Class 93 Tri-mode Loco

[Richard Scott]

Probably (as it's been 10 years since the cl. 68). Good AC traction drives in good rail conditions with high axle loads are usually reckoned to boost usable tractive effort per axle at low speeds by up to about 50% versus a good DC drive, but less so in slippery rail conditions. If you can get close to cl. 66 performance for general freight with two fewer axles, motors and inverters (= less cost) why not?

A quick illustration of DC versus AC tractive effort for a couple of US diesel locos which are basically the same 6-axle loco, other than the AC version being about 4% heavier (and both are 30+ tonne axle load):

DC drive: GE ES44DC - Tractive Effort (starting) 142,000 lbs, Tractive Effort (continuous): 109,000 lbs @ 13.7 mph
AC drive: GE ES44AC - Tractive Effort (starting) 183,000 lbs, Tractive Effort (continuous): 166,000 lbs @ 13.7 mph

(data from https://www.thedieselshop.us/DataGEIndex.HTML )

If these figures are correct then implies a much higher power at rail for the AC drive; would expect a slightly higher value for AC as motors are more efficient but this is significantly more.

 

[LUYMun]

Another YouTube video on the Class 93 by Sim0nTrains:

 

[Peter Sarf]

From the videos I am not even sure the loco is using a diesel engine as its not obvious to me. These tests might be all done on battery ?.

 

[ac6000cw]

If these figures are correct then implies a much higher power at rail for the AC drive; would expect a slightly higher value for AC as motors are more efficient but this is significantly more.

Thanks for pointing that out - checking the figures (which I copied from a usually reliable source), I suspect either the continuous TE or the speed are wrong for the AC drive loco - I'll check. The engine power rating is the same (4400hp 'available for traction') for both DC and AC locos.

 

[Trainman40083]

It sounds like a Hair Dryer.

I thought it was more like a washing machine on spin cycle.

 

[43096]

Thanks for pointing that out - checking the figures (which I copied from a usually reliable source), I suspect either the continuous TE or the speed are wrong for the AC drive loco - I'll check. The engine power rating is the same (4400hp 'available for traction') for both DC and AC locos.

The weights are slightly different for the two types according to the link you provided earlier, ES44DC being 188 tonnes and ES44AC 196 tonnes. How much that accounts for the tractive effort rating, I don't know.

 

[ac6000cw]

From the videos I am not even sure the loco is using a diesel engine as its not obvious to me. These tests might be all done on battery ?.

Without OHLE, I assume it runs in a diesel + battery hybrid mode (with re-generative braking into the battery as well), so how much power comes from each source probably varies dynamically. Also it's only a 1200hp/900kW diesel engine, with exhaust after-treatment plumbing as well, so possibly not very noisy anyway, especially running light engine.

 

[Richard Scott]

From the videos I am not even sure the loco is using a diesel engine as its not obvious to me. These tests might be all done on battery ?.

As already pointed out it will be very quiet, an 88 is almost inaudible when on diesel. Even older designs can be quiet when re-engineered, listen to a Slovakian 757 - you can hear the traction motors over the engine!!

 

[The_Train]

Sounds like my vacuum cleaner when the filter needs changing

 

[hwl]

Thanks for pointing that out - checking the figures (which I copied from a usually reliable source), I suspect either the continuous TE or the speed are wrong for the AC drive loco - I'll check. The engine power rating is the same (4400hp 'available for traction') for both DC and AC locos.

If these figures are correct then implies a much higher power at rail for the AC drive; would expect a slightly higher value for AC as motors are more efficient but this is significantly more.

It isn't that simple unfortunately.
That definition of continuous TE is a also hugely dependent on traction electrical equipment's ability to operate efficiently and and is a measure of when the equipment overheats. 3 Phase variable frequency AC is far friendlier to traction motors.

With AC the dry adhesion is far higher
The power at the rail is higher due to higher efficiency (7-8% higher overall efficiency)
AC traction electrical equipment is much less thermally stressed. e.g. in that example DC continuous = 75% of starting value, AC = 91% of starting value (which is much higher)
AC traction motors typically rotate 30-60% faster than DC so have much greater gearing ratios.

There are no nice simple easy comparisons.

 

[Rail Quest]

From the videos I am not even sure the loco is using a diesel engine as its not obvious to me. These tests might be all done on battery ?.

