Adding an Air Compressor

Discussion in 'Tech/Mech General' started by Peter A Forbes, Apr 13, 2015.

  1. Peter A Forbes

    Peter A Forbes Funster

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    For reasons best known to themselves, or probably because the Mercedes Vario has disc brakes front and rear, Mercedes fitted spring brakes for the handbrake on both the 614 and 814 models.

    The higher capacity 814 has air brakes all round and an engine-driven compressor.

    The 614 has vacuum brakes but still has the spring brakes for parking, but as the vacuum pump takes up the space where the compressor would go, they fitted a very twee little 24V compressor sourced from Knorr-Bremse or Bosch.

    The only problem is, that if the compressor fails, you are stuck, big time.

    The electric compressor is activated by the alternator warning light feed so it only has power when the engine is running, and there are pressure switches to shut it off if the tanks are full.

    So, the choices are:

    Fit an additional pressure source to work in parallel with the existing one, or fit the air compressor from the 814D and arrange an external vacuum pump for the main brakes.

    Of the two, fitting another compressor is the simplest and doesn't affect anything if it fails, but sourcing something suitable is not easy, other than the original which is the wrong side of £1k.

    Ideas would be appreciated, but they must be practical/possible and must be within a budget of £150 max.

    [​IMG]

    [​IMG]

    Peter
     
    Last edited: Apr 13, 2015
  2. DP_JAY

    DP_JAY Funster Life Member

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    Some idea if the compressor output would be useful?
    Would some thing like a ring RAC900 work? or maybe a small mains unit & inverter.
     
  3. Peter A Forbes

    Peter A Forbes Funster

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    I can't find a spec at present, but it will have to be rated for continuous operation at least.

    I had thought about a mains powered unit through a compressor, might be the way to go.

    Thanks,

    Peter
     
  4. gus-lopez

    gus-lopez Funster

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    In reality you only want something to cover the possibility if the original fails ? If so I'd go down the route of small compact mains or battery one, as suggested.
     
  5. DP_JAY

    DP_JAY Funster Life Member

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    Why woul it be in continuous use?
    Surely it only needs too build up enough air to operate the brake as & when it's used?
    From what I can see it is controlled by the pressure switch & only runs as & when the pressure drops.
     
  6. Peter A Forbes

    Peter A Forbes Funster

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  7. Trikeman

    Trikeman Read Only Funster

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    Hi Peter,
    just be a little careful here, you are 'working on' a type approved brake system. Making any changes 'could' result in headaches (prohibition) should it be stopped by DVSA (old VOSA) and I dread to think what could happen in the event (god forbid) of an RTA.

    Just a small pearl of wisdom.(y)

    Regards,

    Trikeman.;)
     
  8. Peter A Forbes

    Peter A Forbes Funster

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    Thanks for that, I'll be adding a feature to enable an external air source to release the handbrake, quite common on trucks, so there shouldn't be any issue.

    Service brakes I'd have a think about it first :)

    I used to fit 3rd line air systems to new Scania units back in the 1970's, all done without any real drawings, but they always worked as they should. They came over with 2-line brakes if they were LHD.

    Peter
     
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