How do electric points work?

There are two main types.
The current LGB points use an AC power supply and a magnetic coil in the motor. The armature inside the coil turns when a DC current is applied (only about half a turn). By reversing the polarity of the DC current the armature turns the other way. Using the AC supply and diodes in the switching wiring both polarities of DC can be selected moving the point in both direction. Two wires are needed to the point motor,
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The other method uses three wires. There are two magnetic coils and a metal bar (is it an armature?) moves in to the centre of which ever coil is energised by a power supply - as far as I know this can be DC or AC. The point blades are connected to the metal bar. This is the system usually used on the smaller gauges.
PL-34_19214_Qty1_diagram.jpg


The CDU is a booster unit and you can ignore it for now.
 
Confused!
Does it mean they don't work in analog DC mode?

Do they need separate power supply of their own?
 
LGB points need an AC supply and a switch unit containing diodes for the most straight forward use.
It is possible to use a DC supply and switch the polarity with a DPDT switch (double pole double throw) and a momentary contact switch - but that just complicates the issue..

LGB switch unit.
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But - older (quite old now and not often bumped into) LGB motors did work on the three wire system - just to confuse you. You cab see the number of wire contacts on the cover of the motor.
Newer 2 wire.
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Older three wire.
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Not sure what your doing with yours Tony but mine give virtually no trouble.
 
I think what people are saying is most point motors are just that ......"motors" put anything from 2volts - 18v dc or ac into the two terminals and the motor spins one way :points change switch the wires over and the motor spins the other way : points change back

Simple simple switching is to use an old cheap train controler (hornby) etc and wire the points as you would the train tracks...turn the dial one notch one way points change turn it the other way points change back Simples
 
That'll work Tony, but dont leave the controller knob on because you might overheat the coil windings in the motor.
 
But you can have automatic of pneumatic points as well, I like the automatic ones -always an excuse to have to clean them and remove bits of debris. The pnuematic/hydraulic ones seem to be the best for reliability...
http://www.argyleloco.com.au/pneumatic_switch_system.htm

Electric ones can be simply done DIY with a magnetic actuator ans a switch in a sealed container
 
Buy LGB point motor and momentary switch unit. Power via your transformer. Ensure instructions are included. Read instructions and follow to the letter.

In use apply WD40 to point mechanism at regular intervals and regularly check for debris fouling point mechanism and check rails ( e.g. ballast, twigs, nails, etc). Don't forget to use LGB graphite paste, or similar, on all electrical connections to minimise any electrical conductivity issues in the longterm. Occaisionaly dismantle point motor and give a good clean out, garden bugs !

After 5 years of operation rip out all the electrical gubbins and go back to manual operation. After another 5 years replace manual operation with fancy air powered point actuators. Much less maintainance and groveling around on the ground.

Max.
I guess tha wraps up my learning curve with powered points.
 
Taking things a step further, I have just replaced a number of points, keeping the original (relatively recent) LGB point motors. This required connecting longer wires in some cases - guess what - several terminal screws have corroded solid. Taking the motor apart I see that it would be possible (carefully) to solder the new wires direct to the very small soldered joints between the terminals and the extremely fine copper wires taking current to the coils. Anybody tried this, and found either that it works, or a better way? And do I then apply grease all over the still-working screws to try and further gnashing of teeth?
 
Eaglecliff said:
Taking the motor apart I see that it would be possible (carefully) to solder the new wires direct to the very small soldered joints between the terminals and the extremely fine copper wires taking current to the coils. Anybody tried this, and found either that it works, or a better way?
Click to expand...
Yes I have! I was 'gifted' a pair of fairly new LGB motors, which had had a year's use.

Like you have found, the problem seems to be with later motors fitted an inferior quality connector block.

I have unsoldered the old terminal block, and replaced with a flying lead. The screw holes and cable entry holes have been sealed with an aircraft grade mastic.

I have linked the lead from these motors to another motor with a serviceable terminal block where I have 2 points in a crossover configuration.

The two I repaired have worked well for several years, and would have otherwise been scrapped by their previous owners....
 
Sleeping Signalman said:
Hi,

How do I make the points 'snap' from one position to the other?
Click to expand...
Mine do?

What voltage are you using if in analogue mode?

If you are DCC then you can adjust a CV setting for a longer pulse.

Need more info....
 
Sleeping Signalman said:
Hi, I'm using 22v DC.
Click to expand...

I guess you are using a DPDT switch then to power the point motor if you are using 22 V DC.
Normally you would use an AC supply for points.

Is there anything in the point tie bar mechanism stopping the blades operating?

Also, are you sure you are actually getting at the end of the cabling to your point motor? Measure and check/replace the cabling if not....
 
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