Custom DDC pump top design

LePhuronn · 18 Apr 2017 at 16:27

Hi hi

If you've seen my Asteria II project log, you'll know that I'm having a few minor niggles with my DDC pump placement. To cut a long story short my original requirements had a pump top with ports on the side since I can't realistically use any ports on the top. Not being able to do that is causing a few headaches and untidiness.

So I thought "let's just make my own exactly how I need it".

Having dissected a few DDC tops, it really does seem to be nothing more complex than a 40mm round space in the middle of the top, 8mm deep, for the pump head, the outlet port positioned to the outside edge of that round space (presumably for maximum speed from centrifugal force) and an inlet port put largely anywhere to get the water in and spinning.

Is it really any more complex than that?

The only thing I'm looking at is the vertical placement of the outlet. Some tops, such as the XSPC one, have the outlet port exactly half way over the base of the round area, so half of the "tunnel" is aligned with the space. Other tops, such as the Alphacool top, have the outlet port aligned central to the top's thickness, which would align the "tunnel" mostly away from the round area.

Tips, tricks and advice please? Smashing a forstner and couple of twist bits through acetal isn't likely to be an issue if I take things very slowly with plenty of lube, it's more the placement of everything I want to confirm.

Cheers.

LePhuronn · 19 Apr 2017 at 15:12

After a bit more reading and discussion, I forgot that the inlet needs to feed directly in the center of the impeller, so that changes things up a bit. Quick sketch to illustrate feeds from the side

8mm deep impeller recess with an 8mm diameter feed (yellow)
6mm diameter inlet into the impeller feed; threaded hole vertically offset a bit (red)
8mm diameter outlet (green)

No crazy angles since I'll just be stabbing acetal with some drill bits in a drill press, but is this the sort of thing I should be looking at?

Any takers?

paradigm · 19 Apr 2017 at 15:22

Can't see why that wouldn't work, though I'd try to have less pronounced steps in the changes in diameter, maybe step down in 0.5mm increments between your 8mm and 6mm drilling.

LePhuronn · 19 Apr 2017 at 15:27

That's a rough drawing showing positions to be honest, although it is to scale. Which bits are you referring to for the stepping? I'm not really changing diameters anywhere, other than than getting G1/4 holes for inlets.

Edit: the green outlet? I'm going to have more of an angle from the top of the impeller recess to the actual 8mm tunnel by virtue of the point on the drill bit (wood bits are 90 degree point), I'm probably only using a forstner bit for the recess itself (and possibly the inlet).

JR23 · 19 Apr 2017 at 15:41

The inlet and outlet will be fine, worst case you can file them out a little and smooth the outlet into the main volute. Not sure why you've drawn those little steps, but yeah 11.8mm holes and a slight chamfer to lead the thread in if you feel like it. 8mm is big enough for sure, could do 10mm if you have room in the part though to keep it the same as fitting/tubing ID. Just make sure the outer face is nice and flat so the fittings can seal properly.

But, way more critically, what shape is your volute going to be? That's the main factor in how effective it will be. With a 4500RPM impeller anything with a hole at the outside will work, but it would be nice to get a nice spiral to it which you can't really cut with a drill, well in acrylic you could probably dremel it out from a round hole but acetal is less receptive to high speed tools.

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JR

LePhuronn · 19 Apr 2017 at 15:57

Thanks for your feedback JR. It's pretty obvious that I'm coming at this blind so all input is gratefully received.

I hadn't considered a spiral simply because from pictures online and dissecting the Aquacomputer top I already have the impeller recess just looked to be perfectly circular at 41mm diameter, and that's what I've been going on. Is the spiral a must or a nice-to-have? I'm using the Alphacool DDC310 pump so it caps at 3100 rpm.

Regarding those little steps I drew, it was a quick diameter reference for the chamfer I'd put onto the G1/4 ports, rather than drawing the chamfer itself (gotta be careful at work

)

LePhuronn · 22 May 2017 at 22:30

Hi, me again.

I've done some musings in Fusion 360 based on tools I have access to to stab some acetal. If I put an STL file up somewhere, would somebody be able to view it and tell me if the design would work?

LePhuronn · 31 May 2017 at 22:22

OK, if anybody's interested here's the pump top I came up with.

It's based around what I can theoretically do with a drill press and some careful measurements, so no spiral volute this time. I'm milling the volute out with a forstner bit so I could, in theory, offset the center a bit a couple of times to fake a spiral, but it won't be smooth and would probably just end up causing turbulence before the water even exits the top, doing an even worse job than just a circular volute.

If you want, here's the STL file.

I grabbed some offcut acetal for a test, hopefully will git a shot next week.

Worth a punt yeah?