Ok so its time for an update.
Things have been progressing nicely. so this is where things are at at present.
The image below shows how the tidal transference system works.
In the image above,
Pump A controls the transfere of water 'from' the main display, into the side compartments that are linked by a common balance pipe. (Generating the low tide phase)
Pump B Controls the transference of water 'back' to the main display. (generating the high tide phase)
Both pumps are controled by computor for set durations with maximum flow rate limited via control taps. In both cases (after some testing and setting of the valves) it now takes a total of 3 hours to transfere the maximum movable volume to or from the main display, giving a 6 hour rise and fall over a full tidal duration.
In the real world it would be more realistic to have a full 12 hour tidal rise and fall, but I have to think about running water from the display to the sump for at least half the time, so 2x 6 hour tidal cycles with 2x 6 hour tank to sump (high tide) phases between are at this point deemed more practicle.
Both pumps are also backed up on industrial maintanance free 3kw float/bilge pump switches that negate the possibility of a pump over running, to the degree it runs dry, or over fills the side compartments. These float switches are basically completely sealed ball bearing tilt switches that move up and down with a rising or falling level, switching contacts as soon as they hit a certain angle. They are also quite large and boyant so they arnt affected by coraline algae growth or perching snails etc and have no moving parts that need servicing unlike the normal aquatic float switches we see, that use a float that slides up and down a shaft.
Additionally to this, the main return pump will be triggerd by a third maintanance free float switch that will only allow the return pump to come on once the tank is back up to its full high tide setting, ready to flow over the weir, through the sump system and back to tank.
The second reason I wanted to use the float switches is that it allows me to add in the monthly rise and fall of the luna cycle.
Although im still working on the exact timings etc, the general premis is that over a daily cycle the tank will run 2 tidal phases of 6 hour duration, 12 hours apart.
The amount of transference (total daily drop and rise in water level) will vary, starting of at the beginning of a 28 day period with a small degree of transference, (maybe an inch or two drop on each tide at the start and end of each cycle) peaking in the middle of the 28 day period with a maximum drop of around 9" each tide over the full 6 hours, reducing again towards the end of the 28 day period where the cycle starts again.
With the switches in place, it allows me to transfere water out for say 15 min each time at the start of the month giving only a small drop in water depth per bi-daily tidal cycle, but i can still run the return cycle for longer. Even though it only takes 15 min to refill again, the switch overides the controler. (this basically saves me having to mess around exactly matching whats pumped 'out' to whats pumped 'back' using two different pumps that may have very slightly differing return rates...basically the switches soak up the variance defaulting the system back to full high tide at the end of each cycle 'regardless' of how much or how little water has been moved, or how long the pumps have been 'asked' to run for via the controler to counter any variances. (im thinking here of gradual reductions in flow rate over long periods as bio buildup in the pipes etc gradually reduces flow rates slightly)....I can simply tell the pump that fills the system back up, to run for an extra 15 min over and above what it 'needs to' with the float switch turning it off regardless as soon as the system is back to full high tide. 6 months down the line, it may need 10 of those extra 15 min due to flow reduction in the pipework, but it will still trip off when required.....It just saves alot of faffing about trying to get things too exact which is a virtual impossibility imo.
So, wheres it all at at the moment....well, the tank is now built and full of fresh water for testing, and the full tidal rise and fall has been running twice a day for the last week or so whilst Ive been fine tuning the float switch limits etc.
Ive also been playing with the wave plunger which is now installed at the back of the tank, although still without motor as thats another job that still needs sorting. plus ive decided that the 50mm feed pipe isnt big enough to allow smooth transference of water backwards and forwards..
Basically I found that having a 50mm pipe plumbed to a 150mm plunger barrel meant that water had to accellorate down the pipe as it was pushed/pulled causing a fair bit of resistance at the beginning and end of each stroke...basically the water rushing along the narrower pipe was carrying so much innertia it wanted to carry on, even though the plunger was trying to change direction...so the cure will be an upgrade prior to final filling to 3" pipe.
despite this though. on testing I was still getting a good 4" wave front to back when pumping manually, so i recon a good 6" wave is possibly on the cards once its all re plumbed and dialed in on a proper motor with exact timing.
Here's a quick Video of the wave action during testing.
Lets get jiggy wid it..
looking along the tank from one end...to give an idea of perspective, the angled wier plate on the far left is 6" high. Note the wave height difference between the front of the tank (left) and back of the tank. (right)...which as i suspected it would be, is caused by the tank narrowing towards the back compressing the wave as it travels.
So, thats how things stand at present...still lots to do.
I'll bang up some shots of the tank and transfere sections tommorow after ive recharged the camera.
Kind regards and a very happy new year to all the MR members and admin...
