DMUs and Mk3s...

Discussion in 'Traction & Rolling Stock' started by simonm, 23 Oct 2011.

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  1. simonm

    simonm Member

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    I have a feeling I already know the answer and it's no but.....

    Can DMU's ever couple themselves to (say) a Mk3 carriage to provide extra seats or a FSO buffet etc? I imagine brakes and electricals wouldn't work, never mind being able to pull it!

    But thought I'd ask anyway!
     
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  3. WillPS

    WillPS Established Member

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    No, most DMUs have either Dellner or more often BSI couplings - Mk3 stock has buckeyes I think? And yeah, that's before you start talking about performance and electrical issues.
     
  4. Oracle

    Oracle Established Member

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    The Pressed Steel railcars were often coupled to a single trailer to supplement capacity. I recall them used on the Paddington-Hayes & Harlington and Greenford off-peaks. The first generation units had I think a towing capacity: I once saw a railcar shunt a coal wagon around Southall depot! However any trailer that any modern-generation units would surely have to be coupled to a control-trailer of some sort to allow driving?
     
  5. ChrisCooper

    ChrisCooper Established Member

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    The first generation DMUs could couple to anything with vacume brakes as they had screw couplings and standard brake connections. The parcels units were often used to haul one or two wagons, and had additional power to cope with it. Other types could haul stuff, but would be pretty sluggish and with anything like a load would likely be tricky in anything but good adheasion conditions or on a gradient.

    The Pressed Steel 121s did have some Driving Trailers built which were basically unpowered and none gangwayed 117 DMSs. They were no different to any other DMU vehicle. The 121s having 300hp in a single coach could easily cope with the trailer, just as many other first generation DMUs did with 300hp for 2 coaches.

    Second generation DMUs have the wrong couplings, either BSI or Dellner, and more importantly have electropnumatic brakes so could not operate the brakes on anything being hauled. They can be hauled, and in extream cases could haul, using a barrier coach or emergency coupling, but without continous brakes.

    The Mk1 and Mk2 EMUs, the 442s and the 325s have drophead buckeyes so can couple to any buckeye or screw fitted vehicles. Most Mk1 EMUs though had high level air pipes only, so needed adapters to couple to other stock with conventional low level pipes. 442s and 325s have both, so can couple to anything. That's more for being hauled though. I don't think there is anything stopping a 442 hauling a coach or two, but I don't think a 325 could, I think the brakes are set up just to allow them to be hauled (I don't think the driver's controller operates the westinghouse brake, just the EP). Like the Parcels DMUs, I think the MLVs were the only ones ever used for haulage in normal circumstances. Mk3 EMUs, other than 442s and 325s, have tightlock couplings which are incompatable with hauled stock couplings other than with an adapter or in emergencies. Like second generation DMUs they also have incompatable brakes. Modern EMUs are the same or have Dellner couplers.
     
  6. Oracle

    Oracle Established Member

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    Going back earlier, I am certain that the GWR AEC railcars could and did pull loads. The parcels cars escpecially.

    I had of course forgotten about the MLVs. They were able to run with air- and vaccuum-braked srock and also convert one to the other.
     
  7. asylumxl

    asylumxl Established Member

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    I know the MPV vehicles can haul freight wagons placed between them, but I don't know about MK3s. Would be an interesting combo though!
     
  8. Old Timer

    Old Timer Established Member

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    It was quite common in the 60s and 70s for DMUs to convey what was known as "tail traffic" - normally one or two vans.

    This was to allow news and parcels vans to be transferred to locations without the need to use a locomotive, thus being more efficient.

    Such services were specified in the WTT, and I recall in the old BR Sectional Appendices, in a table. Entries ran from D1T to D4T as I recall. T indicating the service was authorised to convey tail traffic.

    The table set out the number of powered vehicles in the DMU and the tail traffic load.

    A DMU could not haul more than its own weight in tail traffic as a maximum.

    As parcels facilities were removed from stations and newspapers went more and more towards road distribution, then so the need to convey tail traffic went. added to that is the fact that modern DMUs are not designed to convey tail traffic, and in any case the removal of the traffic that required this facility resulted in the wholesale withdrawal of the vans.

    ChrisCooper has set the situation out pretty well and succinctly.
     
  9. DaveNewcastle

    DaveNewcastle Established Member Fares Advisor

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    I can clearly recall one or two vans being stuck on the back-end of a first generation DMU, usually carrying newspapers, parcels plus an assortment of random & mysterious large trunks.
    What could be a surprise, was to find noisy and lively livestock in one of those vans. It's poingantly significant when we read comments today about over-crowded Standard Class accommodation in services being referred to as Cattle Class. I did find it very odd to be travelling in one of those noisy, green, underpowered, cab-with-glass-rear-panel units to be accompanied by large and noisy animals on board.
     
  10. Hairy Bear

    Hairy Bear Member

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    Class 220/2 can, in theory, couple to a air-brake coach via the Dellner adaptor and switch to two pipe mode . In training I realised that it could be done but the instructor kept saying "don't go there!". ,So it can but you couldn't supply power for air-con/battery charging.
     
  11. WillPS

    WillPS Established Member

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    Is this still true though? The 185s are notoriously overpowered...
     
  12. 73001

    73001 Member

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    I expect it was more to do with braking... rather than going.
     
  13. Old Timer

    Old Timer Established Member

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    The last time I was involved with it, the rules were that no MU could assist a train that exceeded the weight of the assisting unit.

    There are no vehicles designed to be hauled as tail traffic these days and the various Safety Certificates require through brakes to be operational which pretty much rules out hauling "dead" vehicles. In any case the whole purpose of DMUs is to enable additional sets to be marshalled together to operate as a unit.
     
  14. rail-britain

    rail-britain Established Member

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    Wasn't sure about that
    DMUs in Scotland used to operate as :
    DMBS - TSL - DTS
    The powered vehicle DMBS would therefore be hauling / pushing nearly half more its own weight, 50t as against 32t
    However this was rare and only when a DMS was not available
    I remember one such set operating for several weeks, the TSL was swapped for a TBS (which was quite rare it was normally spare)
    The set was restricted to specific routes
    The first time I travelled on it I thought the engine in the DTS was broken, then realised it had no engine!
     
  15. Old Timer

    Old Timer Established Member

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    As you say a special working arrangement. What was the tail traffic ?
     
  16. rail-britain

    rail-britain Established Member

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    This was a normal DMU allocation, due to a lack of spare working DMBS and DMS
    Thus a three car DMU with just one working DMBS (a few weeks later the DMBS was replaced by a DMS)

    ScotRail tried to avoid this if at all possible
    Normally it was reserved for use to strengthen at peak times, thus the six car set had three power vehicles, however during the 1980s they had no choice but to use this unit in normal service

    ScotRail also had a Class 121 "bubble car" and this too was used for a few days in place of the DMS or DMBS
    However this caused a complaint from the unions so ceased (as the guard could not walk through the whole set)
    Initially this was used on the late evening Glasgow - Barrhead (back to Glasgow ECS), a really small diagram!
     
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