I was browsing through the Mainly Trains catalogue recently when I came across '3-shackle screw couplings' by Alan Gibson 'for Southern and 9Fs'. My reaction was, 'what on earth are 3-shackle screw couplings'! A quick browse through my photo collection soon revealed that some Southern locomotives did indeed have a different design of coupling to everyone else. A normal screw coupling as we know them have two shackles (Note: Some LMS locos have shackles made up of more than one component). A 3-shackle screw coupling is essentially a conventional screw coupling with an extra shackle between the coupling and the draw hook. The purpose seems to be that the extra shackle gives more flexibility on curves.
Looking at photographs of the Bluebell Railway's purely Southern locos the following pattern emerges:
Locos fitted with 3-shackle screw couplings:
- 3 x S.E.&C.R. P Class 0-6-0T's
- S.E.&C.R. H Class 0-4-4T
- S.E.&C.R. 01 Class 0-6-0
- S.E.&C.R. C Class 0-6-0
- S.E.&C.R. Q Class 0-6-0
- SR Schools Class 4-4-0 'Stowe'
- USA 0-6-0T
- SR Q1 Class 0-6-0
- 2 x SR U Class 2-6-0's
- SR West Country Class 4-6-2
- 2 x Rebuilt Bulleid 4-6-2's
Locos fitted with conventional screw couplings:
- 2 x L.B.&S.C.R. Terrier 0-6-0T's
- L.B.&S.C.R. E4 Class 0-6-2T
- L.S.W.R. S15 Class 4-6-0
- L.S.W.R. T9 Class 4-4-0
A similar pattern can be found on other preserved railways such as the Mid Hants and in old magazines.
It would appear that the 3-shackle screw coupling originated on the South Eastern Railway possibly at the instigation of J. Stirling as they were to be found on his 01 Class 0-6-0 and the R1 0-6-0T's, which worked the Folkestone Harbour Branch. The design continued to be used by the S.E.&C.R. under Harry Wainwright. Clearly this coupling became a standard design on the S.E.&C.R. as it was subsequently used on Maunsell's N, N1, U and U1 Classes of moguls.
Following the Amalgamation of 1923 Maunsell continued to use 3-shackle screw couplings on his locomotive designs for the Southern Railway such as the Schools and Nelsons. Photographs show that both the L.S.W.R. and L.B.&S.C.R. used a conventional screw coupling. Curiously the King Arthur Class 4-6-0's built in Southern Railway days seem to have been provided with the original Urie coupling. I would be interested to hear if anyone can identify a Maunsell Arthur fitted with a 3-shackle screw coupling.
When Bulleid took over the helm nothing changed and we find all of his locomotive designs fitted with 3-shackle screw couplings including the Leader Class.
With regards to the BR Standard 9F 2-10-0's it would appear that a limited number were fitted with these couplings but the majority of photographs show a conventional screw coupling. I can only surmise that as some of these locos were built at Brighton a surplus of 3-shackle screw couplings in the stores was utilised. However, none of the other Standards built at Brighton Works appear to have been fitted.
One oddball is the USA 0-6-0T on the Bluebell Railway. These locos were formally used for shunting in Southampton Docks and were fitted with simple 3-link couplings. Possibly the Bluebell used a spare pair of couplings to enable it to be used on passenger trains.
I suppose the lesson to be learnt from all of this is don't blindly fit screw couplings to models of Southern locomotives without checking. It might not be prototypically correct!