A4 exhaust question

[rodent279]

Vac brakes were used on European NG lines such as the Soller railway - which still uses them & the pre modernisation Mallorca system, also some German lines

A couple of E. German narrow gauge lines were VB, I think.

Edited December 26, 2018 by rodent279

[rodent279]

Being pedantic I think you'll find that all BR mainline diesel locos from the first Modernisation Plan Pilot Scheme designs onwards were built with air brakes. What I suspect you mean is that the classes you mention were the only earlier designs equipped from new with auto air brakes to allow them to work airbraked trains.

Yes, I did mean train air brakes rather than loco air brakes!

Which makes the decision not to build them as dual braked from the start all the more ill-thought through.

[Grovenor]

Except there was no air brake stock to use with them, the decision to change to air brakes was still well in the future.

Rgds

[slilley]

This passage from Class 47 50 Years of Locomotive History will give an idea of the situation regarding the policy decision to move to aire brakes.

 

 

The adoption of air brakes for locomotives and rolling stock was a matter that had vexed first the BTC, and later BR, for many years. As far back as 1956, the BTC had recommended the adoption of air brakes as standard. This was not progressed, as it was felt that a change from vacuum to air brakes would cause too many operational difficulties. However, by 1962 it was recognised that with modernisation well under way, a review was needed to determine which braking system should be used in future.

   The review had comprised four main elements; present operating conditions, prospective conditions, problems associated with the change-over, and the comparative capital costs. In June 1963, its findings were set out in a paper submitted to the Technical Committee. Its principal conclusion was that the advantages of the increased haulage capacity and line speeds offered by air brakes, would outweigh the disadvantages of operating two braking systems. The Technical Committee accepted this, and at their meeting of 26 June agreed that the air brake should be adopted, initially for all ‘Liner Trains’ and MGR services. Other services, which operated in circuits and where the cost could be financially justified, would be air-braked along with services where the train was to be braked and utilised 32-ton automatic discharge wagons.
   BR’s Planning Committee meeting on 19 August 1964 considered how the change-over would be achieved. New locomotives would in future be dual fitted with both air and vacuum brakes, and there was to be a rolling programme to equip existing vacuum-braked locomotives with air brakes. Air-braked rolling stock would be introduced on selected routes. New Brush Type 4s had been delivered with train air brakes since the previous April, and ultimately 305 of the class were so equipped from new. The BR Board at its meeting on 8 October 1964 decided to adopt the air brake as standard for all future rolling stock.  The first fruits of the new order came nearly two years later, on 16 August 1966, when a Brush Type 4 hauled BR’s first-ever scheduled air-braked passenger train, a Kensington Olympia to Perth Motorail service.

[The Johnster]

We differentiated by describing the loco's air brake, analogous to the steam brake on a steam loco, as the 'straight' air brake; it worked by applying air pressure to the brake shoes to stop the locomotive, which is why the loco was fitted with a handbrake to securely park it even if the straight air brake leaked off, as it inevitably would.  

 

The train air brake worked differently, air pressure being applied to hold the brake shoes off the wheel, in order to incorporate 'fail safe' in the event of a leakage or compressor failure, in other words replicating the action of the vacuum brake, but being capable of being released more quickly on a long train as the compressor needed was far smaller than that needed to blow vacuum brakes off; steam locos could release vacuum brakes much more quickly, one of the reasons for the adoption of air brakes in general.

 

It was a factor in the demise of some of the WR hydraulics, as these had been built to such a size and weight saving philosophy that there was no room aboard them to retrofit air brake equipment; Warships, Baby Warships, and Hymeks were affected.  It is easy to criticise some of BR's decisions in hindsight, but the 1955 plan locos were specced with vacuum brakes only because there was hardly any air braked work except for the Night Ferry stock in 1955, and the decision was, as Mike says, not taken until 1962; air braked stock did not appear for some time after that and even the first production runs of mk2 passenger stock remained vacuum braked only in 1966/7.  Freightiner stock was, IIRC, the first freight stock that was air braked only, though the Cartics may have beaten them to the point; these were probably the first disc braked stock as well.

[jim.snowdon]

Amongst the first air brake only freight vehicles were the bogie 90 & 100 ton tank wagons, although they were also vacuum piped.

 

Jim

[rodent279]

I think the first passenger stock *built* with air operated disc brakes were the much missed class 310's built at Derby, for the Euston outer suburban services. Best EMU's BR ever built.

[Bucoops]

I think the first passenger stock *built* with air operated disc brakes were the much missed class 310's built at Derby, for the Euston outer suburban services. Best EMU's BR ever built.

 

Best apart from the 309s of course

[rodent279]

Best apart from the 309s of course

 

Close second