'Classic' traction braking systems

[timsimmk]

Hi everyone, I'm new here so sorry if this has already been discussed...

I've been trying to find some info on the brake control systems used on first generation diesel locos such as 37s, 25s, 47s etc.

When searching for info about railway brakes on the internet, you often get info about the US Westinghouse system where the driver's brake valve directly controls the brakes directly and the air brake pipes come into the cab. The US system has 3 basic positions: apply/lap/release.

The UK locos often had dual air and vacuum brakes, so I'm wondering how the driver's brake control valve works? Is it an electo-pneumatic type system with notches relating to amount of braking or does it have some kind of apply/lap/release position?

 

[Spagnoletti]

On the dual braked locos I've worked on (26,37,47) the drivers brake valve controls the air pressure in the train pipe. If you're hauling air braked stock then falling pressure in the pipe controls the amount of brake application on the train.

If you're in vacuum then an air-vacuum relay valve sets the vacuum proportional to the train pipe pressure.

The loco brakes are controlled proportional to the train pipe (in air) or the vac pipe (in vac) so loco brakes will always be applied in the event of a divided train etc.

At least this is how I understand it to work.

This is all accomplished by a veritable plumbers nightmare of pipes, check valves, relays, ep valves, distributors and other stuff, designed to give fitters nightmares.

 

[timsimmk]

Thanks for the info. Did the brake handle have notches like the power handle or was it a kind of continuous range like the brake pedal in a car?

 

[fgwrich]

Speaking of Classic traction bracking systems and going off topic for a moment, I see that the first of Siemens Desiro City bogies is about to undergo testing - the non powered bogies appear to have an inside axle Disc mounted breaks - as per the Mk4s and Class 158s, with the motor bogies due to see a return of good old fashioned Tread Breaks!

 

[jopsuk]

Yes, but in normal operation the primary brakes should be the dynamic (motor) braking.

 

[TDK]

Speaking of Classic traction bracking systems and going off topic for a moment, I see that the first of Siemens Desiro City bogies is about to undergo testing - the non powered bogies appear to have an inside axle Disc mounted breaks - as per the Mk4s and Class 158s, with the motor bogies due to see a return of good old fashioned Tread Breaks!

On the 158's these treads are not brakes but what is called scrubbers these are traads that clean the wheel where it makes contact with the rail to stop the wheels from becoming contaminated they do not have hardly any brake force.
--- old post above --- --- new post below ---

On the dual braked locos I've worked on (26,37,47) the drivers brake valve controls the air pressure in the train pipe. If you're hauling air braked stock then falling pressure in the pipe controls the amount of brake application on the train.

If you're in vacuum then an air-vacuum relay valve sets the vacuum proportional to the train pipe pressure.

The loco brakes are controlled proportional to the train pipe (in air) or the vac pipe (in vac) so loco brakes will always be applied in the event of a divided train etc.

At least this is how I understand it to work.

This is all accomplished by a veritable plumbers nightmare of pipes, check valves, relays, ep valves, distributors and other stuff, designed to give fitters nightmares.

Class 67's have a combination of both disc and tread brakes.

 

[driver9000]

Thanks for the info. Did the brake handle have notches like the power handle or was it a kind of continuous range like the brake pedal in a car?

Continuous range braking is available on the handle between initial and full service. There are marked positions such as release,running,initial,full service,emergency and shut down. I'm not sure if the marked positions were notched or if they were simply markings to aid positioning the handle. When the locomotive was running light, ie without a train then the driver would control the brake using the 'straight air' handle which controlled the locomotive brake only. As far as I know when running light the train brake handle was left in the running position.

Stepped brake handles are a feature of EP braked multiple units although some recent builds (such as 175,180) that feature combined power/brake handles have continuous range braking without steps.

 

[Old Timer]

Continuous range braking is available on the handle between initial and full service. There are marked positions such as release,running,initial,full service,emergency and shut down. I'm not sure if the marked positions were notched or if they were simply markings to aid positioning the handle. When the locomotive was running light, ie without a train then the driver would control the brake using the 'straight air' handle which controlled the locomotive brake only. As far as I know when running light the train brake handle was left in the running position.

Stepped brake handles are a feature of EP braked multiple units although some recent builds (such as 175,180) that feature combined power/brake handles have continuous range braking without steps.

As I recall, the combined brake controller had notched positions. When running light the combined brake controller was in shut down in both cabs on locos which had a separate straight air brake.

The straight air was a separate system as it was possible to hold the train on a gradient with the loco brake and apply power without the problem of roll back.

Some of the early locomotives were equipped with separate air and vacuum brake controllers, although I believe that the 47s were the first diesel fleet locomotive to come with the D&M combined brake controller from new.

The 86s were similar. The Class 81 to 85 had separate vacuum and air brake controllers as I remember. as the air brakes were added later hence the three cylinders on the locomotive roof which were added as part of the air brake fitment.

As far as Type 2s were concerned the Class 25 series 3 build was introduced with the D&M combined brake controller.

Hopefully I have got those details right but if anyone can confirm or update it would be appreciated as memory fades with time !

 

[Spagnoletti]

Continuous range braking is available on the handle between initial and full service. There are marked positions such as release,running,initial,full service,emergency and shut down. I'm not sure if the marked positions were notched or if they were simply markings to aid positioning the handle. When the locomotive was running light, ie without a train then the driver would control the brake using the 'straight air' handle which controlled the locomotive brake only. As far as I know when running light the train brake handle was left in the running position.

Yes.
Release is achieved by pushing against a spring, there's also a contact that will weak field the exhauster to build up vac quicker.
I think running, initial & full service are notched - you have to push past the full service notch to get emergency, and lift a pin to get past emergency into shut down.
I'm pretty sure you'd have to put the abv into running to move a light loco as in order to reach shut down you would have to pass through emergency and dump the train pipe.

 

[Smudger105e]

I'm pretty sure you'd have to put the abv into running to move a light loco as in order to reach shut down you would have to pass through emergency and dump the train pipe.

Quite correct, the auto brake handle has to be put into release/running in order to create a train pipe, without train pipe pressure the CCG* (or whatever it was called on different fleets) would remain open and prevent traction power being taken.

CCG* = Control Circuit Governor