Without OHLE, I assume it runs in a diesel + battery hybrid mode (with re-generative braking into the battery as well), so how much power comes from each source probably varies dynamically. Also it's only a 1200hp/900kW diesel engine, with exhaust after-treatment plumbing as well, so possibly not very noisy anyway, especially running light engine.

The sound was definitely mixed but from what I've seen, it does look like they tried her on battery only at one point, which, rather expectedly, just sounded like an 88 on electric. Skip to 0:45 in this video:

She sounded a lot louder at Sheffield, a mixture of engine noise and I'm assuming coolant fans. Initial impressions to my ears are she definitely sounds better than an 88 on diesel, IMO.

 

[Richard Scott]

It isn't that simple unfortunately.
That definition of continuous TE is a also hugely dependent on traction electrical equipment's ability to operate efficiently and and is a measure of when the equipment overheats. 3 Phase variable frequency AC is far friendlier to traction motors.

With AC the dry adhesion is far higher
The power at the rail is higher due to higher efficiency (7-8% higher overall efficiency)
AC traction electrical equipment is much less thermally stressed. e.g. in that example DC continuous = 75% of starting value, AC = 91% of starting value (which is much higher)
AC traction motors typically rotate 30-60% faster than DC so have much greater gearing ratios.

There are no nice simple easy comparisons.

The basic physics is still the same though that Force x Speed = Power (I know strictly should talk about velocity), so if TE is higher at the same speed then rail power is higher. If continuous TE is significantly higher it would follow, for the same rail power, that speed that it occurred at would be lower.

 

[Peter Sarf]

Thanks for pointing out @Rail Quest fr pointing out. Yes I see the difference now.

 

[ac6000cw]

A quick illustration of DC versus AC tractive effort for a couple of US diesel locos which are basically the same 6-axle loco, other than the AC version being about 4% heavier (and both are 30+ tonne axle load):

DC drive: GE ES44DC - Tractive Effort (starting) 142,000 lbs, Tractive Effort (continuous): 109,000 lbs @ 13.7 mph
AC drive: GE ES44AC - Tractive Effort (starting) 183,000 lbs, Tractive Effort (continuous): 166,000 lbs @ 13.7 mph

If these figures are correct then implies a much higher power at rail for the AC drive; would expect a slightly higher value for AC as motors are more efficient but this is significantly more.

The basic physics is still the same though that Force x Speed = Power (I know strictly should talk about velocity), so if TE is higher at the same speed then rail power is higher. If continuous TE is significantly higher it would follow, for the same rail power, that speed that it occurred at would be lower.

Correct.

I've looked at other sources of information for the ES44AC and it's predecessor AC4400CW, which has basically the same electrical equipment and engine power.

If we assume the 'Tractive Effort (continuous): 166,000 lbs' is correct (as the loco can definitely produce that and more at very low speeds), taking the engine power 'available for traction' as 4400hp/3300kW and allowing for transmission efficiency, the balancing speed for that TE is around 9-10mph. 13.7mph is too high, as speed x TE => more power than the rated engine power. Also I've seen mentioned that the transition from the adhesion limited to power limited parts of the TE vs speed curve is about 8-10mph for an AC4400CW, which ties in with the 166,000 lbs (738kN) @ 9-10mph numbers.

As for dry versus wet rails performance, for the ES44AC/AC4400CW I've seen mentioned 40% dry and 35% wet 'factor of adhesion' (percentage of driving axle weights translated into tractive effort). From memory, a good classic DC drive is around 25% 'factor of adhesion'. Note the higher TE and power-at-rail performance of AC drives is a combination of things as hwl said in post #940.

(If anyone is interested in this stuff, the November 2006 (US) Trains magazine has an article called 'CSX's Mountain Climbers'. It's about improving the low-speed TE performance, particularly in bad weather, of AC4400CW locos by increasing the weight to 196 tonnes and improving the traction control performance in varying rail conditions. At the end of the development program, each axle could produce up to 36,000lbs/160kN of TE with an overall loco limit (for coupler stress reasons) of 200,000lbs/890kN. I just find this a phenomenal level of steel wheel on rail performance...)

 

[Richard Scott]

Correct.

I've looked at other sources of information for the ES44AC and it's predecessor AC4400CW, which has basically the same electrical equipment and engine power.

