It's possible to 'top and tail' with a DMU and a steam locomotive where the steam locomotive does the driving in one direction and the DMU does the other and this post reviews times when that's happened.
'Thomas' events
As part of 'Thomas' events, we often ran 'Thomas' coupled to a DMU (posing as 'Daisy' and carrying a 'face' headboard): for instance:-
Day out with Thomas: 2009The Steam/DMU 'Shuttle' was issued with the Shenton staff at Shackerstone and ran down the single line whilst the engine off the service train was running round and watering. The 'Shuttle' only went as far as Headley's Crossing (just over a mile from Shackerstone) before returning. On arrival back at Shackerstone, the next service train could leave for Shenton. This is how we worked the Steam/DMU 'Shuttles' during 'Thomas' events:-
Happy Birthday Thomas! (part 2)
'Thomas' was vacuum-braked for working passenger trains and the 'Modernisation' DMU were also fitted with vacuum brakes, so it was possible to work 'Thomas' coupled to the DMU with braking controlled from whichever was the leading vehicle. The DMU were designed for intensive stopping services with frequent station stops, so they were provided with a special 'high speed' vacuum brake where a second pipe runs down the train to enable vacuum to be re-created quickly, even when a number of units are being worked in multiple. When coupling the DMU to 'Thomas', the shunter had to remember that the vacuum hose on the DMU with the red-painted coupling was the vacuum brake which had to be coupled to 'Thomas'. The other (blue) coupling remained on the stopper. It wasn't actually possible to connect them the wrong way round because, although the hose couplings look similar one is 'Left-hand' and the other 'right-hand'.
With the DMU leading, the driver on 'Thomas' shut off the steam supply to the vacuum ejector and placed the brake application valve in the 'Running' or 'Lap' position so that the DMU driver had control of the brakes. The DMU was driven normally, with the vacuum created by the DMU's exhausters, and 'Thomas' was just 'tail traffic'.
On arrival at Headley's Crossing, the DMU driver usually shut down the cab and moved to the other end of the train. The cab next to 'Thomas' was opened up and the vacuum brake application valve was placed in the 'Lap' position. The DMU driver also needed to operate the 'Deadmans' device (and keep it operated throughout the journey), otherwise 'Thomas'was unable to create vacuum using the locomotive ejector. The DMU final drive was set for the direction of travel and 4th gear selected (4th gear has a 'freewheel' arrangement) with the engines left idling. 'Thomas' was then able to haul the DMU back to Shackerstone as if it were hauling normal coaches. It was possible for the DMU driver to remain in the cab remote from 'Thomas' throughout but I always preferred to 'change ends' to facilitate communication with the steam locomotive.
Jan (this time on 'Thomas') collects the Single Line Staff as Daisy pulls a 'Shuttle' out of Shackerstone back in 2010. Since then, the rules have changed: the staff is now carried by the leading locomotive (photo: Sam Brandist)
'Ivor' events
We adopted a similar operating arrangement during visits from Ivor the engine. My reports are listed below:-
Ivor the Engine
Ivor the Engine: 2008
Ivor: The best laid plans...
'Ivor' with 'half a DMU' taking water in platform 1 at Shackerstone during a 2008 visit.
Operation of GWR Steam/DMU 'Shuttles' during the 2019 Gala
The 2019 Gala timetable called for a frequent Steam/DMU 'Shuttle' between Shackerstone and Market Bosworth, using Great Western 'Light Prairie' 5542. The method of operation has to be revised somewhat when the steam locomotive is a Great Western design. The Great Western were never afraid to be different and this is the case with the their locomotive vacuum brake systems. Whereas other railways were content to operate with a partial vacuum of 21 inches of Mercury (in/Hg), the Great Western decided to use 25 inches of Mercury. This offers a more powerful brake better able to tolerate minor leakage. For a brief introduction to the vacuum brake, see the post MIC - Brakes.
With 5542 leading, the locomotive creates the brake using its ejector at 25 in/Hg. Although the exhausters on the DMU will only create 21 in/Hg, this does not prevent the locomotive creating a higher vacuum in the train pipe and the vacuum brakes work normally.
When the direction of travel is reversed and the DMU is leading, the DMU would normally 'create the brake'. But with the DMU creating 21 in/Hg in the Train Pipe (and below the piston in the brake cylinders) whilst there is still 25 in/Hg above the piston in the brake cylinders (created when the steam locomotive was leading), the brakes will not fully release. This problem occurs with locomotive-hauled stock when a locomotive creating 21 in/Hg takes over a train previously hauled by a Great Western engine, where the solution is to release the brakes by 'pulling the strings' (as described in the post MIC - Brakes).
There's a further problem with the GWR Steam/DMU combination. Great Western locomotives have a crosshead-driven vacuum pump which, at moderate speeds, will maintain 25 in/Hg in the train pipe even with the locomotive ejector shut-off. So, even if 'pulling the strings' has allowed the train to move away with the DMU's exhausters creating 21 in/Hg, at moderate speeds the locomotive's vacuum pump will create a higher vacuum both above and below the piston in the brake cylinders. This is no problem until the driver of the DMU makes a brake application, for instance, to comply with a speed restriction. After passing through the restriction, releasing the brake will create 21 in/Hg in the Train Pipe (and below the piston in the brake cylinders) whilst there is still 25 in/Hg above the piston in the brake cylinders (previously created by the steam locomotive vacuum pump) and the brakes will not fully release. At reduced speeds, the vacuum pump may not 'boost' the train pipe above 21 in/Hg and the brakes may 'drag'.
The solution adopted was to let the steam locomotive create the vacuum in both directions of travel and operate at 25 in/Hg, which worked well. Where a train is worked by two locomotives (either double-headed or 'top and tail') it's normal for only the leading engine to 'make the brake' but, in case of difficulty in maintaining adequate vacuum, the enginemen may agree to a modified arrangement.
For the Gala in 2018, a push-pull 'auto' train between Shackerstone and Market Bosworth had been operated with two single line sections (Shackerstone - Market Bosworth and Market Bosworth - Shenton), together with 'Staff and Ticket Working'. This is described in the post Battlefield Line Steam Gala 2018 (Part 1).
By the time of the 2019 Gala, work on the new passing loop at Market Bosworth had proceeded sufficiently to provide a 'turnback siding' which could be used to 'recess' a Steam/DMU 'Shuttle'. Since the point machines to operate the connections to the siding had not been commissioned, the points had to be manually operated from the ground before being clipped and locked in both the normal and reverse positions.
5542 and 2-car DMU 'recessed' in the 'turnback siding' at Market Bosworth (50th Anniversary Gala at the Battlefield Line)
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