Limit/starter switch question

  1. fizzy Forum Supporter

    Messages:
    4,570
    uk
    Still a bit confused about the start switch on my Colchester lathe.

    Why is it designed like this? You push the switch down - it switches the lathe on - push down a bit further - it switches the lathe off! WHY? At least that is what I think it does.

    I am hoping adjusting the contacts and cleaning will help - there is only a tiny sweetspot where the lathe will actually run.

    When you push down on the plunger the bottom 2 contacts then spring open.

    20191107_204310.jpg 20191107_204319.jpg
     
  2. fizzy Forum Supporter

    Messages:
    4,570
    uk
    Help any ideas?
    Driving me mad.
    Lathe runs beautifully when I push the contacts back down at the bottom but not exactly safe :o
     
  3. Pete.

    Pete. Member

    Messages:
    8,274
    Location:
    Kent, UK
    It's difficult to say anything based on the pic unless someone has already had experience in servicing them. I can't even figure out the operation though I'm sure 'd have it sussed in no time if it were in front of me on the bench.

    20191107_204310.jpg
     
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  4. wyn

    wyn Member

    Messages:
    2,970
    Location:
    Cardiff
    Does the bottom of the plunger connect to a foot operated bar to switch the lathe off?
     
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  5. Pete.

    Pete. Member

    Messages:
    8,274
    Location:
    Kent, UK
    Ok it looks like the terminal above the blue wire is bridged to the blue terminal, which means that when the switch is up blue and yellow are connected, when the switch is down blue and red are connected. Is that so?
     
  6. Seadog

    Seadog Forum Supporter

    Messages:
    4,517
    Location:
    NE London - UK
    It looks like it shorts the blue and yellow phases. Emergency stop perhaps?
     
  7. WorkshopChris Forum Supporter

    Messages:
    4,374
    Location:
    South East Essex
    I would expect that to operate from a mechanical cam with an actuator arm on a shaft that travels along with the saddle as the lathe operates.
     
  8. fizzy Forum Supporter

    Messages:
    4,570
    uk
    The plunger at the bottom is just travel. When you operate the lever on the front of the lathe it pushes that plunger down.
    A little bit of movement switches the lathe on with the top 2 contacts. Red to blue.
    Push down a bit further and the 2 contacts at the bottom snap up shutting the lathe off.
    Just can't work out why.

    Only a small sweet spot where it will run.
    When I adjust the linkage for it to latch in place it has pushed the switch too far down.
     
  9. carbon

    carbon Member

    Messages:
    1,181
    Location:
    S. Glos. U.K
    A few pictures from an operating Colchester student if this helps

    B34A273B-5A10-4A3A-BD09-C9DD5F75DD04.jpeg

    0EA64301-2E67-49EE-BE5F-16E13491308A.jpeg

    8065A539-9779-4F38-BC75-1BD36FDF70CA.jpeg
    First two in the off position, last one on. Handle for operation has approx 4-5” of travel
     
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  10. fizzy Forum Supporter

    Messages:
    4,570
    uk

    Thanks very much for that. It is very similar.
    The problem I have is the lathe will only run when the handle is held in just the right position. Move it further until it latches and the bottom contacts snap up and switch it off.
     
  11. fizzy Forum Supporter

    Messages:
    4,570
    uk
    :o:o:o:o

    Just realised - I think mine might be wired up wrong!

    So fully down is ON with the bottom 2 contacts up in the air?
     
  12. carbon

    carbon Member

    Messages:
    1,181
    Location:
    S. Glos. U.K
    The handle fully down is off as first two pictures. The lot that had the lathe before me swapped the three phase motor for a single phase then had all the current through the limit switch so has some arcing and spring missing. Only has two wires attached as had to rewire it to get motor to rotate in both directions
     
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  13. fizzy Forum Supporter

    Messages:
    4,570
    uk

    Continuity between blue and yellow when switch is up.
    When switch is halfway down continuity between all 3 wires - lathe then runs
    When switch fully down the V shaped switch snaps up continuity red and blue - lathe does not run.

    Running position in the picture below - impossible to set lever to this narrow range
    20191112_193012.jpg
     
  14. Johnnybravo Member

    Messages:
    748
    Location:
    Northiam
    Down is normally forward,up is reverse.
     
  15. fizzy Forum Supporter

    Messages:
    4,570
    uk
    There is a separate tumbler switch for reverse.
     
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  16. jordhandson Member

    Messages:
    409
    Location:
    Dorset
    Hi fizzy which colchester is this for I have the master I should be able to get a photo of it tomorrow if it will help
     
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  17. carbon

    carbon Member

    Messages:
    1,181
    Location:
    S. Glos. U.K
    I think you need to find what is connected to the three wires, which is in and what the others are connected to. Only from memory but is there a wiring diagram on the inside of the electric panel.
     
  18. mtt.tr

    mtt.tr Member

    Messages:
    956
    Essex England

    Glad you said it. Scratched my head
    Might be simpler to put the switch in different positions see what's closed and open go from there
     
  19. carbon

    carbon Member

    Messages:
    1,181
    Location:
    S. Glos. U.K
    Ive been looking at the wiring diagram from the other thread, it shows the red and yellow wires the other way around. Blue is where it needs to be.

    At the panel end the blue wire should be connected to contactor terminal 1, yellow to terminal 9 and red to terminal 2. A bit difficult to see what numbers are on the contactor from your other picture
     
  20. jordhandson Member

    Messages:
    409
    Location:
    Dorset

    On mine when you push the leaver down it is on and motor runs but if you push it down further it does stop and thats where the brakes are
    front lever.jpg
    so in theory it should switch off the further you push the leaver down.
    Is there any adjustment on the lathe at the rear on the arm that pushes the plunger up and down maybe that needs adjusting
    Limit switch rear of lathe.jpg
     
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