• Our booking engine at tickets.railforums.co.uk (powered by TrainSplit) helps support the running of the forum with every ticket purchase! Find out more and ask any questions/give us feedback in this thread!

Diesel v Electric bogies

Status
Not open for further replies.

hexagon789

Veteran Member
Joined
2 Sep 2016
Messages
15,715
Location
Glasgow
Class 37, 50 and 55 shared the same bogies - but what about traction motors? Were they vastly different? I would assume so? I've never looked at the specs on these.

In regards to HST's - there were plans to put bigger engines in, but would the existing traction system including traction motors have been able to cope with the extra power?
All EE538 motors
55s are EE538
50s are EE538/5A
37s are EE538/A

There's something everyone's forgetting
Ignoring the 1960s designs, virtually all the UK CoCo designs post class 47, electric or diesel have been primarily freight locos with a max speed of 80 or less, while the BoBo designs were all passenger or mixed traffic designs with a max speed of 100+. The 89 obviously was an exception. During the 1970s BR developed an antipathy toward high speed CoCo designs, believing they damaged the track, I believe you're still seeing the results of that belief.


37 & 50 were geared differently - one 50 was fitted with 37 bogies to reduce the gearing and try to use it for heavy haulage
And some 37s gained bogies off Deltics (106mph continuous rated speed) to allow them 100mph running which they did for a brief period in the late-1960s doubled headed on a selection few headline expresses.

The feted 2460kW of the class 55s was the maximum power at the engine's output shaft/input to the generator. It would be an absolute maximum determined by the injection settings of the engine. There would be a power loss in the generator, auxiliaries and control gear so the power available to the motors might be 20% lower. Similarly, the class 50 power available at the motors would be lower than the headline 2010kW engine maximum figure quoted. Within those sort of power ranges, it is possible that the EE motors might have been the same (for the 50s and 55s) as DC motors are quite basic designs that can be range rated. The difference in physical size/weight would be minimal and they would fit into the same bogie frame mountings.
Deltics can put 2,640 down at the rail continously (obviously minus any ETH load)
50s are 2,070hp continous (2,400hp motor rating)

That had been dropped by the time the production power cars were built: there was space for a V16 Valenta in 41001/2, but not in 43002 upwards. Production power car main alternators are rated at 1,868kW (against 1,678kW engine output), so not enough margin for a 33% hike in engine power, but then by that stage the V16 plan had been dropped, so why specify the extra capability for something you don't need. I've not seen the rating of the original main alternators in 41001/2 quoted anywhere.
Don't know about the alternator but the quoted output at rail is lower - 1,632.5hp against the usual 1,770hp for production PCs.
 
Sponsor Post - registered members do not see these adverts; click here to register, or click here to log in
R

RailUK Forums

AM9

Veteran Member
Joined
13 May 2014
Messages
14,191
Location
St Albans
... Deltics can put 2,640 down at the rail continously (obviously minus any ETH load) 50s are 2,070hp continous (2,400hp motor rating)
Don't know about the alternator but the quoted output at rail is lower - 1,632.5hp against the usual 1,770hp for production PCs.
So what is the maximum (shaft) output of the engines on them all?
 

hexagon789

Veteran Member
Joined
2 Sep 2016
Messages
15,715
Location
Glasgow
So what is the maximum (shaft) output of the engines on them all?
I don't know what the maximum shaft outputs are, the diagram books only give the engine continuous outputs.

Though I believe Deltics are nominally 1,750hp per engine at maximum continuous rpm but downrated to 1,650hp for traction. The engines themselves are comfortably capable of far more than that of course.
 

AM9

Veteran Member
Joined
13 May 2014
Messages
14,191
Location
St Albans
I don't know what the maximum shaft outputs are, the diagram books only give the engine continuous outputs.

Though I believe Deltics are nominally 1,750hp per engine at maximum continuous rpm but downrated to 1,650hp for traction. The engines themselves are comfortably capable of far more than that of course.
The 'engines' in terms of the design I suppose may be available set for higher maximum power, - usually established during design proving tests, but in terms of the class55 role their downrating involves setting the injectors up to limit the power (to 1650hp each as you say) for reliability and maintenance scheduling reasons. So, at their in-service settings, the engine pair can generate no more than 3300hp, irrespective of the downstream inefficiencies, (e.g. generator efficiency, switchgear, ancillary loads and wiring), meaning that the maximum power available to the motors will be less than 2460kW (3300hp) by varying degrees at all times. Traction motors have conservative continuous ratings that allow specified periods (typically 1 hour) of operation at higher loads, but diesel engines, as I understand it, don't - maximum available power is what it is tuned for when installed, (apart from their state of deterioration between overhauls).
 

