Class 93 Tri-mode Loco

[Noddy]

Are you sure about that? 66s can provide a much higher tractive effort than the 93. It doesn't matter what power you have at the rail, if the locomotive does not have the tractive effort to be able to apply that power.

Consider the worst case of a standing start with an 1800t maximum intermodal on a 1.53% gradient. With the 93 weighing 86t, the tractive effort needed will be 0.0153 x 1886t = 28.85t = 283kN.

The tractive effort available from the 93 is claimed to be just 290kN, presumably under the best conditions. So no margin for error. If that maximum pulling force is reduced in any way by poor rail conditions or any other reason, then the 93 will spin its wheels and the train will get stuck.

Of course, in real life , amtrain on the GOBLIN line will have momentum at the bottom of the gradient, and will coast up and over the hump over the GEML, but I'd be surprised if NR allows the margins to be so tight.

== == == ==

Now consider the WCML. If I were running a FoC looking to use the 93 over Shap and Beattock, I'd want a 50% safety margin on tractive effort. On a 1.4% gradient, that means a maximum trailing load of 145kN/9.8/0.014 - 86 = 970 tonnes.

Because of its higher power (4.6MW), the 93 will be able to pull those 970 tonnes up the hill at nearly three times a fast as a class 66 (1.85MW). But it all depends on what tractive effort the 93 is able to deliver in real life, on wet rails, in leaf fall season. Which is why real life tests with a heavy train are going to be so important for the future of the 93.

I'm really keen to see what maximum trailing load is eventually allowed for the 93 over that section of the northern WCML. I bet it won't be 1800t.

This graph showing the tractive effort of different classes is quite interesting. It looks to me like the max figure is held at 290kn until about 35mph.


Image shows a graph of tractive effort of different class taken from the following article:

Class 93 tri-mode locos on order - Rail Engineer

Listen to this article Rail Operations (UK) has signed a framework agreement with Stadler for the supply of 30 Class 93 tri-mode locomotives, of which an initial batch of ten locomotives will be due for delivery in early 2023. While the Class 93 concept was first proposed in 2018, it was not...

www.railengineer.co.uk

Rail Operations (UK) has signed a framework agreement with Stadler for the supply of 30 Class 93 tri-mode locomotives, of which an initial batch of ten locomotives will be due for delivery in early 2023. While the Class 93 concept was first proposed in 2018, it was not possible to secure funding for this order until Rail Operations was acquired by STAR Capital Partnership in January.

The Class 93 is a Bo-Bo locomotive based on Stadler’s Class 68 and Class 88 locomotives that have been operating successfully in the UK for some years. It was described in detail in the Rail Engineer article Re-engineering Rail Freight (see Issue 185, July/August 2020) and has a maximum speed of 110mph.

Stadler’s first tri-mode locomotive has three different power sources. In electric mode, it can run on 25kV AC overhead lines with a power of 4,000 kW. Its Caterpillar C32 engine has a nominal power of 900kW, which can be boosted by 400 kW for short periods (whilst accelerating or going up gradients) by the Lithium Titanate Oxide (LTO) battery pack when operating on non-electrified lines. Shunting operations can be powered by the batteries alone.

 

[AndrewE]

Are you sure about that? 66s can provide a much higher tractive effort than the 93. It doesn't matter what power you have at the rail, if the locomotive does not have the tractive effort to be able to apply that power.

Consider the worst case of a standing start with an 1800t maximum intermodal on a 1.53% gradient. With the 93 weighing 86t, the tractive effort needed will be 0.0153 x 1886t = 28.85t = 283kN.

The tractive effort available from the 93 is claimed to be just 290kN, presumably under the best conditions. So no margin for error. If that maximum pulling force is reduced in any way by poor rail conditions or any other reason, then the 93 will spin its wheels and the train will get stuck.

Of course, in real life , amtrain on the GOBLIN line will have momentum at the bottom of the gradient, and will coast up and over the hump over the GEML, but I'd be surprised if NR allows the margins to be so tight.

