atlasstone

Benchtop Test Tank

144 posts in this topic

I found that video as well and based my first 4 or 5 designs on it using 6 inch and 4 inch piping because I don't have the space that the 12 inch piping would require (that's how I ended up with the 6 inch pipe i used in my current design :) ).  I used a couple different bilge pumps and modified them to use a prop to simulate the trolling motor.  The current was pretty good but not fast enough for what I wanted to see out of crankbaits.  The biggest issue I ran into was the inconsistency that a prop introduces to the water column.  If you watch the action on the video you can see what I ran into.  The bait, even though it's held stationary, has a tendency to drop and lift with the vortex cause by the prop in the current (I'm assuming anyway).  The cranks I tested would fall out of rhythm and get pushed in and out of the currents. 

 

I tried different props and got the same results regardless of size and running the pump in it's designed centrifugal configuration didn't produce enough speed.

 

I really like the concept of this one though.  I was just not able to get it to work for me, but i"d love to have a design like it, just smaller with an enclosed motor. But, for what it's worth, there are the results of my testing with that design.

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Atlasstone, Thanks for the feedback on that other design. I have a 50 gallon Aquarium 12x48x20. that I have been contemplating trying to build a test tank  for quite some time. I just wasn't sure how to go about it so I was very happy to see yours when you posted it. My idea was to have the water flow from one end of the tank to the other by using a flat piece at each end with many matching holes drilled In both pieces. I was going to let the pump push the water out behind one end between the aquarium wall and the false end wall with holes , hoping that it would flow through the holes to the other false end and  through its holes then have a return pipe pick up the water behind this end piece. I have not tried it yet but am wondering if i could get enough flow  with this design. and not have a lot of turbulence.  I bought a 1250 GPH hr pump but it is a livewell pump which I think would work well with this design if I can get enough flow. Any thoughts?            

John       

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I have posted on this, and I still love the design, but .......  My calculations say that the flow rate is rather slow.  Still, Atlassone's video shows the lure working well, with the exception noted by atlasstone on the other design, turbulence.  I suspect that the design is working because of the turbulence, not in spite of it.  If the water was flowing laminar, the flow rate may have be only about a quarter of a mile an hour.

 

JBlaze, if you put a sock over the outlet of the pump it will reduce a lot of the turbulence, but not eliminate it.  If you then run the water through a stack of straws (YouTube has a lot of videos on creating laminar flow) you can create an almost perfectly laminar flow.  Your concept may work well enough, so if you have the time and funds, it is worth a try.

 

I am not trying to be a buzzkill on the subject.  I still like the concept and I will be working on this when I can.  It appears that I may be moving soon so this is going to kill a lot of my projects for some time.  Still, for those that know the math, check my out.  For all, I still think that Atlasstone is on the right track! 8O

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Anglinarcher, thanks for your input on this. I do not know the math so my method of doing things is mostly trial and error  I am going to start on this one soon, again Thanks.  John

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My design was completely trial and error.  Some of the things I researched were the use of props, tubes, aquariums, bilge pumps and ROV ring thrusters and whatever makes those lap pools work.  I never found the ring thrusters and I couldn’t figure out how the lap pools worked so those ideas got tabled. 

 

I think I understand the concept of the design you are thinking about, JBlaze and after looking at some of the laminar videos that Anglinarcher mentioned, I think it could work.  My main concern would be the turbulence as you mentioned.  I too don’t know the math around it, but when I tested using flat walls I found that the current never got established because the water was not being guided so it cause a lot of agitation.  It got better when I put a wall in the middle to block the disturbance from getting into the flow, much like a sea wall.  The other issue I faced was (what I assume) was a narrow current when I tried to put the bait directly in front of the pump.  The bait would work for a second then fall out of the stream so stability was really difficult. 

 

With your design (if I understand the concept) the holes would be put in place to solve the narrow current issue and the wall on the return side would help the turbulence.  It might be helpful to put a retainer wall down the middle to isolate the current and protect it from any deflection at the other end.  Another idea might be to use a two pump system and a PWM to slow the main pump down slightly so that the return pump can mitigate any build up that might cause the agitation.  With my design, I was not able to get the return to equal the flow because the return on the pump is pulling water from all directions but only pushing water in one direction so that’s why I put it behind the curves.

