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: mini pond/fountain pump workings

  1. Aug 21, 2009 #1

    DaveC426913

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    urgent: mini pond/fountain pump workings

    Well, it's not life-or-death but, I've got a deadline for tomorrow to finish this thing I've been working on for months and I've just came bang up against what might be a showstopper.

    I'm building a pond widget that is powered by an 11W mini pond pump, http://www.homedepot.ca/webapp/wcs/...recN=0&N=0&Ntk=P_PartNumber&showreviews=true". My widget uses the pump for its axle, not for its waterflow. i.e. I've got gears on the pump's axle.

    I've just discovered a very strange behaviour in the pump and I'm not sure what to make of it. It seems as if, occasionally, the magnetic motor reverses its direction. It seems that, say if the motor encounters too much resistance turning clockwise, it will just reverse direction, rotating counter-clockwise. It can flip back and forth like this continuously every few seconds.

    If this is true, I am scrood. It frankly never occurred to me that a pump might change its direction. (operating as a water pump, this behaviour would have no negative effect, since the turbine blades are symmetical. No matter which way the pump turns, the water would still flow the same direction. That lends credence to the idea that this might be designed behaviour - which is bad for me.)

    Can anyone corroborate or disspell this idea?

    I've got to find a solution in the next 24 hours or months of work will be wasted...:cry:
     
    Last edited by a moderator: Apr 24, 2017
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  3. Aug 21, 2009 #2

    Danger

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    Re: urgent: mini pond/fountain pump workings

    I've never heard of such a thing. Have you tried contacting the manufacturer of the pump for tech support?
    My only top-of-the-head suggestion is to sideline the pump and substitute a waterproof motor such as for a submersible vehicle. Or, put the motor outside of the aquatic environment and run a flex cable to your gear mechanism.
    Sorry that I can't be of more help, but this is pretty short notice, and I'm both tired and drunk.
    I am, in fact, going to bed now. I'll check back before your deadline expires, but I sure hope that someone else can help you in the meantime.
     
  4. Aug 21, 2009 #3
    Re: urgent: mini pond/fountain pump workings

    If it is designed behaviour then what is the purpose of it?The first thing that comes to my mind is that it reverses to expel pond debris which might clog up the works.Is the reversal feature programmed in or is it triggered by an increase of resistance?If the former is the case then perhaps you could bypass the programming circuitry, if the latter is the case and if you have to demonstrate your widget in a real pond with real debris(not pure water) then perhaps you could remove the turbine blades.These are just some first impression thoughts.Good luck with it.
     
  5. Aug 21, 2009 #4

    DaveC426913

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    Re: urgent: mini pond/fountain pump workings

    This is my thought, yes.

    Note, btw, that the reversal of the turbine does not reverse the direction of water flow. This is why I never noticed the behaviour; it is only evident when one attaches something to the axle.

    I'm sure that it's caused by resistance. Definitely not programmed.

    Unfortunately, the turbine blades are what I use to attach the driver gear to the axle. The gear is also what causes the friction.
     
    Last edited: Aug 21, 2009
  6. Aug 21, 2009 #5
    Re: urgent: mini pond/fountain pump workings

    This is a very interesting problem. I suspect that this is an AC motor, not an AC-DC (or universal brush) motor, running on AC. Single phase AC induction-type motors are brushless, and need some starting phase shift (either inductive or capacitive), which in your size (11 watts) may be a shaded pole motor. I have made shaded pole motors run in either direction, but only when I cut off the "shades" (copper coils shading about 1/3 of the poles). I suspect that shaded pole motors could run in either direction if the copper shades were very thin, which means minimal starting torque. Is this a reciprocating (piston) pump with flapper valves? Too much pressure (head) may stall the motor, and give the motor a kick-start in the reverse direction.
     
    Last edited: Aug 21, 2009
  7. Aug 21, 2009 #6

    berkeman

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    Re: urgent: mini pond/fountain pump workings

    As a quick temporary fix, maybe install a ratchet mechanism on the shaft, so that it can only turn the way you want it to. If resistance makes it reverse, then when it tries to go backwards and can't hopefully it just goes back to running forward.

    You could use the whatcha-macallitt thing off of a coaster bicycle brake/axle...
     
  8. Aug 21, 2009 #7

    DaveC426913

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    Re: urgent: mini pond/fountain pump workings

    This had occurred to me too. It's a bit of overkill tough.
     
