Hayes - Reading crossovers 1961

[martin_wynne]

Another article from

British Railways Western Region - Civil Engineering Department Bulletin - July 1961

What is interesting here is that these new main-line fast crossovers are in bullhead rail, as late as 1961. That's only about 10 years before the introduction of the 1432mm vertical flat-bottom designs. So given a typical life, these crossovers missed out the inclined flat-bottom era entirely.

The picture shows the GWR-style switch-diamonds (movable elbows) with a backing support rail behind the switch rails. I have never seen these modelled.

(lathes means laths; a diplory is a small 4-wheel bogie)





Martin.

[sp1]

What exactly is a switched diamond?

[martin_wynne]

What exactly is a switched diamond?

 

Diamond-crossings flatter than 1:8 angle are required to be constructed with movable K-crossings, like two switches back to back. Both switches always move together, in opposite directions:

 

 

This is because there is too great a risk of wheels mis-tracking and taking the wrong route on fixed K-crossings at angles flatter than 1:8. Even more so in models with wider than scale flangeway gaps.

 

Model switch-diamonds are much easier to build for slips, because there are no K-crossing check rails to find room for, and much more reliable in running because the wheels see no break in the rail. The downside is the need for extra point-motors.

 

Thanks to Mick Nicholson for the picture. (The switches here have been clamped out of use.)

 

regards,

 

Martin.

[The Stationmaster]

Switch diamonds were known on the Western as (movable) elbows or elbow points.  I remember my surprise on first seeing the running junction at Twyford West (also known at one stage as Land's End - but changed back to the original name as people were getting a bit confused) before it was commissioned and wondering why it had been laid in bullhead rail?

 

I'm sure some of those on that list were never actually laid in  - there was no running junction at all at West Drayton West although there was a slow speed right hand running junction at West Drayton East which which was renewed further to the east; it is now a single lead 70mph running junction having recently been relaid again - it has gradually moved eastwards over the years.  Interestingly at one time it incorporated an experimental movable crossing. 

 

Both the left hand and right hand running junctions at Dolphin were replaced by single leads in August 1973 with a pair of parallel leads for the right hand junction but only a single ladder for the left hand junction.  I think both have been further relaid since then but I'm fairly sure they were not relaid about the time of the MAS scheme in 1963

 

I'm not sure if Maidenhead East was renewed at that time but it definitely remained - and still does but now as a single lead junction

Maidenhead West running junction was taken out in 1963 as part of the resignalling scheme and I've an idea it might at least have been partially flat bottom rail, it certainly hadn't been relaid as part of the above list. 

 

Ruscombe was definitely laid in - replacing Twyford East as a right hand junction and raising the crossover speed to 40mph compared with Twyford, on one occasion i went though it on a train at nearer 60mph than 50mph (according to my stopwatch) and fortunately the driver would appear to have had the sense to release the brake instead of keeping in his late brake application.  Nowadays it is a 70 mph single lead junction with a splitting distant in rear on the Up Relief.

 

Twyford West also survives - again reduced to single leads.

 

I'm fairly sure that most of the relaying to single lead junctions took place in the 1970s at most locations so as it turned out the bullhead junctions had a relatively short life.

[The Pilotman]

I have sometimes wondered just how long a scale OO gauge 70mph crossover (like the Ruscombe ones Mike mentions above) would be. Too long for most layouts, that's for sure.

[The Stationmaster]

I have sometimes wondered just how long a scale OO gauge 70mph crossover (like the Ruscombe ones Mike mentions above) would be. Too long for most layouts, that's for sure.

Ruscombe is 31 chains toe-to-toe, which is 2,046ft, which at 1:76 equates to 26.92ft.  So allow 30 feet and you should be able to get it in - now who is in for back drives on 4mm scale points switch rails?