Could a single diesel loco haul a 16 coach passenger train?

[popeter45]

as a hypothetical if a for some reason a full 16 car rake such as the low/highlander needed diesel haulage what could so do
assuming using a class 92 or 73 as a translator could a single 66/67/68 manage or would you need to double up?

 

[Gloster]

Probably. Over forty years ago I saw a Class 33 take sixteen Mark 1 up Porton Bank…very slowly. Admittedly, that was with lights and heating off.

 

[Sun Chariot]

If the rails are dry and the track isn't on a severe curve and/or severe gradient, then 16 coaches can be started and kept moving by most type 4 upward motive power.

In the 1960s, loco "proving" trains were of impressive length. If I recall, Kestrel took 22 bogies up Lickey unassisted

 

[HamworthyGoods]

It also part depends if you wish to carry passengers on board or run ECS. These days modern air conditioned coaches with automatic interior and exterior doors need quite a high ETH index on the loco and this can be the limiting factor.

In days of old single 50s hauled Paddington to Penzance ‘Jumbo Trains’ with loads of 15/16 coaches but the coaches themselves had a far lower requirement for ETH.

 

[hexagon789]

I think I've mentioned this before, but there is a log of the Paignton to Glasgow/Edinburgh from 1983 or 84 (I forget). The booked 50 failed before departing Paignton, so Exeter sent out what they had - a 31.

The formation was the full 13 coaches (455 tonnes) plus the 50, which is qual to about another 3 coaches, so that makes 16.

There are some stiff climbs out of Paignton, Torquay and Torre with maxima of about 13mph on the worst gradient.

The maximum recorded speed was only 65mph near Exminster.

I suspect even a lesser Type 2 could manage 16 coaches but speeds would perhaps be a little less.

In days of old single 50s hauled Paddington to Penzance ‘Jumbo Trains’ with loads of 15/16 coaches but the coaches themselves had a far lower requirement for ETH.

They were load 13 as I recall (D455 timing). The PV Mk2s were dual heat and in summer (April to October) there would be no ETH load.

 

[12LDA28C]

Yes of course. I've been on the Caledonian Sleeper with 16 vehicles plus a dead AC electric loco, all hauled by a single class 47 from Preston to Crewe via Manchester.

 

[randyrippley]

I counted 16 on a few of the Peak hauled formations on Dawlish sea wall back in the early 1970s. Almost certainly NE-SW (what we now call XC) runs. Whether they were heading over the hills to Plymouth, or for Torbay I don't know.
One train was notable - 12 blue/grey plus four near derelict maroon coaches

 

[popeter45]

It also part depends if you wish to carry passengers on board or run ECS. These days modern air conditioned coaches with automatic interior and exterior doors need quite a high ETH index on the loco and this can be the limiting factor.

In days of old single 50s hauled Paddington to Penzance ‘Jumbo Trains’ with loads of 15/16 coaches but the coaches themselves had a far lower requirement for ETH.

lets say carrying passengers in a planned fashion (e.g. due to divert on unelectrified line) rather than emergency

 

[HamworthyGoods]

lets say carrying passengers in a planned fashion (e.g. due to divert on unelectrified line) rather than emergency

On modern stock I don’t believe there’s any diesel locos which singularly have a high enough ETH index for a train of that length. I stand to be corrected.

 

[pokemonsuper9]

Don't freight locos (e.g. 66) regularly carry ~30 carriage loaded freight trains?
Surely half the carriages would be way easier to pull? (please explain why I'm wrong)

 

[43096]

On modern stock I don’t believe there’s any diesel locos which singularly have a high enough ETH index for a train of that length. I stand to be corrected.

Correct. The ETH rating on the sleepers is such that it runs at a higher voltage (1500V from memory) when over 8-car formation (effectively the electric hauled legs), which keeps the current draw to an acceptable maximum. Class 92 is the only UK loco that is set up to provide 1500V ETH, a relic of the tunnel night stock design parameters. The only other option would be the former EPS generator vans.

