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Author Topic: Gears for measuring flow  (Read 64 times)
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Mattk
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« on: November 08, 2018, 05:05:09 PM »

I would like to build a gear flow meter similar to the one in this image attachmen t.
These gears are only about 1/2" diameter with 23 teeth, im not exactly sure how to draw this in gearotic, what would be the best tooth design to mesh well enough to keep liquid from flowing through the teeth?
I found this article talking about the principal behind how these meters work here: http://www.flowmeters.co.uk/flow-technology-spotlight-comparison-oval-gear-flow-meters-standard-gear-flow-meters/

Any tips for me would be appreciat ed!
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ArtF
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« Reply #1 on: November 08, 2018, 05:36:05 PM »

 Looks like just 2 standard involutes meshed. Involutes should give you the best mesh ,
I suspect these leak somewhat and are only approxima tions of volume?


  Ahh, on reading I see what you mean. I suspect you dont want very tight mesh, since these
are driven by differenc es in pressure, whatever you build the gears should be on good bearings
and not a tight mesh at all, just a loose  coupling that makes them move with only sligth pressure.


Art
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Mattk
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« Reply #2 on: November 09, 2018, 04:42:18 PM »

Thanks Art,
I think I should go for a tighter mesh to prevent leakage through the gears, the operating pressure of the flowmeter is over 300 psi so I do not think I will have a problem getting the gears to spin.
Here is my first try at Gearotic:
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ArtF
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« Reply #3 on: November 09, 2018, 05:00:40 PM »

Looks good.

   I was more worried about just how much different ial pressure develops from the flow.
As the gears rotate backwards to the flow I was thinking it wasnt much as a %. I dont think
operating pressure would mean much, the pressure different al will be between input and output
flows, so I wouldnt think it would be much more than a small % of the actual flow rate.

  I kinda pictured them running very easy but with one on an encoder or something for
a frequency readout. Ill be intereste d in how much force they seem to have when you
get them running, Ive never experimen ted with flow. Once you get it running let me
know how you make out.

Art
 
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Mattk
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« Reply #4 on: November 09, 2018, 05:09:43 PM »

The flow rates are really low so there should not be a tremendou s pressure diff.

The way I was going to read the flow was to press a magnet into the top of one of gears and pick up the magnet with a hall effect sensor.
This way I could seal the chamber completel y and have the hall sensor in a separate cavity to prevent leaks.
Body of the meter will be stainless which will allow magnetic flux through.
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ArtF
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« Reply #5 on: November 09, 2018, 11:15:10 PM »

If its high pressure with low flow, Id suspect you need them so finely meshed that they spin just by
blowing on them, but then I really have no idea. Just sounds right to me that thge pressure wont matter
so low flow is low energy for spinning. Magnets do sound good for transmiss ion of a frequency .

Art
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