== == == ==

Now consider the WCML. If I were running a FoC looking to use the 93 over Shap and Beattock, I'd want a 50% safety margin on tractive effort. On a 1.4% gradient, that means a maximum trailing load of 145kN/9.8/0.014 - 86 = 970 tonnes.

Because of its higher power (4.6MW), the 93 will be able to pull those 970 tonnes up the hill at nearly three times a fast as a class 66 (1.85MW). But it all depends on what tractive effort the 93 is able to deliver in real life, on wet rails, in leaf fall season. Which is why real life tests with a heavy train are going to be so important for the future of the 93.

I'm really keen to see what maximum trailing load is eventually allowed for the 93 over that section of the northern WCML. I bet it won't be 1800t.

Have you seen the TE curves? above about 10 mph 66 TE falls off a cliff and the 93 wins hands down.

 

[Nottingham59]

Have you seen the TE curves? above about 10 mph 66 TE falls off a cliff and the 93 wins hands down.

Yes, and that would be fine on the level.

But on a gradient, the trailing load needs a force on it to keep it moving uphill. If the required force is greater than the maximum tractive effort the locomotive can deliver, then a moving train will gradually slow to a stop and then start to run away back downhill.

For the 93, that happends in any part of the graph above 290kN, where the 93 TE/speed curve doesn't reach. (The same would happen to a class 66 above 420kN. Which is why heavily loaded stone trains heading south from Dore sometimes get stuck on the 1% up gradient to Bradway Tunnel.)

The 93 wins hands down above 10mph, because power = tractive force x speed. Above 10mph, the higher power of the 93 on electric beats the 66. But at slow speeds on a gradient, it's tractive force that matters.

 

[AndrewE]

Yes, and that would be fine on the level.

But on a gradient, the trailing load needs a force on it to keep it moving uphill. If the required force is greater than the maximum tractive effort the locomotive can deliver, then a moving train will gradually slow to a stop and then start to run away back downhill.

For the 93, that happends in any part of the graph above 290kN, where the 93 TE/speed curve doesn't reach. (The same would happen to a class 66 above 420kN. Which is why heavily loaded stone trains heading south from Dore sometimes get stuck on the 1% up gradient to Bradway Tunnel.)

The 93 wins hands down above 10mph, because power = tractive force x speed. Above 10mph, the higher power of the 93 on electric beats the 66. But at slow speeds on a gradient, it's tractive force that matters.

what if it is doing 75 mph at the foot of the bank? How quickly will the 66 lose speed down to 20 mph (when you say it then is the better option) whereas the 93 could keep going over the top at a much more respectable minimum.

I can't really believe the engineers specifying and buying the things were so naive or deluded that they bought a pup...
Oh for a load test!

 

[Nottingham59]

what if it is doing 75 mph at the foot of the bank? How quickly will the 66 lose speed down to 20 mph (when you say it then is the better option) whereas the 93 could keep going over the top at a much more respectable minimum.

Well at 100mph, a train has the kinetic energy equivalent to 100m elevation, so it would coast up a 1% gradient for a distance of 10km (ignoring wind and rolling friction) At 75mph, that's about half the energy, so it would get up a 50m hill, or 5km up a 1% gradient.

But if it had to stop on the hill, then it would not be able to start again if the Traction Effort was not enough to overcome the trailing load drag.

I can't really believe the engineers specifying and buying the things were so naive or deluded that they bought a pup...

The 93 is fine for the southern WCML where gradients don't exceed 0.5%. It'll knock spots off class 66s there. It's only over long steep hills that I question its capability.

Oh for a load test!

That's the key. I suspect that there is a problem with performance under load, which is why we haven't seen load tests yet.

 

[Mollman]

Haven't we been here before with all this discussion on traction effort?

 

[bahnause]

But if it had to stop on the hill, then it would not be able to start again if the Traction Effort was not enough to overcome the trailing load drag.