 

[randyrippley]

I would have thought that in some circumstances with the Peaks and 50s, braking effort over the hills would be the greater limiting factor over power

 

[william.martin]

On YouTube there is a video somewhere of the SVR's 33 hauling 20 coaches from Bewdley to Kidderminster, however that stretch of the line is fairly flat and the distance is fairly short.

 

[12LDA28C]

Don't freight locos (e.g. 66) regularly carry ~30 carriage loaded freight trains?
Surely half the carriages would be way easier to pull? (please explain why I'm wrong)

Freight trains generally don't convey carriages. Freight wagons however vary tremendously in size, weight and capacity and nor do freight trains need a locomotive to power heating, AC or lighting although freight trains can often run in excess of 2000 tonnes which is certainly well in excess of the weight of a 16-coach passenger train.

lets say carrying passengers in a planned fashion (e.g. due to divert on unelectrified line) rather than emergency

Yes.

 

[Vespa]

Hauling it is not the issue, stopping would be difficult with all that weight, you would have to plan ahead, emergency stopping would take longer.

 

[Peter Sarf]

I would have thought that in some circumstances with the Peaks and 50s, braking effort over the hills would be the greater limiting factor over power

I would have thought almost all passenger trains were fully fitted (so to speak). As long as the loco can provide the pressure there is no limit.

Hauling it is not the issue, stopping would be difficult with all that weight, you would have to plan ahead, emergency stopping would take longer.

Surely not - each coach provides its own brake force. Double the number of coaches means double the weight to stop BUT there is double the brake force.

 

[Sun Chariot]

Hauling it is not the issue, stopping would be difficult with all that weight, you would have to plan ahead, emergency stopping would take longer.

As long as all the carriages have working brakes, then - as mentioned above - the ratio of weight vs brake force will be near constant, each time a carriage is added to the consist.

 

[randyrippley]

But you need something to create the brake vacuum / air supply.
If the locomotive braking is irrelevant then why the ban on single car HSTs over the Devon banks?

 

[Sun Chariot]

But you need something to create the brake vacuum / air supply.
If the locomotive braking is irrelevant then why the ban on single car HSTs over the Devon banks?

I've always presumed the "single unassisted DMB" embargo, is to avoid stalling up the banks. I believe the DMBs lack a field divert which - to my ignorance, I think - means they have a greater stall-risk.

 

[12LDA28C]

But you need something to create the brake vacuum / air supply.
If the locomotive braking is irrelevant then why the ban on single car HSTs over the Devon banks?

I've never heard of a ban on single HST power cars over the Devon banks.

However I have heard of a ban on full HSTs running with only a single power car working, hence loco assistance provided...

 

[Magdalia]

as a hypothetical if a for some reason a full 16 car rake such as the low/highlander needed diesel haulage what could so do
assuming using a class 92 or 73 as a translator could a single 66/67/68 manage or would you need to double up?

In the 1970s, with steam heat, the "Royal Highlander" would be load 16 over the Highland Main Line, booked for a class 47 but sometimes with a class 40.

 

[randyrippley]

I've never heard of a ban on single HST power cars over the Devon banks.

However I have heard of a ban on full HSTs running with only a single power car working, hence loco assistance provided...

Thats what I meant - badly phrased

 

[43096]

But you need something to create the brake vacuum / air supply.
If the locomotive braking is irrelevant then why the ban on single car HSTs over the Devon banks?

It’s nothing to do with braking.

I would have thought that in some circumstances with the Peaks and 50s, braking effort over the hills would be the greater limiting factor over power

Have you ever considered why most locos have a lower speed limit when running light engine? It’s to do with braking - basically carriages provide more braking effort (proportionally) than the loco.

 

[12LDA28C]

Thats what I meant - badly phrased

That restriction was nothing to do with brake force though, more the risk of the single power car failing or slipping to a stand and stopping the job.