This is just my theory though as I am certainly no expert.  I know that this can be done and my design is very crude for what it could be.  I based my design on the fact that water flows faster on the outside bends of rivers (which is why I fish them more because they tend to be deeper) and the fact that if I put my thumb over the end of a garden hose I could spray my sister with water from a distance that afforded me the head start I needed as a child to avoid her wrath.  Not exactly a formulaic approach.  ;)

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 Attlasstone, maybe not a formulaic approach but it worked and you did good. And, You did understand my idea perfectly.

 After reading Anglinarchers post, I may try building the false ends out of plastic straws. Will have to do some research to figure out how many straws it will take to build these two walls 12" by 20"  :? .  OK, ( height of sides / divided by diameter of straws) x (width of bottom / divided by diameter of straws). Will that work?   Don't know if I can afford that many straws :eek:

Will keep you posted as this idea progresses. Again, thanks. John

Attlasstone, I hope this is not considered Hijacking your thread. Should I start another one with this?

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JBlaze and Anglinarcher - I have done the sums over and over and only get a flow rate of 0.8" per second. A good flow rate would be 18" to 36" per second. For a flow rate of 18"/sec a pump rate of 28,000 GPHr would be required.

 

This is all based on a full tank with a divider plate down the center with the pump on one side and the test lure on the other. If you reduce the depth from 20" to 10" the flow speed doubles to 1.6" and the pump rate halves to 14,000 GPHr.

 

It all seems like a lot of pump. Maybe someone could check the numbers, I may have missed something.

 

Dave

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It seems to me that a test tank is just that, a starting point for fine tuning a lure, but the best place is in the the lake or river for testing. While I think I will build one myself his summer for winter testing, since it freezes up here in NE Wisconsin. I could cut a slot in the ice I guess. :mad:

Wayne

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JBlaze and Anglinarcher - I have done the sums over and over and only get a flow rate of 0.8" per second. A good flow rate would be 18" to 36" per second. For a flow rate of 18"/sec a pump rate of 28,000 GPHr would be required.

 

This is all based on a full tank with a divider plate down the center with the pump on one side and the test lure on the other. If you reduce the depth from 20" to 10" the flow speed doubles to 1.6" and the pump rate halves to 14,000 GPHr.

 

It all seems like a lot of pump. Maybe someone could check the numbers, I may have missed something.

 

Dave

 

Dave, I suspect you are pretty close to correct.  I think the atlastone video shows a functioning design because turbulance has faster and slower sections.  I think the faster currents in the turbulent flow are what is making the lure work.

 

A lot of assumptions come into play, how tall is the water column, how wide is the water column, is it all flowing the same velocity, etc.

 

Lhur Jensen, a company in the US, use to demonstrate their lures by using a cylinder tank and a motor driving a wire frame.  The lures were attached to the wire frame and they moved in a circular path.  Perhaps this is the direction to go.

 

One thing is for sure, I am not done with this subject.  atlasstone has got something that works for his lure, but may not work for Vodkaman's swimbaits, or mine.  Neverthtless, this has got all of us thinking. :?

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Dave, I was hoping you would sign in on this one. Thanks for your input, I have much respect for your knowledge. Even though your calculations are a little disheartening, I too am going to continue on with this project. I have already spent the money so I might as well try and find a design which will work. Thanks  John

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My estimate comes out at about 0.5 ft/sec...

 

Using

Channel water height = 4 inches

Channel width = 3 inches

Cross sectional area is 3*4/144 = 1/12 sq ft = .083 sq ft

1200 gph = 160.4 cu ft/hr = 2.67 cu ft / min = 0.04456 cu-ft / sec

 

Velocity = 0.04456 / 0.083 = 0.534 ft/sec

 

That is an average velocity through the channel.  It's possible you've got faster flow in the middle and the bait is staying in that faster flow, much like a light ball will suspend in an upward air jet from a vacuume cleaner.  It also looks to me like there's quite a bit of turbulence.  Even so, this looks pretty encouraging. 

