge the joint momentarily and produce needed pulse. The problem here is keeping the then cut pieces of track in line.
Another method is using infra red beam detection. It isn't as complicated as it sounds but in the great outdoors the sensor would need to be shielded from daylight otherwise it simply won't work. It could be placed within a trackside building or similar. This would be good but needs protection from the elements http://www.maplin.co.uk/mk120-ir-beam-breakdetector-27513 < Link To http://www.maplin.co.uk/m...am-breakdetector-27513
Actually this one looks better as it drives a relay http://www.maplin.co.uk/infrared-beam-kit-220033
 
Yes Tim, I see the problem with that infra-red one, but if one end was under the track, and the other on the underside of a gantry, the "darkness" would have to strike. It wouldn't matter if it got false signals as long as it was close enough to the point.

With the 'rail-gap', insulating fish-plates either side of a chair should do the job.

I see a little R&D looming. :'(

Full size railway use things like 'treadles' to detect trains, but from experience with 7 1/4" sometimes, even their weight, it misses.

Going back to the magents for a mo, it could be fitted under a (any?) wagon, that would only leave a problem with light engine.
 
Going back to reeds and magnets, you could always have a wagon with a magnet attached for the use of visiting trains. The only reason I like reeds is that they are simple and if you use the sealed type they are reliable too, especially in the harsh outdoor environment. Infra red detection is good, but after thinking about it I think it may be bringing too much complication into the set up.
Track detection with cuts will be reliable too, but some extra electronics may be required to convert the small pulse into a slightly longer and more useful one. This can be done with a 555 monostable circuit.

I see you edited to the same idea while I was writing with the extra wagon.
 
Just a quick question... I have little idea of the build of the chassis on live steam locomotives (at the moment), are they made from metal that magnets are attracted to anyway? If so you wouldn't need to stick them in place, you would just have to find a suitable place to put it, and it'd stay there itself.
 
No Tim, mostly brass.
 
bobg said:
No Tim, mostly brass.
Click to expand...
That's that idea out of the window then :D How about weight operated detection? I know, I'm getting desperate with ideas now.
 
I've tried treadles with 7 1/4" with very mixed results, but something I did try and was almost 100% successful was a side switch, operated by the wheel-flange. A lever was attached to the inside of the rail and as the flange forced its way through it operated a micro-switch. It did give worse results when a train ran through too fast, as the pulse wasn't always long enough to register. Holding relays had been suggested, but it never got that far.

One of the problems with the current system is that the back-to-backs are actually too small, so it doesn't always push the point blade fully back.
 
Ahah! Here's a thought. Instead of one blade operating a micro-switch, how about two blades. That way the movement would be doubled, and should be enough to operate a micro-switch. The maximum movement woud be from touching the rails, to the back-to-back measurement, probably several millimeters.

NOW a little R&D might be a little more fruitfull! :thumbup:
 
The only small issue is finding suitable waterproof microswitches. Pulse length is not too much of a problem, use a simple 555 monostable to give a longer pulse. How about a small, very thin strip of brass fixed (from the outside) so there is a tiny gap above rail height, when the wheel passes over it pushes down on the strip and makes the circuit. You could even place a small recess in the rail top so the strip sits in it when the wheel pushes down.
 
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