If we assume the 'Tractive Effort (continuous): 166,000 lbs' is correct (as the loco can definitely produce that and more at very low speeds), taking the engine power 'available for traction' as 4400hp/3300kW and allowing for transmission efficiency, the balancing speed for that TE is around 9-10mph. 13.7mph is too high, as speed x TE => more power than the rated engine power. Also I've seen mentioned that the transition from the adhesion limited to power limited parts of the TE vs speed curve is about 8-10mph for an AC4400CW, which ties in with the 166,000 lbs (738kN) @ 9-10mph numbers.

As for dry versus wet rails performance, for the ES44AC/AC4400CW I've seen mentioned 40% dry and 35% wet 'factor of adhesion' (percentage of driving axle weights translated into tractive effort). From memory, a good classic DC drive is around 25% 'factor of adhesion'. Note the higher TE and power-at-rail performance of AC drives is a combination of things as hwl said in post #940.

(If anyone is interested in this stuff, the November 2006 (US) Trains magazine has an article called 'CSX's Mountain Climbers'. It's about improving the low-speed TE performance, particularly in bad weather, of AC4400CW locos by increasing the weight to 196 tonnes and improving the traction control performance in varying rail conditions. At the end of the development program, each axle could produce up to 36,000lbs/160kN of TE with an overall loco limit (for coupler stress reasons) of 200,000lbs/890kN. I just find this a phenomenal level of steel wheel on rail performance...)

Very much in theory then a Bo-Bo wheel arrangement could give over 100,000lbs of TE but it would have a huge axle loading that would not be permitted here? Not sure what axle loading is on a 93, around 21 tons? Be interesting to see what one can achieve on wet rails up Shap?!! How do 88s fare under those conditions? Did someone say 93s have better adhesion characteristics, if so should be more than capable? Would imagine AC drives mean wheelslip is well controlled as AC motors speed up due to frequency and if that's limited theoretically so is wheelslip?

 

[ac6000cw]

Very much in theory then a Bo-Bo wheel arrangement could give over 100,000lbs of TE but it would have a huge axle loading that would not be permitted here?

Correct. In fact there is a cheaper, four driven axles, A1A-A1A version of the ES44AC which is rated at 144,000 lbs starting, 105,000lbs continuous TE (I don't know at what speed).

AFAIK the 68/88/93 are rated at around 6700lbs/300kN of max TE with a 21.5 tonne axle load. Per axle, this is higher than a 66 but lower than a cl. 60 or 70 at very low speeds.

Would imagine AC drives mean wheelslip is well controlled as AC motors speed up due to frequency and if that's limited theoretically so is wheelslip?

That's basically correct, but also a factor is how well the traction system deals with weight transfer effects between axles and different/varying rail head conditions on each axle e.g. in poor weather the leading axles encounter worse railhead conditions than trailing ones (which benefit from the leading axles drying out the railhead).

 

[Suraggu]

Looks like loaded test runs from Thursday.

Realtime Trains | 5Q25 0858 Worksop Down Yard to Sheffield | 30/05/2024

Real-time train running information for 5Q25 0858 departure from Worksop Down Yard to Sheffield on 30/05/2024. From Realtime Trains, an independent source of train running info for Great Britain.

www.realtimetrains.co.uk

Realtime Trains | 5Q26 1007 Sheffield to Worksop Up Receptions | 30/05/2024

Real-time train running information for 5Q26 1007 departure from Sheffield to Worksop Up Receptions on 30/05/2024. From Realtime Trains, an independent source of train running info for Great Britain.

www.realtimetrains.co.uk

Realtime Trains | 5Q27 1123 Worksop Up Receptions to Sheffield | 30/05/2024

Real-time train running information for 5Q27 1123 departure from Worksop Up Receptions to Sheffield on 30/05/2024. From Realtime Trains, an independent source of train running info for Great Britain.

www.realtimetrains.co.uk

Realtime Trains | 5Q28 1231 Sheffield to Worksop Up Receptions | 30/05/2024

Real-time train running information for 5Q28 1231 departure from Sheffield to Worksop Up Receptions on 30/05/2024. From Realtime Trains, an independent source of train running info for Great Britain.

www.realtimetrains.co.uk

Realtime Trains | 5Q29 1330 Worksop Up Receptions to Sheffield | 30/05/2024

Real-time train running information for 5Q29 1330 departure from Worksop Up Receptions to Sheffield on 30/05/2024. From Realtime Trains, an independent source of train running info for Great Britain.

