DIY Red Dragon Pumps, gathering ideas.

[hahnmeister]

tarzan,
water spinning around in the volute is trying to get out... if your outlet is say... 1", and your volute depth is 2", the water that is moving around that 1" that doesn't have an outlet tends to keep spinning... so the pump is wasting power on just spinning water inside itself. If the outlet was 2" just like the volute thickness, you provide all of the water with a path to get out. That being said, its not the ONLY way... you could contour the edges of the volute to funnel the water out through the outlet even if it is smaller, but then you have a venturi effect on the outlet... it would just be more efficient to make the outlet diameter the same as the volute depth/thickness. If you want to increase the volume of the volute/impeller well, but cand make your outlet larger, then I would suggest using a larger diameter instead. It really just comes down to efficiency... you dont NEED to do it that way, but why not?

I have some doubts about higher speed pumps used as needlewheels. The biggest factor I have seen with needlewheels more than anything is the volute diameter/thickness. Making this larger gives a proportional jump in air intake it seems.

Most water pumps have an ideal operating range of 2000-4000rpm... when you start to go outside this, you lose efficiency because of the density and viscosity of water... not to say you MUST stay within these speeds, but that if you used, say, a 6500rpm motor, you have more cavitation problems, and you aren't getting the most out of the pump as far as the wattage is concerned. Go too slow, and the water just tends to flow back around the impeller (imagine a very slow impeller... the water would just move around the impeller and for the most part, stay in place).

Simply put, the flow rate increase you might see from changing the speed of a pump from 2000-4000 rpm is likely to be almost proportional, but the increase you see from going to 6000rpm from 4000 isnt going to be as much.

Anyways... the air bubbles in an asperating skimmer tend to slow things down a bit even more. Impellers cant get as much out of the water because the bubbles are going to try to slow down.

So I would suspect that the best efficiency range for a needlewheel is likely lower than a normal water pump... as in, going up over 3000rpm might be a waste. Replacing a 100 watt pump with a 200 watt one if the same speed and bias is going to do more for you than replacing a 100 watt pump with a 200 watt pump where the major difference is the speed is 2x. I cant speculate too much what the best speed for a needlewheel pump is, but I would suspect that the range is less than the 2000-4000rpm range that most water pumps are... maybe more like 1200-2800? When I try a 6500rpm needlewheel pump, the benefits are minimal.

 

[Klaus Jansen]

<a href=showthread.php?s=&postid=13628760#post13628760 target=_blank>Originally posted</a> by hahnmeister

I cant speculate too much what the best speed for a needlewheel pump is, but I would suspect that the range is less than the 2000-4000rpm range that most water pumps are... maybe more like 1200-2800? When I try a 6500rpm needlewheel pump, the benefits are minimal.

@Hahn,

i can say you this : ... 3800 - 4000 rpm. Thats the best speed for Needlewheel Pumps. Plastic-Meshwheels max. 2800 - 3000 rpm. HC-Meshwheels max. 3500 rpm.
Speeds more as 4000 is a big Problem for balance the wheel and the Noiselevel. More as 4000 rpm, the Energyconsuption is significant go up. I have a DC.Dragon here with 6000 rpm... Nice Toys.....

regards..Klaus

 

[BeanAnimal]

water spinning around in the volute is trying to get out... if your outlet is say... 1", and your volute depth is 2", the water that is moving around that 1" that doesn't have an outlet tends to keep spinning...

Not really. The outlet of the pump (the whole pump) works on the principle of pressure. The size of the output port may or may not add to the head pressure, depending on many other factors. When fluids are under pressure, they don't "try" to get out, they just get out...

That being said, its not the ONLY way... you could contour the edges of the volute to funnel the water out through the outlet even if it is smaller, but then you have a venturi effect on the outlet...

Not really. If the output plumbing is 1" then the countoured port enrtance will reduce some turbulance. The WHOLE PUMP works on the Bernoulli principle. We are back to an orifice plate vs a contoured venturi again. The orifice plate offers more resistance. So YES the contoured edges may increase througput, but not for the reasons you appear to be putting forth (semanticaly speaking).

would just be more efficient to make the outlet diameter the same as the volute depth/thickness.

Not really for the reasons you are stating. Pressure drives the output. A wider port opening simply reduces turbulance where the fluid transitions to the narrower output plumbing. The overall shape of the volute and impeller have a much greater effect on the efficiency than the opening "size" of the port.

