I'm looking for a 'tank' to test the performance of a small electric outboard, (PWM speed controllers, batteries, hydrodynamic slipstreaming mods etc) so am thinking of a circular tank, possibly about 3' / 90cm in diameter so that I can set the outboard off to one side and get the water circulating around the tank, rather than just turbulating in it (as when in a dustbin etc). It would also need at least around 18" deep sides to stop the water climbing / splashing out.
So, after a bit of Googling I came across the IBC water containers and
1) wondered if anyone knows where there might be one that still holds water (at least over the lower half) near Nth London that someone might like to see the back of and 2) if you think it might be suitable for my needs please (or if not, why not etc). If not there seem to be plenty on eBay cheap enough.
Would it being nearly square (all be it with round corners) with maybe something in the middle to ensure water actually flows 'round' the container be free moving enough or do you think I'd need to fit a round liner inside it?
If the bottom (inside) isn't flat or couldn't easily be made flattish (from a water flow POV) could I use the top half upturned instead (I could fit my own drain c*ck etc).
Any other ideas around the above welcome of course. ;-)
Not sure about a round tank, but it would be fairly straightforward to form a rectangular trough from sheet material (OSB?), drape a thickish sheet of polythene inside and fill with water?
Nice 'outside of the box' thinking Nige, thanks. ;-)
An octagonal or even hexagonal box would probably be close enough for my water-flow needs and could be screwed or (cable-tie?) hinged together if it had a waterproof lining (I don't think there would be that much pressure at 18" deep and if there were, nothing a couple of ratchet straps wouldn't hold)?
It might be easier to make something rectangular (and if I was making it myself I could of course) with angled inner corners and a central baffle to create a 'circular' water path?
A concern may how much strength there will be left once to top is cut off though the one I have seems fairly heavy gauge material and you still have the reinforcing cage to help with that, but you may have to cut that down as well.
The bottom is fairly flat apart from a section a bit lower for the tap.
To satisfy the above concerns it would seem like a lot of kerfuffle to do rather than but a round tank in the first place from a suppler like an agricultural merchant.
How much depth do you need? I've seen an instant garden water feature made by using a section of concrete pipe lined with an off cut of pond liner , the latter can often be found as remnants at water garden supplies but for intermittent use a bit of DPC membrane should suffice. As would doing the same with a large truck or tractor tyre but that could lead to disposal problems later.
If you go down the IBC route what it originally had in it may have a bearing, mine had contained a detergent that was for washing supermarket food crates so rinsed clean easily, some that tend be at the cheaper end of prices asked have had things like fibre glass resin in which is harder to deal with for some applications.
You can also get half size 500l ones but being rarer and sough after tend to actually cost more.
If you leave it in the metal frame, that will still support the container adequately. I have a couple which I use to store spring water and/or harvest rainwater at a stables and these have large (600 mm square) holes in the top to allow for periodic cleaning with a pressure washer. (As an aside, standard paddling pool / swimming pool floats containing a chlorine tablet more or less eliminate algae).
My question is what sort of power are you talking about here? Unless it is pretty small, it could get exciting. Even a small one will need a pretty strong and secure support.
Ok, thanks. Do you think it would impact the flow of water round the tank, assuming it's going at about 5mph and I'm not looking for lab standard of water flow? ;-)
From what I have found so far, such sized tanks are about 250 quid? ;-(
You can get a loft tank for ~£150:
Underground tanks are even more:
I've not measured accurately yet but something like 18 inches (of water) should cover it easily. Basically my best hope would be the space either side of the prop (between the outside of the tank and the inside barrier (imagine a doughnut)) is about the same as the depth of water. Eg, if the tank is 4' diameter with a 2' diameter 'centre that only leaves a 12" width 'channel' for the water (the prop is only about 9" diameter). So, the centre of the prop could be 6" off the bottom of the tank and as long as the top of the prop is sufficiently covered to prevent cavitation, that should work.
That's a good idea (half a truck tyre, cut like you would a bagel) but I don't think it would be deep enough without some additional material (nice one though).
Understood. I'll try to get one that has previously contained something pretty innocuous or has been fully cleaned out.
I'd need the size the 1000l tanks give I think.
If I go that way I then just need to find something suitable as a centre (a length of reasonable diameter plastic pie or water container etc that can have hole in (to stop it trying to float) and some gravel or summat to hold it in place. Or, if it was an upside-down bucket shape I could joint it to (underneath) the cross member (4 x 2) that will also act as the outboard mount.
If I want to make the inside wall of an IBC tank 'rounder' I might be able to find an 8x4' sheet of some of that thin foam filled plastic, cut in half down it's length, joined lengthwise (overlap) formed into a circle and just dropped inside should be sufficient. I might have to trim it to fit round the tap mount etc? I'll try it without first of course. ;-)
The idea is to get as clean a flow of water around the circuit as reasonable so that I can get some reasonable linear flow related measurements (simulating being on a small dinghy).