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Wchilton - I put your numbers into my spread sheet and get the same, once I had converted to US gallons :)

 

Dave

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I've considered building some sort of test tank for a while so have "run the numbers" on a few configurations.  Thinking about this one (today) I realized you may be getting some retained momentum because of the recirculation (like some wind tunnels) so velocity may be quite a bit higher than the .5 ft per second you'd get from pump output alone in a straight-through configuration.  You could measure water speed by filming a small object traveling with the water through the test section.  Something light like a piece of feather would be good, preferable have it suspend in the water rather than float on the surface or sink to the bottom.  A couple of strips of tape can mark the distance and frame count will give you accurate enough time.

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...You could measure water speed by filming a small object traveling with the water through the test section.  Something light like a piece of feather would be good, preferable have it suspend in the water rather than float on the surface or sink to the bottom.  A couple of strips of tape can mark the distance and frame count will give you accurate enough time.

 

 Get out of my head man!  :)

 

I did exactly that last night and would have had this posted but decided to go to bed while YouTube processed the video.  Anyway...

I made 4 runs, each with the center section in slightly different places to test the difference in the current.  Some of the flows are not optimal to run a lure in, but the point was to test the speed.  The video was shot and edited at 60 frames per second but if you don't trust my math on the video and decide to do it yourself, then you will need to use 30 frames per second because YouTube renders all their videos to 30 frames per second (at least that is what I understand... I would need to confirm that though)

 

The tape is approx. 3/4" and I counted frames across a 6" span.  I hope this hepls!

 

 

Edited by atlasstone

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I've considered building some sort of test tank for a while so have "run the numbers" on a few configurations.  Thinking about this one (today) I realized you may be getting some retained momentum because of the recirculation (like some wind tunnels) so velocity may be quite a bit higher than the .5 ft per second you'd get from pump output alone in a straight-through configuration.  You could measure water speed by filming a small object traveling with the water through the test section.  Something light like a piece of feather would be good, preferable have it suspend in the water rather than float on the surface or sink to the bottom.  A couple of strips of tape can mark the distance and frame count will give you accurate enough time.

This is my thoughts are taking me.  I started putting it together last night will hopefully have something to show in a couple of days. I thought maybe a suspending lure might do the trick as far as measureing the speed/flow. Thanks for the reinforcement

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JBlaze,

I tried a lure but without a tension point it doesn't have the control needed to measure it.  I used a disk made from PVC with a little bit of weight in the center to keep it running as straight as possible.  I didn't think about it until you mentioned the suspending lure, but you could use the same concept with the disk maybe and just add enough weight to give it neutral bouancy.  I still have mine set up so if it would help, I can mess with it and see what happens.

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Atlasstone, I think that is a good idea, worth trying.

I have another idea also, I'm not sure this would work but maybe drop in a small hose from an aquarium air pump and blow a single bubble and see how far it traveled before surfacing. No weight or mass to affect its momentum so it would instantly travel at the speed of the flowing water. I think  :? Geez, I can't sleep at night for thinking about this thing.

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I'll give it a shot and see what happens.  I'm sure others that are more physics savy can confirm this, but I don't think the object itself really matters.

For the purpose of testing, I chose a round shape so that the distance traveled would be as accurate as posiible regardless of if it spun.  If it were a rectangle and the object spun 90 degrees in the middle of the measurement, it would throw the calculations off because I would need to compensate for the added length at the end... and I'm just too lazy and not that smart.

If the object is unhindered from moving in anyway, then I think any object that is suspended in, or floating on the water column would move the same speed as the current. Much like a boat with a drift sock. If there is no wind to move the boat faster than the current, then the drift sock is useless because it will move at the same rate as the boat which is identical to the speed of the current. Only when another force acts against it will there be a change.

 

Here is a link that explains it a little better:

http://wiki.answers.com/Q/How_does_mass_affect_speed

 

I think the question I need to answer by suspending the object is whether the current under the surface is the same speed as the current at the surface.

