Three may keep a secret, if two of them are dead. - Benjamin Franklin.
you cant fix stupid no matter how hard you try.
Just an idea, if the drum is a larger diameter with solid sides except for a small section in the center to let in 1- 4" pipe for in feed and a 2" or 3" debris drain then it would eliminate the need for a seal.
Might be harder for maintenance but if you had a removable section of screen for access as in some of the commercial units it could eliminate the seal requirement.
A 20" drum with a 7" opening in the center would leave 6" for water level and 1/2 to spare. Would that give enough scree to filter with?
Also you could then do a partial rotation for cleaning at a slow rotation and expose a clear section for filtering.Would take some programming to set the rotation rinse setting but an Arduino should be able to work.
Thought of that; the problem is getting the debris in the tray out of the unit. I agree that for really large units, that's the way to do it.
Hi Kimini, was putting the idea out for others to try on another build. The tray could be elevated with a drain to the center of the drum, 4" feed in line on one side and a 4" debris drain line out the other. The feed and drain pipes could be used as an axle center shaft as well. Might even be able to find a seal that fits the pipe. Would have to make a removable screen section in the drum for cleaning out string algae.
Last edited by Ronfire; 08-25-2018 at 10:24 PM.
Zoran
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Well, this is a tough post to write, but when I created this thread, it was to show the good - and bad - so people could learn. The bitter pill is that I've decided to replace the RDF due to its debris leak paths that are deemed too difficult to correct in a timely fashion.
As Zac Penn once said, without cutting parts via CNC, it's very difficult to ensure a perfect fit and seal. It's that, but also the underlying design. For example, I made the drum inlet the same size as the outer housing port, the one that the sliding seal mounts to. This means that the seal has no tension to keep it tight. The drum inlet needs to be maybe 1/2" smaller in diameter but I was able to fix the seal and expected that to be the end of the problems.
Unfortunately, debris is still getting through. I know this because I have course screens on the outlet ports which keep moving-bed media from back-flowing into the RDF. Even at 1/4", they slowly collect little bits of debris, so there's still a leak path. I suspect it's how the stainless screen is held against the drum by the large stainless grid. Even though it's tight, there are still places where the screen is not hard up against the drum for whatever reason. Little telltale signs of algae tell that's the likely debris path.
This can certainly be addressed, but the problem is the time it'll take, during which the system is down. If I were retired, I'd be looking forward to getting it sorted, but as it stands, I'm very likely to eat my pride and purchase a commercially-made unit. In hindsight, getting an RDF to work perfectly the first time may be a bridge too far. I know exactly how I'd make the second (third?) one, which I'm confident wouldn't have any issue, but my schedule and time at this point in my life don't allow that. I learned a lot and regardless of what's purchased, I'll know dang well I'll be able to fix it!
Onward and upward.
Last edited by kimini; 09-19-2018 at 04:29 PM.
Which brand have you decided purchase?
The brand that I don't read any complaints about... other than the spectacular thread we had here about a year ago, but I don't count that as valid - Profidrum. It's also because in all the pictures I've seen of it, I always think that's how I'd do it if building the next version.
Last edited by kimini; 09-19-2018 at 09:48 PM.
I'm really sorry to hear about your frustration with the seal leakage, but seeing how much you have put into this build it won't surprise me if eventually you wind up giving it a go at resolving the problem. I know that sometimes when I step back from something I'm really burnt out from struggling with, I'll come back after awhile and come up with a solution. Which ever direction you decide on, I hope it comes to satisfaction for you. I really do appreciate you sharing your build with us, including the problems. You have pointed out potential problems to think about as I work on my own RDF build, and hopefully I have focused enough effort on solving these issues. I have to thank you, and all the other good folks that have freely shared information and their builds with us. To me, that is what makes Koiphen a great forum.