I might even try to measure the water speed (Arduino project) as that and the current drawn are the two main criteria.
It is a Yamaha M12 (re badged Minn Kota) electric outboard or 'trolling motor' as they call them in The States and gives about 30lb thrust on full.
'Full' is about 30A and at 12V that would make 360 watts (~0.5 hp).
However, on speed 3 (of 5) pushes our 3m folding dinghy along (3 + dog) at the rivers speed limit of around 5 mph but silently. ;-)
However, these smaller outboards often use what they call 'speed coils' (load resistors) to lower the current for the speeds 1-4 and so I've got a PWM speed controller from China that I can plug in series and see what speed increases (hopefully) I get for the speeds 1-4. It may be slightly less efficient on speed 5 as that would normally be the battery connected directly to the motor. However, whilst it's nice to have that extra 'oomph (relatively speaking etc), the current draw is disproportionately high for the increase in hull speed so we generally don't both and just enjoy the range instead. ;-)
I also recently picked up 6 x 16000 mAh LiPo packs with the though of making a lighter and higher power replacement for the 60Ah traction lead acid battery we currently use but the complexity (charging, storage charging and transporting), cost and risks outweighed the short term (it's only an issue when carrying the batteries from the car to the boat) advantages. So I'm probably going to get two (or more [1]) new lighter traction batteries, mainly to make it easier for the Mrs to handle.
So the goal is to try to get a days cruising with a combination of individually weight manageable LA batteries and efficiency improvements on the outboard (PWM power control, hydrodynamic fairing on the tubular shaft and a spinner on the prop).
That's why I need a suitable test tank to be able to reasonably accurately measure or at least compare pre / post 'improvement' values. ;-) [2]
Cheers, T i m
[1] Basically we are only limited to the weight of battery we would want to carry in the car as the boat is rated for '4 Persons' and there would typically be only 2 of us. ;-)
[2] Whilst some of it is academic on the folding boat(s) we intend to mainly use, I also have a 16' Canadian canoe that would probably give a higher speed through the water for a given battery load, plus I like the saying, 'You can manage what you can measure'. ;-)
I have an electric outboard ("John Azur"), and a PWM controller from China, presently awaiting tuits...
I've also looked at this and its brothers: "Digital LCD DC combo Meter Watt Power Volt Amp RC Battery dis charging Analyzer"
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which does current times voltage over time, and could work as a "fuel gauge"...
If you want to see what's possible -- look for "Torqueedo" outboards. They have an accurate range estimate in miles in their system, using a GPS. (Note: for the price, you will be ble to hire someone to paddle you upstream for a week).
As to the tank -- Dunno about round, and the water moving in a circle: the watter current would speed up, dropping the electric current, and the water would start to climb up the sides of a circular container, and the outboard might start to move to the side and the propeller hit the container wall. Turbulent flow would provide a more constant load.
Other than that: rainwater butt? Inflatable pool? a "Fast set pool", 8 ft diam for 30 quid (which would required external support for the motor)?
Or, here, I'd be looking at mortar pans, like here: bit small, but very cheap
I bought something similar recently (supposedly 130A rated) and as it was from China, probably the same inside. ;-)
Yup. I was going to use mine for both the testing / modification and general running stage, at least to start with.
Yup, already looked at those but are way outside my price range and comfort zone (if something goes wrong outside warranty etc). They also seem to be a bit noisier than the typical trolling motors?
Whilst I'm sure you are right to a degree, this is why the container needed to be reasonably big to increase the water volume and reduce the speed. That plus I'm only talking about ~5mph so that shouldn't become an issue (but I'll keep the thought in my mind of course).
Not if I've fitted it it won't , plus if the container is plastic, that won't be as bad as the prop hitting some rocks on the bottom of the river. ;-(
But wouldn't help with my hydrodynamic fairing and prop spinner tests?
Yes, I've considered all those as well but don't feel they would be robust enough to last if left out etc. That said, it's possible that once I have done my initial tests I won't need it so something I can fold away might be a good idea. The '4 ring' inflatable paddling pools look cheap / deep / large enough. I already had a 3 legged design for a frame that would stand over the pool, support the outboard and any cylinder that was going to create the 'core' in the middle (an upturned cylindrical water container or large diameter drain pipe etc). It would have to be suspended from such a frame if used on an inflatable pool as it won't be so easy to hold such in place on the bottom without risk of damaging it etc (but not impossible with care etc).
Yeah, that was the sort of style but as you say, probably a bit small.
