Another SCWD MOD

[ejmeier]

I already cut my SCWD open at the bottom, but I think this might be even better. My drum thing was snapped in half too, but I just super glued it back together. But, it seems like this is a very common problem, and it might be just another accident waiting to happen.

I have been thinking about completely re-doing the SCWD in an all PVC/ABS housing. I'm still wondering if its doable. A lot of stuff has all ready been swapped out and DIYed on the SCWD, so why not build one entirely from scratch? Only the gears and what holds the gear-compartment in place are the items that would be taken from the SCWD.

Maybe if I'm bored someday. That might be a long way off though.

 

[Giovanni]

d.can82,

I have thought about the 1" MOD. I am not sure how big you can go. If You go that big, the drum will have to be made taller to shut it off, not a big problem though as there is room in the top. Also if there are 3 -4 outlputs, this would incease the flow anyhow. Only the bottom would need to be made bigger to accomidate the increased output. I already have a MOD in mind that will alow for better in flow and adjustment for switching frequency. Stay tuned over the next week or so and you will see what I have in mind.

I am off to work tonight and for the next five nights so things will slow down for a few days.

 

[kenny77]

nice work.
I always wanted to know how the SCWD work. ANd now that I see it from inside I understand less.

Can somebody explain me how the drum work. And why the drum have those holes. What is the purpose and how does it inprove it?

 

[Giovanni]

kenny77,

I just got home from working all night and am very tired, but here is goes. The holes in the drum alow the water entering from the bottom to pass to the top. At the inlet there is a little turbin that turns a set of gears which turn the drum. The drum is a half circle and as it turns it blocks off one of the outputs. Stay tuned and you will see the complete workings. Heck I may even make a video. We will call it Mystery of the Black SCWD revieled. Forever will be gone the days of seeing this thing as a magic black box of great mystery. HEHE. I have been up way to long.

 

[ejmeier]

Re: Another SCWD MOD

<a href=showthread.php?s=&postid=7350297#post7350297 target=_blank>Originally posted</a> by ICURN
The hole in the middle has 4-20 threads.

Do you mean 4-40 threads?

 

[fat-tony]

http://www.reefcentral.com/forums/showthread.php?s=&threadid=815716

here's mine that has some of those pic included

 

[Giovanni]

ejmeier,

Sorry it has 1/4-20 threads.

 

[Giovanni]

Necessity is the mother of all invention

Necessity is the mother of all invention

"Necessity is the mother of all invention." Unknown Author

This all started because my original drum had split, and necessitated the need to open and fix my SCWD in the first place. The split was through the threaded part of the drum which meant that the gear box no longer had enough grip to turn the drum. I tried to glue a piece of ABS to the original drum but it would not glue for some reason. When I discovered this, I decided to make a new one. One I came up with a new drum I felt would hold up, I knew I had to make the top with a wide mouth design to get the new one in. I headed to Lowe's to see what I could use. I knew the SCWD was made of ABS and my local Lowe's just added a new ABS section in the plumbing department. I was in luck.


I will start by showing the making of the drum.

 

[Giovanni]

The New drum

The New drum

The drum is made of a 1 1/2 inch PVC plug with a flat bottom.

1. Locate the center of the plug on the bottom side. It is important to get it close so that the drum will turn true in the SCWD and to be wedged against the side and bind. It does not have to be perfect, and if your first one does not work, they only cost $1.27 at my Lowe's.

2. Use a 1/16th inch drill bit to drill the hole. Starting with a small bit will keep the hole from moving on you when you drill it.

 

[Giovanni]

The New drum

The New drum

3. Finish drilling the whole with a 3/16 bit. Be careful to drill your hole perpendicular to the bottom of the plug. If it is not, it will wobble as it turns in the SCWD.

4. Now use a 1/4-20 tap to cut the threads that will hold the drum in place on the OEM SCWD gearbox. The gearbox already has the 1/4-20 threads. Thanks goodness the manufacturer made them standard! The gearbox need not be removed from the SCWD as I will show when I do the final assembly.

 

[Giovanni]

The New drum

The New drum

5. Now mark a line 3/4 inch from the bottom all the way around the plug. I did this buy using the old drum a rest for my pen and turning the plug 360 degrees.

