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Thread: Rice mechanics

  1. #1 Rice mechanics 
    Forum Ph.D. Leszek Luchowski's Avatar
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    I'm planning to build a bird feeder with a remotely-controlled rice dispenser.

    My idea is to have a supply of about 1kg (2lb) of rice in a horizontal V-shaped "trough" with a gap at the bottom (made of two long pieces of plywood that do not quite meet). This gap will be covered by a thick and heavy cylindrical rod. When a button is pushed at the remote "command post", a solenoid actuator will push the rod up a little bit, allowing some rice to slip out before the rod falls back into position:



    The yellow plywood sideboards and the grey rod are, say, each about 30cm (12in) long in the direction perpendicular to the drawing. The black pushing pin extending from the blue solenoid through a hole in one plank is 4mm in diameter. I am planning to have one such effectuator in the middle of the length of the trough, but might place one at either end if need be.

    Now my question is - can this work? I have no experience with the mechanics of granular materials, and I have doubts that I cannot solve on my own without experimenting:

    - Won't the rod get stuck in the rice without returning to the bottom of the trough, thus staying out of the reach of the pushing pin and/or allowing all the rice to fall out at once?

    - How far do I need to push the rod to make sure the rice starts falling out? One solenoid I have seen on sale has a pin that moves by just 3mm, I am worried if this is enough, even if my rod travels a bit more, due to inertia.

    - What is the best diameter and weight for the rod? I don't want it to be too heavy in case the whole feeder is ripped off in a windstorm and its wreckage falls down, possibly onto people or cars. But I plan to make it quite sturdy, and the window is only about 4m (12ft) above the ground so it's not a life-threatening height.

    - How will weather conditions affect the rice and the functioning of the dispenser? The feeder will have a roof (with the dispenser forming a kind of "attic" underneath), but wind may still blow some drizzle into it, and I don't know if dew can form inside.

    I am open to other suggestions as to the dispenser. The purpose is to have a bird feeder that does not require me to open the window every time I want to give the birds a meal.

    I have 1 month to complete the project.

    Thanks in advance,
    Leszek.


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  3. #2  
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    I may be telling you something you already know, but many homemade or commercial bird feeders operate on a similar idea, but without any actuator. There is a floor an inch or so under the hopper, and the feed will pile up and stop the flow until the birds come along and eat some.

    Here's another idea. You could have a small hole in the side of your hopper and a small auger, perhaps made from an auger type drill bit and electric motor to dispense the rice.
    http://www.ereplacementparts.com/aug...-p-193559.html


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  4. #3  
    Forum Ph.D. Leszek Luchowski's Avatar
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    Yes I know that Harold, thank you, but - perhaps due to an overestimate of the demand of the, erm, "volatile market" - I imagine that the birds will eat in a day all that is made available to them.

    The window in question is hard to access, and my idea is that I will refill the feeder once in a week, and then my wife - who is less of a climber than I am, and a great animal lover - will enjoy pushing the button as many times a day as she likes.

    I would love to use a small helical screw conveyor, but those are hard to buy cheaply and by the unit - most manufacterers don't even have a retail price.
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    one thing to note. if the bird feeder is not a consistent food source the birds may not check very often to see if your wife has pushed the button and rice has been released.
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  6. #5  
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    If you're interested in a screw conveyor, you could probably build something workable if you can bend a metal tube into a spiral.

    Anyway, back on topic, I know that a lot of granular feeders of this type (things I've seen of How It's Made, etc) need to keep things shaking to prevent the material from clumping up and jamming. It might be enough for the shaker to operate during the dispensing cycle though. (And birds are smart. They'll learn that that sound is associated with food. )
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  7. #6 Re: Rice mechanics 
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    Quote Originally Posted by Leszek Luchowski
    I'm planning to build a bird feeder with a remotely-controlled rice dispenser.

    My idea is to have a supply of about 1kg (2lb) of rice in a horizontal V-shaped "trough" with a gap at the bottom (made of two long pieces of plywood that do not quite meet). This gap will be covered by a thick and heavy cylindrical rod. When a button is pushed at the remote "command post", a solenoid actuator will push the rod up a little bit, allowing some rice to slip out before the rod falls back into position:



    The yellow plywood sideboards and the grey rod are, say, each about 30cm (12in) long in the direction perpendicular to the drawing. The black pushing pin extending from the blue solenoid through a hole in one plank is 4mm in diameter. I am planning to have one such effectuator in the middle of the length of the trough, but might place one at either end if need be.

