Zephrant
Premium Member
DIY Monster Beckett
Over the last few days, I built a large Becket Skimmer for my system (200 gallons currently, planed expansion to 500 gallons). I had made a much smaller downdraft skimmer many years ago, and this is an enhancement on that design.
Equipment used: Table saw with Acrylic cutting blade, router with flush trim and 1/4" round over bits, Vertical Mill with fly cutters, 14-20 tap and misc. hand tools.
I started with the base box. I drew it up in Autocad and sized it to handle the 6" main tube, and the single 3.5" injector tube. I used Weldon 16 to assemble it, and weighted it down to dry. Note that I should have cut the exit bulkhead hole before this step.
(All pictures located on my own server since I can't wait 3 days for them to upload to RC.)
Next was the fabrication of the top plate. I wanted to try a few tricks, so bear with me. It will all be clearer in a picture or two. I used a fly cutter to cut the two 3.5" holes, then used a 1" forstner bit to cut holes around one of them. I had to sand the hole a little to get a nice tight fit against the tube.
I measured out the 3.5" tube, cut 45 degree miters on them, and pushed them though the holes.
Next up was welding in the cross piece- This will force all the water that comes down the injector tube well up in to the 6" main tube, reducing greatly the bubbles in the output stream, and providing over 100" of water/air contact time.
Next up was the flanges. I drew up a pattern of eight bolt holes on a 7" circle, printed it a full size, and glued it down to a 8" square piece of acrylic. My mill has a rotary vice that allows me to spin it to any angle, then lock it down. I used the printout to align the mill to the exact center, then used the degree markings to drill the 8 holes for the first pair of flanges. The next part was trickier. I screwed the acrylic to the wood underneath and removed the clamps. Using a router bit in the mill, I routed the outside 8" edge using 2 passes. This gave me a clean edge, and as long as I was not "climb cutting" was reasonably safe. I finished off this set of flanges by using a fly cutter carefully adjusted to the 6" OD to cut the centers out of the pieces, then tapped the threads. This made the top flange on the main tube, and the flange the lid bolts to on the collection cup.
I completed the rest of the flanges- the 6" to 3.5" adapter flange on the base of the collection cup, and the lid on the top of the collection cup, and started gluing things together. Things went fast at this point. I was not able to make the "key-holes" that are a feature of other skimmers, but I think I have that figured out and will try it next time. I added in a 1/2" discharge port and completed the collection cup. I used a mixture of Weldon 4 and Weldon 16, depending on how tight the joint was. The bolts are Nylon 1/4-20.
I centered and attached the 6" tube to the base, and attached the base to the box. I water tested the 3.5" "U" first, and it was water tight. Then I caped the 1.5" bulkhead and water-tested the rest, and it held water too! I dried out everything well, and the next day finished routing and final assembly.
Next up was the beckett injector. My design goals were to run about 1000 GPH though the unit, and have minimal bubbles exit the unit, hence the tall design. I also wanted the beckett to be easily cleanable because I have heard they can clog up over time. I determined that a 3" PVC cap fits perfectly over 3.5" OD Acrylic tube and decided to use it. Until this point I had not used any PVC which gave it a more professional finish, but the time involved to make my own caps was not worth it. With a few adapter pieces, I came up with a design that uses a friction fit to hold the beckett in. In about 10 seconds I can have the top off the injector column and the beckett removed for cleaning, without any tools. Since this combination of a down-draft and a beckett pulls a slight vacuum, I added a CPVC air valve so I could control the amount of air entering the column.
Some more final pictures:
Top assembly:
Finished, ready for transport:
Running on my system:
Gunk from the test run:
I ran it for about 20 hours, then tore it down to take it in to the LFS (Ocean View Aquatics) for show and tell. I'm leaving it down there for a week or so then hope to take it over and set it up on a large tank and see if it will out-perform a commercial model.
Over all size: 49" tall, minimum of over 100" of water-air contact time, with a water capacity of around 8 gallons.
From the calculations I did, I expect this skimmer to easily handle a 500 gallon system. I will be building an auto-shutoff collection container for it next, then maybe on to a kalk reactor.
