Track design

[mojo36]

In the period 1930-39, were single and double slips often or rarely used on main lines and/or sidings?
What would be the reasons for using or avoiding them?
Maurice C.

[Hatfield Shed]

It's simple in principle, the more complex the point work the greater the first cost and maintenance burden. So simple single lead points were preferable wherever possible. Where space was restricted, but flexibility in routeing was necessary, then the track engineer does what is required. Kings Cross station throat an obvious example.

When it comes to model railways, (which are always space restricted unless the builder has plentiful wedges of green) the compactness of the double slip means that Peco have probably sold 10x and more the quantity they should have sold, if the prototype ratio of single lead points to slip points was scrupulously observed. (Wild guess under the influence of a most delicious Rioja, alternative opinions might be sought.)

[kimballthurlow]

Yes the Rioja is great. I never quite got it, is it a district or a grape variety?

Regarding the original question it is a bit like asking how long is a piece of string.
But anyway from my observation the Midland Railway was a great believer in single slips where the entrance to a goods yard was often a single slip off the main line.
This was probably for the reason of compactness (in real life) as explained by Hatfield Shed.
Single or double slips were just as much used in larger goods yards or station throats (plenty of photo evidence) for the same reason.

While the engineering draftsman might have included slips in working drawings which were then installed, the question of whether they got used is another one.
I have evidence that double slips were sometimes replaced during their working life by conversion to single slips or even cross-overs.

Kimball

[Atlantic 3279]

The single slip of course was a commonly used device in arrangements for access to / exit from goods yards across double running lines as it allowed a facing point and necessary point lock to be avoided.

[manna]

G'Day Gents

I would except the GNR, who loved single and double slips, who seemed to use them as crossovers at (almost) every station on multi track lines.

manna

[Hatfield Shed]

Yes the Rioja is great. I never quite got it, is it a district or a grape variety?...

It's a defined region of Spain, the qualification is that any grape variety grown there can be used to make wine carrying the name Rioja.

And back to slips...

[LNER4479]

The single slip of course was a commonly used device in arrangements for access to / exit from goods yards across double running lines as it allowed a facing point and necessary point lock to be avoided.

Indeed. The key factor is whether the slip is being used in trailing or facing configuration in relation to the running lines. The example quoted by Graeme is the trailing configuration and was much more common. It did indeed avoid the use of facing point locks (thus saving money) but the trade off was often a reversal to gain access to said goods yard. Facing points are more dangerous than trailing points, as the former potentially diverts a train into the path of another if set incorrectly or if the interlocking somehow fails. The adoption of the hydraulic point clamp in more modern times has improved the situation and nowadays there tends to be ladders of plain points rather than slip points.

In the period you state, use of single slips in trailing configuration on mainlines would be 'typical' (sometimes paired up to form a trailing crossover - there are three such examples on Grantham). Use of one in the facing configuration would be less common (interestingly, there was one at Grantham but it had been removed by the late 1930s, which coincides with ever-increasing speeds of operation). Use of a double slip on running lines was largely in station areas where train movements were slow speed only - VERY unusual (I hesitate to say 'never', because there'll be an exception somewhere that proves the rule) on running lines where the line speed was not especially restricted and trains could be moving at (say) 60-70mph or higher.

[john coffin]

Checking the useful GNR engine shed books by Griffiths et al have a number of track diagrams which show how
the GNR used both slips and offset diamonds in many yards.

Paul

[StevieG]

" .... In the period you state, use of single slips in trailing configuration on mainlines would be 'typical' (sometimes paired up to form a trailing crossover - there are three such examples on Grantham). Use of one in the facing configuration would be less common (interestingly, there was one at Grantham but it had been removed by the late 1930s, which coincides with ever-increasing speeds of operation). Use of a double slip on running lines was largely in station areas where train movements were slow speed only - VERY unusual (I hesitate to say 'never', because there'll be an exception somewhere that proves the rule) on running lines where the line speed was not especially restricted and trains could be moving at (say) 60-70mph or higher."

I would just add that the various slip layouts mentioned as being in GNR running lines, not only often lasted well after (often by around 30 years) the period being queried, but mostly originated from several decades earlier, such as at the referred to King's Cross, and at very many other GN main line stations, frequently being little altered over time or when resignalling was carried out.

Interestingly, the significant, and later expanded, layout at the LNER's approx. 1926-built Welwyn Garden City station, was one where, for crossing local trains across the Fast Lines, particularly, from the Down side to the Up (a need which became even more frequent into and throughout DMU days), one of the GNR's typical "Through" or 'ladder' crossovers usually connecting all lines and any principal sidings from one side to the other of the layout with trailing single slips in the intervening lines, would have certainly been useful.
But one was never installed there, with most connections instead being simple two-ended crossovers from one line to the next, thus the crossing moves were physically, and time-wise, longer and more involved, necessitating reversals (sometimes two or three), including, for Down-to-Up crossings, one reversal very inconveniently having to be done on the Down Fast.