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  1. #1
    Wal's Avatar
    Lives in Stockport, United Kingdom. Current Activity: Viewing Has been a member for 5-6 years. Has a total post count of 315. Received thanks 29 times, giving thanks to others 12 times.
    Hello all,

    I'm currently building a small parts tumbler in which I intend to tumble aluminium parts amongst 3mm porcelain beads.

    Some pics below:

    Click image for larger version. 

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    Although the 12v 350mA 20RPM motor spins the tub reasonably well (provided that the static friction remains low) I'm thinking of adding an identical motor below it and connecting it via a nitrile o-ring belt so that it's 'helping out' the motor that's directly driving the tub, like so:

    Click image for larger version. 

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    Now, let's say that an O-ring with an inside diameter of 100mm fits perfectly (un-stretched) around the two couplers:

    Click image for larger version. 

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    I'm guessing that this wouldn't be ideal as there'd be very little traction or transfer of torque - so my question is: how much stretch percentage should I introduce to the o-ring for it to do its job as a conduit between the two motors? 10%? 20%?

    Cheers!

    Wal.
    Last edited by Wal; 09-05-2014 at 06:30 PM.

  2. #2
    Why not just introduce a third pulley as an idler/tensioner and have a play? G.

  3. #3
    Would this be a better arrangement ? two motors at the back.

    Click image for larger version. 

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    Spelling mistakes are not intentional, I only seem to see them some time after I've posted

  4. #4
    With any of these systems, do you not think the motors need synchronising?

  5. #5
    Wal's Avatar
    Lives in Stockport, United Kingdom. Current Activity: Viewing Has been a member for 5-6 years. Has a total post count of 315. Received thanks 29 times, giving thanks to others 12 times.
    Geoffrey - agreed that experimenting is good, but rather than add a pulley I may just buy a selection of o-rings at varying inside 's...

    Eddy - yep, I had a look at a driving roller and a second idling roller design, trouble is that the motors I have run at 20rpm - so the tub would rotate at about 2rpm in that config...

    I didn't want to get into bigger motor territory - 12v small and quiet(ish) was the aim!

    At 60p/o-ring I may just buy a handful and report back on what works, just thought there might be a 'rule of thumb' for these things.

    Wal.

  6. #6
    Wal's Avatar
    Lives in Stockport, United Kingdom. Current Activity: Viewing Has been a member for 5-6 years. Has a total post count of 315. Received thanks 29 times, giving thanks to others 12 times.
    Quote Originally Posted by GEOFFREY View Post
    With any of these systems, do you not think the motors need synchronising?
    Nah... They'll take their power off the same source - there may be a smidgen of discrepancy when they start spinning, but as long as they're spinning at the same rate they should sort themselves out...

    Wal.

  7. #7
    Use a flat belt with a spring loaded idling tension pulley between the two motors.
    Spelling mistakes are not intentional, I only seem to see them some time after I've posted

  8. #8
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Last Activity: 4 Hours Ago Has been a member for 9-10 years. Has a total post count of 1,831. Received thanks 192 times, giving thanks to others 5 times.
    Experimentation will be the key.

    I'd say try running the tumbler with just the 'helper' motor connected to see how much effect different o-rings have, as that way the motor/o-ring will get put under a good bit load, and let you know if it's going to work or not.
    Avoiding the rubbish customer service from AluminiumWarehouse since July '13.

  9. #9
    may I be so bolt as to ask why you wouldn't simply use a washing machine motor and drum

  10. #10
    Quote Originally Posted by nobby View Post
    may I be so bolt as to ask why you wouldn't simply use a washing machine motor and drum
    Because:
    Quote Originally Posted by Wal View Post
    I didn't want to get into bigger motor territory - 12v small and quiet(ish) was the aim!
    :)
    .Me

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