Zeph
Over the last few days, I built a large Becket Skimmer for my system (200 gallons currently, planed expansion to 500 gallons). I had made a much smaller downdraft skimmer many years ago, and this is an enhancement on that design.
Equipment used: Table saw with Acrylic cutting blade, router with flush trim and 1/4" round over bits, Vertical Mill with fly cutters, 14-20 tap and misc. hand tools.
I started with the base box. I drew it up in Autocad and sized it to handle the 6" main tube, and the single 3.5" injector tube. I used Weldon 16 to assemble it, and weighted it down to dry. Note that I should have cut the exit bulkhead hole before this step.
(All pictures located on my own server since I can't wait 3 days for them to upload to RC.)
Next was the fabrication of the top plate. I wanted to try a few tricks, so bear with me. It will all be clearer in a picture or two. I used a fly cutter to cut the two 3.5" holes, then used a 1" forstner bit to cut holes around one of them. I had to sand the hole a little to get a nice tight fit against the tube.
I measured out the 3.5" tube, cut 45 degree miters on them, and pushed them though the holes.
Next up was welding in the cross piece- This will force all the water that comes down the injector tube well up in to the 6" main tube, reducing greatly the bubbles in the output stream, and providing over 100" of water/air contact time.
Next up was the flanges. I drew up a pattern of eight bolt holes on a 7" circle, printed it a full size, and glued it down to a 8" square piece of acrylic. My mill has a rotary vice that allows me to spin it to any angle, then lock it down. I used the printout to align the mill to the exact center, then used the degree markings to drill the 8 holes for the first pair of flanges. The next part was trickier. I screwed the acrylic to the wood underneath and removed the clamps. Using a router bit in the mill, I routed the outside 8" edge using 2 passes. This gave me a clean edge, and as long as I was not "climb cutting" was reasonably safe. I finished off this set of flanges by using a fly cutter carefully adjusted to the 6" OD to cut the centers out of the pieces, then tapped the threads. This made the top flange on the main tube, and the flange the lid bolts to on the collection cup.
I completed the rest of the flanges- the 6" to 3.5" adapter flange on the base of the collection cup, and the lid on the top of the collection cup, and started gluing things together. Things went fast at this point. I was not able to make the "key-holes" that are a feature of other skimmers, but I think I have that figured out and will try it next time. I added in a 1/2" discharge port and completed the collection cup. I used a mixture of Weldon 4 and Weldon 16, depending on how tight the joint was. The bolts are Nylon 1/4-20.
I centered and attached the 6" tube to the base, and attached the base to the box. I water tested the 3.5" "U" first, and it was water tight. Then I caped the 1.5" bulkhead and water-tested the rest, and it held water too! I dried out everything well, and the next day finished routing and final assembly.
Next up was the beckett injector. My design goals were to run about 1000 GPH though the unit, and have minimal bubbles exit the unit, hence the tall design. I also wanted the beckett to be easily cleanable because I have heard they can clog up over time. I determined that a 3" PVC cap fits perfectly over 3.5" OD Acrylic tube and decided to use it. Until this point I had not used any PVC which gave it a more professional finish, but the time involved to make my own caps was not worth it. With a few adapter pieces, I came up with a design that uses a friction fit to hold the beckett in. In about 10 seconds I can have the top off the injector column and the beckett removed for cleaning, without any tools. Since this combination of a down-draft and a beckett pulls a slight vacuum, I added a CPVC air valve so I could control the amount of air entering the column.
Some more final pictures:
Top assembly:
Finished, ready for transport:
Running on my system:
Gunk from the test run:
I ran it for about 20 hours, then tore it down to take it in to the LFS (Ocean View Aquatics) for show and tell. I'm leaving it down there for a week or so then hope to take it over and set it up on a large tank and see if it will out-perform a commercial model.
Over all size: 49" tall, minimum of over 100" of water-air contact time, with a water capacity of around 8 gallons.
From the calculations I did, I expect this skimmer to easily handle a 500 gallon system. I will be building an auto-shutoff collection container for it next, then maybe on to a kalk reactor.
Zeph
