Southern Region Compressor

[Ted633]

After my final journey on the 455’s yesterday, a thought came to me.
To the best of my knowledge, these are the last units in service (preservation aside) that use the ‘chugger chugger’ compressor (DH.25 I believe). I understand these compressors were also used on the slam door stock and watching videos of the old Waterloo & City line trains, they seem to be fitted with it as well which would make it 85 years of service if it is the same one.
My question is, how long have these compressors been in use? Quite a distinctive sound on south London’s railways thats about to disappear.
(Saw something on instagram that they were fitted to the original 3Sub units in 1916, but haven’t been able to find anything to confirm that)

 

[eastwestdivide]

I found a very similar sound on older trams in Turin in 2016. Wonder if they’re still in service, or similar elsewhere?

 

[Taunton]

These are reciprocating compressors, with a piston (electrically driven) and valves that open and close as air is sucked in and then pushed into the compressed air line. The pulsating sound is of the valves opening and closing. Old Westinghouse compressors mounted on the sides of air-braked steam locomotives used to make the same sound, plus being on the outside you could actually see the piston rod going up and down. They have been used since the dawn of air brakes, around 1880 for steam locomotives and from first introduction of electric trains.

More recent compressors are rotary, like a turntable, which just rotate as they operate and make more of a continuous noise.

 

[yorksrob]

For someone growing up in Kent, they were the sound of the railway. I didn't realise they went back before EPB traction.

 

[KevinTurvey]

Not an expert on SR EMUs at all but someone told me the 455 compressors were the ACTUAL same ones used on the 405's recycled from when they were scrapped, meaning yes, if true they have been in service for 85 years, and possibly longer if recycled from other stock?

 

[Taunton]

In youthful times we used to board the old Wirral electric units at West Kirby terminus on the way home from school. They were left at the platform quite unattended (and never came to any harm) until a minute before departure. Pressing the door open button on the motor car, if that operation, with a fine hiss, dropped the air line pressure below the lower limit the reciprocating compressor would start up, quite on its own. Less knowledgeable colleagues would say I had "started the engine".

More recently Southern 4-REP units had these, and the power was trainlined down to the 4-TC unit compressors. This gave rise to the unlikely situation that the compressor would start up while standing at Weymouth, 30 miles beyond the conductor rail, taking power from the Class 33.

 

[yorksrob]

In youthful times we used to board the old Wirral electric units at West Kirby terminus on the way home from school. They were left at the platform quite unattended (and never came to any harm) until a minute before departure. Pressing the door open button on the motor car, if that operation, with a fine hiss, dropped the air line pressure below the lower limit the reciprocating compressor would start up, quite on its own. Less knowledgeable colleagues would say I had "started the engine".

More recently Southern 4-REP units had these, and the power was trainlined down to the 4-TC unit compressors. This gave rise to the unlikely situation that the compressor would start up while standing at Weymouth, 30 miles beyond the conductor rail, taking power from the Class 33.

Not so unlikely, as the thumpers had them as well.

 

[Rescars]

For someone growing up in Kent, they were the sound of the railway. I didn't realise they went back before EPB traction.

Some of my earliest memories of train travel in 4-SUBs - the compressor chugging away beneath the floor at station stops and the roller-coaster ride in between!

 

[Sad Sprinter]

I remember being on the Porto trams in 2016 with my Dad and both being delighted to hear that familiar chugga chugga chugga sound.

Another sound I’ll always remember is that of a slam door set pulling in, always sounded like rainfall.

 

[contrex]

Not an expert on SR EMUs at all but someone told me the 455 compressors were the ACTUAL same ones used on the 405's recycled from when they were scrapped, meaning yes, if true they have been in service for 85 years, and possibly longer if recycled from other stock?

More like 75 (ish) years. The first 'Sheba' 4-SUB unit, 4101 was completed in 1941, 84 years ago, and the remainder of these, 4102-4110, in 1944, 82 years ago. The main run of 'Queen Mary' SUBs started in 1946 and finished in 1951, 74 years ago. The compressors were recovered from the last SUBs in service, and these would have been the last ones built (they were being withdrawn from the late 1960s onwards, mainly oldest first).

== Doublepost prevention - post automatically merged: 17 Dec 2025 ==

I remember being on the Porto trams in 2016 with my Dad and both being delighted to hear that familiar chugga chugga chugga sound.

I once read an account of a retired New York Subway driver who was on holiday in London in the late 1980s and stayed in a B&B in Forest Hill and travelled in each day. He said the first time a train pulled up at the other platform the sounds it made took him right back. It would have been an EPB, but these used the same compressors as far as I know.

 

[Taunton]

I once read an account of a retired New York Subway driver who was on holiday in London in the late 1980s and stayed in a B&B in Forest Hill and travelled in each day. He said the first time a train pulled up at the other platform the sounds it made took him right back. It would have been an EPB, but these used the same compressors as far as I know.

