EU "Digital Automatic Coupler" and its implications

[HSTEd]

So as people may be aware, the EU sponsored a competition to select a future coupler for EU railfreight, to replace chain and buffer type couplings.

After a competition the resulting coupler selected is a Scharfenberg, with the reference being a design developed by Voith.

One oddity is the selected coupler has a rated tensile strength of only 1000kN. Which is much greater than screw couplings sure, but even given limits of ~775m for EU freight trains it may prove to be somewhat inadequate.

A string of 50 loaded MWA wagons can weigh 5,080 tonnes, and keeping that train moving at constant speed up Lickey Incline would require tractive effort of 134tonnes-force or 1322kN - which would exceed rated coupler load.
Now sure, that's an extreme example, but to put it another way, given that modern CoCo locomotives can produce up to 600kN of starting Tractive Effort, doesn't seem much margin there. Distributed power would help but still seems like a significant restriction on flexibility.

Obviously its fine for most freight trains but it does seem rather silly to select a coupler that can't do all a freight coupler needs to do.
It's not as if there is not plenty of experience with fully automated Janey/AAR couplings which are much stronger (~1750kN tensile).

It's notable that whilst the competition did include a fully automated SA3 coupling, it was withdrawn from consideration and no Janney option was considered at all. (the Voith coupler, a Dellner, a Scwab and a CAF-designed SA3 were considered).

This could have implications on the UK rail industry if the coupler becomes common in Europe with Eurotunnel freight trains.

If we are going to have a fancy new coupler spec, wouldn't it be better if it could do everything we might want?

 

[Nottingham59]

A 5000T train on a 1% up gradient would need 500kN to maintain speed. So a rated tensile strength of 1000kN sounds very sensible to me. (Assuming that modern driving practice avoid shock loading of couplings.) What is the steepest up gradient that a fully-loaded aggregates train normally encounters in the UK?

EDIT: I note for example that Lawley St aggregates terminal has only one path in and out per day. The empties go back to the quarry down the Lickey, but the full wagons go via Banbury.

Realtime Trains | 6M17 2136 Machen Quarry (Flhh) to Lawley Street Aggs Term | 14/03/2023

Real-time train running information for 6M17 2136 departure from Machen Quarry (Flhh) to Lawley Street Aggs Term on 14/03/2023. From Realtime Trains, an independent source of train running info for Great Britain.

www.realtimetrains.co.uk

 

[Irascible]

The implication is also that each vehicle has to be digitally compatible! *fatigued hurrahs*

I don't feel like doing back of envelope calcs about shocks ( or reading about the thing's shock mitigation ) but on first glance you're right, that doesn't seem to leave a vast margin given this is a standard that might last a century or two, and might be expected to deal with rather harder accelerating freight at some point in future.

 

[dosxuk]

As with any standard, if you gold plate it and make it compatible with every foreseen use, nobody will end up using it because it's too expensive to actually implement at scale, only the common bits will end up being used.

 

[zwk500]

If we are going to have a fancy new coupler spec, wouldn't it be better if it could do everything we might want?

As with any standard, if you gold plate it and make it compatible with every foreseen use, nobody will end up using it because it's too expensive to actually implement at scale, only the common bits will end up being used.

Would it not be possible to have a 'normal' and 'heavy' standard, if there were appreciable benefits to the lighter design that wouldn't be needed for too many trains?

The implication is also that each vehicle has to be digitally compatible! *fatigued hurrahs*

Would this include provision for @HSTEd's favourite of ECP brakes?

 

[HSTEd]

Would it not be possible to have a 'normal' and 'heavy' standard, if there were appreciable benefits to the lighter design that wouldn't be needed for too many trains?

That could cause some long term operational issues however.
A more likely solution is that heavy aggregate trains end up push-pull/top&tail.

Would this include provision for @HSTEd's favourite of ECP brakes?

As I understand it, yes.

I don't know if it will be the AAR backed specification, a two wire generic tech specification that includes inbuilt support for multiple unit control is hard to deny.
But it is the EU, however it doesn't seem the electrical specification has actually been agreed yet.

Ideally (from my perspective) it would be two wires for that, and then a couple more wire pairs for any passenger vehicles to use for optional interfaces that freight vehicles don't have to bother with.

 

[43096]

Now sure, that's an extreme example, but to put it another way, given that modern CoCo locomotives can produce up to 600kN of starting Tractive Effort, doesn't seem much margin there.

Other than niche applications, what current loco designs go above 500kN starting reactive effort? The Stadler Euro 9000 Co-Co is 500kN and that is top end of the scale.

 

[Irascible]

Other than niche applications, what current loco designs go above 500kN starting reactive effort? The Stadler Euro 9000 Co-Co is 500kN and that is top end of the scale.

Two of them!

Not something you'd need often I'd imagine, but it's not hard to reach that 1000kN. If the coupler provides support for DP control then not relevant at present unless there's an operational need to put all the power at one end. These things are going to need a fair bit of maintenance...

 

[Nottingham59]

If the coupler provides support for DP control

What's DP control, please? Is it Distributed Power?

 

[Irascible]

What's DP control, please? Is it Distributed Power?

Apologies, yes it is. I thought it'd been defined up the thread already.