I know countless places where I could no longer start my train after a stop. However, this is not relevant in day-to-day operations because we don‘t stop there.

 

[Richard123]

There’s 66s with 1400t on intermodals on the WCML now, You can be sure that 93s, with almkst twice as much power at the rail, will be hauling at least that with impunity.

And that gradient on the Gospel Oak line will simply not be a probem.

There does seem to be an echo chamber of enthusiasts convinced of their shortage of axles compared to the locos of their youth. A trip to continental Europe might shock; electric freight locos have four axles and do alright.

I suspect their use will have far more to do with EC4T charges vs diesel price, until FOCs are incentivised to consider their effect on route capacity.

So more class 66s crawling along mainlines at 30mph...

Yes, and that would be fine on the level.

But on a gradient, the trailing load needs a force on it to keep it moving uphill. If the required force is greater than the maximum tractive effort the locomotive can deliver, then a moving train will gradually slow to a stop and then start to run away back downhill.

For the 93, that happends in any part of the graph above 290kN, where the 93 TE/speed curve doesn't reach. (The same would happen to a class 66 above 420kN. Which is why heavily loaded stone trains heading south from Dore sometimes get stuck on the 1% up gradient to Bradway Tunnel.)

The 93 wins hands down above 10mph, because power = tractive force x speed. Above 10mph, the higher power of the 93 on electric beats the 66. But at slow speeds on a gradient, it's tractive force that matters.

You are only considering <10mph on the gradient because you are thinking in Class 66 terms!

A class 93 will crest Shap far more comfortably than a 66 with the same trailing load.

 

[Rail Quest]

Is there a speculative thread regarding possible uses for the 93s? If so, would probably make sense to migrate this bit of the discussion over now

 

[Nym]

So why is it we're comparing the TE of a 4 axle locomotive with a 6 axle locomotive? They're fundamentally different in the roles that they're designed for.

 

[Nottingham59]

I'm just trying to understand the capabilities and performance of the 93.
Which seems an appropriate subject for the discussion on this thread.

EDIT: In particular whether it is suitable for hauling full length intermodals, i.e. with a trailing load of around 1800t.

 

[Richard Scott]

The other thing to consider is AC verses DC drives, AC is much less prone to slipping. Ok out and out force at rail will be relative to adhesive weight to some degree but once moving that matters less and less.

 

[themiller]

I'm just trying to understand the capabilities and performance of the 93.
Which seems an appropriate subject for the discussion on this thread.

EDIT: In particular whether it is suitable for hauling full length intermodals, i.e. with a trailing load of around 1800t.

Don’t forget that the 93 wasn’t designed to be a heavy hauler - that’s the domain of the 99 which should knock spots off a 66 under the wires. The 93 should cope sufficiently well on long intermodal just like the 88s do.

 

[43096]

The 93 should cope sufficiently well on long intermodal just like the 88s do.

I suspect West Coast main line users would dispute that given the chaos caused by the 88s on the 4S43 Daventry to Coatbridge job.

 

[Nottingham59]

Don’t forget that the 93 wasn’t designed to be a heavy hauler - that’s the domain of the 99 which should knock spots off a 66 under the wires. The 93 should cope sufficiently well on long intermodal just like the 88s do.

Not a heavy hauler, but when it was originally announced, ROG suggested it would be capable of hauling 2500t loads under the wires.

For comparison, can anyone tell us what is the maximum permitted trailing load for an 88 on the WCML? Say, on a flat bit like Crewe to Weaver, and a hilly section like over Shap or Beattock?

EDIT:

"Karl considers that the Class 93 will be a true go-anyway mixed-traffic locomotive, with the ability to haul fast passenger trains and freight trains of up to 2,500 tonnes on fully electrified routes."

