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Thread: DIY RDF "2.0", The Beast

  1. #201
    kimini is offline
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    10-day update after the motor upgrade: New motor and chain are working perfectly.

    Other news:
    As part of trying to further improve the RDF's reliability, I looked into alternative non-contact sensors to detect water level. The most promising are the capacitive units that can detect water right through the side of even opaque containers and pipes. In case anyone's interested, the candidate sensors are:

    https://www.ia.omron.com/products/fa...75/lineup.html

    http://www.gemssensors.com/level/sin...0-level-switch

    https://www.automationdirect.com/adc...ies)/CK1-00-2H

    (Thanks to Rayrod2030 for the tip on finding the third unit.)

    I ended up going with the CK1 sensor mostly because of how it can be "taught" what empty and full means, plus its output can be programmed on the spot to pull high or low, something the other sensors can't do.

    Once I get past the nerve-racking part of the new pond switch-over I'll try out this unit.
    Last edited by kimini; 2 Weeks Ago at 06:20 PM.
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  2. #202
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    30-day update:
    After the motor upgrade it's just been chugging along, so well that attention could (finally) turn toward finishing the rest of the pond upgrade.
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  3. #203
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    Quote Originally Posted by kimini View Post
    30-day update:
    After the motor upgrade it's just been chugging along, so well that attention could (finally) turn toward finishing the rest of the pond upgrade.
    Great to hear everything is working well!

  4. #204
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    Forgot to mention that it's since been switched over to the new pond, with the clean water it's cycling about once an hour. That said, it doesn't really mean anything due to all the variables involved; flow rate, particulate density, fish load, food load, screen grid size, and drum size all play a part.
    Last edited by kimini; 1 Week Ago at 08:36 PM.
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  5. #205
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    I don't brag about my RDF, instead letting the results - good or bad - speak for themselves. A side benefit is that when a train wreck happens, I don't have to fish my pride out of the wreckage... sigh.

    I was working near the filter yesterday, plumbing in two new SG filters - life was good - when the RDF kicked on like normal, but from the sound, something had failed - the chain came off. This was odd because it's been working great for about a month without a hitch, so what changed? Apparently the chain has stretched, which is normal, but it no longer engages the large drum gear as well as when new - the links no longer dropping easily into the cogs. This is important because this is on the "downwind" side of drum rotation - the slack side. The chain is being counted on to easily drop back into the gear cogs which is no longer happening. I think it's time to up my game...

    I know that "real" RDFs use direct-drive gear motors but chose not to do so for cost reasons, plus the motors aren't all that easy to find. Now I find myself contemplating how I've spent more than what a direct-drive solution would have cost, but complaining about it isn't going to fix anything.

    I've always been nervous about the big gear motor that's running it now - it can easily destroy the entire filter if it felt like it - it has so much torque it simply doesn't stop. My fear is that the chain could get bound up such that the motor "reels in" the drum and breaks it apart, so that's one reason to get away from it. Another is how fussy chain alignment is - if it's off by even 1/16", it can ride up out of engagement, which effectively shortens its overall length. This in turn lifts the drum up off its bottom rollers and applies an enormous torque to the upper roller, bending the entire filter housing. Then there's the stretching issue which is a given, and about the chain not dropping into the gear cogs, that may be due to how the gear teeth were cut (on a water jet) but is something I don't want to chase by dumping even more money on.

    To buy some time I bought another chain of the same type, and in the meantime I'll try to find an appropriate direct-drive gear motor which runs on 12V and turns at 2-4 rpm. The reason to go with 12V is partially for simplicity - it's what the controller runs on - but also for safety. A direct-drive motor mounts on the center axis of the drum where's there's a higher chance of it getting wet. Even with GFI outlets I don't want 120VAC anywhere near the water.

    There is actually a bright side to this: building a large RDF means that the drum doesn't need to be fully submerged to provide a good flow rate. The drum can be run submerged slightly less than half way, which completely avoids having to deal with a water seal. This is a big deal as far as simplicity goes. Time will tell.
    Last edited by kimini; 2 Days Ago at 05:08 PM.
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  6. #206
    Grumpy is offline
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    Would a chain tightener work with your setup? Keeps constant tension on the chain.

  7. #207
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    Lots of high torque low RPM 12 volt units available for use on large portable BBQ rotisseries. If it will turn a whole pig a drum filter shouldn't be a problem.

  8. #208
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    Quote Originally Posted by BWG View Post
    Lots of high torque low RPM 12 volt units available for use on large portable BBQ rotisseries. If it will turn a whole pig a drum filter shouldn't be a problem.
    Hah, you beat me to it - I came back to say that that's exactly what I found and have ordered, http://www.makermotor.com/12V_variab...ear_motor.html

    The nice thing is the coupler, allowing it to be attached to a main shaft that extends into the drum.
    Last edited by kimini; 2 Days Ago at 11:34 AM.
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  9. #209
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    Quote Originally Posted by Grumpy View Post
    Would a chain tightener work with your setup? Keeps constant tension on the chain.
    I have a chain tensioner which worked but things had progressed to the point where it would have to be too tight to prevent the chain riding up out of the gear. I realize that spring-loaded tensioners are available but at this point I feel like it's throwing good money after bad (and chasing a moving target). I now feel strongly that a direct-drive setup is the most reliable solution.
    Last edited by kimini; 2 Days Ago at 11:35 AM.
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