Tiny Might skimmer rockin'

<a href=showthread.php?s=&postid=7865284#post7865284 target=_blank>Originally posted</a> by ChemE
I wasn't directing that at any one person least of all you, I've just seen Hahn take a beating on a few different threads recently and have felt badly for him.
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^^^ and thank you ChemE for feeling bad for me before...:beer:
 
<a href=showthread.php?s=&postid=7892389#post7892389 target=_blank>Originally posted</a> by hahnmeister
Bean, and anyone else looking for acrylic domes/domes with flanges. You can get them here...
http://www.calplastics.com/custom/stockhemi.html

Or here...
http://www.acrylicdomes.net/acrylicdomes.htm

The cool thing is that you can get them with the flange ring as part of the dome so you can easily tap it for screws, or route it for a twist lock flange.

I still question the use of a dome as a reducer neck though. Remember that old physics/geometry problem where there is a marble on a ledge, and the marble can take one of three tracks to get to the bottom, but one is faster than the others... the choices include a diagonal line from point a to point b, and two cycloids (1/4 circles), in the two possible orientations? The marble will fall the fastest on the cycloid that starts with the steep incline and then less before point b. Using a dome as a riser neck is a bit like that. Granded, these are bubbles and dont accelerate the same if anything at this point, but the idea behind most reducers is to both slow the ascent of the bubble, and maintain its velocity as much as possible in the upwards direction. A dome collection neck doesnt slow the rise of the bubbles, and then adds a horizontal motion at the top, angling the bubbles so that they exit sideways at the top, which is really adding alot of turbulence to this area of the skimmer that should be as calm as possible. This is why you really want to have a curved funnel/trumpet shape, not a dome.
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Maybe this is the case in some scenerios, but not true in my skimmer. The bubbles entering the riser neck are more stable than any I have seen. And I have a curved funnel skimmer to compare with. MAYBE it is the use of the diffuser plate. I don't know which is doing the job, but there certainly is no added turbulence.
 
I would bet its more an attribute of your bubble plate than the neck... the dome adds a horizontal component to the bubbles that you really dont want that close to the top where the bubbles are collecting. Just a hunch, but I bet thats why you dont see too many 'dome top' skimmers made by skimmer mfg's.
 
Granted, these are bubbles and dont accelerate the same if anything at this point, but the idea behind most reducers is to both slow the ascent of the bubble, and maintain its velocity as much as possible in the upwards direction....

...I would bet its more an attribute of your bubble plate than the neck... the dome adds a horizontal component to the bubbles that you really dont want that close to the top where the bubbles are collecting. Just a hunch, but I bet thats why you dont see too many 'dome top' skimmers made by skimmer mfg's.
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Fisrtly, thanks for the link to the domes!

Secondly, (said with a smile) where in the world do you come up with the stuff? Horizontal components? Cycloids? Added turbulance?

I am not trying to be mean, but this is getting almost silly. Didn't you just try to say that bubble plates in tall skimmers were bad?

Rich you are speaking of the brachistochrome problem that was btw postulated and solved by Bernoullis father and uncle and it really has no application here other than to confuse the issue.

Why do manufacturers not used domed neck? Why don't they port their pumps and refine their poor designs? Why do TVs come with awful color calibration? Rich, tweaks cost money. Most companies shove the bare minimum out the door. As long is it is a bit better than the competition, thats all that matters. Anything more is a money loser.

I enjoy your posts and your critical thinking, but you can't just paste a science book into every conversation and use YOUR understanding of it to connect all the dots.

The important thing here is that the skimmer neck has no flat horizontal surfaces and is smooth with no cavities. Could it be refined with some study, obeservation, and application of science? Sure. Is it the critical component at this point? I guess that is up to smj.

I am not trying to be hard on you but these scientific forays and some of the assumtions and applications of science are getting hard to swallow and seem to be grinding away at all of these threads.

Can we knock the science down a notch so that the rest of the passerbys can follow along?
 
<a href=showthread.php?s=&postid=7893649#post7893649 target=_blank>Originally posted</a> by BeanAnimal


Fisrtly, thanks for the link to the domes!

Secondly, (said with a smile) where in the world do you come up with the stuff? Horizontal components? Cycloids? Added turbulance?

I am not trying to be mean, but this is getting almost silly. Didn't you just try to say that bubble plates in tall skimmers were bad?

Rich you are speaking of the brachistochrome problem that was btw postulated and solved by Bernoullis father and uncle and it really has no application here other than to confuse the issue.

Why do manufacturers not used domed neck? Why don't they port their pumps and refine their poor designs? Why do TVs come with awful color calibration? Rich, tweaks cost money. Most companies shove the bare minimum out the door. As long is it is a bit better than the competition, thats all that matters. Anything more is a money loser.

I enjoy your posts and your critical thinking, but you can't just paste a science book into every conversation and use YOUR understanding of it to connect all the dots.

The important thing here is that the skimmer neck has no flat horizontal surfaces and is smooth with no cavities. Could it be refined with some study, obeservation, and application of science? Sure. Is it the critical component at this point? I guess that is up to smj.

