@Northern_Loki, i am a true masochist, in HEUI I have owned 1x 7.3, 2x 6.0s and cats 3126 (both generations).
If i can make a six-litre squirt good, I can make AA squirt good too.
EDIT
But really, common rail is the way to go…
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How cool is that! That’s some heavy duty gear for driving around town 
Worked on the Cat ECM design team circa late 90’s or thereabouts. Only reason I even know what HEUI is
Sorry for the interruption Trichome Dome contestants, carry on.
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That kind-of sounds like RIU in general. I don’t get it.
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I dont want to get much more off topic, but yes, my wife and I used to contract for site overlay design and deployment at special events - temp power, structural, etc. Generators, trucking… did a good chunk of 2010 Vancouver Olympics. Burnt a LOT of diesel over the years 
On topic though, one of the pioneers in air assisted spray (spraying systems co) has an office on Annacis island, right in my backyard. I’ll be taking advantage of that
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Oh wow! Im liking the direction this is going, but how about we move it over to my build thread? We can get into details and nitty gritty good stuff!!
Hmmmm - or maybe we should start a new thread on HPA & AA nozzle design?
Im good either way.
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I’ll answer this to get you started.
The ideal droplet size is between 20 -80 microns. Cycle timing depends on the volume of the root chamber, number of nozzles, and flow rate.
You want the ON time to be just barely enough to fill the chamber with the correct size droplets. You need enough nozzles so that the entire chamber is uniformly covered. Preferably no voids or overly wet areas, and the mist should not spray directly on the roots if possible. The ideal OFF time is just short of the time the mist starts to fade away - just a little less than the hang time. Again the goal is to provide the roots with an environment that is as stable, and uniform as possible, at the perfect ‘wetness’ level.
I should point out that I have not achieved that ideal yet. Im still in the wet/dry cycle stage, but getting better.
So far, the best timing I have come up with for my 45 gallon chamber was 0.4 seconds ON and 75 seconds OFF with three of the old Aeromist nozzles. That was putting out aprox 0.5 gallons per day total - I think. I need to review my notes.
I dont have a good cycle time for these new nozzles yet. I will have to develop that as the roots grow. I think it will have to be a somewhat higher ON/OFF ratio, because these nozzles have a lower flow rate, but that might be offset by the smaller droplet size. I’ll have to figure that out based on how the roots are growing.
Oh - the two main types of AA nozzels are siphon fed and pressure fed as far as water delivery. From what I have gathered, either will work fine. I would lean towards siphon fed just to reduce the need for one more pump and regulator. The feed air pressures I have seen are fairly low - 20-40psi.
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I’ve always been impressed with how well some of those events are staged, in particular, I’ve wondered how these things are planned from a safety perspective. Though, I’m certain you probably have some good, behind the scenes, stories to tell.
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So pretty much the same as spraying paint HVLP? Either a gravity feed or a pressure pot, except with a smaller median droplet.
This sounds a lot like a xf/vf atomization on a spray gun. I have a few high quality spray guns, but the finest nozzles I have for those would have their median droplet towards 250um, in the medium range.
I’ll give spraying folks a call later today. Already have a proper stationary compressor in the shop. One hole in the wall gets an airline to the grow space.
I guess need to deal with drip and find some solenoids for control now.
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Im not up to speed on how HVLP systems are built, but yes.
You want a nozzle that will work with a relatively low volume of air, at low pressures, with fine control of air pressure, and of course timing. Too much air flow can blast the roots.
There are lots of options for solenoids and timers. My advice it to try to keep all parts using the same type and size fittings where ever possible. Adapters can add a.bunch to the total cost.
You will want an oil filter on the air line, or use an oilless compressor.
Some comments and numbers from Atomizer for flow rates, timing etc. As far as I know, there would apply to HPA and AA. They assume good droplet size, coverage and good hang times.