 

[devon_belle]

Steam trains certainly could, so I'd assume any competent diesel would manage.

 

[ac6000cw]

As a quick comparison of the hill-climbing performance of various diesel locos on the severe 2.7% gradient of the Lickey Incline, below are links to photos of the allowed loco limits (in tonnes I assume) on the panel at Gloucester PSB back in 2014 (by Llangollen Signalman on Flickr):

https://www.flickr.com/photos/llangollen_signalman/14545175978/in/set-72157645880526091

https://www.flickr.com/photos/llangollen_signalman/14731809435/in/set-72157645880526091

This the info combined from the two photos. Ignoring the ETS issue, note that any modern freight loco could haul a 16-coach Cally Sleeper up the Lickey, and that the maximum gradients Euston - Inverness are below 2%

 

[Peter Sarf]

As a quick comparison of the hill-climbing performance of various diesel locos on the severe 2.7% gradient of the Lickey Incline, below are links to photos of the allowed loco limits (in tonnes I assume) on the panel at Gloucester PSB back in 2014 (by Llangollen Signalman on Flickr):

https://www.flickr.com/photos/llangollen_signalman/14545175978/in/set-72157645880526091

https://www.flickr.com/photos/llangollen_signalman/14731809435/in/set-72157645880526091

This the info combined from the two photos. Ignoring the ETS issue, note that any modern freight loco could haul a 16-coach Cally Sleeper up the Lickey, and that the maximum gradients Euston - Inverness are below 2%

View attachment 144492

Interesting.
A couple of puzzles.
A 37/4 (so with ETH ?) can drag an extra 100 (tonnes) ?.
A 67 looks dire ?. (no wonder the 68s are believed better !).

 

[Cowley]

Interesting.
A couple of puzzles.
A 37/4 (so with ETH ?) can drag an extra 100 (tonnes) ?.

Presumably more to do with them being fitted with an alternator instead of the generator fitted 37/0s?

A 67 looks dire ?. (no wonder the 68s are believed better !).

Yes that figure doesn’t seem right does it?

 

[hexagon789]

Interesting.
A couple of puzzles.
A 37/4 (so with ETH ?) can drag an extra 100 (tonnes) ?.
A 67 looks dire ?. (no wonder the 68s are believed better !).

Presumably more to do with them being fitted with an alternator instead of the generator fitted 37/0s?


Yes that figure doesn’t seem right does it?

I'd guess for the 37/0 vs 37/4 it could be a combination of the generator vs alternator but also the 37/0s had their original 106mph geared bogies, the 37/4s were given CP7s (if I've got the right designation) with an 80mph gearing.

For the 67s, the starting and continuous tractive effort with 125mph gearing are quite low compared with other classes.

 

[ac6000cw]

For the 67s, the starting and continuous tractive effort with 125mph gearing are quite low compared with other classes.

Yes, that's my take on it too.

The high speed gearing on the 67 also means the maximum continuous TE is at a much higher speed than e.g. a 66 (92 kN at 75 km/h versus 260 kN at 25.6 km/h, according to Wikipedia) - this is important on somewhere like the Lickey, if climbing from a standing start.

At the 'heavy' end of the table, I suspect a solo 59, 60, 66 and 70 all having basically the same rating (1045-1075 tonnes) might have more to do with coupler strength limitations than anything else e.g. a 66 with a 66 banker is rated at 2400t whereas a single 66 is 1070t.

As for comparisons with the Stadler 'UKlight' loco family (68, 88, 93), this TE comparison graph from Rail Engineer is useful, as it has 37, 66, 91, 93, and 2 x HST power cars on it. I would expect the 68, 88 and 93 to have very similar lower/mid speed tractive effort as they all appear to use the same/very similar bogies, ABB traction motors and traction drives. Incidentally, note the very low TE for the 2 x HST power cars.