Train Questions

[Andy317345]

I have a few questions that I struggled to find the answer to online:

1. Are the C315 compressors reused from the 306s? They make a different noise from the other PEPs.

2. Why are the motors on older trains lower pitched? (313, 411, 507/8 ect) It seems the new trains (or anything past 1992) like the Aventras and Electrostars have higher pitched motors.

2b. Why do the Desiros make that distinctive warbling noise? Something to do with the motors?

3. Why wasn't 4-SUB 4101 saved? It started the fleet of SUBs and the eventual development into the EPB.

4. Why are so many Class 60s stored?

5. Why are there 11 year old 379s and 20 year old 175s in store but 40 year old 150s and 51 year old trains on the London underground? Is it just a problem with money?

6. What trains in the UK had the first air-operated doors?

 

[778]

Not sure about 1-4.

5. Lots of discussion about 379s and 175s on this forum.

6. 1920 tube stock for the piccadilly line.

 

[swt_passenger]

I have a few questions that I struggled to find the answer to online:

2. Why are the motors on older trains lower pitched? (313, 411, 507/8 ect) It seems the new trains (or anything past 1992) like the Aventras and Electrostars have higher pitched motors.

2b. Why do the Desiros make that distinctive warbling noise? Something to do with the motors?

2. Modern trains use electronic traction converters, and produce 3 phase AC at variable voltage and frequency to drive the motors at effectively infinitely variable speeds, hence they are all now AC trains, even those that only tun on third rail. The oldest electric trains generally used DC motors, with a transformer rectifier if running on AC overhead.

2b. Different manufacturer use 3 phase traction converters with slightly different control electronics, the noises reflect the detailed type of electronic switching devices.

 

[sprinterguy]

4. Why are so many Class 60s stored?

Largely due to the downturn in, and rail traffic generated by, the traditional heavy industries that they were built to serve: Coal and steel in particular, though I'm also not sure that the petroleum sector is as prolific as it once was.

As well as impacting the class directly, the downturn meant that EWS, later DB Schenker, had newer class 66s to spare and to standardise on that could handle a lot of the traffic that remained.

In addition to this, while Wisconsin Central bought up the three trainload freight business that accounted for all the heavy haul traffic 25 years ago to create EWS, new entrants to that particular market in the form of Freightliner and GBRf in particular have successfully won a proportion of the available heavy haul traffic over the intervening years and decades, largely with class 66 locos of their own; while EWS/DB have been reticent to sell on the 60s to competitors (It's only comparatively recently that ten have made their way to GBRf).

== Doublepost prevention - post automatically merged: 9 Nov 2023 ==

5. Why are there 11 year old 379s and 20 year old 175s in store but 40 year old 150s and 51 year old trains on the London underground? Is it just a problem with money?

On the national network, it comes down to the franchise bids approved by the DfT (or relevant national assembly) from the winning bidder, and the rolling stock leasing contracts that then result.

For example the Greater Anglia and Transport for Wales franchises were agreed with terms of complete fleet renewal from KeolisAmey and Abellio respectively, while Arriva essentially only specified replacement of the Pacer units in their bid for the Northern franchise.

Often, the proportion of fleet replacement or expansion, if any, expected from prospective franchise bidders is set out by the DfT in the Invitation to Tender document.

 

[JonathanH]

3. Why wasn't 4-SUB 4101 saved? It started the fleet of SUBs and the eventual development into the EPB.

The 2-BIL currently in the care of the NRM at Shildon was set side for preservation in 1971.

Unit 4101 appears to have been withdrawn in 1972. Was it really noteworthy enough to be preserved at that time? Even modern day units are difficult to generate any preservation interest. An all compartment suburban unit doesn't exactly represent a romantic notion of rail travel.

 

[WatcherZero]

4. They have a lot of power but are gas guzzlers, slow, and near the end of their life. Many arent in operational condition as they have been cannibalised for parts to keep others running as they were in low demand it didn't really justify ordering new parts when something broke. It made more sense to use newer more fuel efficient traction even if less powerful like the 66, 68’s and 70’s or even to convert the 56’s into 69’s with similar performance to 66’s.

 

[43096]

4. They have a lot of power but are gas guzzlers, slow, and near the end of their life. Many arent in operational condition as they have been cannibalised for parts to keep others running as they were in low demand it didn't really justify ordering new parts when something broke. It made more sense to use newer more fuel efficient traction even if less powerful like the 66, 68’s and 70’s or even to convert the 56’s into 69’s with similar performance to 66’s.

Gas guzzlers? 60s are far more fuel efficient than the 66 fleet. Fuel economy is one reason to keep them!

 

[Magdalia]

2. Why are the motors on older trains lower pitched? (313, 411, 507/8 ect) It seems the new trains (or anything past 1992) like the Aventras and Electrostars have higher pitched motors.

The oldest electric trains generally used DC motors, with a transformer rectifier if running on AC overhead.