Nige's idea about making something from say OSB and lining it with some DPM or pond liner could be a good compromise as it could be made fairly cheaply and fairly easily (it could be stitched together using cable ties) and then flat-packed or reused for other roles if / when the project was over.
Square (or rectangular) would be the easiest and possibly the most self supporting (square corners), the top edges could be stiffened with a bit of batten (and / or the outboard supporting frame) and a circular inner wall could be formed inside the liner, to manage the water flow if required.
1 x 11 x 1220 x 2440mm (£15) for the base and two sides and another for the remaining two sides and maybe some inner corners to make an octagon plus 20 quid for 3 x m of DPM? A bag of cable ties to stitch it all together or some lightish line?
I was thinking on that if I wanted to slow the water circulation speed / apply some (more) load to the motor I could just build a weir under the water (engineering bricks?) maybe 90 degrees behind the position of the outboard around the tank?
They have a system I'd love to have: flexible roughly folding-boat-shaped solar panels, Li-ion batteries and a small motor. If going slowly enough in enough sun, the panels give enough power to keep on going all day, and end up with full batteries...
Several (many) thousands, though.
Or truly round, using cooper techniques: tongue-and-groove boards, i.e. decking, cheap paneling? Plain boards, and ratchet straps around the outside?
Ratchet straps, which are also useful in other ways, afterwards.
Hmmm, I just read that out to our daughter (she sends her regards btw) and she asked why I couldn't use our existing corner bath . Easy to fill and empty and I can still do my experiments when it's raining. ;-) I just need a lift out frame to mount the outboard on ... ;-)
Thanks for the thoughts and offer Tim. Are we talking a traditional rectangular water (rather than CH header) galv tank here ... (as you mentioned the scrap skip) or plastic? If it's plastic and one of the larger sizes I'd like to consider the dimensions and see if I can do something with it please?
Hehe ... luckily I can get to our bit of the Lea easier than getting to yours and whilst some of these tests can be conducted 'live', I'd prefer to do them on the bench (so to speak) and leave the real boating to being just 'fun'. ;-)
Maybe in California Thomas , but I agree, they seem to be a very clever and well thought out package.
Quite. My point was I can buy several Minn Kota outboards and traction batteries for the same money *and* could use easily use a car battery if I had to or try LiPo or LiIon if I wanted to. The Torquedo is a bit too propitiatory for my wallet and needs.
;-)
Wow, that would be a project and probably require more patience than I've got! When you say that a hot tub comes to mind ...
True and I already have plenty of them. I still think the corners might appreciate being held together, at least initially, along with the sides being held to the bottom, till it's filled with water? Easy to do with some cord stitching. Just lay each section against it's partner and drill though both with say a 10mm bit. Then you just run a line (or releasable cable ties) though each hole to 'stitch it together into the basic shape. Add liner and water and you are away and nothing is going anywhere. Add the 45 degree corner sections to make the octagon and you wouldn't need the liner to make it circular and it would brace the sides so you don't need the straps. ;-)
Hehe! ;-)
Cheers, T i m
p.s. I Googled your 'John Azur' outboard and they look like they might be quite old? I do like the design of the underwater unit though, especially how they return the diameter of the motor housing down to that of the prop and then get close to the diameter of the prop (so not having a central hub etc).
I note it also has the tubular pole connecting the underwater head to the rest and I think I understand that a tubular section has 5 times the drag of an aero/hydro-foil of the same diameter. Now, I know these outboards don't go though the water at the same speed as many IC outboard but at the same time we would be looking to maximise the efficiency of what little power we have available. The lower leg of most IC outboards are have a hydro dynamically efficient shape.
So, because I have a 3 printer and like to play, I was going to design and print some clamshell type 'trims' to add to the lower leg to both help with the hydrodynamics and with the steering (it acting like a small rudder when the motor is off).
Well, I can, if the structure isn't waterproof etc ...
Oooh, now that looks interesting, unless I could find a second hand one they don't look cheap though:
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I think the hex one would be the best option but after Googling around I saw a round composter made from a wire mesh. Given that I could line something with DPM to make it waterproof, maybe a wire ring with a semi rigid sheet and then the liner might be ok?
Good cleaned ones can still be found at those prices and the smaller ones (500L) are more so.
When you buy whatever normally comes in them (I know of PVA glue, car polish, something to do with printing, jam?) do you normally have to pay 'on top' for the IBC or is it incorporated in the price of the product?
Are any re-cycled by the suppliers (by default)?
All types?
Excellent ... and from memory there were quite a few!
£35 for a good clean one that had held a detergent/disinfectent bought this spring.
seller is still listing them at that price
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only thing to watch for is mine came with the finer thread rather than the more common coarse one but that would only matter if you wanted to put a pipe connection or different tap on the outlet. Both sizes are easily obtained but pays to wait until you know what you have.
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