6. Now drill about 5 3/8 inch holes around the center of the plug. If the new drum remained solid, when the water entered through the bottom of the SCWD, it would be restricted. I could have removed half of the plug the way the OEM drum was designed, but it just did not feel balanced to me. I chose to leave it round and drill the holes. See the photo at the start of the tread comparing the OEM drum with the one I made.

 

[Giovanni]

The New drum

The New drum

7. Now cut the plug in two on the side of the line opposite of the bottom. Leave the line. If you want you could even make the drum taller. There is room and if you opt to make the outputs bigger with me later, you will not have to make a bigger drum.

8. Now mark the lip that is left on the plug so that it is divided in half. I used the OEM drum as a guide. You will be removing a "C" shaped section of the lip. This allows the water to flow while the part the is left on the opposite side block the flow of the water. As it turns, it alternates the flow of water from one side to the other. In a later MOD I will make the SCWD with 3-4 outputs and show how changing the size and placement of the lip can change the timing and duration of flow to any particular output can be changed.

 

[Giovanni]

The New drum

The New drum

9. Start removing the C section buy cutting down perpendicular to the bottom. Only cut to floor of the plug. You will then cut along the floor from the outside edge to the first two cuts to remove the C section.

Look close at this photo and you can see the perpendicular cut I have already made.

Here you can see the C section removed.

You now have your new drum. I will show later in the assembly process how it simply screws onto the gearbox in the SCWD.

 

[ejmeier]

Did you have to ream out any area on the inside of the SCWD to get the 2" cleanout adapter to fit in the top?

 

[Giovanni]

ejmeier,

No it is a flush mount. Sorry I don't have time to elaborate now, working another 13 hour shift tonight. I will be detailing the lid MOD in a few days when I get the new SCWD. I will have detailed photos then.

 

[douggiestyle]

icurn or is it giovanni?

that is a wonderfull diy as well as tutorial.

thanks

 

[coralnut99]

ICURN / Giovanni gets a big old standing ovation from me too on this one. Great job, and thanks a million for sharing in the midst of what seems to be a hectic and tiring schedule.

How has the modded scwd performed so far? In just looking at the new drum, it would seem to be heavier, and have a slightly different flow pattern from the OEM drum.

Thanks again!

 

[NCNBilly]

Nice! I have two of these lying around I've been meaning to send back - both died within 6 months. The one I'm using now has been going strong for about that so it'll be nice to keep spares around that I can clean.

Kudos to you!

 

[Giovanni]

coralnut99,

The SCWD has preformed great. Seems to work just the same as when it was new.

Concerning drum design, I believe that if I add more or larger outputs, the holes in the drum may become the bottle neck. I do have a work around for this though. One could add an extra input in the top. The bottom one would be for driving the gearbox and the top one would be for the added flow. The lid could be made to have an input very easily. This would eliminate the bottle neck of the water traveling from below the drum to the top of the drum where it exits through the outputs. This may be why others who have added larger input and output ports have experienced only modest flow increased. A pair of ball valves could be used to regulate how much water goes in the top verses the bottom. This would have the added benefit of allowing the switching rate to be changed. The less of the water that goes in the bottom, the slower the switching rate. If all this is not clear, I will clear it up when I document the port size and number increase MOD. Maybe someone could calculate the flow potential for five 3/8 inch holes for me? That is what is in the drum.

Well it is off to bed, three more nights to go. I should have the new SCWD Wednesday and I cannot wait to get the lid mod documented and start on the other mods. I also have a new rio hf32 pump coming that I will use to test flow rate increases and total flow increases. Should be fun.

 

[ejmeier]

ICURN, I think you're right about the bottle neck at the drum. But really, the SCWD is very tiny to start with. Forgive me if my math is off, but:

R^2 * PI = A
.1875^2 * 3.14 = ~.11
And 5 * .11 = ~.44

So, five 3/8" holes will flow about .44 square inches of flow. For reference, a 3/4" pipe (assuming it is exactly 3/4" ID) has ~.44 in^2 and a 1" pipe is .785 in^2. So its about the exact same area as a 3/4" pipe (good guess when you were drilling the holes!) But the flow is nearly doubled when you move up to a 1" pipe, so it would quickly become a bottleneck if you tried to go with more flow.

But, time permitting, what I am going to do on Monday is build a SCWD from scratch, ditching the restrictive SCWD body. That way I can use a full 2" PVC body, and make a bigger drum. The switching time whould be a lot slower too, but I won't say anything more until I actually do the deed.