A junction question

"Andy Sollis- Churnet Valley model Railway Dept." wrote in news:dv3vm4$hvc$ snipped-for-privacy@newsg3.svr.pol.co.uk:

I don't know the real answer but most prototype track plans I've seen relating to this situation give the impression that that the doubled track following the junction prior to the single line appear to be long enough to accomodate at least a typical branch line train and still leave the juctions (with the main and the single) clear. IOW long enough to be a crossing point.

Of course I don't know if this is definative or not but it appears to make sense.

It was at least as common if not more so for the single line to commence immediately at the junction where the junction signalbox could handle the branch token or staff and all the points would be in rodding range of the box. For an extended double line section to be any good as a passing place it would have to be 440 yards plus a train length to allow a branch train to be accepted without blocking the main, or be equipped with a trap point and sand drag. A train waiting to enter the branch cannot be given the token while waiting so it was best if it could wait before the engine passed the junction signal box, with a busy main line this would suggest a loop line off the main before the junction rather than off the branch after it. But this will certainly fall into the 'prototype for everything' department. Keith

Keith & Chris, Many thanks on the help... I'm not planning on using it as passing, just straight from the main (At the end of the station) to the single branch to the sidings. Does not using it for passing make a difference ?

Andy

It was at least as common if not more so for the single line to commence immediately at the junction where the junction signalbox could handle the branch token or staff and all the points would be in rodding range of the box. For an extended double line section to be any good as a passing place it would have to be 440 yards plus a train length to allow a branch train to be accepted without blocking the main, or be equipped with a trap point and sand drag. A train waiting to enter the branch cannot be given the token while waiting so it was best if it could wait before the engine passed the junction signal box, with a busy main line this would suggest a loop line off the main before the junction rather than off the branch after it. But this will certainly fall into the 'prototype for everything' department. Keith

"Andy Sollis- Churnet Valley model Railway Dept." wrote in news:dv4tjq$1o7$ snipped-for-privacy@newsg2.svr.pol.co.uk:

My answer = lots more doubled track after the junction before becoming single to travel up the branch.

Kieth's answer (and probably the more common of the two) = just enough doubled track to clear the main line to somewhere close by and convenient to make the change to single track.

There is a photo in An Historical Survey of Selected LMS Stations Volume

1 of Marton Junction which shows that the double track section is just long enough to hold an 8F locomotive. The caption points out that there has been a breach of the signalling regulations for this actual event to have occurred ;-)

I suspect that the junction layout is exactly what Andy has in mind as it is a absolutely minimum space arrangement to achieve a working junction.

Regards

Kevin Martin

Chris,

I believe the modern 'simplification' of such a junction is a crossover on the double track main, immediately followed by a turnout onto the single track branch. This avoids the need for a diamond.

Jim.

Another, more costly alternative would be to use a normal set of points plus a single slip, this would just give a run onto the 'branch' without any standing room, but which may be o.k. for the circumstance of the layout. This would make the 'branch' more of a siding. Regards, Bill.