I would recommend root chamber no less than 15"-16 deep for high pressure aero. As for mist timing,a lot depends on the mist quality (droplet size range), nozzle flowrate, coverage and level of control you have…
In an ideal system, you would set the misting duration based on flowrate and chamber volume. For early growth, the misting duration would provide 0.02ml -0.04ml per gallon of chamber volume. For later growth, 0.06ml per gallon.
The interval between mistings is adjusted to provide the target daily throughput, which will be somewhat dependant on environment variables (light,heat etc). As an example, a 26 gallon chamber with one 1gph nozzle would need a 0.5- 1 second misting duration in early growth and upto 1.5 seconds for later growth. The interval between mistings for early growth would be 35-70 seconds (dependant on the misting duration setting) with a target daily throughput of 1.3 litres. For later growth, the interval would be around 50 seconds with a target daily throughput of 2.65L. The name of the game is to inject mist little and often to maintain an optimal aeroponic environment.
Most aeroponic systems have flowrate, coverage and/or control limitations which provides a defined wet/dry cycle rather than a constant mist environment.
Choosing the correct nozzles involves matching the mist pattern to the chamber and/or planting layout. Nozzles come in a wide range of types, full cone, hollow cone, flat fan etc. To make things more interesting, there are various.cone angles and short and long throw. Consider which nozzle pattern/type provides full and even mist coverage with the fewest number of nozzles (as this affects the system flowrate). For example,.narrow cone long throw nozzles are best suited to long narrow chambers with rows of planting sites. The mist is directed horizontally into the space between the two rows, This will generate two walls of roots running the length of the chamber with an open corridor of space allowing mist distribution. Be aware that roots can and will thwart even the best laid plans as they can sense where the nozzles are located and will try to grow towards them., Roots can grow horizontally into open space ( defying gravity),they can climb UP a sheer chamber wall and even attach themselves to the slick underside of a chamber lid to get closer to a nozzle. Making the nozzle locations adjustable is a good idea as is having nozzles that are accessible from OUTSIDE the chamber for easier maintenance.
A starting point for the pause duration is not as easy, a stopwatch is useful for checking how long the mist hangs. After that you
ll have to judge if you have too little or too much pause time based on how wet the roots are. Adjustments may take an hour or so to become apparent, increasing the pause time allows the roots to use up excess standing droplets but you could find youve overshot it and theyre too dry after a couple of hours. Similar situation when decreasing the pause where youll see excess droplets forming on the roots.
There
s no wet/dry time with AA, the roots are suspended in constant mist. Finding the right mist density is the first hurdle, too much, too moist or too large a droplet size and everything is soaked. Too little or too small a droplet size gives too dry a mist the roots cant use. Pause length is set to let the mist gradually fade down to a light haze just before the next pulse. Use too long a cycle and the mist is completely gone (too dry), too short a cycle and excess droplets start building up on the roots (too wet). Youll need a fairly long pulse to fill a 1100L chamber
The target daily throughputs are based on full coverage of 5-80 mist which hangs for the entire pause duration and then some so the roots are never without mist. If you dont have it, the best approach is to make the pulse as short as practical to maximise the number of mistings and adjust the pause based on root wetness and structure. In a lot of cases you`ll find the target daily throughput numbers are reasonably close even though the pulse and pause timing will be different. If the ideal total nozzle flowrate for a chamber is 4.5LPH, and you need 3 x 4.5LPH to get the coverage, you are forced to use 3x the pause to achieve the same daily flowrate.
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Larry is correct – we doubled our harvest and more than halved our nutrient use with our first run. However to be fair the HPA run is lit by 4 QB-300’s vs the soil room that runs a shitload of older HPS fixtures (new bulbs every run). We are thinking of adding a few soil buckets to the HPA room this run so we can better compare the LED vs HPS.
His inability to share information is the entire reason I posted my grow log listing every part w/ links. It’s also the reason my grow log is not on RIU and is over here instead.
Hell yeah man – the more people experimenting and sharing details the better off everyone is. I’ve made plenty of mistakes, but I’d rather post them so someone else can learn from my failures instead of having them waste their time and money.