Modern trains use electronic traction converters, and produce 3 phase AC at variable voltage and frequency to drive the motors at effectively infinitely variable speeds, hence they are all now AC trains, even those that only run on third rail.

The last trains built with dc motors were classes 317-322, and the first trains built with ac motors were the Networkers class 365/465.

So you are right that around 1992 is the time when traction motor noise changes on new trains.

But I can't explain why trains with dc motors and trains with ac motors sound different!

And I'm not convinced that the motors themselves are the prime reason for the difference. Various EMUs have been fitted with new traction packages without there being (to my untrained ear) a discernable difference in the noises made.

== Doublepost prevention - post automatically merged: 10 Nov 2023 ==

Largely due to the downturn in, and rail traffic generated by, the traditional heavy industries that they were built to serve: Coal and steel in particular

This is one of the consequences of almost completely eliminating the use of coal to generate electricity in the UK.

 

[LNW-GW Joint]

5. It's up to the owners (the Roscos) to find work for them, at their financial risk.
There's little demand for surplus EMUs, with the recent large fleet orders (mostly Aventras) still to be put into service (which will release more spare EMUs).
175s are a different story. They have been troublesome while at TfW and will need significant attention (ie cost money) before finding new work.

 

[Bigvernicus]

2 -

Older Traction motors were DC driven and were a direct drive via the rotor shaft to a motor pinion onto a direct drive gear fixed to the axle, these are geneally covered in a gearpan (made in two halves to enable motor/ wheelset renewal) which was lubricated with grease, the specific pitch of the gears give these motors their particular noise. Generally these motors are large to give the power and run at a much lower pitch and much louder sound wise.

Modern traction motors are genearlly run on AC and are brushless, so are much smaller, these then drive a much smaller pinion ususally through a flexible coupling onto a gearbox fitted to the axle which converts the drive through several gears to increase torque, these gears are much smaller and are incased in a gearbox which is ususally filled with oil, so run much quieter and at a higher pitch sound wise. As the motors can be changed without removing the wheelset and vicea versa

 

[norbitonflyer]

Unit 4101 appears to have been withdrawn in 1972. Was it really noteworthy enough to be preserved at that time? Even modern day units are difficult to generate any preservation interest. An all compartment suburban unit doesn't exactly represent a romantic notion of rail travel.

A 4SUB was preserved - 4732 - but it is not always the first in class that gets preserved. Condition counts for a lot. The first ten 4SUBs "Queen of Shebas" were non-standard in many ways - one 11-compartment trailer, and one with first class (although first class was abolished on suburban services before they were completed) and wood-and-canvas roofs.

== Doublepost prevention - post automatically merged: 10 Nov 2023 ==

2. Modern trains use electronic traction converters, and produce 3 phase AC at variable voltage and frequency to drive the motors at effectively infinitely variable speeds, hence they are all now AC trains, even those that only tun on third rail. The oldest electric trains generally used DC motors, with a transformer rectifier if running on AC overhead.

Note though that even if the supply is ac and the motor is ac, there has to be dc in between: the 50Hz supply signal has to be removed before the variable frequency needed by the motors can be applied

== Doublepost prevention - post automatically merged: 10 Nov 2023 ==

5. Why are there 11 year old 379s and 20 year old 175s in store but 40 year old 150s and 51 year old trains on the London underground? Is it just a problem with money?

Partly money, and partly horses for courses. Neither a 379 nor a 175 would be much use on the Picadilly Line!

As for the 175s, simple age is not everything - I recall the younger batch of Glasgow "Blue Trains" (Class 311) were withdrawn some years before their older Class 303 cousins, because the 311s, being younger, had not yet had the midlife refurbishment that the 303s had.

And there was the 1983 Tube stock saga - a small fleet, and with some build quality issues - not worth adapting to work with the new 1996 stock being built for the Jubilee Line extension.

The 175s have not been trouble-free, and only one depot is familiar with them, so no-one wants to take them on.

 

[ac6000cw]

Gas guzzlers? 60s are far more fuel efficient than the 66 fleet. Fuel economy is one reason to keep them!

Indeed - the good fuel economy of the Mirrlees Blackstone MB275T engine was a significant factor in BR choosing the Brush design for the class 60 (due to lower whole-life cost).

2b. Why do the Desiros make that distinctive warbling noise? Something to do with the motors?

This a bit technical...

On modern trains with AC traction motors, they are driven from an 'inverter', which produces a variable frequency, variable voltage alternating current (AC) output from a DC input.

The frequency controls the motor rpm, so it varies from a low note to a higher note as the train speed/motor rpm increases. Overlaid on top of that is a higher 'chopping' frequency - the inverter 'synthesizes' the AC waveforms by chopping the DC input at a high frequency, generating a train of pulses which are then 'smoothed' to produce the AC output. To avoid generating interference at certain frequencies used by railway signaling systems, the chopping frequency usually varies in steps, depending on the required motor frequency range.