Re-engineering Rail Freight - Rail UK

Re-engineering Rail Freight - Featured

railuk.com

 

[themiller]

Not a heavy hauler, but when it was originally announced, ROG suggested it would be capable of hauling 2500t loads under the wires.

For comparison, can anyone tell us what is the maximum permitted trailing load for an 88 on the WCML? Say, on a flat bit like Crewe to Weaver, and a hilly section like over Shap or Beattock?

EDIT:

Re-engineering Rail Freight - Rail UK

Re-engineering Rail Freight - Featured

railuk.com

A quick Look at the Daventry to Coatbridge Tesco trains on Realtime Trains Gives it as diesel hauling 1400 tonnes but 19 twin wagons with 38 containers can be over 1800 tonnes. I seem to remember one through Carlisle with 42 containers on 21 twins so it must have been about 2000 tonnes.

 

[Nottingham59]

A quick Look at the Daventry to Coatbridge Tesco trains on Realtime Trains Gives it as diesel hauling 1400 tonnes but 19 twin wagons with 38 containers can be over 1800 tonnes. I seem to remember one through Carlisle with 42 containers on 21 twins so it must have been about 2000 tonnes.

That's helpful, thanks.

(But I would expect Tesco containers to weigh less on average than most containers on deep sea routes, as they wil have more food than the average mix.)

 

[hwl]

I'm really keen to see what maximum trailing load is eventually allowed for the 93 over that section of the northern WCML. I bet it won't be 1800t.

88s are max 1400tonnes and struggle in autumn (need to run lighter or be double headed), if you are adhesion limited (only 4 axles) the extra short term boost the 93 has is meaning less.

 

[themiller]

That's helpful, thanks.

(But I would expect Tesco containers to weigh less on average than most containers on deep sea routes, as they wil have more food than the average mix.)

That’s right but you have to factor in the maximum permissible just in case there’s a run on heavy goods such as water. I remember when the container terminal was moved from Stockton to Wilton, it was in the ICI news that containers weighing greater than would be permitted to go by road could be carried as the Wilton terminal was inside the ICI property.

 

[hwl]

A quick Look at the Daventry to Coatbridge Tesco trains on Realtime Trains Gives it as diesel hauling 1400 tonnes but 19 twin wagons with 38 containers can be over 1800 tonnes. I seem to remember one through Carlisle with 42 containers on 21 twins so it must have been about 2000 tonnes.

An average container on the GB network is only about 1/3 of the max, lots of low density stuff being moved...
e.g. Very high end cars are exported by container and the contents can weigh less than the container!

Obviously there are some heavy ones with mineral water / whisky /scrap metal but most aren't.

 

[Nottingham59]

88s are max 1400tonnes and struggle in autumn (need to run lighter or be double headed)

Thank you. Class 88 have a nominal tractive effort of 317kN, so I expect that the class 93 with only 290kN nominal TE will struggle even more in leaf-fall season.

Though ROG did claim that the traction electronics on the 93 is better than any that had gone before. Maybe they will still get authorised to haul 1800t or even 2500t on the WCML south of Crewe (i.e. where gradients are less than around 0.5%, I think.)

 

[hwl]

Though ROG did claim that the traction electronics on the 93 is better than any that had gone before. Maybe they will still get authorised to haul 1800t or even 2500t on the WCML south of Crewe (i.e. where gradients are less than around 0.5%, I think.)

No that was very carefully worded - they weren't comparing it to an 88 (or anything newish) just 66s etc.

 

[Richard123]

88s are max 1400tonnes and struggle in autumn (need to run lighter or be double headed), if you are adhesion limited (only 4 axles) the extra short term boost the 93 has is meaning less.

Friction is (perpendicular) weight x surface co-efficient, not number of axles.

The 66s are far heavier but also massively underpowered leading to a crawl up sustained inclines where a more powerful train with a run-up can bring its momentum and speed through shorter issues. They also lack the kind of precision control on modern locos.

So swings and roundabouts. Similar locos do perfectly well in continental Europe so what is different here?

