If you register, you can do a lot more. And become an active part of our growing community. You'll have access to hidden forums, and enjoy the ability of replying and starting conversations.

Vacuum Brakes

Discussion in 'Carriage & Wagon M.I.C.' started by 25321, Apr 2, 2009.

  1. 25321

    25321 New Member

    Joined:
    Aug 27, 2008
    Messages:
    27
    Likes Received:
    0
    Occupation:
    Student
    Location:
    Riddings, Derbyshire
    Hi,

    Does anybody know how long vac brakes are supposed to hold before releasing?

    I seem to remember its about 20 minutes. Can anybody think of anything different?

    cheers,
     
  2. Edward

    Edward Member

    Joined:
    Jul 19, 2008
    Messages:
    424
    Likes Received:
    8
    Location:
    Midlands
    You should NEVER rely on any form of continuous brake after the loco has been detached.
     
  3. arthur maunsell

    arthur maunsell Active Member

    Joined:
    Sep 6, 2008
    Messages:
    859
    Likes Received:
    1
    Location:
    Co Cork Ireland
    it all depends on their condition I guess...the more worn the seals are, the quicker the brakes will leak off.
     
  4. 25321

    25321 New Member

    Joined:
    Aug 27, 2008
    Messages:
    27
    Likes Received:
    0
    Occupation:
    Student
    Location:
    Riddings, Derbyshire
    Yeah, I know that. I am a passed guard :)

    I was just planning a pretty long fitness to run exam for a day next week as I have a feeling some are leaking off very soon indeed!!
     
  5. Edward

    Edward Member

    Joined:
    Jul 19, 2008
    Messages:
    424
    Likes Received:
    8
    Location:
    Midlands
    I suspect that you wont find a figure in any publication aimed at operating staff, for the reason we both understand. However, there has to be some sort of spec for maintenance. There was a chap offering Mk1 manuals on here recently.

    http://railways.national-preservation.com/viewtopic.php?f=43&t=18721

    Could be just what you need?
     
  6. Calan

    Calan Member

    Joined:
    Dec 2, 2007
    Messages:
    505
    Likes Received:
    0
    Occupation:
    Student & Volunteer.
    Location:
    Tenterden, Kent
    From what I've seen it can be hours, weeks and months.
     
  7. Avonside1563

    Avonside1563 Active Member

    Joined:
    Jul 13, 2007
    Messages:
    1,086
    Likes Received:
    173
    Gender:
    Male
    Location:
    Bolton's Sidings, just behind the running shed!
    Heritage Railway Volunteer:
    Yes I am an active volunteer
    According to the BR 1969 manual for Mk1 coaching stock the test on the vehicle gives allowable drop of 2" over 5 minutes from a created 20-22" of vacuum in the main pipe with all the brake fittings on.
     
    Jack Enright likes this.
  8. markb846

    markb846 New Member

    Joined:
    Dec 29, 2010
    Messages:
    149
    Likes Received:
    0
    The leak rate is for the train pipe side, from what i rember when I used to work on VB stock the res should hold the brakes on for at least 2o mins. However if the cylinder sliding band, or rolling ring is in good order, and the release valve seals, and cylinder joint seals are in good order this should be no problem.
    Other things which can cause issues with the train pipe side are the DA [direct addmission] valve and the pass com, and any of the other rubber wear in the system.
    many small leaks in a vacuum system can lead to a big problem.
     
  9. jtx

    jtx Well-Known Member Friend

    Joined:
    Jul 4, 2007
    Messages:
    1,874
    Likes Received:
    792
    Gender:
    Male
    Occupation:
    Happily retired
    Heritage Railway Volunteer:
    Yes I am an active volunteer
    I've never been a guard, or dealt with coaches, other than hooking them on or off my engine, but I know from personal observation and chats with some of our C&W staff, that it's not uncommon to come to a set which had been stabled the previous day and which still has 18-20" in the reservoirs.
     
  10. John Webb

    John Webb Member

    Joined:
    Mar 2, 2010
    Messages:
    443
    Likes Received:
    54
    Occupation:
    Retired
    Location:
    St Albans, Herts
    Heritage Railway Volunteer:
    Yes I am an active volunteer
    The (reprint of) "Handbook for Railway Steam Locomotive Enginemen" says that the driver, as part of a brake test when coupled to a train, should check the time taken from forming a vacuum of 21inches in the train pipe for the vacuum to drop to 12 inches. If 20 seconds or less there is an excessive leakage and the source of the leakage should be found.
     