So on a modern EMU, the 'traction noises' you hear are usually a mixture of gear noise, AC traction motor current noise and inverter 'chopping' noise. (You hear the 'current' noises mostly because the iron/steel cores of motors and smoothing chokes vibrate as the magnetic fields within them vary, due to it being alternating current).

See https://en.wikipedia.org/wiki/Power_inverter

 

[DarloRich]

They have a lot of power but are gas guzzlers,

I thought the 60 gave good "gas mileage"!!!!!!!!! I am no expert but recall someone who was ex BR telling me this. He was an expert on this sort of thing!

 

[Magdalia]

2 -

Older Traction motors were DC driven and were a direct drive via the rotor shaft to a motor pinion onto a direct drive gear fixed to the axle, these are geneally covered in a gearpan (made in two halves to enable motor/ wheelset renewal) which was lubricated with grease, the specific pitch of the gears give these motors their particular noise. Generally these motors are large to give the power and run at a much lower pitch and much louder sound wise.

Modern traction motors are genearlly run on AC and are brushless, so are much smaller, these then drive a much smaller pinion ususally through a flexible coupling onto a gearbox fitted to the axle which converts the drive through several gears to increase torque, these gears are much smaller and are incased in a gearbox which is ususally filled with oil, so run much quieter and at a higher pitch sound wise. As the motors can be changed without removing the wheelset and vicea versa

Thanks, this is very illuminating!

So, if the traction motors are changed, but the gearing stays the same, then much of the noise will stay the same too?

 

[swt_passenger]

[…]
Note though that even if the supply is ac and the motor is ac, there has to be dc in between: the 50Hz supply signal has to be removed before the variable frequency needed by the motors can be applied

Sure, I didn’t want to go into that level of detail, I always think that’s already implied in that the overhead is only single phase; but too much detail about ac/dc/ac conversion possibly goes over the heads of part of the membership...

 

[ac6000cw]

A classic, entertaining, demonstration of traction inverter noise are the 'musical' OBB cl. 1016/1116 Taurus locomotives (Siemens ES64U2):

Translated from https://de.m.wikipedia.org/wiki/Siemens_ES64U2#Geräuschentwicklung :

Noise​

When switching on from a standing position, a sound can be heard that is reminiscent of playing through a scale on a tenor saxophone. It is produced in the three-phase motors by the control of the power converters. The noise is twice the clock frequency of the pulse inverters, which is gradually increased.

The frequency changes in whole and semitone steps over two octaves from d to d" in the tone reserve of the root tones. It is a Dorian scale on the root note D.[7] Theoretically, it would be possible to program the locomotive to emit completely different sounds. However, the manufacturer has opted for a scale because these sounds are perceived as pleasant by the human ear. [8] This makes it possible for the wheelsets to be skiddled (e.g. through wet rails) to produce a four-voice approach tone. [9]

 

[WatcherZero]

I thought the 60 gave good "gas mileage"!!!!!!!!! I am no expert but recall someone who was ex BR telling me this. He was an expert on this sort of thing!

If used to haul a large formation like coal on non-electrified routes they are efficient because of their single low reduction gearing, but its like flying an A380 with 100 passengers, overkill for the task so over 80% of them on average have been continually stored/out of service while faster and more efficient diesel-electrics and bi-modes have proliferated for container freight.

 

[4SubAsociation]

3. Why wasn't 4-SUB 4101 saved? It started the fleet of SUBs and the eventual development into the EPB.

Not heard of any appeal for 4SUB 4101 to be preserved. At the time EMU preservation was in its real infancy. The 1st privately preserved EMU did not happen until March 1972 (4DD 3 carriages from 4002), then later the 2BIL, 4COR Motor Coach from 3131 and 4COR Buffet Coach from 3084 went to the National Collection and 4COR 3142 being preserved by late 1972/early 1973 with a carriage swap with 3135 (and motor coach 3135, and TCK from 3159).

With 4SUB 4732 by 1982 it was the last one left with a orignal compartment trailer, hence the green livery, then kept on after 1983 as it could opperate with 2BIL 2090, by the time the special services had finished and was the last complete 4SUB left.

 

[43096]

A classic, entertaining, demonstration of traction inverter noise are the 'musical' OBB cl. 1016/1116 Taurus locomotives (Siemens ES64U2):

Translated from https://de.m.wikipedia.org/wiki/Siemens_ES64U2#Geräuschentwicklung :

Having just come back from a trip that included a few days in Austria, I can safely say that is a sound I will never, ever get bored of hearing. They are fantastic locomotives: classic design to go with the sound and an amazing performance specification. They are can do almost any job, from lugging freights through the Alps, through powering double-deck regional services through the centre of Vienna, to powering a RailJet at 230km/h.

Not often realised is that DB's ICE1 (the second batch; sets 51 to 90) and ICE2 power cars are/were similarly musical - at least until they had IGBT converter upgrades - but the music is often drowned out by the sound of the blowers.