Water drop results of Shako PU220AR solenoid valve
When photographing water drop collisions, three things affect drop volume:
- Valve pulse duration, which we tweak with wild abandon
- Head pressure, which is just as important, and just as big a factor
- Orifice diameter, a choice of different valves
Pressure through an orifice area for a duration produces a certain volume of flow.
Then of course, to form good clean drops without scatter, the nozzle size must be appropriate for this volume created, not too big, not too small.
This is about the Shako PU220AR solenoid valve (Specs and more detail on power and source and such). It is a 24V valve with a 1.5mm orifice. Note that 12 or 24 volts does not change the flow, it merely opens the valve. I use the 1/8 inch NPT fitting size, believing a smaller water reservoir inside the nozzle is a plus (but that size fitting is harder to find locally).
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Three pressure cases are shown with drop sample results (each group is marked with a colored left border):
All cases shown here are Two drops, spaced 40 ms Toff with Stopshot (some say Toff needs double that - maybe I will redo it soon). The sensor is at 17 inches on the yard stick, bottom of nozzle at 24, center line of valve at 26, flash to sensor timing 142 ms. Head measurement method is shown at right. |
Based on this, I summarize these cases being possible to produce clean drops for easy and good collisions for:
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These are just a few spot check numbers, so the actual working range is of course a bit wider, more overlap. Also see the CTS 2P valve which works well at 7 to 20ms pulse with 4 inches of head with 1/8" ID valve. It is actually faster than the Shako, but needs a lower height for water drops due to the orifice size (it outputs a LOT of water). This page covers a span of six inches of head pressure, nearly 2 to 1. Certainly there are combinations of head, pulse, and nozzle that are just not going to work. We can see that 14.5 inches of head is becoming enough pressure to be a lot of water, even through the 1.5mm orifice. But the Shako works easily over a wider range, a pleasant valve to use.
Some non-working combinations were shown for the purpose of showing 1) how principles of pressure/pulse/nozzle interact, and 2) to show how good drops look very different than bad drops, and 3) to emphasize how many combinations in fact do work great. Two and only two nice clean and consistent drops actually achieved are going to be no problem in collisions. One big point though, is when the drop pulse isn't doing it for you, then also try changing the head pressure. My choice is the Shako valve, usually around 11.5 inch head, and pulse about 10 to 20 ms with a 3/32" ID nozzle. Make sure the valve and nozzle are plumb, vertically straight. Make sure there is no air between valve and bottle. A set of drill bits is handy to determine nozzle ID.
| Valve | Orifice mm | Orifice Inches | Area mm² |
|---|---|---|---|
| STC 2V 035 | 1 | 0.039 | 0.78 |
| Shako PU220AR | 1.5 | 0.059 | 1.77 |
| STC 2P 025 | 2 | 0.079 | 3.14 |
| Orifices are about half the diameter of these nozzles | |||
| Nozzle Description | Nozzle ID inches | mm | ID % Increase | |
|---|---|---|---|---|
| Drilled Pipe plug | 0.0625 | 1/16" | 1.59 | - |
| for 1/8" tubing | 0.09375 | 3/32" | 2.38 | 50.0% |
| for 3/16" tubing | 0.125 | 1/8" | 3.18 | 33.3% |
| for 1/4" tubing | 0.1875 | 3/16" | 6.35 | 50.0% |
1/8" pipe plug, drilled 1/16 inch. Easier to drill straight from inside.
8.5 inches head (measured by yellow marking above)
Above: 7 ms pulse, 1/16" ID nozzle.
Above: 10 ms pulse, 1/16" ID nozzle.
Above: 14 ms pulse, 1/16" ID nozzle.
Above: 20 ms pulse, 1/16" ID nozzle.
Above: 28 ms pulse, 1/16" ID nozzle.
NOZZLE CHANGE Above: 7 ms pulse, 3/16" ID nozzle.
Above: 10 ms pulse, 3/16" ID nozzle.
Above: 14 ms pulse, 3/32" ID nozzle.
Above: 20 ms pulse, 3/32" ID nozzle.
Above: 28 ms pulse, 3/32" ID nozzle.
Above: 40 ms pulse, 3/32" ID nozzle.
NOZZLE CHANGE Above: 7 ms pulse, 1/8" ID nozzle.
Above: 10 ms pulse, 1/8" ID nozzle.
Above: 14 ms pulse, 1/8" ID nozzle.
Above: 20 ms pulse, 1/8" ID nozzle.
Above: 28 ms pulse, 1/8" ID nozzle.
Above: 40 ms pulse, 1/8" ID nozzle.
Above: 55 ms pulse, 1/8" ID nozzle.
Above: 75 ms pulse, 1/8" ID nozzle. Second drop at extreme top.
11.5 inches head
Above: 7 ms pulse, 1/16" ID nozzle.
Above: 10 ms pulse, 1/16" ID nozzle.
Above: 14 ms pulse, 1/16" ID nozzle.
Above: 20 ms pulse, 1/16" ID nozzle.
Above: 28 ms pulse, 1/16" ID nozzle.
NOZZLE CHANGE Above: 7 ms pulse, 3/32" ID nozzle.
Above: 10 ms pulse, 3/32" ID nozzle.
Above: 14 ms pulse, 3/32" ID nozzle.
Above: 20 ms pulse, 3/32" ID nozzle.
Above: 28 ms pulse, 3/32" ID nozzle.
Above: 40 ms pulse, 3/32" ID nozzle.
NOZZLE CHANGE Above: 10 ms pulse, 1/8" ID nozzle.
Above: 14 ms pulse, 1/8" ID nozzle.
Above: 20 ms pulse, 1/8" ID nozzle.
Above: 28 ms pulse, 1/8" ID nozzle.
Above: 40 ms pulse, 1/8" ID nozzle.
Above: 55 ms pulse, 1/8" ID nozzle.
Above: 75 ms pulse, 1/8" ID nozzle (Second drop at extreme top)
NOZZLE CHANGE Above: 20 ms pulse, 3/16" ID nozzle.
Above: 28 ms pulse, 3/16" ID nozzle.
Above: 40 ms pulse, 3/16" ID nozzle.
Above: 55 ms pulse, 3/16" ID nozzle.
Above: 75 ms pulse, 3/16" ID nozzle. Second drop at extreme top.
14.5 inches head
Above: 7 ms pulse, 3/32" ID nozzle.
Above: 10 ms pulse, 3/32" ID nozzle.
Above: 14 ms pulse, 3/32" ID nozzle.
Above: 20 ms pulse, 3/32" ID nozzle.
Above: 28 ms pulse, 3/32" ID nozzle.
Above: 40 ms pulse, 3/32" ID nozzle.
NOZZLE CHANGE Above: 10 ms pulse, 1/8" ID nozzle.
Above: 14 ms pulse, 1/8" ID nozzle.
Above: 20 ms pulse, 1/8" ID nozzle.
Above: 28 ms pulse, 1/8" ID nozzle.
Above: 40 ms pulse, 1/8" ID nozzle.
Above: 55 ms pulse, 1/8" ID nozzle.
Above: 75 ms pulse, 1/8" ID nozzle.
NOZZLE CHANGE Above: 20 ms pulse, 3/16" ID nozzle.
Above: 28 ms pulse, 3/16" ID nozzle.
Above: 40 ms pulse, 3/16" ID nozzle.
Above: 55 ms pulse, 3/16" ID nozzle.
Above: 75 ms pulse, 3/16" ID nozzle.
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