I am not trying to be hard on you but these scientific forays and some of the assumtions and applications of science are getting hard to swallow and seem to be grinding away at all of these threads.

Can we knock the science down a notch so that the rest of the passerbys can follow along?
Click to expand...

Boy, I wasn't even going to respond! Bringing up the tall skimmers with bubble diffesers comments, you hit it right on the head Bean! Ha! Ha!
If nothing else I think the dome looks COOL! Now that is scientific!
 
A note on the wonderful links that hahn posted for the domes.

The first link is very limited... and expensive.

I just got off the phone for the second link. These guys are great. The prices are good and the domes are flawless vacuum formed units. They do custom work, but the CUSTOM FORM guys is off for the summer due to an accident. So at this point your stuck with the stock diameters (which is fine for you acrylic guys) as they seem to be in 1" increments.

They have about a 2 week lead time between order and doorstep, as each piece is custom made to order.
 
PVC pipe has a 6.625" OD. It is 1/4" pipe so the ID should be around 6.125"

My goal is to build the neck with an integral (or glued on) flange. The PVC body would also have a glued on flange.

I am considering building up an MDF form and trying to vacuum form my own (I have a big vacuum pump that I have never put into service). I am thinking of capping a few 4" 8' pvc pipes and drawing a vacuum on them to use as a resevoir. That way I can suck the hot plastic down quickly without waiting for the pump.

I am nust not sure what to use as the vac bag... I to look into the melting temps of the rubber or vinyl. I am afraid once it touches the hot acrylic it will melt.
 
Maybe if you use 6 inch pvc to draw the vacuum you wouldn't need the bag. You can only stretch the acrylic dome 3 inches without it crazing anyway. I would probably stop at 2 inches to be sure.
 
Yeah, I was thinking of just making a clamping frame with a gasket. The claming frame would have the correct OD and the vacuum hose would be attached to a box that the frame fits on.

Heat the frame and the plastic... toss it on the box with a gasket and open the vacuum valve.

The problem is that I am not quite sure what to do next. I guess I leave it under vacuum while it cools?

I can see it now.... a dozen sheets of wasted 1/4 cast acrylic.
 
That is exactly what you do! Just let it cool while under vacuum.
Just remember don't pull more than 3 inches, 2 inches to be sure you can avoid crazing.
 
Have you vacuum formed acrylic?

Damn... now i have to finish the vacuum pump project bofore I can finish my skimmer!

Check out joewoodworker.com for a decent set of plans. I have had a ghast pump (ebay) for a few years, but never got the MAC valve and vacuum controller.
 
No, but I did some research on it before I pressed mine. I was going to vacuum form it but was having trouble getting my hands on a pump. In fact the guy at the second website gave me pointers when I was trying to decide how I was going to do it.
He told me that is precisely how they make the domes.
 
<a href=showthread.php?s=&postid=7893649#post7893649 target=_blank>Originally posted</a> by BeanAnimal


Fisrtly, thanks for the link to the domes!

Secondly, (said with a smile) where in the world do you come up with the stuff? Horizontal components? Cycloids? Added turbulance?

I am not trying to be mean, but this is getting almost silly. Didn't you just try to say that bubble plates in tall skimmers were bad?

I didnt say that they were bad, just not as effective. And, FWIW, I was only talking about how the bubbles at the top, in the collection cup area would be effected, not the whole skimming process. The taller the skimmer gets, the more bubbles will disperse and the more turbulence will settle on its own as you go higher in the water column. Lets say you have a 6' tall skimmer... do you think that how the bubbles are moving at the top are going to be effected very much by a bubble plate down below? Maybe if the skimmer is 3' in diameter with 5000gph needlewheel pumps.... but with a 6-8" diameter it just doesnt do much. I wouldnt consider smjtkj's new skimmer to be so tall as to not benefit at all from the bubble plate, and I dont know how the other skimmer he has is built, so I cant compare. I can only suggest that perhaps in this case, the first skimmer was just so much more turbulent in comparison that the bubble plate does do something in smjtkj's new one (or just the design in general is better, perhaps due to other things like height, flow, etc... but those options werent presented at the time) Simply put, its a different skimmer so a controlled comparison isnt possible. The only way to know for sure would be to test it for a while with the dome, then again with a curved funnel, and see which works better.

Rich you are speaking of the brachistochrome problem that was btw postulated and solved by Bernoullis father and uncle and it really has no application here other than to confuse the issue.

Why do manufacturers not used domed neck? Why don't they port their pumps and refine their poor designs? Why do TVs come with awful color calibration? Rich, tweaks cost money. Most companies shove the bare minimum out the door. As long is it is a bit better than the competition, thats all that matters. Anything more is a money loser.

your point is valid, but its not like a dome would cost more to make than a funnel or curved funnel... they would cost about the same to make. Same process, same materials, etc. So I wouldnt consider it a 'tweak' as a fundamental design attribute that could just as easily be made one way or another.

I enjoy your posts and your critical thinking, but you can't just paste a science book into every conversation and use YOUR understanding of it to connect all the dots.

