Another SCWD MOD

[Jaygar]

I agree with the math re the area of the 5 holes and the 3/4 in. pipe/hose except for the final step. I get .552 sq. in. But I'm not sure that 3/4 is the relevant diameter to be working with since the inside diameter of the inflow and outflow stems on el scwd is 7/16 in. , not 3/4 in. I would use 7/16 (.4375)=> .4375/2=.2188 =radius
=> .2188^2= .0479 => .0479x3.14=.1503 sq. in.

.552/.1503=3.673

So, my calculation is that the five holes combined provide a bit over 3 1/2 times as much cross section as that of the inflow and outflow stems. Given the spinning and the turbulence I suspect that the actual flow capacity is less than what would be able pass through the five holes if they were static. This may not be a significant effect. But even if it were to cut the flow by 50% the five hole disc would still accomodate the flow through the oem stems.

Perhaps there's a hydraulic engineer lurking on this thread who could tell us what assumptions we should be using - if it really even matters, given the imprecise world of DIY.

Regardless of all this math stuff ICURN's work and everyone else's comments are really great. And it's all been very helpful to me in making my decision to employ a SCWD in my system.

Jay

 

[Giovanni]

Eric ,

Adding an input in the top, will eliminate the flow restriction through the drum all together. No need to reinvent the wheel, just improve the tire, axle and bearing for higher speed and side load.

Jay,

I think you are correct about the turbulence cutting down on the flow. Comparing the flow to a 3/4 inch pipe only under ideal conditions neglecting resistance etc. Not a problem is the drum is taken out of the equation.

This thing is going to look like an artificial heart when it is done.

 

[Barto]

<a href=showthread.php?s=&postid=7365469#post7365469 target=_blank>Originally posted</a> by ICURN
This thing is going to look like an artificial heart when it is done.

Introducing: the Jarvic 5100 MWCSD
(Modified Water Current Switching Device)

Sorry, couldn't resist

Great mod, Thanks!

 

[psst]

great job .. and nicely documented.
thanks for the input and pix.

so after all the test and calculations ... with the mod, does the flow gets weaker? and is it still 10 sec on each side or did it change? shorter or longer time

 

[coralnut99]

Icurn, Just a thought on your basic design, since you're concerned about the holes being an issue. Have you thought about going to essentially the original layout for the bottom of the drum? From the photos, it looks like the PVC is a lot more substantial than the original abs drum, and if you cut the bottom to somewhat emulate the original, you'd be improving it by simply going to better matrials. Just a thought.

 

[Jaygar]

Coralnutt99,

Now you've got me thinking. In the case of impellars in motors where the speed of revolution is very fast the design is probably important. But the more I think about the actual mechanics of the SQWD the more I have convinced myself that since the drum is rotating in the range of only three to ten cycles per minute the limiting issue is most likely the total area available for water flow. I'm just speculating, and I suspect that the holes and the hemicircle give equally satisfactory results given the relatively slow flow we're dealing with here. But everything else being kind of equal here, I think, I kind of like the esthetics of the holes. You know - balance & symmetry - like a beautiful sculpture. (I think I'm going to be sick, lol.)

Jay

 

[Giovanni]

psst,

The flow at about 600gph is not decreased with the mod as is. The concern is that when we approach 1000 or more gph it will drastically be reduced. I have not gotten as far as modding it for that much flow. Heck I do not even have the lid mod details up yet.

As for the drum, I to have this weird affinity for balance and symmetry. I work in an intensive care unit and my patients always seem suppressed by my obsession with the need to have all my IV lines, monitor lines, etc all so neatly arranged. I am mostly a pig at home with most things, but not with my patients nor my reef tank.

 

[coralnut99]

Icurn, at least you have your priorities straight!

 

[pvtschultz]

<a href=showthread.php?s=&postid=7368803#post7368803 target=_blank>Originally posted</a> by coralnut99
Icurn, Just a thought on your basic design, since you're concerned about the holes being an issue. Have you thought about going to essentially the original layout for the bottom of the drum? From the photos, it looks like the PVC is a lot more substantial than the original abs drum, and if you cut the bottom to somewhat emulate the original, you'd be improving it by simply going to better matrials. Just a thought.

Another thing that you could do is move the axis of the holes out further towards the sides and drill 6 larger holes. Then pair up the holes and connect them creating oval like ports. This will leave you with 3 spokes instead of 5 creating a much larger opening.

Holes in a flat plate do remove a considerable amount of head from the pump decreasing overal flow. This generally goes up with about the square of the flow rate so doubling the flow will increase the head loss by 4 times.

