Packing behind Cambrian wagon buffers

[NCB]

For a long time I've been aware that some Cambrian wagons had a packing piece inserted between a buffer and the wagon body, without really wondering why they did this; just thought it was a Cambrian curiosity. A couple of days ago I was browsing some of the Cambrian's own wagon plans, one of which had the packing pieces, when a thought struck me. Out came the ruler, and the reason was obvious. The visible stem of the buffer head on the wagon with packing pieces was shorter than the stem on the wagons without; the packing piece simply causes the face of the buffer head to be the standard distance of 18" (or there abouts) from the wagon body.

 

Why the Cambrian had buffer heads with shorter stems is anybody's guess. I did wonder if it was to do with different types of buffer springing; the Cambrian seems to have used two types, leaf springs and what appears to be rubber shock absorbers. But amongst the drawings I found examples of the shorter stem on both types of springing. Maybe it's just a historical thing; perhaps the standard distance used to be less than 18". The buffer heads seem to be the same basic design; just the stem lengths differ.

 

Anybody any thoughts on this?

 

Nigel

[Guy Rixon]

The LNWR used longer buffer-guides on their heavier wagons: 7-ton wagons typically had 10" guides and 10-ton wagons sometimes had 12". This reduces the unsupported length of the buffer ram while keeping constant the stroke and the headstock-to buffing-face distance. The difference, for the LNWR, was not to accomodate screw couplings as they had two further lengths (13" and 15") of guide for that. Therefore, it seems reasonable that they wanted stronger buffers for the heavier stock.

 

The pads on the Cambrian wagons do the same job more cheaply and without having to stock two sizes of buffer guide.

[MarcD]

The NER had two sizes of Mineral wagon buffers. The shorter and earlier ones being packed out with wooden blocks as the Cambrian ones were.

 

From the NER wagon designs there is a gradual development of buffers. Dead-buffer, Dead-buffer drilled out to take a standard buffer head (there must have been a tube of some sort inside), Short cast guide with wooden packing piece and finally long cast guide with no packing. This is best shown by looking a P1 4ton hopper, early 4plk P5 11 1/2 ton hopper, S1 6ton Iron ore hopper and the later 21ton P7 hopper.

 

Sorry to answer a question with a question but It might either be a cost related or a date of build related? Were any of the Cambrian wagon rebuilds from dead buffered wagons?

 

Marc  

[Quarryscapes]

Packing only affects the buffer guide, and therefore stroke of the buffer. It does not affect length unless self contained. Measuring a GA drawing proves nothing, on stock that was built in both fitted and unfitted you will find 2 dimensions on the same drawing for buffers, and on Cambrian G.A.s you will find drawn a style of buffer that didn't actually seem to exist. 

 

 

Were any of the Cambrian wagon rebuilds from dead buffered wagons?

 

 

Yes there were many of these under the Aston regime. Can anyone say what they looked like? Probably not. 

[NCB]

The figures on the G.A. drawings back up the measurements I did with a ruler. The buffer guides themselves seem the same in both cases. Looking at the details of the buffers on drawing where it's given, it does seem that packing was used where the buffer head stem was shorter. From the drawings I have it appears that the packing pieces appeared mainly on 19th century wagons. My guess us that it boils down to the Cambrian having some reason to use buffer heads with shorter stems, maybe cost, maybe quality reasons such as the length of unsupported stem deemed acceptable.