Re: Slip Coaches: Back When British Express Trains Detached Passenger Cars at Speed
Author: Dr Zarkoff
Date: 07-08-2018 - 18:48
> Britain was slow to adopt brakes other than hand brakes
Odd you would say this because the air brake was invented in the UK -- in 1843 by Samuel Cunlliffe-Lister.
> Westinghouse started his demos ca 1871,
Westinghouse patented and introduced his straight (train) air brake in April of 1869. His researches and progress toward an automatic brake began in 1871. His first concept triple valve came in 1873, and the first successful production model, the A-10, in 1874/1875.
Westinghouse's famous demo train didn't run until 1888, after his automatic system failed in the 1887 Burlington Trials (actually, all continuous brake system tested in 1887 failed).
> there was a large competition at Newark in 1874
1875, on the Midland Ry between Nottingham and Newark.
> and GW greatly aided Capt Galton in his landmark investigations of 1879. Newark and the Galton experiments clearly showed the superiority of WAB, if one's criteria was safely stopping trains i.e.; quickly.
The 1878-1879 Galton-Westinghouse tests weren't so much concerned with the superiority of one brake system over another as they were to determine the details and limitations of brake shoe-wheel-rail interactions.
> When it became obvious that the Westinghouse Automatic was the only worthwhile brake, the good old boys bent every effort against it, until a certified Britain could come up with a vacuum brake.
It also had a lot to do with the difficulties compressing air and the costs of manufacturing air compressors. WIth Hodge/Martin-duTremblay/Smith-Eames vacuum brake systems, all you needed was a relatively cheap and mechanically simple steam ejector.
The superiority of the Westinghouse system had more to do with train length and weight. In these respects, the Westinghouse ABD/ABDx control valves are, still today, superior to the European distributor valves. The ARA (Australia and NZ) don't permit distributors to be used on goods trains.
> Vacuum today?
> Museums only,
and Angola, Nigeria, and Ethiopia
What did in vacuum in the UK was freight car weight. Once the cars reached something on the order of 80 tons (mid to late 1950s), the diameter of the vacuum cylinder necessary was so great it stuck out beyond the sides of the wagons so far that there were interminable clearance issues. So BR threw in the towel with vacuum brakes and converted to air (pressure) brakes.
And last but not least,, prior to WWII, the Key System was "slipping cars" (trailing Key Units) with EB trains from SF at the Bridge Yard. A train with two destinations left SF. Upon reaching the bridge yards, a motorman entered what was going to be the leading cab of the second train, cut in the brake valve, put a handle on it, pressed the uncoupling button, and made a stop, and the leading unit(s) didn't stop. No sure when the process was done away with in favor of stopping the whole train, uncoupling, and the leading unit(s) proceeding. In this latter form, the procedure lasted until abandonment (I recall being on a train where it was done). When the Lindenwold line opened, they borrowed a Key System rule book to study the process but didn't adopt it for moving trains.