Thank you. Class 88 have a nominal tractive effort of 317kN, so I expect that the class 93 with only 290kN nominal TE will struggle even more in leaf-fall season.

Though ROG did claim that the traction electronics on the 93 is better than any that had gone before. Maybe they will still get authorised to haul 1800t or even 2500t on the WCML south of Crewe (i.e. where gradients are less than around 0.5%, I think.)

If leaf-fall is so severe as to affect operation, the maximum TE will be irrelevant.

 

[hwl]

Friction is (perpendicular) weight x surface co-efficient, not number of axles.

Err no you need to take your thinking further:
you get less adhesion on leading axles as the coefficient of friction is lower, hence the average achievable value across all axles is higher when you go from 4 to 6 axles (or 8 /12 too)
More axles means you don't need to achieve as high a coefficient of friction to deliver the same TE at lower speeds, hence when there is severe leaf fall you do better with more driven axles and 66s have less problems than 88s.

The 66s are far heavier but also massively underpowered leading to a crawl up sustained inclines where a more powerful train with a run-up can bring its momentum and speed through shorter issues. They also lack the kind of precision control on modern locos.

The 66s get up unlike 88s
Which is why the 99 on electric (3.35x 66) will be much better up sustained inclines than the 66 or 93.

 

[Richard123]

Err no you need to take your thinking further:
you get less adhesion on leading axles as the coefficient of friction is lower, hence the average achievable value across all axles is higher when you go from 4 to 6 axles (or 8 /12 too)
More axles means you don't need to achieve as high a coefficient of friction to deliver the same TE at lower speeds, hence when there is severe leaf fall you do better with more driven axles and 66s have less problems than 88s.



The 66s get up unlike 88s
Which is why the 99 on electric (3.35x 66) will be much better up sustained inclines than the 66 or 93.

The 66s are 126 tonnes! You also get less TE off the leading axle because of the rotation of the bogie. But that means more weight on the trailing.

I wonder how those European hills are not full of stranded Vectrons...

 

[furnessvale]

A quick Look at the Daventry to Coatbridge Tesco trains on Realtime Trains Gives it as diesel hauling 1400 tonnes but 19 twin wagons with 38 containers can be over 1800 tonnes. I seem to remember one through Carlisle with 42 containers on 21 twins so it must have been about 2000 tonnes.

Although FOCs could never rely on it, many containers are not loaded to their full weight capacity and the trains will be below these stated weights.

Of course the railway must allow for restarting from an out of course stop half way up Shap on a dirty winter's night when it is lashing down!

 

[nigelsporne]

Normal conditions then!

 

[ac6000cw]

The 66s are 126 tonnes!

They vary a bit depending on the exact spec, but they are nominally 21 to 21.5 tonnes per axle, same as an 88 or 93.

You also get less TE off the leading axle because of the rotation of the bogie. But that means more weight on the trailing.

That's exactly what hwl is saying...

The 66s are far heavier but also massively underpowered leading to a crawl up sustained inclines where a more powerful train with a run-up can bring its momentum and speed through shorter issues. They also lack the kind of precision control on modern locos.

Momentum (stored energy) only helps for short climbs - Shap and Beattock are long climbs (by UK standards). Also you can't guarantee a run-up.

Yes, modern AC traction drives in the 68/88/93 can make better use of *available* adhesion (friction) than the DC drives in the 66, but it won't make up for only having 2/3 the number of axles in poor railhead conditions. If you can't generate the tractive effort needed to lift the train up the hill - due to wheelslip - and the climb is long enough, you're not going to get over the summit...

 

[Belfastmarty]

It's all gone very quiet on the class.93 front. Has anyone any update regarding how the testing is going ?

 

[Class15]

It's all gone very quiet on the class.93 front. Has anyone any update regarding how the testing is going ?

How it has been going since the 93 arrived, basically. Very little to report. 93001 has been at Worksop since the most recent round of WCML testing.