www.realtimetrains.co.uk

Realtime Trains | 5Q30 1508 Sheffield to Worksop Down Yard | 30/05/2024

Real-time train running information for 5Q30 1508 departure from Sheffield to Worksop Down Yard on 30/05/2024. From Realtime Trains, an independent source of train running info for Great Britain.

www.realtimetrains.co.uk

 

[bahnause]

Very much in theory then a Bo-Bo wheel arrangement could give over 100,000lbs of TE but it would have a huge axle loading that would not be permitted here? Not sure what axle loading is on a 93, around 21 tons? Be interesting to see what one can achieve on wet rails up Shap?!! How do 88s fare under those conditions? Did someone say 93s have better adhesion characteristics, if so should be more than capable? Would imagine AC drives mean wheelslip is well controlled as AC motors speed up due to frequency and if that's limited theoretically so is wheelslip?

Wheelslip protection has come a long way since the first ‘primitive’ systems. Today's AC locomotives often have very complex software for controlling (not necessarily eliminating) slip. The natural ‘good-natured’ behaviour of AC motors doesn't even has come into play that much. Depending on the condition of the track and speed, the amount of slip required (yes, you do want wheelslip) to maximise adhesion varies. There is also the comfort factor, the maximum utilisation of adhesion due to the constant rapid changes in tractive force is not always comfortable. Some vehicles even allow the driver to adjust the maximum slip as required:

If there is no or only a small difference between the requested and the currently
tractive or braking force, the adhesion control tends to work more defensively.
more defensive. The locomotive runs with little or no slip.

If there is a greater difference between the requested and the current tractive or braking force, the adhesion control tends to work more aggressively and, utilising the maximum possible slip, constantly seeks the best possible tractive or braking force.

This does not override physics, but it does allow it to be utilised as effectively as possible.

 

[Meerkat]

Those high level orange jumper sockets (??) really do look like devil eyes!

 

[Rail Quest]

Clip of the 93 on today's loaded run mentioned earlier:

 

[ac6000cw]

Clip of the 93 on today's loaded run mentioned earlier:

Anyone know what the gradient is at that location?

It's hauling 6 x Mk3 + 1 x Mk2, so a bit under 300 tonnes trailing load?

 

[Suraggu]

Anyone know what the gradient is at that location?

It's hauling 6 x Mk3 + 1 x Mk2, so a bit under 300 tonnes trailing load?

250 tonnes according to TOPS.

 

[ac6000cw]

250 tonnes according to TOPS.

Oops - I looked up the weight of Mk 4s instead of Mk 3s and Mk 2s, so yes 250t is correct!

 

[Bryson]

250 tonnes according to TOPS.

I guess this answers the doubters who said it could never move a train in diesel mode . Didn't someone say it couldn't even move its self?

(Before I get shot down - yes, I know this isn't a heavy Freight and that the location isn't Shap)

The location appears to be the overbridge at Bernard road. The 93 is making the climb up from Nunnery Mainline Junction towards Woodburn Junction.

 

[LAX54]

Anyone know what the gradient is at that location?

It's hauling 6 x Mk3 + 1 x Mk2, so a bit under 300 tonnes trailing load?

Coaches nicely turned out by ERS at Yarmouth

 

[Suraggu]

I guess this answers the doubters who said it could never move a train in diesel mode . Didn't someone say it couldn't even move its self?

(Before I get shot down - yes, I know this isn't a heavy Freight and that the location isn't Shap)

The location appears to be the overbridge at Bernard road. The 93 is making the climb up from Nunnery Mainline Junction towards Woodburn Junction.

Those people who said that will now turn and say 'It's doesn't have any prospective customers'.

Getting a new locomotive certified is a feat in itself and is more complex than an 88 so not surprising its taken time to get to this point.

 

[craigybagel]

Anyone know what the gradient is at that location?

It's hauling 6 x Mk3 + 1 x Mk2, so a bit under 300 tonnes trailing load?

Was the ETH on I wonder?

 

[Richard Scott]

Was the ETH on I wonder?

Are they able to supply ETS on diesel? Know this was of some debate with 88s, due to low installed power on diesel.

 

[Smoggy]

Was the ETH on I wonder?

Yes, the ETS was on, every vehicle was also switched on to provide heating and lighting on every trip.

 

[Richard Scott]

Yes, the ETS was on, every vehicle was also switched on to provide heating and lighting on every trip.

Answers my question too then!