Very cool. Anxious to see a video too of this desing.
Benchtop Test Tanktest tank
143 replies to this topic
Posted 01 February 2013 - 04:08 PM
Very cool. Anxious to see a video too of this desing.
There is a link to a video that shows it running in the original post. I had some difficulty embeding a video and getting the post down to 10 pictures so it's not very obvious. Is that what you are looking for?
Posted 01 February 2013 - 09:33 PM
Nicely done, that took a lot of thought and to make it work, even more impressive. Not all ideas work the first time. Congrats!!
Posted 10 February 2013 - 09:09 PM
Here is another design which I found on youtube, a totally different approach but does the job well.
Posted 13 February 2013 - 03:49 PM
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.
Posted 13 February 2013 - 10:03 PM
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?
Posted 14 February 2013 - 12:43 AM
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!
Posted 14 February 2013 - 06:26 AM
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
Posted 14 February 2013 - 12:40 PM
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.
Posted 14 February 2013 - 05:37 PM
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
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?
Posted 18 February 2013 - 10:39 PM
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.
Posted 18 February 2013 - 11:30 PM
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.
Posted 19 February 2013 - 12:28 AM
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.
Posted 19 February 2013 - 05:28 AM
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
Posted 20 February 2013 - 02:22 AM
JB - thanks. I am really hoping my numbers are wrong for you
Posted 20 February 2013 - 03:15 AM
My estimate comes out at about 0.5 ft/sec...
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.
Posted 20 February 2013 - 04:00 AM
Wchilton - I put your numbers into my spread sheet and get the same, once I had converted to US gallons
Posted 21 February 2013 - 01:09 AM
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.