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A nozzle up-date. These nozzles are for sure different from the Aeromist nozzles. I cant decide if its better or worse. I for sure havent found a good timing setting yet.
The plant looks good up top and is growing, but it seems to be growing a little slowly to me. Its hard to judge that because Ive never grown this strain before.
This was it on the day I put it in the chamber. - 2 Nov
This is it today - 5 days later. Its hardly any taller, but is spreading out.
The roots are what have me the most concerned. They are staying very thin and not growing very fast - at least not compared to the previous unknown seedling. There is also no sign yet of any fuzzy hairs.
The other seedling had started to explode with roots by this same time.
Ive been running slightly longer ON times with these nozzles because of the lower flow rate, but Im now thinking that they are still not long enough. 0.4 seconds was great with the old nozzles, so I thought 0.5 would be good, but it seems too dry. I bumped it up to 0.6 and that still didnt seem to do it, so Im now at 0.7. I need to give that at least several hours to see how the roots respond.
Im wondering if the smaller average droplet size is part of the ‘problem’ as well. A percentage of the droplets may be too small for the roots to use easily.
I may need to order some additional nozzles with the next size up orifice - havent decided yet.
The people I got these from - EchoLogic - seem like nice folks, and they had no problem shipping me out some new springs, but they are slooooow compared to the Aeromist guys. Its taking them more than a week to get me parts. Thats hard to take after getting spoiled by 2 day shipping from Amazon and 3 days from Aeromist 
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Not by any means HPA expert here, but they look like “looking for water” roots (more alongared than bushier).
Sometimes (in DWC) I get these roots when I have some nutrient imbalance (too high/low EC), as they are perhaps “searching” for food/better food source.
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Yeah, thats a possibility I guess, but I think I have everything fairly close as far as nutes. PH is staying in the 5.7-6.2 range, and EC is 0.6.
Not much change this morning after 6 hours at the longer timeing. They still look very thin. Im leaning towards the droplet size being too small - which would be inline with your thinking they are looking for water. Im going to swap the Aeromist 0.024 nozzles back in for a day and see what happens.
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Some days I am just tooooo stupid to grow weed - or toooo stoned?
This morning I was messing with the nozzles, checking for clogging, mist patterns etc. As part of the testing, I put small Dixie cups over two of the nozzles while I check the third one.That way, I only have one mist stream at a time.
I bet you can guess what I did - or didnt do - when I was done… crap! I didnt look at the baby until tonight after more than12 hours of running on only a single nozzle. The leaves were all droopy and some of the roots are all shriveled up. There had been one small spot this morning that was just starting to show fuzzy hairs too!
arrrggghhhh!
On another note - I have been trying since I started this project, to think of other ways to generate a 50 micron mist in a root chamber that does not involve using hi-pressure or AA nozzles.
Over the last few days I have seen a few pics from guys doing DWC with roots that are super fuzzy and white - above the water line. Like this shot from @SquirtleSquad
https://overgrow.com/uploads/default/original/3X/f/8/f8f9e552d7ce9bd57f9f447de157b00dd738a345.jpg
Obviously, those super fuzzy roots above the water are very happy, and they seem to be getting just about the perfect droplet size and amount.
So, the question is - could that be duplicated in a pure aero root chamber using some sort of water container and aeration of some sort?
I dont want to do dwc or have a huge tank of water sitting at the bottom of the chamber. I want pure aero roots. Not for any good reason - I just do So, ideally, no water roots at all.
Im now trying to think of a good way to generate small bubbles using an air pump in some sort of circular container mounted near the top of the chamber. I dont like air stones, but I have not come up with a better way to generate small bubbles in large volumes in a small chamber.
@Northern_Loki was using a needle wheel pump to generate some super fine bubbles in his setup, but I have no first hand experience with those. I am worried they would generate too much flow through an open trough type container? No clue.