ac6000cw

Established Member
Joined
10 May 2014
Messages
3,121
Location
Cambridge, UK
All EE538 motors
55s are EE538
50s are EE538/5A
37s are EE538/A
Re. motor interchangeability (from memory) - when the 50s were transferred to the Western Region in the mid-1970s, the sustained 100mph running on the IC trains created traction motor problems, so BR swapped some of the motors with those from 37's (which had internal motor construction differences).
 

hexagon789

Veteran Member
Joined
2 Sep 2016
Messages
15,715
Location
Glasgow
The 'engines' in terms of the design I suppose may be available set for higher maximum power, - usually established during design proving tests, but in terms of the class55 role their downrating involves setting the injectors up to limit the power (to 1650hp each as you say) for reliability and maintenance scheduling reasons. So, at their in-service settings, the engine pair can generate no more than 3300hp, irrespective of the downstream inefficiencies, (e.g. generator efficiency, switchgear, ancillary loads and wiring), meaning that the maximum power available to the motors will be less than 2460kW (3300hp) by varying degrees at all times. Traction motors have conservative continuous ratings that allow specified periods (typically 1 hour) of operation at higher loads, but diesel engines, as I understand it, don't - maximum available power is what it is tuned for when installed, (apart from their state of deterioration between overhauls).
In which case I'm not really sure what you were asking with your question?


Re. motor interchangeability (from memory) - when the 50s were transferred to the Western Region in the mid-1970s, the sustained 100mph running on the IC trains created traction motor problems, so BR swapped some of the motors with those from 37's (which had internal motor construction differences).
Quite possibly, as I said the 37s gained Deltic bogies themselves to permit 100mph running so it may well be the motors were just as readily interchangeable.
 

randyrippley

Established Member
Joined
21 Feb 2016
Messages
5,082
Quite possibly, as I said the 37s gained Deltic bogies themselves to permit 100mph running so it may well be the motors were just as readily interchangeable.
If I remember correctly, Brian Reed in his book about the hydraulics was emphatic that contrary to belief the 37s used in those test runs were NOT modified with different bogies motors or gearing.

However you have to view that alongside statements that 37s were rejected for use on Waterloo-Exeter because it was believed their traction motors would overheat - suggesting they were different from 50/55 motors
 

norbitonflyer

Established Member
Joined
24 Mar 2020
Messages
2,276
Location
SW London
In which case I'm not really sure what you were asking with your question?



Quite possibly, as I said the 37s gained Deltic bogies themselves to permit 100mph running so it may well be the motors were just as readily interchangeable.
I read that some early Deltic bogies suffered from cracks and so they were all swapped out for a modified design - some of the swapped-out bogies were used in new 37s - presumably the stresses at lower speeds made them less prone to such problems.

On the general point, I understand that the dynamic behaviour of a two-axle bogie is easier to predict than a three-axle one, and also presumably can negotiate tighter curves. Thus if axle weight allows it, a two-axle bogie is preferred
 
Last edited:

randyrippley

Established Member
Joined
21 Feb 2016
Messages
5,082
On the general point, I understand that the dynamic behaviour of a two-axle bogie is easier to predict than a three-axle one, and also presumably can negotiate tighter curves. Thus if axle weight allows it, a two-axle bogie is preferred
BR claimed that at speed a three axle bogie would oscillate both vertically and laterally around the middle axle - which effectively became a pivot point
 

Railperf

Established Member
Joined
30 Oct 2017
Messages
2,923
I read that some early Deltic bogies suffered from cracks and so they were all swapped out for a modified design - some of the swapped-out bogies were used in new 37s - presumably the stresses at lower speeds made them less prone to such problems.

On the general point, I understand that the dynamic behaviour of a two-axle bogie is easier to predict than a three-axle one, and also presumably can negotiate tighter curves. Thus if axle weight allows it, a two-axle bogie is preferred
The French BB 26000 'Sybic' design was a 7'500hp design dsigned to haul 16 corail (longer and heavier than a UK MK3) coaches at 200km/h (124mph) or 2,050t freight at 80 km/h (50mph) on a 0.88% or 1 in 115 gradient. Not sure any UK loco can match that.
I wonder what advantage the monomotor bogies played a part in that? The B-B configuration being similar to a bo-bo except one large motor per bogie rather than two!
 

hexagon789

Veteran Member
Joined
2 Sep 2016
Messages
15,715
Location
Glasgow
If I remember correctly, Brian Reed in his book about the hydraulics was emphatic that contrary to belief the 37s used in those test runs were NOT modified with different bogies motors or gearing.