Common in the USA as well. Here's a video of a 1930 streetcar in the Baltimore museum. The compressor fires up at 4:45

 

[edwin_m]

The compressor would often noticeably slow down if it was running when the train started away, presumably due to the voltage drop.

 

[D7666]

More like 75 (ish) years. The first 'Sheba' 4-SUB unit, 4101 was completed in 1941, 84 years ago, and the remainder of these, 4102-4110, in 1944, 82 years ago. The main run of 'Queen Mary' SUBs started in 1946 and finished in 1951, 74 years ago. The compressors were recovered from the last SUBs in service, and these would have been the last ones built (they were being withdrawn from the late 1960s onwards, mainly oldest first).

Except.

It did not work like that.

All BR SR EMU items like that were treated as what we call these days LRU (line replaceable units) with compenent exchange each time any unit went for electrical or mechanical overhaul.

Items like compressors were removed, and replaced with another overhauled one; the EMU did not come out with its same items as i went in with.

The removed item went off to workshops, stripped down, rebuilt, placed in stores, to be used on any EMU. All items rebuilt as new as far as possible irrespective of age. Item placed in stores irrespective of age. Devices supplied new with 1940s Subs would be muddled with those new on 1970s Veps, and so on, across any component of any fleet.

What could be fitted to a Sub at one time could have been in a Vep an v.v., and many times, each time the unit went to m&e overhaul.

It is true when Subs were withdrawn, items like compressors, traction motors, etc were recovered, but those could have originated anywhere in any type of any age. The recovered items all went for overhauls and tipped into the same big pool. What was fitted to a new 455 might have been last fitted to a Sub, but could have originated anywhere, and through time been fitted to any number of different unit types. The 455s themselves went through m&e overhauls and the swaps continued.


Same applied to EE507 motors, with one exception, that I will explain in a bit. From late 4Subs on, EE507s in various types, 507B 507C 507D etc were supplied new. The trainspotting books always listed these letters, but after a few years are incorrect. What happened was when any EE507 motor EMU went to Chart Leacon for e&m overhaul (200000 miles on a Mk6 motor bogie unit, 100000 miles on a Mk4) the motors were removed, overhauled ones fitted. The removed motors went off to the motor shop, the armatures seperated from the carcasses, each overhauled as seperate items, and on completion any armature with any carcass. Each motor overhauled, armature and fields rewound, etc, to the latest spec, then put on a test rig. All such things vsry slightly, the motor shop recorded each motors own characteristics, and matched 4 as close as possible, and those went as a set to stores for the next unit. Does not matter where they came from, supplied new to or taken off a Sub EPB Cig Cep Vep etc did not matter. So you could have older or newer armatures in older or newer carasses, fiited in older or newer units. The only disctinction between all types was 'oiler' or 'roller' for journal or roller bearing motor suspension tubes - these had to match the bogie of the receiving unit. The EE507 motor exception was 456s (and the chopper 455s when they existed). These had EE507J EE507 motors captive to that class. Often written these EE507 were new from GEC but even those were not. They were ex older EMU recovered and sent to GEC for total rebuild. 456s had thyristor traction packs (half a 319 pack) and their DC pack output is not the same as the DC ripple direct from substations neede to be different. But they could have originated anywhere.

 

[MadMac]

Common in the USA as well. Here's a video of a 1930 streetcar in the Baltimore museum. The compressor fires up at 4:45

Same sound as the original Glasgow’ Blue Trains’.

 

[Strathclyder]

Same sound as the original Glasgow’ Blue Trains’.

Ears pricked up at that sound instantly for that reason. Such a distinctive part of the 303's soundset:

 

[Ken X]

Being born in Hampton that compressor is a very familiar sound. Combined with many, many slam doors. Waterloo would echo with this soundscape.

 

[yorksrob]

Common in the USA as well. Here's a video of a 1930 streetcar in the Baltimore museum. The compressor fires up at 4:45

Sounds very familiar !

 

[Tony73E]

Except.

It did not work like that.

All BR SR EMU items like that were treated as what we call these days LRU (line replaceable units) with compenent exchange each time any unit went for electrical or mechanical overhaul.

Items like compressors were removed, and replaced with another overhauled one; the EMU did not come out with its same items as i went in with.

The removed item went off to workshops, stripped down, rebuilt, placed in stores, to be used on any EMU. All items rebuilt as new as far as possible irrespective of age. Item placed in stores irrespective of age. Devices supplied new with 1940s Subs would be muddled with those new on 1970s Veps, and so on, across any component of any fleet.

What could be fitted to a Sub at one time could have been in a Vep an v.v., and many times, each time the unit went to m&e overhaul.