Anyway - if a good setup could be built - I picture this as being able to generate a constant supply of fine droplets coming down from the top of the chamber - no wet/dry cycles - all with no hi-pressure pumps, accumulators, solenoids, timers, or expensive AA nozzles.
Anyone have any ideas on this?
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Have you looked into “fogponics” yet, with an ultrasonic fogger in a rez constantly making fog? In my research (internet rabbit hole) i came across a few who managed.
I’m still waiting for the AA nozzle folks to get back to me on a 1-2gph 20-100u 10-30psi gravity feed nozzle.
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Yes, Ive looked into them a fair bit. The biggest problem is they produce droplets that are too small - sub 5 micron in most cases. That makes the fog too ‘dry’. The other big issue is that they build up a film on the surface of the oscillator that requires frequent cleaning and can be hard to get off. Kind of like the film that you get from boiling a pot dry. That and the cheaper ones dont last long when run 24/7.
Ive been wondering if they could be ‘tuned’ to produce larger droplets, but that still leaves the other issues of cleaning and life cycle.
Your comment about the HVLP sprayers got me to wondering if one of those could be adjusted/modified/McGyver’ed to put out smaller droplets? That still would not be really cheap, but maybe a step in the right direction. I need to look into how they are built.
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If they can suggest an inexpensive nozzle that does the job, that would be awesome.
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Aside from general stupidity, and forgetfulness, I can add failure to do simple math to my list of bad habits.
I may have found another part of the reason these nozzles are not doing as well as I hoped.
The Aeromist nozzles have a flow rate of 1.176 GPH or 1.23 ml/sec. I was running them at 0.4 seconds ON, for a flow volume of .492 ml per ON cycle.
The EcoLogic nozzles have a flow rate of .706 GPH, or .742 ml/sec, or about 60% of the flow rate. Some how I came up with 0.5 seconds having an equal flow volume, but thats way off. 0,5 x .742 = .371 ml/sec. I need at least 0.7 sec ON time to have the same flow per ON cycle. 0.7 sec ON = 0.519 ml/ cycle. A little higher, but better to be safe, so Im going up to 0.8 until the roots recover. If they dont start bouncing back soon, I may jump up to 1 second for a while.
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It occurred to me I can easily test the air stone droplet generator idea. I have an air pump, and tubing. I’ll pick up a couple of cheap air stones and try this out. I can use the same techniques I use to evaluate the mist in the chamber now. Just turn off the lights n the room, and use the cat toy or my small flashlight to illuminate the top of a container while its bubbling. If I rig this up in an enclosed space, so there are no air currents, I should be able to see if there are any hanging droplets.
I had another idea about this. Droplets that are in the right size range will float in the air easily. The air coming out of the air stone, should b e able to lift them up easily. However, larger, heavier droplets that are the wrong size, will tend to drop out sooner. It might be possible to “tune” the droplet size by placing the air stone in a container with tall sides that are adjustable in height. As you raise or lower the sides of the container, you should be able to control the size of the droplets - at least to some degree. The volume of air flowing would also be another way to tune the droplets sizes.
Maybe.
I should be able to test this this weekend.
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Yes, fairly high flow rate out of the pump. For those not familiar, a needlewheel pump is basically an aquarium pump with a modified impeller that looks like some sort of torture device. The impeller beats the fluid into submission instead of “pushing” it. It amount to an inefficient aquarium pump with a damaged impeller that’s also sucking in air. It’s primary purpose is to produce fine bubbles for protein skimmers. To do so, it needs to run at a fairly high RPM to finely “chop” up the air entering the pump all-the-while producing sufficient turbulence + flow to keep any larger bubbles from conglomerating. It’s purposefully designed to be a crappy pump.
With that said, out of the box one of these pumps likely has more flow than you’d need / want and would take some jiggering to balance things out. Some tuning for off-label use may be required. Off-topic, Larry and I saw some interesting dissolved O2 results (possibly going super-saturated by several percent) from the data on the system I have here. I’ll need to get back to testing / posting results at some point but the out-door season + life has had me busy on other things lately.
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