On another note, please be very carefull about what you do with the end product. Who ever makes the SCWD has a patent on the turbine assembly and if you are taking their product, modifying (or copying) it and then reselling it for profit you may have legal troubles that you won't be able to afford. Doing it for yourself is one thing, but I wouldn't suggest doing it for others.

 

[ck1]

Damn-
I had a scwd break on me a couple of months back, I wish I would have saved it to do this mod.

Chad

 

[Giovanni]

SCWD LID MOD

SCWD LID MOD

The SCWD Lid MOD

After coming up with a new drum, I needed to get it in there and keep it clean. I decided that the best way was to add a lid to my SCWD. Here is how I did it.

1. You will need to buy a 2" ABS cleanout adapter. It should have a shoulder like the one in photo one. The reason for this is to give you a larger surface area to glue the lid to the SCWD. This will become clearer as we get the mod done. You will also need a threaded plug to act as a cap for the SCWD. I purchased mine from Lowe's for just a couple of bucks total.

 

[Giovanni]

SCWD LID MOD

SCWD LID MOD

2. First start buy drilling a 3/8 inch hole to get your dremel bit in so you can rough cut the 2 inch opening in the top of the SCWD. Be sure not to drill to close to the edge. If you do you may damage the side of the SCWD and ruin it. Make sure not to let the drill go in more than an inch deep and ruin the drum of gears of the SCWD.

3. Use your dremel to rough cut the hole making sure to leave a little material around the inside edge. This is a messy process and it would be to hard to get a nice finish on the inside edge at this stage.

 

[Giovanni]

SCWD LID MOD

SCWD LID MOD

4. Next clean all the extra melted and cut away material and do a final clean up job of the inside edge. Turn your dremel down and go slow. You want it to be nice and smooth. I did my final clean up with 320 grit wet/dry sandpaper. At this point you can remove the old drum by turning it counter clock wise to unthread it from the gearbox.

Here is a photo of the gearbox and drum removed.

 

[Giovanni]

SCWD LID MOD

SCWD LID MOD

5. Now you have to smooth/surface the top so that it will have a nice flat surface to glue the new lid to. I did this with a file to get a rough cut and then finished surfacing it with a piece of 320 grit sandpaper on a piece of glass.

 

[Giovanni]

SCWD LID MOD

SCWD LID MOD

6. The SCWD is now ready to accept the new Lid so we must MOD the ABS cleanout adapter to fit the SCWD. Start by rough cutting the bottom part of the adapter off at the ledge. Leave a little of the bottom so you can make a nice finished surface. The reason for using this type adapter, which is stepped instead of just straight, is so that there will be a bigger surface area to glue to the SCWD. You will see this better in a few steps.

 

[Giovanni]

SCWD LID MOD

SCWD LID MOD

7. Now surface the adapter the same way you did the SCWD so that you have a uniform look and it is nice and smooth. It is important to do this so that the SCWD and adapter will glue without voids, which would have great potential to leak. Once this is complete, the SCWD and lid are ready to glue together.

 

[Giovanni]

SCWD LID MOD

SCWD LID MOD

8. Use a generous amount of ââ"šÂ¬Ã…"œOatey All purpose cement for PVC, ABS, CPVCââ"šÂ¬Ã‚. Once you apply a nice coat to both pieces, allow them to sit for about 20 seconds, then coat them again. Quickly put the two parts together pressing firmly and giving a slight clockwise twist. Make sure the inside of the two pieces are aligned all the way around. Also hold some pressure for about 1-3 minute while the glue dries a little bit. Place the SCWD on itââ"šÂ¬Ã¢"žÂ¢s top and allow it to sit undisturbed for 24 hours. After 24 hours install the drum by carefully screwing it on with a clockwise motion being careful that it threads on straight.

 

[acan_guy]

Looks great. I am still looking for used and broken scwds for my gf new tank.

 

[Giovanni]

Next I am going to plumb a rio hf32 with one inch pvc, pump 10 gal of water and time it. Then I will add a one inch T and time it. Then replace the T with the SCWD with stock drum and modded drum to establish some base line data. I will then add the input to the top and retest. Then add one inch ports and test. Finally I will add a third and fourth outputs and test. The rio claims better than 1900 gph at 0 head. I will try modding the SCWD to achieve less than 10% loss at greater than 1200gph flow. This is assuming the rio will pump that much.

 

[coralnut99]

I hereby nominate this thread for the RC DIY hall of fame!

Great job, and thanks for the step-by-step. Couldn't possibly be any clearer.