I have some doubts about higher speed pumps used as needlewheels. The biggest factor I have seen with needlewheels more than anything is the volute diameter/thickness. Making this larger gives a proportional jump in air intake it seems.

The larger volute allows more fluid to bypass. In our case thise allows that slurry to continue to be recyclesd through the eye of the impeller and "chopped". Too small a volute and the larger bubbles never get chopped before they take a trip through the eye out out to the perimeter and directly to the output port.

As for you RPM guidlines, I am not sure I agree. The fact is that there are MANY variables that come into play so any rough estimation is not really valid unless we talk about the rest of the pumps configuration and application.

Sorry to be so "in your face" regarding fluid dynamics Jon, but you certainly appear to be offering up a lot of detailed explanations that don't quit fit the physics. I.E. your appear to be a stickler for detail but don't appear to be getting the details right. Many of your conclusions are valid, but the explanations are not quite right.

 

[tarzan]

Bean, at least he answered my question - i haven't found anything but repairing of his semantic in your post - as far as my question is concerned.

I have an extra question - if i was to increase the volume of the volute/impeller well with increasing diameter of them (or at least increase the volute's ID), would it mean I could get better results i.e. better air suction or not? How is it with the efficiency - would that mean that the pumps cosPHI would drop or not? (I would assume yes, since everything is bigger the rotor would feel bigger torque and power factor would drop - or am I wrong?)

I kindly suggest that you post suggestions in my Custom volute for MJ skimmer pump thread , so that I don't take over this one.

 

[hahnmeister]

<a href=showthread.php?s=&postid=13629041#post13629041 target=_blank>Originally posted</a> by Klaus Jansen
@Hahn,

i can say you this : ... 3800 - 4000 rpm. Thats the best speed for Needlewheel Pumps. Plastic-Meshwheels max. 2800 - 3000 rpm. HC-Meshwheels max. 3500 rpm.
Speeds more as 4000 is a big Problem for balance the wheel and the Noiselevel. More as 4000 rpm, the Energyconsuption is significant go up. I have a DC.Dragon here with 6000 rpm... Nice Toys.....

regards..Klaus

That sounds about right. The needlewheel would benefit more from higher speed (more blending of the air) where mesh does just as well a job at lower speeds (mesh tends to blend better)... you dont want to get the air TOO blended. Along those lines it might be accurate to say that using a needlewheel/paddlewheel hybrid at higher speeds would allow for rpm's that are even higher??? Then cavitation is an even bigger concern though.

 

[BeanAnimal]

<a href=showthread.php?s=&postid=13630682#post13630682 target=_blank>Originally posted</a> by tarzan
Bean, at least he answered my question - i haven't found anything but repairing of his semantic in your post - as far as my question is concerned.

It is my opinion that his "sematic" indicates a lack of understanding in some regards, as evidenced by some of the thoughts in the Venturi thread. He sometimes builds partialy or fully incorrect explanations on what I feel is unstable footing and does so with a tone (wording) that indicates he is an expert in the field. It is however very frustrating to read page after page such "scientific" style explanations that I and others clearly do not feel are valid. I truly like Jon (even though I am sure he would argue differently) and his many valuable posts on many subjects. His observations are also very valuable and in many cases repeatable and helpful. It is the "explanations" about "how and why" that are suspect in some cases.

I have an extra question - if i was to increase the volume of the volute/impeller well with increasing diameter of them (or at least increase the volute's ID), would it mean I could get better results i.e. better air suction or not?

You will get lower flow through the pump and more bypassing of fluid which would in turn equate to lower air eduction.

That said, Jon (hahn) likely has very good observations on what such a change will do to the air that IS educted with regard to bubble size and foam stability.

How is it with the efficiency - would that mean that the pumps cosPHI would drop or not? (I would assume yes, since everything is bigger the rotor would feel bigger torque and power factor would drop - or am I wrong?)

Power consumption would likely drop, as the pump would be doing less work. Less work = Less water. Less water = Less air (all other things being the same).

 

[Young Frankenstein]

<a href=showthread.php?s=&postid=13630778#post13630778 target=_blank>Originally posted</a> by hahnmeister
That sounds about right. The needlewheel would benefit more from higher speed (more blending of the air) where mesh does just as well a job at lower speeds (mesh tends to blend better)... you dont want to get the air TOO blended. Along those lines it might be accurate to say that using a needlewheel/paddlewheel hybrid at higher speeds would allow for rpm's that are even higher??? Then cavitation is an even bigger concern though.

