Tuesday, 23 March 2010

Train Tyres

Train Tyres

March 2010

During my recent visit to the South Devon Railway I was given a peep into the engineering sheds and was introduced to the world of train tyres.

Loco wheels, with new tyres and freshly bored for the con rods.

When you use the word "tyres" one inevitably thinks of the pneumatic variety which adorn cars, lorries and bicycles, but a look at the dictionary reveals an older application: "a steel rim fitted round a wooden  cartwheel". I never realised that train wheels had "tyres" fitted to them but this small engineering workshop operated by a heritage railway in sleepy South Devon specialises in the process.

A train wheel is cast in steel and then turned on a huge lathe to create a perfectly circular disc, at which point a tyre is added. The tyre is also cast in steel and is individually turned inside and out to ensure a perfect match with the wheel it will be attached to. The process of attaching the tyre to the wheel is achieved by heating the tyre to make it expand and then belting the cooling ring into place with subtle application of sledgehammers. A thin "O" ring added to this process, which is rammed into the joint under hundreds of tons of pressure, and finally bent over to create an enduring fix.

The amazing thing is that all locomotive wheels have tyres on them and there are only four machines in the whole UK to do "O" ring process, and two of them were in the workshop I was looking at.
Luckily for train operators, both modern and heritage, these tyres last a bit longer than the rubber variety those on my trusty Mondeo. The mileage you can expect from a pair of locomotive tyres is measured in the millions, and for a heritage steam railway a new set will normally last a generation. And that is just as well because each one will cost considerably more than the original price of my whole car.

South Devon Railway engineering workshop

The good news is that if your train tyre gets a flat (spot) the whole thing can be re-turned several times and made as good as new. And when there is no more tyre left to cut, it's out with the gas axe and on with a new tyre.

Having aroused my curiosity I did a Google search for "railway tyres" and was underwhelmed by the lack of results. The search did however throw up some accounts of experimental rubber tyres which had been applied to small trains and other rail based vehicles to achieve greater traction. Interesting, but I can't see them being adopted on the West Coast Mainline anytime soon.

So, if your train get a flat, don't call E-Tyres. Run on your rims and plan an early trip to Newton Abbot.


Halfie said...

I'm in the middle of reading Tom Rolt's book "Red for Danger - the Classic History of British Railway Disasters" (first published 1955). (Not nearly as readable, incidentally as other books of his I've read; and not as good as O. S. Nock's similar account of railway disasters.)

The first accident Rolt attributes to a failing tyre was in 1847 at Southall on an express train on Brunel's Great Western main line (7 foot gauge). Fragments of the tyre flew through the air to bombard a passing goods train. Two drovers were killed; the goods train was derailed, but the express proved the stability of the broad gauge, holding the rails and carrying on to Paddington.

Rolt describes more accidents attributable to failing tyres. After one in which seven people died a coroner's jury stated "The deceased met with their deaths from the breaking of the tyre of one of the leading wheels of the engine, in consequence of the defective weld."

Needless to say (Rolt continues), railway wheel tyres are no longer welded. They consist of continuous rings of cast steel which are shrunk on to the wheels.

Captain Ahab said...

What a strange coincidence to be looking at the same thing at the same time!