  11. 1472

    1472 Active Member

    Joined:
    Aug 26, 2008
    Messages:
    1,285
    Likes Received:
    962
    MT 276 - not for coaches but the BR standard for mainline steam before privatisation gives figures for acceptable leakage rates for both train pipe and reservoir side of GW locos with vacuum brakes. It would be suprising if there was no corresponding C&W standard.
     
  12. K14

    K14 Member

    Joined:
    Nov 6, 2011
    Messages:
    317
    Likes Received:
    203
    Location:
    Catford
    Heritage Railway Volunteer:
    Yes I am an active volunteer
  13. olly5764

    olly5764 Well-Known Member

    Joined:
    Dec 29, 2006
    Messages:
    1,642
    Likes Received:
    394
    Gender:
    Male
    Occupation:
    Engineer
    Location:
    Normally in a brake van somewhere
    Heritage Railway Volunteer:
    Yes I am an active volunteer
    If memory serves me correctly, you should blow the brake up, then put 5 inches of brake in (ie, drop to 16" if you are blowing them up to 21") hold it at that for 5 minutes, and re-check to see if the blocks are still on, re-create the brake and then put the lot in, the brake should hold for at least 15 minutes. I could check next time I'm at Bewdley if you like?
     
  14. wplinge

    wplinge New Member

    Joined:
    Jul 20, 2015
    Messages:
    4
    Likes Received:
    1
    Gender:
    Male
    Heritage Railway Volunteer:
    Yes I am an active volunteer
    I always thought twenty minutes was about right. Many years ago we dug out an old ventilated van from the dock siding and took it to C&W for repairs. The following week they tried to move it and struggled, because none of them expected the brakes on such a decrepit vehicle to last for minutes, let alone days!
     
  15. LMS2968

    LMS2968 Well-Known Member

    Joined:
    Sep 1, 2006
    Messages:
    1,759
    Likes Received:
    1,049
    Gender:
    Male
    Occupation:
    Lecturer retired: Archivist of Stanier Mogul Fund
    Location:
    Wigan
    Heritage Railway Volunteer:
    Yes I am an active volunteer
    Vacuum holds up longer than air pressure. Firstly, the maximum 'pressure' applied cannot exceed atmospheric, i.e. 14.7 p.s.i. Secondly, the effect of vacuum is to draw items such as connections together, and so help seal them. Air pressure is both about four times higher and also tends to force joints apart, thus encouraging leakage.
     
  16. threelinkdave

    threelinkdave Well-Known Member Friend

    Joined:
    Aug 1, 2013
    Messages:
    1,798
    Likes Received:
    894
    Gender:
    Male
    Occupation:
    Retired
    Location:
    Stratford-upon-Avon or in a brake KD to BH
    Heritage Railway Volunteer:
    Yes I am an active volunteer
    Rolling rings in the cylinders seem to hold vac better than the GWR wiping seals. When prepping a set of BR standards left for a week most brakes will still be on. Prep a GW set left overnight and most will have leaked off.

    Totally agree you should never rely on the automatic brake but it must be effective at holding the brakes on for suficient time to secure the stock. For example a coupling brakes at the rear of the train with the brake in the middle.Having come to a stand you find your scotches explain to the fireman who has joined you whats up. instruct your TTI to secure the door at the split to stop anyone falling out. As you walk back check no one is in the 4foot having fallen out. Apply the scotches to hold 3 mk1s at 90 ton on a 1:100 gradient. Secure the end door. Walk back as far as you think necessary to check no one is lying in the 4 foot. And the standard is 20 minutes? You then have to set a strategy. Buckeye failure - get the red coupling and drop buckeyes. I now have to set back onto the stranded 3 with the other 5 and loco and we might now be relying on 2 bits of timber if the brakes only held for 20 min. Solution bring stock back short of touching but close enough to connect vac. Split vac pipes at other end of first coach and couple pipes at split. Create and destroy vac to set brakes. Disconnect vac at the split. Buffer up to the stranded 3 and get the coupling up asap. Re connect other vac pipe. Do a continuity test and remember to then remove scotches. 20 minutes - thanks for rolling rings lasting more than 20 munutes
     
    759e likes this.

Share This Page