Well both wrong..........lower rpm and larger NW does the same as a small NW and high rpm. Thanks.... been there done that.........

 

[BeanAnimal]

<a href=showthread.php?s=&postid=13630778#post13630778 target=_blank>Originally posted</a> by hahnmeister
That sounds about right. The needlewheel would benefit more from higher speed (more blending of the air) where mesh does just as well a job at lower speeds (mesh tends to blend better)... you dont want to get the air TOO blended. Along those lines it might be accurate to say that using a needlewheel/paddlewheel hybrid at higher speeds would allow for rpm's that are even higher??? Then cavitation is an even bigger concern though.

That I would agree with. Though, in your opinion what is wrong with TOO much blending? If the thing could pump out shaving cream....

 

[JCTewks]

<a href=showthread.php?s=&postid=13630880#post13630880 target=_blank>Originally posted</a> by Young Frankenstein
Well both wrong..........lower rpm and larger NW does the same as a small NW and high rpm. Thanks.... been there done that.........

But does the large NW low RPM pump operate safely within the mfr's specs for the pump? I've put some HUGE MW's on pumps, and gotten some incredible #'s (when they start)...but always outside the electrical specs of the pump, which would ruin the pump pretty quickly if run for more than a few days.

 

[BeanAnimal]

I owuld imagine there is not too much wiggle room for overloading these pumps. My bet would be that they are boarderline overdriven to begin with.

 

[hahnmeister]

Bean, I just wanted to describe it in the simplest means possible, but there wasn't anything wrong with what I said. If I dont have to start mentioning bernoulli, flow, gradients, etc... why bother? The water/air mix in the volute is spinning, trying to move outwards from the axis while it gets spun, but doesn't move as easily from side to side unless the water next to it gets displaced (but the will the water from either side take its place or will the water moving outwards from the impeller take its place instead?). The bottom line is that if the water spins around the volute and cant find an easy out, it can just keep spinning around wasting power. Sure, its all about pressure and flow, but thats all going a bit overboard. There are several things that could be pointed out 'wrong' (something Im sure you would love) with even CNC made volutes for these pumps, because you would need to use injection moulding to make the proper change in outside diameter/thickness with regards to the outlet to eliminate seperation of flow at the output, more contours, diffuser vanes, double volutes for less vibration, maybe even enclosed impellers... but I dont remember mentioning anything with regards to head pressure. That doesn't have much to do with what was asked.

All that stuff you said about Bernoulli, contours on the inside... etc... huh? 'not really, but yeah, the same thing...'??? Really, just because someone explains it differently doesn't mean its wrong. I was using simple forces, if you want to use bernoulli, great. Whatever... now you want to imply that I am wrong based on semantics? BASED ON ANOTHER THREAD? What are you, a secretary? Its right, it may not be the way you would have put it, but then again, Im not trying to teach a physics class, and Im not trying to pass your final exam either. Just because I didn't agree with you in another thread doesn't mean I asked you to watch everything I write to try to correct or 'add more' to, okay mom? There are plenty of people who make errors in other forums, why dont you go watchdog them instead? Not to mention, I have caught you posting some BS as well... need I remind you? You 'seemingly win' at the time, but should we revisit some 'old arguments' that time has proven you wrong? How about PVC piping leaching out chemicals which hurt fish? You scoffed at it without even listening to my reasoning with all the confidence in the FDA and EPA... and now? Gee... they 'reopened the case' based on recent findings. So I suppose I should find your reasoning and semantic 'lacking' and start posting stuff about how you always like to tell people they are wrong yet never offer up any corrections or reasoning other than your opinion. What a bag of wind.

What it really comes down to is the scope of the thread, and who is asking. I dont think Tarzan is interested in me linking him to a bunch of websites with equations and information on Bernoulli... I assume he wants the simplest response possible unless asking otherwise. If it was you asking, maybe then I would consider something more detailed. Like I mentioned, to make a proper volute, we would need more than a CNC lathe.... we would need injection moulded volutes. Without that, all those ideas you are mentioning are rather hart to produce... contoured outlet pipes and such. These DIYers are making volutes with flat sides, okay? So good luck with that. I mentioned that THERE ARE OTHER WAYS, but the 'rule of thumb' is to just make the volute the same thickness as the outlet diameter. That way, no matter where the water is in the depth of the volute (front to back), as it spins outwards, it has a potential outlet without having to hit a baffle, the outer wall, etc.