It is true when Subs were withdrawn, items like compressors, traction motors, etc were recovered, but those could have originated anywhere in any type of any age. The recovered items all went for overhauls and tipped into the same big pool. What was fitted to a new 455 might have been last fitted to a Sub, but could have originated anywhere, and through time been fitted to any number of different unit types. The 455s themselves went through m&e overhauls and the swaps continued.


Same applied to EE507 motors, with one exception, that I will explain in a bit. From late 4Subs on, EE507s in various types, 507B 507C 507D etc were supplied new. The trainspotting books always listed these letters, but after a few years are incorrect. What happened was when any EE507 motor EMU went to Chart Leacon for e&m overhaul (200000 miles on a Mk6 motor bogie unit, 100000 miles on a Mk4) the motors were removed, overhauled ones fitted. The removed motors went off to the motor shop, the armatures seperated from the carcasses, each overhauled as seperate items, and on completion any armature with any carcass. Each motor overhauled, armature and fields rewound, etc, to the latest spec, then put on a test rig. All such things vsry slightly, the motor shop recorded each motors own characteristics, and matched 4 as close as possible, and those went as a set to stores for the next unit. Does not matter where they came from, supplied new to or taken off a Sub EPB Cig Cep Vep etc did not matter. So you could have older or newer armatures in older or newer carasses, fiited in older or newer units. The only disctinction between all types was 'oiler' or 'roller' for journal or roller bearing motor suspension tubes - these had to match the bogie of the receiving unit. The EE507 motor exception was 456s (and the chopper 455s when they existed). These had EE507J motors captive to that class. Often written EE507J were new from GEC but even those were not. They were ex older EMU recovered and sent to GEC for total rebuild. 456s had thyristor traction packs (half a 319 pack) and their DC pack output is not the same as the DC ripple direct from substations neede to be different. They did some mods to the 507s to accomodate that, and called them EE507J. But they could have originated anywhere.

Chart Leacon did not do rewinds of field coils or armatures - they went to Eastleigh. Motors had a light overhaul, i.e. new armature bearings, armatures blown out of carbon dust, commutators turned, slotted and vee'd, field coils and/or interpoles replaced and brush gear overhauled. In my days at Chart you could only static test traction motors.

 

[D7666]

Chart Leacon did not do rewinds of field coils or armatures - they went to Eastleigh. Motors had a light overhaul, i.e. new armature bearings, armatures blown out of carbon dust, commutators turned, slotted and vee'd, field coils and/or interpoles replaced and brush gear overhauled. In my days at Chart you could only static test traction motors.

errrr yes re-reading what I wrote, I implied Chart did it, but was not what I meant; I should have said "Eastliegh" motor shop, not just motor shop that implied Chart.

 

[nw1]

I'm sure 456s also have them, which would make sense given they're compatible with 455s. I recall taking a 456 from Wanborough to Guildford in October 2014 and hearing it. It was a real blast from the past!

 

[AM9]

I remember them on the original GE EMUs, (what became class 306 as a units). The compressor noise when stationary was more noticeable in their DC days as there wasn't the transformer background hum. I also remember the chugging of the compressors on the Central line's 'standard' tube stock. The 1959/62 stock had faster (presumably rotary) types fitted.

 

[Lemmy282]

There is a tram from Oporto at Crich tramway museum with the same type of compressor, always makes me think of EMU'S when it kicks in

 

[norbitonflyer]

Except.

It did not work like that.

All BR SR EMU items like that were treated as what we call these days LRU (line replaceable units) with compenent exchange each time any unit went for electrical or mechanical overhaul.

I recall reading that a 4SUB could be fitted with buffers saying "Pullman" on them, as they were originally fitted to a 5BEL or 6PUL but got intermixed over time.

 

[AY1975]

More recent compressors are rotary, like a turntable, which just rotate as they operate and make more of a continuous noise.

Indeed, some 455s seem to have had their original compressors replaced by a more modern compressor like the one you describe.

Also, as I recall the Merseyrail 507s latterly had one of those whereas the 508s retained traditional compressors until withdrawal. Likewise, IIRC the 314s latterly had those modern compressors whereas the 315s always had traditional compressors. Not sure about the 313s, though.

More recently Southern 4-REP units had these, and the power was trainlined down to the 4-TC unit compressors. This gave rise to the unlikely situation that the compressor would start up while standing at Weymouth, 30 miles beyond the conductor rail, taking power from the Class 33.

I presume the 442s had traditional sounding compressors as their traction motors were reused from the 4-REPs?

 

[Minerva05]

From what I recall, the 442s had reciprocating compressors not unlike the 455s, but they made quite a distinctive sound…possibly a different design?
The 313s had a more modern compressor (similar to that on class 319 and 321 I think) that made a higher frequency sound than the ‘traditional’ type used on the 315.
In my younger years I travelled often on GE line e.m.us (308, 309, 312 and the compressor sound is so evocative…takes me right back…