Could a steam loco act as a brake translator?

[alexl92]

This might be a stupid question… From what I understand, if you want to operate an air braked locomotive on a set of vacuum braked coaches, you need a brake translator which is usually in the form of a dual-braked diesel loco.

I’m just curious to know whether a steam locomotive can be used in that role as a brake translator to allow an air-braked diesel loco to haul vacuum braked coaches?

 

[hexagon789]

This might be a stupid question… From what I understand, if you want to operate an air braked locomotive on a set of vacuum braked coaches, you need a brake translator which is usually in the form of a dual-braked diesel loco.

I’m just curious to know whether a steam locomotive can be used in that role as a brake translator to allow an air-braked diesel loco to haul vacuum braked coaches?

I don't think even a dual-braked one would be set up to enable this.

73s certainly can - when newly introduced the feature was demonstrated by a train being formed of an EP/Auto Air slammer, coupled to a 73, coupled to vac braked Mk1s.

The driver in the EMU cab was apparently able to control braking throughout the train with the 73 proptionally reducing the vacuum on the Mk1s.

Was in either a Modern Railways or Railway Magazine of the period, no idea of issue.

 

[GC class B1]

My understanding of how dual braked Diesel and Electric locomotives is that the drivers brake valve always operates to reduce the pressure in the Air Brake Pipe.

In vacuum mode the locomotive brakes are still operated by reducing the air brake pipe pressure but there is a valve (I think it is called the air/vacuum relay valve) that controls the vacuum train pipe in proportion to the reduction in the air brake pipe.

If the dual braked locomotive acts as an air to vacuum translator vehicle, the reduction in the air brake pipe pressure as a result of a brake application from the air braked locomotive will cause the air/vacuum relay valve to vent the vacuum pipe and apply the vacuum brakes on the vehicles.

I am not sure about steam locomotive but I believe any that have both air and vacuum brakes have separate drivers brake valves (one operating the air brakes and one operating the vacuum brakes) and they do not have an air/vacuum relay valve.

If this is correct then they cannot act as brake translator vehicles.

 

[jamieP]

This might be a stupid question… From what I understand, if you want to operate an air braked locomotive on a set of vacuum braked coaches, you need a brake translator which is usually in the form of a dual-braked diesel loco.

I’m just curious to know whether a steam locomotive can be used in that role as a brake translator to allow an air-braked diesel loco to haul vacuum braked coaches?

Simple answer is yes. Duel brakes steam engines have all the same equipment as a duel braked diesel. Attached picture of the DV2 valve fitted to A4 60009.