How to wire this unusual point configuration

[Simon Glidewell]

I came across this unusual combined diamond crossing and right hand point (Tonbridge) on this forum. This would fit my plans for the first extension on St. Mary Hoo perfectly and would obviate the need to build two diamond crossings for the industrial railway to cross the main line. Would anyone know how to wire this and where the polarity switches would go, plus where would the electrical breaks be?

http://www.scalefour.org/history/images/mrc09-01.html

Many thanks
Simon

[nigelcliffe]

This is how I'd approach the electrics.

Red and Blue lines are the main track feeds for running. The other colours; yellow, green and magenta are switched areas.

crossing-turnout.jpg

For routes through the turnout (to A or B), then the turnout crossing (1, green) has to be switched with the blade movement. Just like a normal turnout.

In addition, routes through the diamond have to be defined and switched. Crossing via the turnout (to either A or B) will switch the diamond crossings (2 yellow connect to red, 3 magenta connect to blue). Crossing the other route (to C) will switch the diamond crossings to the opposite polarity (2 yellow connect to blue, 3 magenta connect to red). With luck, some other turnouts, or signals, away from the diamond can indicate which route over the diamond is currently active, so those turnouts (two contacts required) will change the diamond and a separate switch for users to remember to change can be avoided.

[Simon Glidewell]

That's very kind of you Nigel; the diagram is much appreciated. The electrical aspect of it sounds quite complex for an idiot like me! Am I right in believing that there would be three polarity switches required?

All the best
Simon

[grovenor-2685]

Yes, 3 polarity switches, just one minor quibble, the 3 insulated joints in the small triangle where green buts onto the red and magenta sections could make the track build difficult, I would extend the green onto the crossing track by including a bit of the red and magenta, so the insulated joints can be in the longer red and magenta rails.
Regards
Keith
PS This wouldn't bother Nigel as he is used to doing it in 2mm.

[Simon Glidewell]

Yes, 3 polarity switches, just one minor quibble, the 3 insulated joints in the small triangle where green buts onto the red and magenta sections could make the track build difficult, I would extend the green onto the crossing track by including a bit of the red and magenta, so the insulated joints can be in the longer red and magenta rails.
Regards
Keith
PS This wouldn't bother Nigel as he is used to doing it in 2mm.

Many thanks Keith for the advice. I now just have to price it all up from the C & L website using Exactoscale chairs. One of the hardest bits is going to be working out the lie of the timbers around the diamond crossing area as it's not very clear from the photo; most of the timbers throughout the point appear to be the normal horizontal to the flow of the track, but the ones on the right hand side of the diamond (the right exit) seem to be at a slight angle.

All the best
Simon

[Phil O]

Hi Simon

Diamond timbering is usually square to the centre line through the common crossings.

Phil.

[grovenor-2685]

Hi Simon

Diamond timbering is usually square to the centre line through the common crossings.

Phil.

In this case there are two superimposed diamonds with 4 common crossings so that idea doesn't work. In the example in the photo the timbers look to be aligned at 90 degrees to the centreline of crossing one, ie the turnout crossing. i would go with that, start by putting a timber under each crossing nose and try to space the rest out to suit the special chairs as much as possible. There is no right answer, just a best fit.
Keith

[Simon Glidewell]

Thanks Phil and Keith. I will just have to play around with my ply sleepers and see if I can replicate the arrangement in the photo... somehow!