However you have to view that alongside statements that 37s were rejected for use on Waterloo-Exeter because it was believed their traction motors would overheat - suggesting they were different from 50/55 motors
I don't know about the test runs but for the accelerated services a batch of Class 37s (D6875-6892) were dedicated to the diagrams (running double headed) and were regeared specifically.

Sources differ on whether the rated speed was 105 or 106mph but either way it's more than their original 90mph nominal gearing


The French BB 26000 'Sybic' design was a 7'500hp design dsigned to haul 16 corail (longer and heavier than a UK MK3) coaches at 200km/h (124mph) or 2,050t freight at 80 km/h (50mph) on a 0.88% or 1 in 115 gradient. Not sure any UK loco can match that.
I wonder what advantage the monomotor bogies played a part in that? The B-B configuration being similar to a bo-bo except one large motor per bogie rather than two!
What about the older CC6500? I thought they were even more powerful.

I read that some early Deltic bogies suffered from cracks and so they were all swapped out for a modified design - some of the swapped-out bogies were used in new 37s - presumably the stresses at lower speeds made them less prone to such problems.
Yes, I've read about those issues though I have seen anything about what was swapped and whether any 37s got them
 

Railperf

Established Member
Joined
30 Oct 2017
Messages
2,923
What about the older CC6500? I thought they were even more powerful.
Only 8,000 hp if i remember correctly - so 500hp more but a larger heavier C-C design. Though the C-C was interesting as the bogies had a GV (grande vitesse) and a PV (petite Vitesse) gearing. The petite vitesse gearing dropped maximum speed from 200km/h to 100km/h - but haulage capability and tractive effort were hugely increased for freight.
 

Wyrleybart

Established Member
Joined
29 Mar 2020
Messages
1,623
Location
South Staffordshire
Wabtec (GE as was) in the US builds new A1A-A1A locos (model ET44C4).
And did some of the genesis of that come from "lift axles" where the middle wheelset of each bogie could be minutely "lifted" so that the tractive effort could be more usefully placed on the end axles of each bogie. Did it ever work out ?
 

hexagon789

Veteran Member
Joined
2 Sep 2016
Messages
15,715
Location
Glasgow
Only 8,000 hp if i remember correctly - so 500hp more but a larger heavier C-C design. Though the C-C was interesting as the bogies had a GV (grande vitesse) and a PV (petite Vitesse) gearing. The petite vitesse gearing dropped maximum speed from 200km/h to 100km/h - but haulage capability and tractive effort were hugely increased for freight.
Quite a few French locomotives had switchable gear ratios as I recall, the diesel equivalent of the CC6500s the CC72000s had an option between 140/160 (depending on batch) and 85km/h. The 85 setting was designed for freight but there was at least one passenger service where the stiff gradients of part of the route meant the 85 setting was used even though linespeed was higher than 85.
 

ac6000cw

Established Member
Joined
10 May 2014
Messages
3,121
Location
Cambridge, UK
And did some of the genesis of that come from "lift axles" where the middle wheelset of each bogie could be minutely "lifted" so that the tractive effort could be more usefully placed on the end axles of each bogie. Did it ever work out ?
Yes, it did - BNSF Railway has over 1200 of the ES44C4 version with four powered axles, normally used on intermodal and general freight trains. They are meant to roughly match the performance and initial cost of a six-powered-axles DC-drive loco, but with the benefits of reduced maintenance/greater ruggedness of AC motors. From what I've read, in most circumstances they do meet the design brief, but the six-powered-axles DC-drive version can perform better (to some extent) in poor rail conditions.

In usage terms they are like a modern version of a four-axle GPxx loco (which were the common loco choice on 'fast freight' years ago, but as engine power increased they got too heavy and had insufficient fuel capacity, so railroads stopped buying them after the GP60 series).

If you stand by the side of the BNSF (ex-SantaFe) LA-Chicago mainline you'll see a procession of trains hauled by a mixture of GE C44-9W (DC-drive), ES44DC (DC), ES44C4 (AC) and ET44C4 (AC) used interchangeably.
 
Last edited:

gimmea50anyday

Established Member
Joined
8 Jan 2013
Messages
3,456
Location
Back Cab
Don't know about the alternator but the quoted output at rail is lower - 1,632.5hp against the usual 1,770hp for production PCs.

I wonder if that quoted difference is down the the propotype PCs providing standard ETH at 1000v DC whereas production PCs used a 415v AC 3 phase ETH supply and how much power the different ETH supplies drew out of the engines output as a result
 

43096

On Moderation
Joined
23 Nov 2015
Messages
15,164
I wonder if that quoted difference is down the the propotype PCs providing standard ETH at 1000v DC whereas production PCs used a 415v AC 3 phase ETH supply and how much power the different ETH supplies drew out of the engines output as a result
There’s very little difference in power consumption between a LHCS and a HST Mark 3.
 

