another damned noobe....

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another damned noobe....

Post  jagwaugh on Tue Jan 04, 2011 10:01 am

Hello,

I ran across the forum while searching for ideas for our garden. I've read up a bit, and read many of the patents, have a half decent grasp of physics, machining and such, but I still have a few questions.

1) If I plan to use a single pump to drive 2 nozzles at dia "d" can I use 2*d as the value for caclulating the pump pressure and flow, presuming that the pump is an equal distance from each nozzle, and the piping is all the same size? (I presume "yes", but not everything is as intuitive as it seems).

2) What is the smallest orifice that anyone has actually achieved?

3) Has anyone experimented with making a double helix fountain? I would love to try this, I can think of 2 methods of getting the stream to form a helix, a) Offset the body and rotate so that the nozzle rotates around the centre, or, b) make a cranked tube for the nozzle and rotate that.


Best regards

Andrew

Z├╝rich, Switzerland

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Re: another damned noobe....

Post  John on Tue Jan 04, 2011 3:34 pm

Welcome Andrew!

1. Yes, if everything is equal same lengths and same tubing and same distance apart from the pump, then yes you can just use 2*d.

2. There have been some really small nozzles here. A couple of mini nozzles with a diameter of .25" (I'm guessing you'll have to look through all of the archives to verify.) There was a fellow from Germany and one from Spain who build these. I think liteglow also built one.

3. That sounds like a really cool idea. That would be really neat to see. One note is that these nozzles are extremely sensitive to vibration. It could potentially loose its laminar properties when rotating it. I really want to see that one!
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Re: another damned noobe....

Post  jagwaugh on Wed Jan 05, 2011 12:05 am

John,
Thanks for the response. Just to get clear on the 2*d question, if the pump were offcenter then the pressure/flow would differ according to the ratio of the distance from the pump at each jet. What about height differences? i.e. one orifice higher than the other? I would think that if the pump is centered, and pipes and orifices are the same dia (i.e. losses between pump and orifice are equal) then the heights of the parabolas would be equal, but the higher would have less flow and pressure at the orifice, am I right?

As to the vibration issue, as a hobbyist clock and watch maker/repairer I am fairly good at close tolerance mechanisms, and have the tools to machine and polish surfaces accordingly. I am thinking of using a rubber sheet as a sort of damping gymbal, and decoupling the drive to reduce (stepper)motor vibrations. The mass of the jet would be easier to handle if I could rotate that along its c/l and offset the orifice, otherwise I end up having to add weight to balance it out which is inelegant to say the least.

.25" is pretty small, I would think that is about the practical limit for outdoor use, considering wind effects and such. What about multiple orifices in the same chamber?

To get started I am thinking of using a plastic bottle for the body, these are from a water carbonating system here, called "Soda Club". The bottles have fairly thick walls, and spherical ends, and with a bit of jiggery pokery I can drill a hole in the end and assemble the straws and such in a "Ship in a bottle"way. This would leave me with the cap easily removeable to make orifice changes. Anyone have a good suggestion for gluing PET?

Andrew

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Re: another damned noobe....

Post  superpants on Mon Jan 10, 2011 9:30 am

On the nozzle size- I have made a small nozzle with a 4mm hole size, which worked quite effectively. It probably won't suit a large outdoor installation. Running on pressure from the kitchen tap, I get about a 500mm throw before the stream breaks up.

The helix idea sound great- look forward to seeing it!

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