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46100 to York 23/11/17 - The Christmas White Rose

Discussion in 'What's Going On' started by Spamcan81, Nov 23, 2017.

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  1. Spamcan81

    Spamcan81 Nat Pres stalwart

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    Sounds a mighty strange way of operating a train's braking system.
     
    Spamcan81, Nov 26, 2017
    #21
  2. odc

    odc Member

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    My understanding is the loco (like Clan Line and several others) is still braked by the LMS combined SteamVac system, which can be controlled proportionally from the air system. Drop in air will then drop the vac and apply the steam brake, but as you come to a stop you want the train brakes to be releasing. You then want the loco brake to hold the train still so you apply the steam brak by operating the LMS brake handle (and shut off the ejector as it is no longer required to hold the steam brake off). So this seems perfectly normal rather than strange. In all vac days a wedge was used to hold the steam brake on whilst allowing the vac to releave but I imagine this would be heavily frowned upon on a main line engine now.
     
    odc, Nov 28, 2017
    #22
  3. Spamcan81

    Spamcan81 Nat Pres stalwart

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    I can get my head round a system applying air to the train but steam/vac to the loco as we have something similar on 34081 for the Santas but I'd read it that the driver had used both air and vacuum in the train brake.
     
    Spamcan81, Nov 28, 2017
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  4. odc

    odc Member

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    From what I have seen of 92 (and I've not seen her since the last overhaul) the air for the Santas just goes to the control valve and so is completely separate from the vac system and does not have any control over it, so yes your driver would have to operate the other independently. This is unacceptable for a mainline registered loco as it effectively makes the loco unbraked so you have to combine the systems together to work under one control. The use of the vac control is only permissible in this case as a parking brake as it bypasses all the mainline safety systems and use of it Tangmer's Vac brakes that way in the lead up to its SPAD a few years ago was a secondary contributory factor in the incident (Read RAIB article)

     
    odc, Nov 28, 2017
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  5. Spamcan81

    Spamcan81 Nat Pres stalwart

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    AIUI 34081 has a "proportional valve" or whatever it's called and when the driver applies the brake, the air brakes on the carriages are applied and the loco/tender brakes come on too but independently from the train brake as the loco/tender is not air braked.
     
    Spamcan81, Nov 28, 2017
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