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Old 07-22-2016, 01:04 PM   #771
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Water tank cradle

I came up with a design that I'm ok with to hold water tanks. Each tank is possibly 400 lbs. Factor in the weight of the steel itself, and all the tanks and we're looking at close to 2000 lbs of stuff swinging around.

I'll get that low COG with full tanks.

Drawing with tanks fitted


Drawing with tanks hidden, revealing frame mounting. Not shown are the bottom side clamps holding in place, nor the frame crossmembers to keep sliding fore-aft.



Drawing of what needs to get built. Some bits are welded, many parts are bolted. Certain points have mounting tabs welded to support the members assembly.

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Old 07-22-2016, 11:29 PM   #772
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This looks great and will have plenty of water sustain for quite some time!

Question.....
What kind of pump are you going to use? Will you have to prime it, or mount it under the chassis also, so it gets gravity fed? How much head pressure do you think may be required to to get adequate pressure at per say, the shower head?

Just curious, because I'm thinking of mounting an under-body water tank also for use in warmer climates along with an interior mounted tank for colder weather.

I figure by mounting one underneath, I'll have more interior space to play with.
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Old 07-23-2016, 01:29 AM   #773
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I plan on using dual shur flo pressure demand pumps, one for each fresh water tank, mounted at the lowest water level possible. (Down in the bay)

Its about 10 feet of head pressure, which is easily accommodated by one of those pumps for a shower head.

So, yeah gravity primed. I'll set up a cross flow connector to equalize the tanks before the pumps. After the pumps, check valves, then tee them together to a common auxilary pressure bladder. That then feeds the rest of the vehicle.

Normal operation would be both pumps powered.

I have these neat little pwm flow sensors (cheap!), for the fluid status system.

The fluid status is an arduino that takes analog capacitance values of the tanks to get their level. Its basically some self stick metal foil on the side of the tank and a capacitor, with some fancy programming.

That gives me tank levels, and the same controller can cut power to either pump and trigger alarms if they are running with no flow after a certain amount of time.

All this nerd box crap costs some time and effort, but the savings are realized when I can use a cheaper instant hot water heater (Gerard?) They are pretty sensitive to flow rate changes, and I should have the components to intelligently compensate for flow rate changes.

The same system will monitor temperature in the bay. The heaters for the tanks will be very simply wired (no computer) but will alert the control system if its available. Bay will be foam insulated as well.


PS:

Link to flow meter
https://www.adafruit.com/product/828

Capacitive level idea: (there are lots of variations)
http://www.instructables.com/id/Buil...Liquid-Sensor/

Some other considerations:

Using the "odometer" on the pumps can give interesting information, like a failing pump, blockage, and water usage stats.

Its just a matter of knowing initial volume and usage over time to calculate a time vector to empty. (Just like a car computer miles to empty)

Quote:
Originally Posted by MuddaEarth View Post
This looks great and will have plenty of water sustain for quite some time!

Question.....
What kind of pump are you going to use? Will you have to prime it, or mount it under the chassis also, so it gets gravity fed? How much head pressure do you think may be required to to get adequate pressure at per say, the shower head?

Just curious, because I'm thinking of mounting an under-body water tank also for use in warmer climates along with an interior mounted tank for colder weather.

I figure by mounting one underneath, I'll have more interior space to play with.
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Old 07-23-2016, 08:51 AM   #774
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Dude....thanks so much for for the awesome response. You never cease to amaze me with knowledge on how to get things done! I'll be keeping an eye on your water system. I'm looking at using an instant water heater also and was wondering about pressure fluctuations.

What water heater and bladder are you going to purchase? I'm trying to get most of my components purchased.....I'm getting really close to starting the interior!

Oh yeah....thanks for the links. I'll get to research'n!
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Old 07-24-2016, 03:45 PM   #775
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Not sure on the heater, Gerard(sp?) makes a unit that is regarded as OK, but sensitive to flow.

Pressure bladder probably just a whatever from home depot.

Quote:
Originally Posted by MuddaEarth View Post
Dude....thanks so much for for the awesome response. You never cease to amaze me with knowledge on how to get things done! I'll be keeping an eye on your water system. I'm looking at using an instant water heater also and was wondering about pressure fluctuations.

What water heater and bladder are you going to purchase? I'm trying to get most of my components purchased.....I'm getting really close to starting the interior!

Oh yeah....thanks for the links. I'll get to research'n!
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Old 07-24-2016, 03:46 PM   #776
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Random interior shot. Towards the rear. This work is endless.

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Old 07-24-2016, 06:57 PM   #777
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What are you going to use to build your tanks? Plastic, stainless? You probably said it somewhere but I can't find.

