Recirc Stand-behind/Hang on Skimmer

[dzeadow]

it hasn't been so far!

[FishAreFriends2]

any updates to how the AC's are doing? Did you find a solution?

[dzeadow]

not yet, I haven't been working on it though.. probably will here shortly. I'm waiting for the FedEx guy/gal to get here so i want to make sure I can hear the door bell. I'm pretty sure I have to reduce the height of the impeller well...almost 1 1/2" is too big.

[happyface888]

Whats coming from fed ex today?

[dzeadow]

snails, crabs, algae eating blennie.. I was hoping my rod's onyx were coming via fedex as well, but they may be coming ups which doesn't get here until late.

I don't know about this AC mod now.. I can only get 8-10scfh out of it. I only have about 2g of water in a bucket though so it's nothing like the 24-36" Hahn had mentioned testing his. I put 3 layers of enkamat on it, used 1" and 3/4" inlets/outlets, different kinds of venturis... there's one more venturi I'd like to try, I just don't have the urge to do it right this second, looks like the picture though, supposedly you can get more air pull if you use multiple sources of air as opposed to one giant source, so drilling 4-8 holes in the piece of 1/2" piping in the center, it apparently should work better.. we'll see though.

[JCTewks]

Danny, Have you experimented with covering some of the water intake with your hand to see if that increases air any?

[dzeadow]

No i haven't. I thought that 1/2" restriction was enough already, but I can try it out. wouldn't adding more restriction to the water cause more air to be sucked in and more choking? or am i wrong in theory here?

[dzeadow]

as i put my finger over the intake and all it does is drop from 8 to 0 slowly, so apparently that's not it.

[JCTewks]

maybe try the opposite, enlarge the 1/2" reducer and see if that helps. It does sound like ther is too much air...but that shouldn't be the case with the new volute, so maybe it's not enough water thats the problem. Have you heard from Jon yet?

[dzeadow]

no I haven't. But according to his mod, he used 3/4" on both inlet/outlet, used 3/8 airline (not sure if it was 3/8 id, or od) and didn't have a problem. I'm wondering how the new set up is done that he put pictures up of on the other thread. He had a T on it. so I'm wondering if pulling the airline back further allowing more water to get sucked in will allow more air? His initial set up showed that his airline "venturi" was in the 45 elbow that he slipped on what appeared to be a 1" section of possibly 3/4" pipe.

Here's some interesting info that liveforphysics sent me when I pm'ed him about venturis, he's some kind of hydro engineer or something:

CSA = Cross Sectional Area. Sometimes called XSA. Sorry about the field specific jargon.

The diagram you included does show the method for manifolding multiple air inlet points that I was trying to describe.

By stretching PVC you can easily drop 1" PVC down to a 1/4" ID. It's important to remember that you will not see such a critical flow choke from this sort of drop in CSA provided the taper is smooth and gradual, which is how PVC naturally forms when you heat and pull it.

So basically, taking a piece of 1" pvc pipe, heating it, and pulling it to get 1/4" id inside, you could speed up the water so fast that it's pulling vast amounts of air. he also suggested using the manifold method I mentioned either here or the other thread by drilling multiple holes in the stretched pipe to get many smaller holes vs. one air source.. here's where he said to put it:

Due to the turbulence caused by the steps when the reducer bushings are used, I recomend stretching the PVC to create the desired drop in CSA. After stretching, I would drill a series of small radial holes directly behind the thinnest CSA point.

Since connecting these holes to a common feed would be very difficult, I recomend slipping this proper venturi into the next size larger PVC or bushing or whatever part it slips into easily. Then drill a single large hole, thread it and thread a large barbed nipple into the side of that bushing/pipe that fits over the outside of your venturi.

This should enable you to have a proper venturi for a low cost with excellent performance.

So in essence, stretching a piece of 1" pvc to have 1"id hole ends, and whatever we deem as practical as the smallest id in the "middle" and then as soon as the thinnest part starts to increase in diameter again, drill a few small holes around the radius, then take this stretched pvc and hopefully some how get it into a T fitting or a 1 1/4" piece of pipe. then thread a fitting on or just glue the airline directly to the pipe, which I think would be easily done on a T vs. the straight pipe.

Sorry, this got really long, but is very interesting. it's obvious that some pumps will only be able to handle so much air before choking, but this seems logical on how to get more air in. The problem it seems that is brought up with choking is that the air bubbles coming in are way too large and causing the pump to stop and start, if the air was brought in by a bunch of tiny bubbles, I think there wouldn't be a chance for the pump to stall, but would chop them up... what do you think Jeff? did you catch all that

[FishAreFriends2]

man my head hurts from reading that stuff, I pretty much don't understand whats going on lol. Guess I'm not a DIYing custom guy thats pretty dam hard for me to understand.

[dzeadow]

lol... yeah I had to read it a couple of times. Just imagine this drawing, but instead of using 3 pieces of differing pvc sizes, using a 1" piece stretched to do the same thing:

[FishAreFriends2]

I'll let whoever chime in on the design, so hows the skimmer going now? I haven't seen any updates to what its pulling?

[dzeadow]

the neck gets nastier faster now that's for sure. I'm still working on getting that ac70 going.. I think getting more air in the neck will allow better skim. It's not showing much, probably still in the 1/3cup range, but it just looks nasty. I just added some more clean up crew and another fish.. so now I have 5 in my 45g , seems like a lot to me, so I'm glad I have the big guy back there.. workin OT!

[FishAreFriends2]

I have 10 fish in a 50g and if I recall happy had like 7 x.x NOW SELL ME YOUR BALCO

[dzeadow]

holy buckets! 10 fish !!! I guess you really do need this thing. Are your fish small or what?

[JCTewks]

that makes a lot of sense danny! You'll not want as small as 1/4"ID i'm sure...but you'll want to experiment with what ID XSA will work best on an aspirating venturi. The 1/4" XSA is what is typically used in a venturi that will be driven by a pressure pump, so the physics are the same, but the implementation is a little different

What he said about turbulence from steped down pipes makes sense...I had never really thought about just heating and stretching

It's really about finding that nice balance between water and air!

[FishAreFriends2]

so how are things going now?

[luke33]

You can make that venturi easily. I've done it quite a few times. Take a piece of 3/4" pvc or 1" pvc and take a metal hose clamp and boil it for a few minutes, take it out and put the squeeze on the metal hose clamp, it'll squeeze a bit, then keep doing that until you get to 1/2". Its a smooth transition. I'm actually pondering over a new venturi that i think will be better than any of these but i need to put it into play before i tell people about it.

[dzeadow]

so secretive! I might try it this weekend if I have nothing going on. I'm going to take it easy since I caught this god aweful cold/flu thing the other day. But I'd like to try the manifold version to see how it works.

[happyface888]

Luke has a picture of that venturi, but I don't know where it went. Its lost somewhere in the octopus hob thread x.x and thats going to be a pain to search for.

[dzeadow]

i remember seeing that one. I'd like to try stretching a piece, I think that'd have interesting results.

[FishAreFriends2]

Having a custom venturi instead of the normal one seems to work better,. I am wondering how come your not using 1/4 air tube instead?

[dzeadow]

1/4" airline instead of what? I'm using 1/4" ID airline while testing this stuff if that's what you're asking.