The important thing here is that the skimmer neck has no flat horizontal surfaces and is smooth with no cavities. Could it be refined with some study, obeservation, and application of science? Sure. Is it the critical component at this point? I guess that is up to smj.

But why would not having any flat surfaces be important? Is there any proof that that is bad? Not really when you look at it. So its really just YOUR understanding coming into play as well (just pointing out that although you may not agree or want to bother with any of my 'understandings', that those thoughts are based in your 'understandings'... so neither is more valid than the other when you look at it like that).
I think I related the potential problem of a domed neck rather well... The example of a kid going off of a waterslide is exactly what I am talking about. Imagine that the slide starts out relatively flat, then as the slide goes on, the incline becomes greater. The kid would start out slow, then accelerate at the end and by the time he hit the water, be going straight down into the water. This is really what we want in our skimmers, but with bubbles that rise of course. Slides that start out steep and then level out at the end send the kid across the water as he hits the water. This related to a dome skimmer in that the bubbles that rise into the dome hit the sides, dont slow down until the very top, but at that point they get discharged not upwards, but across the opening at the top after nothing has been done to slow their speed. You really dont want this in your bubble collection area. There is the possibility that the bubbles are just so slow that is doesnt matter... they just slow as they get to the top of the dome, and then just fall upwards over the edge... but then why not just use a flat plate?

I am not trying to be hard on you but these scientific forays and some of the assumtions and applications of science are getting hard to swallow and seem to be grinding away at all of these threads.

Can we knock the science down a notch so that the rest of the passerbys can follow along?
Click to expand...

You know, Im really at a crossroads here. You and one or two others get 'miffed' when I add a scientific aspect to this stuff... claim that I am bogging it down with stuff to just make myself look smart or something... or whatever. And then if I simply mention my opinion w/o any detail (what you might prefer), then I get seen as just being negative and critical by others like Spazz and smjtkj because I didnt give my reasoning. I think Ill post what I like, thank you. If you see no value in using some physics here or there when applicable, fine... but that doesnt mean it doesnt apply. FWIW, my opinion is much like Calfo's...

"BTW... my casual opinion on the skimmer plates is that in most skimmers they are more harm than good. Furthermore, the latest wave of skimmers to are patently and obscenely over-engineered to the extent that they will never deliver a value to offset the added expense of their testosterone driven construct (plastics thickness/quality, price to buy, price to operate, PR bejeweled pump designs, etc). It really is not rocket science to make small bubbles in saltwater attract proteins. The only argument or reason I can accept for buying such skimmers is luxury preference. That I can respect and accept. But claims of performance value are bunk IMO. "

-Anthony Calfo

So I figure that if we are going to spend time trying to get that extra 1-2% out of our skimmers, we might as well make sure we are correct, and that often means using exact science to do so. Otherwise all we are doing is playing with water and plastic. Almost anyone can tinker around and get a decent car engine... but to make one that has the most output with the greatest efficiency requires engineers that look at the finer details. I figure that although skimmers arent as complicated as that usually, with bubble plates, domes, etc... we are entering the realm where higher science is required, or else we are just putting a bunch of crap features on our skimmers that we have no idea what they are doing (and possibly hurting).
 
Hahn, I am officially done having discussions with you. You are in no way Calfo! I don't need these petty discussions with you in my life. Have a nice life!
 
smjtkj, I never said I was Calfo... I simply stated that I agree with what he thinks on skimmers. That quote is directly from him I might add. I dont see where you are coming from... Why the defensive/offensive reaction?
 
<a href=showthread.php?s=&postid=7894483#post7894483 target=_blank>Originally posted</a> by smjtkj
Hahn, I am officially done having discussions with you. You are in no way Calfo! I don't need these petty discussions with you in my life. Have a nice life!
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Hahn is bringing valuable discussion here. If you dont agree with him, fine, but that doesnt mean his points may not be valid, and aren't worth being expressed. Whats the problem?
 
I will just be frank in hopes of not dragging this out. I think your a smart guy, but you simply mis-apply science in a regular basis. It not so much that science isn't welcome as part of the discussion....

...well lets put it this way, to pick each post apart piece by piece in an attempt to show you where your error is, only leads to another barage of mis-applied science. Once the whole "Cliff Claven" chuckle wears off, it gets very cumbersome to deal with. We get "miffed" because your "scientific aspect" is simply off track but you fail to see it and instead go through gyrations trying to defend or explain it. So it is not that science or physics don't apply, it's that fact that they are being mis-applied.

There is certainly room for those type of discussions, but they rarely fall into the realm of the hosting thread.

Like I said, I appriciate your eagerness to contribute and help design and tweak... but if you toned the pseudo-science down a bit...

Regarding Anthonys comments:
He is the founder and member of our local club here in Pittsburgh. We have talked a bit about skimmers, but mostly CC designs due to their simple and cheap nature. Please note that he used the words "casual opinion". The rest of his comments are geared towards the trend of cost vs performance. I value Anthonys input, but certainly don't take it as gospel or an authoritative answer on all subjects. He (like the rest of us) has great knowledge in some areas, informed opinions in other areas, and wrong opinions to boot.
 
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