How not to start an electric bench drill

Discussion in 'Modding' started by Crash Dummy, Apr 30, 2007.

  1. Crash Dummy

    Crash Dummy Member

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    Refer to the title.
    http://www.youtube.com/watch?v=2ZglKBX1F_4

    Presented by Crash Dummy
    Filmed by MSmola2002

    Now on a serious note. Does anyone know what I need to do to fix this ? Should I just buy another one or do I just continue doing as I have done in the video ?

    The drill is actually brand new and hadn't been used. It's just been sitting in a shed for many years so warranty repair / replacement isn't an option.
     
  2. =XTG=

    =XTG= Member

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    LOL hey thats a pretty good idea!
    i thought this was one of those crazy stunts.. and when you tied the starter cord to the wheel i was just expecting it to suddenly whirr into life!
    never knew they used a capacitor to start them. maybe yeah just replace the cap :) could it be like something jammed? (noob with these things)

    -j
     
  3. khendar

    khendar Member

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    Going to be an interesting day when that cord doesn't release from the gear and you start living up to your name :p
     
  4. pugsley

    pugsley Member

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    Ha brilliant! I will have to remember that trick if mine ever dies.
     
  5. OP
    OP
    Crash Dummy

    Crash Dummy Member

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    Just in case anyone here knows what's going on the standard cap is labeled as being I think 3.2mF while I do have another cap from another AC motor on hand I can try it is rated at 4.3uF

    I haven't got much idea what the ratings mean when it comes to capacitors. Just that the voltage matters most when finding replacements. The replacement is rated at 415v so I'm set there.

    I'm very aware of the potential electric shock risk too from a possibly charged capacitor. I'll have to find a way to discharge it first before I do any work on the motor. I'm thinking set of alligator clips hooked up to a light globe or something and just touch it onto the leads for a few seconds. Then dead short it with my insulated screw driver ? (Obviously while unplugged from the mains :p)
     
    Last edited: Apr 30, 2007
  6. ojk007

    ojk007 Member

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    RS sell all sorts of caps you would undoubtedly be able to find one there, Just make sure its the same one. Rating i mean.

    As far as discharge google has some very good results
    http://www.google.com.au/search?hl=...&ct=result&cd=1&q=discharge+capacitor&spell=1
     
  7. OP
    OP
    Crash Dummy

    Crash Dummy Member

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    I was just thinking. If I stuck my multimeter on the capacitor to show voltage it will show a voltage when charged right ?
     
  8. pugsley

    pugsley Member

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    Thats if the capacitor is getting charged at all.
     
  9. OP
    OP
    Crash Dummy

    Crash Dummy Member

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    Well that's it aye. Exactly what I was thinking.
     
  10. mAJORD

    mAJORD Member

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    haha

    I did this when I was about 14-15 on a similar type of motor that uses a Start winding + centrifical switch instead of the cap. (very easy to tell these motors as they make an audible click on turn on, and another just before they stop turning.)

    Anyway I used the start cord method just to run it for a while and see if it was burnt out before attempting to fix the rest of it up, and somehow, after starting, it ended up winding back the cord with my thumb caught in it. Back went my hand in no time, got wrapped around the pulley and nearly broke my wrist. Thankfully it was only 1/4HP and it jammed, with me in an extremely unco position, and soiled pants.

    Any more it would have certainly broken something. Never again :p

    Still very very torquey motors for their HP rating though once synced, and could have easily been a lot worse.
     
  11. kombiman

    kombiman Dis-Member

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    You overclock your drill?

    Howdidyoudothat?


     
  12. Cererus

    Cererus Member

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    You're better off going to an industrial electrical suppler rather than RS of Farkenhell for motor start caps
    Turks or TLE, GEC or look for motor rewinders in the yellow pages.
     
  13. dmandn

    dmandn Member

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    Make sure every rating on the cap is the same as the replacement, if you get the wrong one you could either screw up the cap or the circuitry around the drill, especially if charged volt is higher than current ones charged volt, can't remember what its called but that can kill the whole thing.
     
  14. elementalelf

    elementalelf Member

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    i gotta try this with my sander, it has the same problem(cant see any caps tho :( )
     
  15. Symon

    Symon (Plugging your Socket)

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    Two main things matter with capacitors of this type - size and voltage rating. 415V is fine since you are running it off 240V. If the one that has died is a 3.2uF, you should be fine with a 4.5uF. The only problem with a larger capacitor is that there will be a higher torque created so it will draw more current. Depending on the size of the motor this may cause circuit breakers to trip.

    Forget the component suppliers (RS, Farnell etc), just rock down to your local electrical store and they should have a capacitor for you. Should be dirt cheap too.
     
  16. LethalCorpse

    LethalCorpse Member

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    Smallest Jaycar sells is 6uF, Symon is best to comment on whether this is too big. Of course, if part of you trouble is bearings seizing, the extra torque will help for a while, until they explode. Best to pull it apart and give everything a lube
     
  17. LethalCorpse

    LethalCorpse Member

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    sounds fine, thought make it a few minutes and lose the screwdriver concept - the globe will get it flat
     
  18. jizzwiz

    jizzwiz Member

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    My dad has exactly the same bench drill, with the same problem. I never thought to do that when i last unsuccessfully tried to use it!
    Maybe its a common problem for that model. Anyone else?
     
  19. =XTG=

    =XTG= Member

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    yeah just short the cap using an INSULATED screwdriver..

    -j
     
  20. OP
    OP
    Crash Dummy

    Crash Dummy Member

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    Yeah could be a common problem aye. I have posted this on a couple of forums and one response I got was that it might not actually be the capacitor. There is likely to be a centrifugal contact setup in the motor that has the capacitor circuit closed up until a certain RPM point where the contact throws out and no longer energises the circuit. It is very possible that this device is sticking and just flat out not working which really does make sense.
    Go find a bench drill or some other reasonably big single phase AC motor and fire it up. Notice the click you hear on start up then when the motor slows back down when you turn it off. I'm assuming that is the contacts clicking on and off.

    I think the next step is to grab a multimeter and see if there is any voltage getting to the capacitor. If not then it would be safe to assume the motor needs a tear down and the contact setup needs repairing.
     

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