  9. Aug 23, 2009 #8

    Danger

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    Re: urgent: mini pond/fountain pump workings

    So... did you get 'er going?
     
  10. Aug 23, 2009 #9

    DaveC426913

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    Re: urgent: mini pond/fountain pump workings

    Sigh. No. I gave it to my friend in its unoptimized state. The deadline was Saturday, which was his G-scale railroad http://davesbrain.livejournal.com/277928.html". Such a shame for something I've been working on for two years.

    The motor is just way too finicky. If its axle is out of alignment by micrometers, the rotor seizes. Trying to put a pulley on that axle, which pulls on the axle, is a losing game.

    So, with his help, we're going to use a non-submersible motor, located above the pond surface to drive my widget. I'll post pix of the thing.
     
    Last edited by a moderator: Apr 24, 2017
  11. Aug 23, 2009 #10

    Danger

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    Re: urgent: mini pond/fountain pump workings

    Bummer, but I look forward to seeing the thing when you're done. (Also the rest of the train set-up.)
     
  12. Aug 23, 2009 #11

    DaveC426913

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    Re: urgent: mini pond/fountain pump workings

    I will photograph it as it is now, and post.

    You can see it in the link provided above.
    But that's only last year's. He's built a whole nother street this year. I'll shoot that too and post it.
     
  13. Aug 23, 2009 #12

    Danger

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    Re: urgent: mini pond/fountain pump workings

    Oops; I didn't realize that there was a link in there. Neat. (I think that the bridge to the bedroom would freak me out a bit, though, given my acrophobia. Stumbling across that sucker drunk would be no fun at all.)
     
  14. Aug 23, 2009 #13

    DaveC426913

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    Re: urgent: mini pond/fountain pump workings


    ?
    Oh. Ha hah.

    For a second, I thought you were talking about a train running over a bridge into the bedroom...

    Those are two unrelated blog entries. One friend had an open house of his new house, the other had an open house of his train layout. They just happened to be on the same day.
     
    Last edited: Aug 23, 2009
  15. Aug 23, 2009 #14

    Danger

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    Re: urgent: mini pond/fountain pump workings

    :redface:
     
  16. Aug 23, 2009 #15
    Re: urgent: mini pond/fountain pump workings

    If you do buy a new motor, why not just take the load off the motor?
     
  17. Aug 23, 2009 #16

    Danger

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    Re: urgent: mini pond/fountain pump workings

    I don't follow. :confused:
     
  18. Aug 24, 2009 #17

    DaveC426913

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    Re: urgent: mini pond/fountain pump workings

    Nor I.

    A different motor will still require a pulley on its axle. I'll just have to brace it, is all.


    Ironically, I do have the solution already in-hand. You see, one of the step-down gears that I use to reduce the RPM is a http://upload.wikimedia.org/wikipedia/commons/thumb/9/98/Schneckengetriebe02.jpg/800px-Schneckengetriebe02.jpg" [Broken], which has no tendency to distort its axle. If I could get the pump driving the worm gear directly, I'd be golden. But I can't get the worm gear onto the motor axle.
     
    Last edited by a moderator: May 4, 2017
  19. Aug 24, 2009 #18

    Danger

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    Re: urgent: mini pond/fountain pump workings

    Does this thing involve a lot of torque? If not, I've had a lot of success using chunks of gas-line or vacuum tubing, aquarium hose, etc. to connect mismatched parts. Or, you could use JB Weld to build up a connecting collar (but it might take a fair bit of work to balance it).
     
  20. Aug 24, 2009 #19

    DaveC426913

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    Re: urgent: mini pond/fountain pump workings

    Not really a lot of torque, no. But one of the reasons I'm using all these step-down gears is to get some torque from the motor to overcome the inertia of my widget.

    The trick is that the impellor is rotating at ~1000-2000RPM, so the connection has to be quite robust, and at the same time very small to fit in the space.

    I've been looking at jerry-rigging connections, yes. Your methods sound very much like mine. I put screws through the face of the pulley and used the heads of the screws to clamp to the impellor of the motor.

    But I think you're right. I need to ditch the pulley and go back to driving the worm gear directly. That will eliminate and sideways torque on the impellor axle.
     
  21. Aug 24, 2009 #20

    Danger

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    Re: urgent: mini pond/fountain pump workings

    Your mention of the screws reminded me of one other technique that I've used. It's tricky as hell, and you have to be very careful, but it works.
    You can either thread the outside of the shaft, or, even harder, drill a hole through the centre of the shaft and tap it internally.
     
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