Locomotive Buffers

[SGJ]

I am wondering why some class of locomotives ( mainly class 37 and class 56 ) have different shape buffers some have round and some have a near oval shape, is there a reason for this or is it that a particular type was cheaper to use at the time of being built / location of being built ?

SGJ

[LMS2968]

To allow for swing out on curves. The longer the distance from the pivot point to the buffer head, the further it will move outwards on curves, and if it moves too far the buffers will lock behind those of the vehicle behind the loco. So oval buffers increase the swing out before buffer locking occurs.

[pH]

I’ve wondered about the use of ‘non-round’ buffers (call them ‘oval’, though not all are) on British steam locomotives. I originally thought they were to stop buffer locking, as LMS2968 says, but I’ve come to the conclusion that, in many cases, they were used purely for appearance, not for function.

 

In general, I think steam locomotives with oval buffers can be put into three groups:

• engines designed for the GCR (too many to list) or derived from them (e.g. Thompson O1, D11/2)
• LMS/LMR pacifics – Princesses, Duchesses, Duke of Gloucester
• Large passenger tanks (e.g. Fowler/Stanier/Fairburn/BR Standard 2-6-4T, LB&SCR Ix and Jx, LT&SR/L&YR/G&SWR Baltic tanks)

 

If they were functional, why weren’t other engines of the same type fitted with them? For example, why were no other Pacific classes fitted (I know about 70045 as a ‘one-off’), or big LNER tanks e,g, L1s and A8s? And why could engines from classes where they were generally fitted work quite happily with round buffers – LMS 6200 in its original state, some D11/2s, and the GWR ROD/3XXXs?

[LMS2968]

 

LMS Standard classes fitted with them included the pacifics, with a very long throw over at the front end ( 6200/01 originally had round buffers but they were soon changed to oval. Funnily enough, 6203 was also fitted with round buffers for a while in the 1950s); and the 2-6-4 tanks, which had a long throw over at the bunker end. The Stanier pacifics had a much longer throw over than those of other railways, including BR Standards, so that might answer the question.

 

Another point is the size of the standard round buffer head, which was sometimes quite small. LNWR and L&Y certainly had these, but the LNWR later increased the size as standard, while the L&Y fitted oval buffers to its 4-6-4 tanks (not the 4-6-0 equivalents), possibly because of the large throw over at the trailing end?

[PatB]

I suspect the type of traffic to be worked also plays a role.  I'm currently modelling LNER Y7 68089 as used on the North Sunderland Railway.  Whilst the "strandard" Y7 had round buffers (AFAIK), photos in Alan Wright's book on the line show 68089 with oval buffers (which also incline upward at a jaunty angle towards the centre of the loco).  I assume that they were fitted as part of the package of modifications performed to allow the loco to work passenger trains and to run cab first in inclement weather.

 

Incidentally, if anyone knows what type of buffers these were or were likely to be and where I might obtain a set in 7mm, any information would be gratefully received.

[dvdlcs]

I had been wondering about this too - both for wagons and locomotives.

 

I can understand about the physical dimensions of stock determining the type of buffers fitted, but what about the case where different members of the same class were fitted with different types of buffers? For example, I've seen Class 56 diesels with round and oval buffers, and as a 'dedicated' freight locomotive, presumably not because of passenger work for some members.

[Grovenor]

The required width of the buffer head is determined by the end throw, which in turn depends on the minimum radius to be negotiated, the height of the buffer on the other hand is only dependent on the suspension characteristics and this variation is much smaller than the width requirement.     As the calculated width requirement increases the designer has the choice of fitting larger round heads or using ovals, the functionality depends on the width, usually the height does not matter, but in some cases, eg stock with end doors the height has to be restricted hence the clipped buffers.

One of the issues arising with the softer suspensions of some modern stock is that mating ovals near the limits of throw significantly reduces the vertical tolerance, hence the rectangular buffers more common on the continent.

See http://www.norgrove.me.uk/GWRtracknotes/R1774A.pdf

Keith