Maunsell Restriction Coaches

So I have been watching alot of Southern films that feature services that run through Surrey, Sussex and Kent, so far noticed that these were used because of the restricted clearances of certain lines.

Also noticed they run in Devon and Cornwall, even though they had no restricted clearances.

So how come that was?

 

Building coaches to the most restrictive dimensions, allows for the widest availability.
It is always best to have a fleet which can be used on as much of your route network as possible. The question might be reversed, why would one build any vehicles which cannot be used on some of the lines?

 

Touché.

 

The Southern Railway built the Maunsell design of carriage in 3 different profiles, Restriction 4 (largest, initially used mainly on the Western and Central sections), Restriction1 (available everywhere except the Hastings line, and the Canterbury & Whitstable) and Restriction 0 (for the Hastings line). Some ex-Brighton carriages were Restriction 6, I believe. Restriction 1 carriages were mainly used on the Eastern Section (ex SE&CR). The pinch points on the Eastern section were gradually dealt with until by the 1940s and 1950s (when Southern Railway Bulleid carriages and BR Mark Is came in), SR Restriction 4 or BR C1 carriages could be used almost everywhere except the Tonbridge-Hastings line (and Grove Junction to Tunbridge Wells West, as I recall). Maunsell Restriction 0 stock continued to be used on the Hastings line until it was replaced by the Hastings diesel-electric units which were also narrower than standard, with flat sides. The Hastings line only became usable by most carriages when the track was singled through some of the tunnels on electrification.
That's from memory and no doubt over-simplified. David Gould's book on Maunsell carriages (Oakwood Press) will give full chapter and verse.

 

To add to that: the cause of the restriction on the Hastings line was that the contractors skimped on the construction of the tunnels on the line, using four layers of bricks for the lining when the specification called for six. The cheapest and easiest remedy was to add the missing two layers to the inside (the alternative would have been to remove all the existing lining, rebore the tunnels, then re-line with bricks). The effect was to reduce the diameter inside the lining, with clearance problems thereafter. As well as the Restriction 0 carriages, the Schools class locos had sloping cab side sheets to enable them to be used on the line.

Tom

 

There is also a a useful page hidden away on the Bluebell's web-site:

https://www.bluebell-railway.co.uk/bluebell/cw/restriction.html

According to another source, a small number of ex-LSWR coaches were assigned to Restrictions 2 & 3, but I don't know exactly what they were.

 

And to round out ahead of the inevitable question, the reason "normal" stock can now work the Hastings line is that in the mid 1980s the track through the tunnels was singled to provide the necessary extra clearance, and allow integration with the rest of the SE electrified network.

 

So affectively, Restriction 4's were seen in Devon, Cornwall and other Southern Region Western section routes.

Restriction 1's were seen on Southern Region Eastern section except the Hastings/Canterbury + Whitstable.

Restriction 0's were seen on the Hastings, Canterbury + Whitstable and effectively the now Spa Valley route.

 

Oh that's a shame, would have been nice if they had left the track how it was and built specific units to work on said lines, be something of an experience.

 

The operational nuances of that list are quite interesting.

For example:

RESTRICTION 4.
Vehicles so marked may pass over all portions of the line except between:-
(Snip)
(h) Hawkesbury St. Junction and Archcliffe Junction (Dover) **.

** May work between Hawkesbury Street Junction and Archcliffe Junction providing no other train is allowed on the adjacent line between those points at the same time.
​

So one wonders how the signalman at each end of that line dealt with the restriction. They couldn't reasonably be expected to examine every vehicle in a train before signalling it, so did they just treat it as more or less single track, i.e. invariably wait for one train to be out of section before allowing another to pass the other way? Or was it primarily of relevance to a platform inspector to authorise the passage? Or just of primary concern for the train planners?

Tom

 

Meanwhile, this Restriction 0 carriage is getting ever nearer completion:

https://www.bluebell-railway.com/brps/cw-news-3687/

Tom

 

Having once been an Orpington commuter, I’m afraid I shed no tears. There was a brief period when one of the Hastings DEMUs covered some duties on the line as the old EMUs were starting to be withdrawn, and the tighter loading gauge was noticeable and uncomfortable.


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Thanks for the link. Good to see another of Mr Maunsell's carriages being restored.

Noticeable how, on both the Maunsell Restriction 0 carriages and on the Hastings DEMUs, the carriage foot-boards stick-out a long way from the body. The Maunsell carriage end-plate quotes an overall width of 9ft, even tough the body width is only 8ft. In the narrow Hastings Line tunnels, the tightest clearances appear to have been at cantrail level, hence the narrow bodies. But given that the track spacing on the line was in some places less than the normal 6 foot, the carriage foot-boards must also have been passing at less than usual clearances.

 

Interesting.
Then again, a lot of these R0's and V's were seen on the North Downs line, a line that didn't have these restrictions, otherwise a certain GWR 78xx or 43xx type wouldn't be allowed to travel on it.

 

The North Downs line could take the SR Restriction 4 and BR Standard coaches, which are 9ft 3in wide over door handles and hinges.

The 78XX and 43XX engines are 8ft 11in wide - but of course that width is over their low-slung cylinders, which come close to station platform edges.

GWR "red triangle" coaches were up to 9ft 7in wide, but I don't think any standard-gauge GWR engine was wider than 9ft 0in.

 

What is often overlooked is the difference between kinematic gauge where the moving vehicle can tip, tilt and bounce to the limit of the suspension and the static gauge (vehicle stationary). Obviously the nearer the point on the vehicle is to the rail the less that movement can be. Typically the greatest movement will be at the cantrail or roof gutters hence why many vehicles are shaped as they are most obviously on tilting trains where allowance must be made for any vehicle which sticks in the tilted position not to hit things. (Also consider the situation where two such failed vehicles need to pass meaning greater track separation is required).

Vehicle length and overhangs are also critical on any curved track or gradient change. The differences between kinematic and static gauge also apply to cylinders and platforms with several speed restrictions for some locos and routes. Gauging is actually a complex science and also has to consider not just the new and as built dimensions but the impact of wear and things like tyre turning.

 

Well, that was a nice surprise!
Although I might be wrong, seems all these wondeful coaches completely bypassed Hampshire (asides The Billy and some cross country services).

Would have been nice travelling in some of these Maunsell Restrictions in my local area (near Havant) rather than the Mark 1's and the electric units, but never mind Guildford, East Croydon and Horsham weren't too far away.

 

The restriction codes continued to apply long after Maunsell's departure. Southern Region Mk I coaches were dual marked, restriction 4 for Southern Region and C1 for the rest of Britain. The codes were also applied to the emu and demu stock.

 

(Deleted). It seems my education was wanting.

 

I think in that case "kinematic" (and @Herald) is correct. Kinematics is the science of objects in motion.

I think the etymology of both "kinematic" and "cinema" go back to the same Greek word, implying in both cases motion.

Tom