    Now my question is - can this work? I have no experience with the mechanics of granular materials, and I have doubts that I cannot solve on my own without experimenting:

    - Won't the rod get stuck in the rice without returning to the bottom of the trough, thus staying out of the reach of the pushing pin and/or allowing all the rice to fall out at once?

    - How far do I need to push the rod to make sure the rice starts falling out? One solenoid I have seen on sale has a pin that moves by just 3mm, I am worried if this is enough, even if my rod travels a bit more, due to inertia.

    - What is the best diameter and weight for the rod? I don't want it to be too heavy in case the whole feeder is ripped off in a windstorm and its wreckage falls down, possibly onto people or cars. But I plan to make it quite sturdy, and the window is only about 4m (12ft) above the ground so it's not a life-threatening height.

    - How will weather conditions affect the rice and the functioning of the dispenser? The feeder will have a roof (with the dispenser forming a kind of "attic" underneath), but wind may still blow some drizzle into it, and I don't know if dew can form inside.

    I am open to other suggestions as to the dispenser. The purpose is to have a bird feeder that does not require me to open the window every time I want to give the birds a meal.

    I have 1 month to complete the project.

    Thanks in advance,
    Leszek.
    A few comments)

    1) If you have only one actuator acting at a point on your rod, it will indude a torque and not move the rod parallel to its axis. This will complicate things quite a bit. I suggest eight two actuators.

    2) The distance that you want to move the rod will depend on the grain size and dohesion of your rice grains. I would expect that you would want to move the rod so as to pen a slit of width at leat two grain lengths, more would probably be better.

    3) The rod should probably be on the heavy side, consistent with the capabilities of the actuator to ensure resealing. You might consider a rod with a triangular cross-section rather than a circular cross-section. A triangular rod should re-seal well and not be prone to trapping rice grains underneath it.

    4) Harold's obserevation of bird feeders with not moving parts suggests a much simple and more robust solution. I have one and birds can empty it in an afternoon quite easily. It holds about two liters of bird seed.
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  8. #7  
    Forum Ph.D. Leszek Luchowski's Avatar
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    Thanks for all the replies, and looking forward to more discussion.

    I am now tempted to use the kind of design Harold pointed at, plus an electric effectuator.

    I mean, put the seeds (probably rice) into a bottle, hang the bottle upside down, and suspend a shallow tray underneath its opening. Attach a small electric motor to the tray, with a weight mounted excentrically on its shaft, like a jumbo version of a mobile phone vibe. Keep all of this unaccessible to the birds.

    Vibrating the tray should make rice fall off it, onto the "floor" of the feeder.

    Another option I am thinking of is to slowly rotate the tray around a vertical axis which does not coincide with the center of the bottle neck. This way, the neck of the bottle will push some rice off the tray. This has a nicer deterministic feel but will require a motor with a reduction gear - again, a difficult item to get my amateur hands on.
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  9. #8  
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    Quote Originally Posted by Leszek Luchowski
    Thanks for all the replies, and looking forward to more discussion.

    I am now tempted to use the kind of design Harold pointed at, plus an electric effectuator.

    I mean, put the seeds (probably rice) into a bottle, hang the bottle upside down, and suspend a shallow tray underneath its opening. Attach a small electric motor to the tray, with a weight mounted excentrically on its shaft, like a jumbo version of a mobile phone vibe. Keep all of this unaccessible to the birds.

    Vibrating the tray should make rice fall off it, onto the "floor" of the feeder.

    Another option I am thinking of is to slowly rotate the tray around a vertical axis which does not coincide with the center of the bottle neck. This way, the neck of the bottle will push some rice off the tray. This has a nicer deterministic feel but will require a motor with a reduction gear - again, a difficult item to get my amateur hands on.
    That will probably work without any of the electr0-mechanical devices. If you want to add them just for the heck of it, that will probably work also.
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  10. #9  
    Forum Ph.D. Leszek Luchowski's Avatar
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    Thanks again.

