How would one know there was biofilm on the screen? Is it a brown film?
Thank you for the explanation.
Installed the drum to see how it fit - it does - now. It was put in bare because fully assembled it's too awkward to handle; one design goal was to be able to work on the unit without assistance. Once installed it became apparent that the rollers were too narrow; if the drum moved away from the front port slightly it would drop off all four rollers and getting it back on was a pain. The rollers will be widened so the drum stays on regardless where it is in the box. While another roller will keep the drum butted up against the front port, it won't always, like during filter screen changes when having it fall off the bottom rollers would be really inconvenient.
This was the chance to test whether the hold-down screen could be installed in-place - it went in fine. The actual filter screen won't be installed until the unit is in-place. The tank was designed large enough so that the hold-down screen could be backed away from the drum far enough so that the filter element could be fed onto the drum in-place; this way the drum doesn't have to come back out.
With the overhead lighting just right it was surprising to be able to see the distortion caused by welding heat. Half-inch material is substantial, but so is welding distortion!
In an emergency it can be converted to a washing machine...
Last edited by kimini; 1 Week Ago at 11:09 AM.
Would it be feasible to cut a "groove" into the roller that the drum would key into? This should help prevent the drum from running off the rollers.
I thought of it but the few times I've tried it in other applications, the roller either jammed or caused the thing riding on the rollers to climb up out of the groove. It may work fine but I'm too chicken to try it in this application.
What about increasing the height of your roller mounts 1/4" - 1/2" above your roller? This way there is a limitation on how far the drum will move away from the front. Only issue might be a clearance issue with your screen clamp.
I know you used rollers, but you ever considered casters? You can notch out a middle channel on the wheel and it should fit the width of the drum ring. No movement and super strong.
Widened the drum rollers so now the drum can't fall off, though it can't with the thrust bearing in place but it was bugging me.
To plan the spray bar, a couple tests were run with the bar from the old RDF. With the nozzles 2" apart, the spray bar needs to be at least 3" above the drum for 100% coverage.
Next, the drum drive motor was mounted. The shaft is too short to align the sprockets when mounted to the outside of the enclosure. Either the motor has to be inset or it needs a shaft extension. I was concerned that the expected side loading would complicate it and also need a bearing at the far end, so a port was cut and an inset panel welded to the inside of the enclosure. The motor will eventually be enclosed in a Tupperware container to protect it from spray and rain.
The chain was added and the motor temporarily run off a car battery to see how it worked. It was a reminder that a chain tensioner isn't optional because the chain is always too loose or too tight. Running it now was also a chance to see how long half a rotation takes, which was 12 seconds. The battery may have been weak because the math said it should have been 10 seconds, but the variation's not a big deal.
Last edited by kimini; 1 Week Ago at 12:23 PM.
If you had to build this rdf for a pump fed application, how would you approach the water level detection issue? I'm looking for a way to get a proper water level probe to work for my design idea.
I've been thinking about the float switch in my gravity-fed situation and I think this idea could work for you as well:
Have a float on both sides of the drum (inlet and outlet) connected to a "teeter-totter" sort of thing with a tilt switch on it. That way if the water level in the pond changes - which it always will do - both the inlet and outlet levels rise or drop the same yet wouldn't cause false cleaning requests. As far as the rest of the assembly goes it would probably require a full enclosure with a watertight cover. I'd be concerned about how much pressure is being applied though since that pressure is applied over every square inch.
Lets say for example the RDF is working fine and has only 0.1 psi difference across the screen - that's pretty much nothing. But let's say in a pressurized setup, water pressure is being pumped into the RDF with oh, 2 psi head because the outlet goes up 4-5 feet. That's 2 psi across ever single panel. Let's say that the entire housing is 36" wide and 24" tall, so that means that one panel alone has 1728 lbs of force pushing on it. Whatever it's made of will need to be really robust.
Last edited by kimini; 1 Week Ago at 05:54 PM.
Any update on rdf? How much more was done?
Do you have a part number for that gear and chain for the drive motor
The chain, like many of the parts, is from McMaster.com, 6846K4
Regarding the gear, I had it custom made. I used this motor: http://www.makermotor.com/brush_gearmotor.html. In hindsight, the cost of the motor, chain, and gear ended up being enough that a direct-drive gear motor (meaning that it drives the drum axle directly with no need for a chain or gear) could have been used. Note that Makermotor makes a lot of different motors which could be used, both 12VDC and 115VAC.Something like this maybe, http://www.makermotor.com/Rotisserie_motor.html
Last edited by kimini; 2 Days Ago at 09:28 AM.
This weekend's progress:
Spaced the drive sprocket up another 0.25" away from the drum for better motor/drum alignment:
Drum seal, Mcmaster #2614T38, held in-position by a fiberglass strip. I may add more screws to keep the rubber from being able to slide out sideways in between the existing screws.
The seal only needs to extend higher than the maximum incoming water level.
Front outset panel provides clearance for the water pipes so they don't interfere when installing or removing the drum. The partial panel is for observation of drum operation and maintenance. The upper portion will be removable and also serves as the mount for the 48" drain pipe assembly.
Figuring out placement and orientation of the slide valves, done now to determine port locations for the two 4" BD and 3" skimmer inlets.
Close-up of above. The thinking is (was) that the BD water enters from below, with the first Tee feeding a 3" drain to waste so that the BDs can be purged (and partial water changes) by opening the valve momentarily. The upper Tee (which will be changed to a street sweep) feeds the water to both the RDF and to a standpipe. The standpipe is so that a chimney cleaner element can be fed in to clear the BD pipes.
I changed my mind later, relocating the 4" valves to be at the bottom right on the inlet pipes. That way, if the 3" purge valve fails open, the flow can be shut off without draining the pond!
Last edited by kimini; 2 Days Ago at 04:50 PM.
Looking at that last picture, I see an issue with the 2" drain valve because it's connecting to a threaded bulkhead port. If it has to be unscrewed, it'll be blocked by the 3" skimmer valve above it - all the others don't have that issue since they use Uniseals. Good to stare at stuff and try to catch this sort of thing early-on!
I also realized that at some point soon it needs to be leak-checked, probably before the ports are cut.
Last edited by kimini; 2 Days Ago at 05:16 PM.