Thanks.
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Old 07-24-2016, 08:26 PM   #778
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I got 4x of the 47 gallon plastic tanks on ebay. They're just sort of barely the wrong shape, but close enough that you can't beat the price. If they were about 3 inches shorter and wider to keep the same volume they would have been perfect. Instead, they don't fit under the frame rails without a fight.

I'm using the "no mans gap" between the tanks for the insulation and heater.

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Originally Posted by Vlad View Post
What are you going to use to build your tanks? Plastic, stainless? You probably said it somewhere but I can't find.

Thanks.
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Old 07-25-2016, 01:49 PM   #779
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I'd like to do something similar to sense the level in my fresh and waste tanks. Quite some time back.. around the time when OffGr1d mentioned the capacitive sensor system she'd used on her tanks, I think it was.. I experimented with building my own. I used a rectangular poly tank from Inca Plastics. For the capacitor plates I bought a roll of copper foil tape and arranged it similarly to what was shown in her photos: Two strips oriented vertically on the tank wall, parallel and near to each other. The tape was 1 inch wide and I made two passes, so each plate was almost two inches wide by the height of the tank. I believe I just used the capacitive sense library to hack a quick Arduino sketch and connected these two plates to a digital I/O pin and ground, probably with a resistor in there too. I put only a gallon or two of water in the tank to keep it lightweight, then rolled the tank around so that the amount of plate "under water" varied. While it did work, kind of, it was pretty coarse. The raw data looked adequate for a switch but not even close to good enough to make a level sensor.

I've been meaning to try again with hardware more purpose-built -- a microcontroller with dedicate cap-sense inputs, or maybe a discrete Quantum QProx chip (now owned by Atmel, owned by Microchip). Haven't had time to get back to it though.

Have you prototyped anything for yours yet? I'm interested to see whether maybe I just built it wrong. For example I don't recall what sort of wire I used between the sensor plates and the micro; maybe its inherent capacitance was great enough to swamp out any changes on the electrodes due to water level. Or maybe it's more complicated than what's shown in the instructable you linked because the tank walls are thicker.
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Old 07-25-2016, 02:31 PM   #780
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The setup I've prototyped was very crude - all analog circuit on a breadboard, stuck to a 12 gallon plastic tote and I filled it with water. I, to used the capactitive sense library.

I found that just touching the tote or standing next to it would affect the measurements.

I think using the TI FDC1004 chip makes this far more reliable and easier. (i2c bus)

The other way that I might go about this would require a lot of little wires, but might be fine as well. I was thinking of a 4067 16 channel analog multiplexer, and "listen" to the capactive levels of 16 individual patches on the tank.

This sort of turns creating the tank sensors into an arts and crafts project with lots of little copper squares, but by turning each level into a threshhold measurement instead of one special sensor it will ultimately be less sensitive to interference.

I figure 5x 4067 chips (one used with ttl signal levels to control each of the remaining 4 4067s) and a couple resistors and capacitors. You only need one capactitive circuit for all 64 level sensors. (from 4 tanks)

Measurement period for each capacitor should be relatively quick, approx 100 ms, about 6-7 seconds for all the sensors. This is a fast enough refresh period for me.



Quote:
Originally Posted by family wagon View Post
I'd like to do something similar to sense the level in my fresh and waste tanks. Quite some time back.. around the time when OffGr1d mentioned the capacitive sensor system she'd used on her tanks, I think it was.. I experimented with building my own. I used a rectangular poly tank from Inca Plastics. For the capacitor plates I bought a roll of copper foil tape and arranged it similarly to what was shown in her photos: Two strips oriented vertically on the tank wall, parallel and near to each other. The tape was 1 inch wide and I made two passes, so each plate was almost two inches wide by the height of the tank. I believe I just used the capacitive sense library to hack a quick Arduino sketch and connected these two plates to a digital I/O pin and ground, probably with a resistor in there too. I put only a gallon or two of water in the tank to keep it lightweight, then rolled the tank around so that the amount of plate "under water" varied. While it did work, kind of, it was pretty coarse. The raw data looked adequate for a switch but not even close to good enough to make a level sensor.

I've been meaning to try again with hardware more purpose-built -- a microcontroller with dedicate cap-sense inputs, or maybe a discrete Quantum QProx chip (now owned by Atmel, owned by Microchip). Haven't had time to get back to it though.

Have you prototyped anything for yours yet? I'm interested to see whether maybe I just built it wrong. For example I don't recall what sort of wire I used between the sensor plates and the micro; maybe its inherent capacitance was great enough to swamp out any changes on the electrodes due to water level. Or maybe it's more complicated than what's shown in the instructable you linked because the tank walls are thicker.
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