    Yes I know an inverted bottle can keep the supply running without any electric effectuators, until it is emptied. But as you mentioned, the birds can gobble two litres of food in one afternoon - which is not what I am looking for. My purpose is to bring them in for a snack a couple times a day, at the expense of a handful of rice each time, and at the - should I say labor cost? - of having to climb to the window not more than twice a week; preferably once.

    I like the idea of the birds learning to recognize the sound of the motor Pushing the button will be all the more enjoyable.
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  11. #10  
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    Quote Originally Posted by Leszek Luchowski
    I like the idea of the birds learning to recognize the sound of the motor Pushing the button will be all the more enjoyable.
    It will be interesting to see if the birds actually learn to respont to the sound of the motor.
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  12. #11  
    Forum Ph.D. Leszek Luchowski's Avatar
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    I think I can withdraw what I said about small screw conveyors being hard for an amateur to get. I can probably make one by fitting an ordinary screw (say an M8x60) onto the shaft of a small motor/reducer assembly. Laying that in a narrow horizontal passage filled with rice and open on one end should do the job. The opposite (upstream) end of the passage should form a part of the bottom of a narrow, vertical container.

    The idea is taking shape... Goodness, I feel forty years younger doing this
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  13. #12  
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    Quote Originally Posted by Leszek Luchowski
    I think I can withdraw what I said about small screw conveyors being hard for an amateur to get. I can probably make one by fitting an ordinary screw (say an M8x60) onto the shaft of a small motor/reducer assembly. Laying that in a narrow horizontal passage filled with rice and open on one end should do the job. The opposite (upstream) end of the passage should form a part of the bottom of a narrow, vertical container.

    The idea is taking shape... Goodness, I feel forty years younger doing this
    For small quantities you may not even need a screw. The powder tricklers used by hand loaders use a simple tube with an inlet hold to admit the powder. Simply turning the tube allows a small amount of powder to be transfered to the open end, where it falls out. The screw will be more efficient and move the rice more quickly, but you will need to decide if you need the mass transfer rate enabled by the screw. If you do and ordinary threaded rod would probably work.
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  14. #13  
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    I had in mind an auger type of drill bit, the kind you use to drill a hole through wood. A small one would be all right. I think you could get one for just a few bucks. If you use that drill bit to drill the hole through the side of your box, and you make that a fairly thick board, then the hole you have just drilled could serve as the bearing for your auger. You could drive it with something like a cheap electric drill or an electric screwdriver. That would set you back about $15 or so.
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  15. #14  
    Forum Ph.D. Leszek Luchowski's Avatar
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    Yes Harold, I have been thinking along those lines as well. And I imagine it's a good idea to spin the drill backwards, so the rice is pushed by the blunt side of the.... um, what's the opposite of a groove? anyway, the blunt side of the helix, rather than pulled by the sharp edges meant for drilling. This way it will jam less, and crush fewer grains.
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  16. #15  
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    How about a small slider in the bottom of your container, held in place with a spring. Pull on a string to open the slider.
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  17. #16  
    Forum Ph.D. Leszek Luchowski's Avatar
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    Pulling on a string would require the operator to open the window every time the birds are to get a meal. This is a bit of bother because of desks standing in the way, plus, in winter, it would make our room less cosy and our gas bills (for heating) even bigger.

    A thin low-voltage electric cable can be placed across the window sill, then the window simply closed on it.
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    Of course I don't know the lay-out of your house, but with a little imagination you can go far.

    To allow the string to be pulled when the window is closed, you could put a very small tube on the windowsill and close the window on that. To not a allow the string to slip away from you, and to pull it more easily, you can put a wooden ring on the end of it. To let it go around corners, you could put small flexible tubing around those corners, and pull the string through those (a bit more elaborate, but still easier than your solution, is to put pulleys at the corners).

    I think it's a more elegant solution than the one you are now considering.
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  19. #18  
    Forum Ph.D. Leszek Luchowski's Avatar
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    My opinion is that electricity is a much easier and reliable way to control things at a distance and around walls than strings are. There is a reason why even door bells aren't operated by strings any more.

    Nevertheless thank you Calimero for trying to help.
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