 

Am I off base on this?

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Atlasstone, I think you are spot on. But, I am not a physics major neither.

A couple of days ago, after reading and trying to understand the things I read about Laminar Flow. I decided that my end pieces with matching holes drilled was no good.

I liked the idea of building a baffle out of straws but if I figured right, it was going to take close to 8000 cut straws placed in a frame side by side and top to bottom with each straw glued together. Dont think I have that much time or patience.

So instead I am opting to build a baffle for each end made of stacked and glued strips of corrugated plastic sign material. The plastic is very thin and strong and should have several thousand small holes/channels for the water to flow through. I am thinking that the secret to a good strong flow will be to have the pump pumping the maximum amount of water that this baffle will allow to flow through all those holes. If it pumps more than the baffle will handle then the space between the baffle and the end of the aquarium will overflow. On the opposite end, The same thing should occur since the baffles will be identical and the return  inlet of the pump should be pulling from behind this baffle the same amount of water it is pumping out to the other end. This may take two or three pumps. I have no idea how to figure how many gallons of water can flow through this thing. 

My biggest worry with using the corrugated material is that the channels are so small that there may be too much friction and the water may not flow well.

Ain't but one way that I know to find out  if it will work or not so with that said. I am going to be busy for a few days.

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Would your design allow you to scale down at all? Perhaps only fill 1/4 of the tank and see what happens.  You could bujild a frame to hold the straws and run the pump slow enough that you can just use friction to hold the straws in.  Just trying to save you a little time and energy  :)

 

Did the video with the speed tests help at all?  I'm not sure what posts are getting through because I seem to have posts disappear and re=appear.

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............... Thinking about this one (today) I realized you may be getting some retained momentum because of the recirculation (like some wind tunnels) so velocity may be quite a bit higher than the .5 ft per second you'd get from pump output alone in a straight-through configuration...............

The video indicates that you may be dead on.  Either that or the pump is pumping more then it claims. 

 

This has been bothering me some just like others on this site.  Most pumps are rated with some "head".  For example, it will pump x gpm at y feet of head.  A bildge pump does not have that rating, nevertheless, I assume it is normal to assume it is pumping that at about 5' of head to get it over the top of the boat.  With no "head" or vertical lift, you could be getting much more then the 1200 +/- GPM claimed.  Hmmmmmm

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Atlasstone said:

 

 

"I think the question I need to answer by suspending the object is whether the current under the surface is the same speed as the current at the surface.

 

Am I off base on this?"

 

No, you are not off base at all.  In water flow systems design, we often use a trapazoid shape so that the water on top flows closer to the flow rate at the bottom.  If you do any stream fishing with "floats" and weighted flies/lures/baits, you will often see the float tip forward because the slow flow at the bottom holds it back some.

 

The real question is "is there enough of a difference in the 4 or so inches of the tank to matter?".  I kind of doubt it, but then again, I doubted the velocities that you clearly have proven with the latest video.  Only testing would prove one way or another.

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 I am opting to build a baffle for each end made of stacked and glued strips of corrugated plastic sign material. The plastic is very thin and strong and should have several thousand small holes/channels for the water to flow through...My biggest worry with using the corrugated material is that the channels are so small that there may be too much friction and the water may not flow well.

 

Friction slowing things down would be my concern as well.  If you already have the material and don't mind spending the time it's worth a shot, though.  I think it might be possible to make a laminar flow nozzle a lot smaller than the whole channel size.  Part of what got me interested in this post was I recently saw a DIY project to make a laminar flow fountain and was considering whether what I had gleaned from that could be used for lure testing.  Just do a google search on "laminar flow fountain" and you'll get lots of hits.  The project I was looking at was at makezine.com.  So my thinking was to either put a laminarizing nozzle on the pump to create laminar flow before entering the main stream of water or to fabricate a small jet pump (powered by the sump pump) to pull water from the main channel and force it all through a larger laminarizing nozzle followed by smooth expansion back to the main channel.  The trick, of course, is going to be minimizing friction loss so that you only need the small pump.

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