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Sunday, 16 June 2013

The Wooden Chassis Revealed

Ever wondered how the wooden chassis of a railway wagon might look?   No, me neither to be honest.   In fact it is as clever a bit of geometry as can be.   Later wagons had steel chassis but the earlier ones were wood, as below.

Today I removed the floorboards - rotten and therefore dangerous.   This revealed what we really needed to see - the wooden chassis.   Something over half of it is in quite good order and there will be an expert examination tomorrow by Robert Handy of The Wonder of Wood Ltd.

You can see that the chassis consists of what most people would call buffer beams at each end (headstocks) and four longitudinal members - one at each side (solebars) and two down the middle.  Shorter pieces of wood brace these longitudinals.

click any image to enlarge

By 1909 there was serious concern about the many types of wagon on Britain's railways and their variable states of repair.   The Railway Clearing House (RCH) decided to act and drew up a specification for all the railway companies and private owners to follow.   They set 1923 as the date for compliance, after which non compliant wagons would not be allowed on the main lines.   The two drawings below show some of  the requirements:

Our wagon is clearly a 1923 compliant layout with a couple of modifications.   The buffer springs on the diagrams show transverse leaf springs.   Our wagon does not have the transverse leaf springs, though perhaps it did originally.   In fact it has different types of springs at each end:

At what is now the southern end of our wagon are coil springs, one behind each buffer.

In the middle of the wagon are the 'coupling springs' made of rubber and metal composite materials.   This is the very clever gadget that takes the entire load of the train instead of that going through the wooden chassis.

At the northern end behind the buffers are rubber and metal composite shock absorbers.   The rubber parts are marked BR Standard - implying they are later replacements.

Although some of the chassis timbers are beyond salvation I hope to be able to retain as much of the original timber as possible, replacing the rotten bits with properly profiled new wood.   Fortunately, those bits that need replacing have corresponding good bits on the other side which we can copy.

If your head is hurting after all that, go and have a nice cup of tea.
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