2 questions~Over/Under and PSI

[omnicron]

Ok guys here's how today went, I blocked off 4 tubes. I was seeing about 40 psi at half throttle. Did not see any extra flow in the box though. Suction seemed like it had a little more, it was hard to tell.. So I unblocked 2 tubes and I was seeing 22psi at half throttle and about 40psi at wot. Didn't notice any difference in suction or water in the box. I took out the last two restrictors and was getting 22psi at half throttle and 40psi at wot. So I'm not sure where to go from here.

I did lift the tail end of the sluice out of the water and my lower section was clearing a lot better, but the upper section was not clearing rocks. I tried raising the head of the box up to 8" of slope and still not clearing rocks. I did notice I only had about 1" of water above the 1/4" mesh. So I lowered both screens down all the way, about 3/4" each. I have about 3" of water above the screens but still not clearing rocks. Once again I change the angle of the box, the angle of the flare and no-go still. Here's what I'm thinking. I also have rocks not clearing out of the flare. I think my flare is to wide. It's 18" and my box is 20. I'm thinking that the water and rocks are losing their momentum at the flare. That's causing the rocks to not to tumble on down the sluice. They are stopping on the screens. Only when I'm at a extreme angle do they make it to the riffles. Am I thinking right?

Oh and my under current is catching fine gold like I've never seen one catch. When I pulled my sluice down after a hour of running, in the very bottom of the deep vribs was a crap load of maybe -200 gold. Lots of it.

 

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[principedeleon]

Yeah that should help.. Making it around 15" should be better And your flare is kinda square so it takes more water than a rounder one with the same width; so it will lower a lot the water velocity.

 

[goldgit'r]

I made a flair 10'' wide for a 10'' sluice on a 2 1/2 dredge and had the same problem you are having.
Sounds like you have already figured it out. Wes

 

[Timberdoodle]

Have to agree that the flair is to big. You shouldn't have rocks not clearing the flair. I had to make smaller than normal flares to pass material over grizzly classifiers fast enough to maintain momentum and it sounds like you might be faced with the same problem. If you can fold up some sides to fit into your existing flare you might be able to move them until you find the right size.
I'm confused why you are getting the same readings from 6 jets to 8 jets.
Did you ramp up to 50psi for 4 jets? Were you able to get flow in the box with 4 jets the same as 6 or 8 jets? If you found the same flow rate in the box with 4 jets at 40psi then you must have increased suction. Perhaps 5 is the right total size of jetting?
Sounds like you built a great dredge Omni, just have to tweak a few things to get everything moving right.

 

[omnicron]

I'm confused with the readings also. But truthfully I didn't put much focus on that aspect. I was more concerned with getting the rocks to clear and if my underflow section was working. I never wot with 4 tubes. When I hit about 2400 rpms on my tach and checked the pressure, I checked the suction and buried the nozzle in in the gravel and let it dig it's own 3'x3'x3' hole while I tended the box, changing the angle and kept the parking lot clear.
I'm just so amazed how much a 6" dredge will move. The nozzle would dig it's own 3x3x3 hole in a matter of minutes. I'm very hopeful for a great season and a better life for my family If I can get the issues worked out.

Another strange problem I'm having is when I fire up the first engine, it's blowing the flapper of the other foot valve back. I start my engines and let them idle to warm up. They are brand new keene valve and you would think they wouldn't do that.

 

[Timberdoodle]

I never ran 2 engines, but I would expect the pressure created from the first engine to do this until the second is running. I would probably remove the flapper valve in the 2nd engine footvalve and let the first engine prime the line in the second to remove all the air until it's started. Just a thought. I'm sure others have run into this and have solutions.

Further thought on the jet. If your not getting different readings with 6-8 jets then maybe there is a issue with turbulence or some other factor in the manifold that is not allowing for linear operation. I would disconnect the suction hose and raise the front of the jet for visual inspection while running the pumps. You should see linear operation throughout the speed of the pumps and see linear psi readings on the gauge also. If you find non-linear operation then something is certainly effecting this and should be found. I would try and fix this before moving forward with other mods which are dependent on flow.

 

[omnicron]

From what I have notice, the second engine will not pump under this condition as it seems like its just in a state of cavitation. Idk it seems like 2 engines are much more of a hassle then 1 was.
I'm thinking of cutting my flare down to 14" at the oval opening, leaving it 48" long.
Can anyone that runs a 6" dredge with a 20" box measure the oval part of their flare (ID) and let me know please?

 

[Timberdoodle]

From what I have notice, the second engine will not pump under this condition as it seems like its just in a state of cavitation. Idk it seems like 2 engines are much more of a hassle then 1 was.
I'm thinking of cutting my flare down to 14" at the oval opening, leaving it 48" long.
Can anyone that runs a 6" dredge with a 20" box measure the oval part of their flare (ID) and let me know please?

I think the cavitation is caused by the valve closing and locking air in the second pump. Removing the flap would probably help pump the air out. You may need to start the first and ramp it up to do this before starting the second pump.

 

[principedeleon]

How you reduced your suction noozle ? Maybe is restricting your hose from sucking 6 inches of water.

I just remembered you have to reduce it to 5"..