Railperf

Established Member
Joined
30 Oct 2017
Messages
2,923
There’s very little difference in power consumption between a LHCS and a HST Mark 3.
if you could fit a transformer and the associated equipment into an HST power car - removing the engine and creating an 'electric' HST, i wonder what the power at rail would be?
 

apk55

Member
Joined
7 Jul 2011
Messages
438
Location
Altrincham
Yes, it did - BNSF Railway has over 1200 of the ES44C4 version with four powered axles, normally used on intermodal and general freight trains. They are meant to roughly match the performance and initial cost of a six-powered-axles DC-drive loco, but with the benefits of reduced maintenance/greater ruggedness of AC motors. From what I've read, in most circumstances they do meet the design brief, but the six-powered-axles DC-drive version can perform better (to some extent) in poor rail conditions.

In usage terms they are like a modern version of a four-axle GPxx loco (which were the common loco choice on 'fast freight' years ago, but as engine power increased they got too heavy and had insufficient fuel capacity, so railroads stopped buying them after the GP60 series).

If you stand by the side of the BNSF (ex-SantaFe) LA-Chicago mainline you'll see a procession of trains hauled by a mixture of GE C44-9W (DC-drive), ES44DC (DC), ES44C4 (AC) and ET44C4 (AC) used interchangeably.
This is the complete opposite of using using slugs. Having none powered axles might have some relevance for high speed passenger locos but for freight (even fast freight) tractive effort is normaly a major factor.

There is no reason why DC motors can not give equally high tractive to AC motors. If controlled by a fast acting and intelligent control system (eg microprocessor chopper control) then you can run them at same adhesion levels. You are comparing old crude control systems to modern systems. 87101 showed what could be achieved by even simple electronic power control in that it could haul considerably more than a standard 87.

However AC motors do have some advantages over DC motors. They are lighter, smaller, cheaper to make, more robust and lower maintance than an equivelent DC motor. However they do require a more complex electronic drive system that somewhat reduces the cost advantage.
 

43096

On Moderation
Joined
23 Nov 2015
Messages
15,164
if you could fit a transformer and the associated equipment into an HST power car - removing the engine and creating an 'electric' HST, i wonder what the power at rail would be?
You mean "what's the maximum rating of the traction motors"?

This is the complete opposite of using using slugs. Having none powered axles might have some relevance for high speed passenger locos but for freight (even fast freight) tractive effort is normaly a major factor.

There is no reason why DC motors can not give equally high tractive to AC motors. If controlled by a fast acting and intelligent control system (eg microprocessor chopper control) then you can run them at same adhesion levels. You are comparing old crude control systems to modern systems. 87101 showed what could be achieved by even simple electronic power control in that it could haul considerably more than a standard 87.

However AC motors do have some advantages over DC motors. They are lighter, smaller, cheaper to make, more robust and lower maintance than an equivelent DC motor. However they do require a more complex electronic drive system that somewhat reduces the cost advantage.
As I understood it, the reason GE went down this route was to give equivalent performance to a DC-motored loco, but with the maintenance advantages of AC motors, but at an equivalent price to a DC loco as GE uses an inverter per axle, so it saves on two inverters and two traction motors.
 

Railperf

Established Member
Joined
30 Oct 2017
Messages
2,923
You mean "what's the maximum rating of the traction motors"?


As I understood it, the reason GE went down this route was to give equivalent performance to a DC-motored loco, but with the maintenance advantages of AC motors, but at an equivalent price to a DC loco as GE uses an inverter per axle, so it saves on two inverters and two traction motors.
You mean "what's the maximum rating of the traction motors"?
Yes.. Maximum. And continuous pls.
 

ac6000cw

Established Member
Joined
10 May 2014
Messages
3,121
Location
Cambridge, UK
There is no reason why DC motors can not give equally high tractive to AC motors. If controlled by a fast acting and intelligent control system (eg microprocessor chopper control) then you can run them at same adhesion levels. You are comparing old crude control systems to modern systems. 87101 showed what could be achieved by even simple electronic power control in that it could haul considerably more than a standard 87.
I'm not doing the comparison - my comments are based on what GE and BNSF said when the ES44C4 loco development was first announced. BNSF ordered an initial 25 units and decided they liked them enough to order more than 1200 subsequently (and 250+ of the later ET44C4 version).

As 43096 says, the design is about producing an AC-motored loco at a similar price and performance level to a DC-motored loco of the same power, but with the lower maintenance costs of (fewer) AC induction motors (and spares commonality with their all-axles-powered ES44/ET44 brothers that BNSF also own). Basically BNSF is replacing some of its older six-axle DC-drive fleet with these.

I'm well aware that electronic Sepex control of DC-motors can give you wheelslip control performance close to AC-drive systems, but you still end up with the higher maintenance costs and lower robustness of DC-motors (and the extra power electronics adds cost). Plus from the manufacturers point-of-view DC-drives are obsolete technology so why put development money into it?

(As far as I know, the EMD early 1980's vintage 'Super Series' DC-drive wheelslip control is electronic, using thyristor control of the alternator excitation, but of course that's per-loco rather than per motor)
 
Last edited:

hexagon789

Veteran Member
Joined
2 Sep 2016
Messages
15,715
Location
Glasgow
I wonder if that quoted difference is down the the propotype PCs providing standard ETH at 1000v DC whereas production PCs used a 415v AC 3 phase ETH supply and how much power the different ETH supplies drew out of the engines output as a result
No idea, but the difference surprised me when I discovered one existed. I have no reason to doubt it either - 3 sources agree on the figures within reasonable margins of rounding errors.

50s traction motor gearing was 2.9:1, but I'm not sure about 37s and 55s.
I have 2.94:1 for 50s and 2.81:1 for 55s and most 37s. 2.22:1 for 37/0 & 37/6s.
 

43096

On Moderation
Joined
23 Nov 2015
Messages
15,164
No idea, but the difference surprised me when I discovered one existed. I have no reason to doubt it either - 3 sources agree on the figures within reasonable margins of rounding errors.
Are those sources all using a single source that has been "handed down" and is wrong? In much the same way that multiple publications reported the VP185 power cars as rated at 2,100hp (they never were and are not).

41001 was comparable for power to production power cars when it was operational, and those who drove it reckoned it was a good one for power.
 

hexagon789

Veteran Member
Joined
2 Sep 2016
Messages
15,715
Location
Glasgow
Are those sources all using a single source that has been "handed down" and is wrong? In much the same way that multiple publications reported the VP185 power cars as rated at 2,100hp (they never were and are not).

41001 was comparable for power to production power cars when it was operational, and those who drove it reckoned it was a good one for power.
They are all British Rail or BRB documents

One can be viewed publically on the Railways Archive
 

AM9

Veteran Member
Joined
13 May 2014
Messages
14,191
Location
St Albans
if you could fit a transformer and the associated equipment into an HST power car - removing the engine and creating an 'electric' HST, i wonder what the power at rail would be?
That would depend almost entirely on the ratings of the current motors. The transformer would have to be rated for the maximum draw of all services and the motors running at their maximum short-term output. I doubt that running a transformer outside its design limits would do much for waveform quality as modern traction designs are designed with minimum iron to keep the weight and size down. That became a problem when the class 700s self-protected as the supply frequency dropped below 48.5Hz (ISTR), and although the trip level was probably a bit overcautious, there isn't much leeway in the design for abuse.
 

hexagon789

Veteran Member
Joined
2 Sep 2016
Messages
15,715
Location
Glasgow
That would depend almost entirely on the ratings of the current motors. The transformer would have to be rated for the maximum draw of all services and the motors running at their maximum short-term output. I doubt that running a transformer outside its design limits would do much for waveform quality as modern traction designs are designed with minimum iron to keep the weight and size down. That became a problem when the class 700s self-protected as the supply frequency dropped below 48.5Hz (ISTR), and although the trip level was probably a bit overcautious, there isn't much leeway in the design for abuse.
I believe the maximum rating is 1,868hp for the four motors together if I recall rightly.
 

apk55

Member
Joined
7 Jul 2011
Messages
438
Location
Altrincham
You could potentially convert almost any diesel electric locomotive (or multiple unit) to an electric locomotive (or MU) by removing the diesel engine and replacing with a transformer and rectifier. The maximum tractive effort and speed would determined by the traction motors although you might be able to get a bit more power at speed depending on how well rated the traction motors are. I think this has been done in a few cases abroad.

Would not be too easy as you would have to sort out roof space for mounting a pantograph and circuit breaker. A transformer is generally lighter than an equivalent rated diesel so no weight problems and you would require a controlled rectifier on the output to provide a variable voltage to the traction motors. While in the past you could probably just used a phase angle controlled thyristor rectifier on the output, modern requirements would probably require a better power and form factor and more complex system would be required. Probably not worth doing except in a few specialist cases.
 
Status
Not open for further replies.

Top