"It is my opinion that his "sematic" indicates a lack of understanding in some regards, as evidenced by some of the thoughts in the Venturi thread. He sometimes builds partialy or fully incorrect explanations on what I feel is unstable footing and does so with a tone (wording) that indicates he is an expert in the field." -Beananimal

Translated: "I like to correct people alot (or rather, just say they are 'wrong'). After I correct them once, they need to keep being corrected, not even if they are wrong, but if I had to correct them once, I should keep doing it because they are suspect of being wrong. I like to think other people have a lack of understanding that only I can provide, and nobody should talk but me because otherwise they might 'sound like an expert' and only I can do that."

Go make yourself some blueberry jello with snickers bars in it.

"TOO MUCH BLENDING" = making bubbles that are too small causes problems too. Many have talked about it in the past.

 

[hahnmeister]

<a href=showthread.php?s=&postid=13630880#post13630880 target=_blank>Originally posted</a> by Young Frankenstein
Well both wrong..........lower rpm and larger NW does the same as a small NW and high rpm. Thanks.... been there done that.........

Ill let you discuss that with Bean and Klaus. Bean seems to know what I mean, and Klaus has had similar results as I have. But with regards to your response... I dont know that you and I are talking about the same thing even.

 

[tarzan]

THX Bean, i guess that making volutes ID larger wouldn't do any good - after increasing it too much I would than need to make well bigger (bigger mesh actually) and it would just mean i would push th pump in area of lower efficiency.

Would you agree with that Hahn?

Thank you both.

T

 

[Young Frankenstein]

hahn what I am saying .and this is after experimenting with my pumps...you can have a low rpm pump give the same results as high rpm pump..it all depends on the design of the volute and the needlewheel. Size makes a diffrence.

 

[alpine]

Ok so how did this thread go from diy red dragons to maxijets volutes?

Also I thought the sole purpose of creating smaller bubbles,was for more surface area and better foam production.Now Hahn is saying that making bubbles to small can cause problems?

IIRC I could swear before the dc red dragons came out that Klaus had posted in a thread saying the pumps would be capable of 10k rpm.

Now you guys are saying that spinning the pump to fast can cause problems.I dont see how rpm is relevant in this thread since the pumps we are suppose to be talking about do not spin that fast.When will the shananigans end and we all get back to the original thread?

Bean & Hahn,while your debates are very informative.You guys need to realize when your debates have become a whos right and whos wrong discussion,and just call it a draw.After a while you two really start to derail some threads .

 

[tarzan]

Originally posted by alpine
Ok so how did this thread go from diy red dragons to maxijets volutes?

Who made a thread about MJ? I asked a simple question about what you get if you increase volute/impeller well/outet ID - the same physics apply for all pumps so i don't think there was anything wrong with my question. I just explained my findings after testing with MJ, if i had a laguna, i would have tested it, but i don't. In my second question I also apologized for posting here and asked everybody to post answers in other thread.

and you are also no angel:

<a href=showthread.php?s=&postid=13606245#post13606245 target=_blank>Originally posted</a> by alpine
Hey Hahn what do you think of this pump? It looks just like the lagunas with the cage.The wattage is high at 270,but it might be an alternative to the expensive lagunas.

I actually just bought 2 of them off ebay for cheap.I will post some info on them when I get them if you want.

http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=95965

Please don't take it as an attack (counter strike) - i really respect your contribution to RC and DIY-ing, but to call me a thread stiller hurts my feelings.

About too small bubbles i also read that they actually can be too small - I will try to look it up but i can't promise anything.

I definitely agree with you about B_Vs_H - if the debate is more than 5 posts long at the end you usually don't even know what they were talking about at the beginning - it really takes me running my brain on 200% for getting through it.

Regards,

Tarzan

 

[hahnmeister]

<a href=showthread.php?s=&postid=13634210#post13634210 target=_blank>Originally posted</a> by tarzan
THX Bean, i guess that making volutes ID larger wouldn't do any good - after increasing it too much I would than need to make well bigger (bigger mesh actually) and it would just mean i would push th pump in area of lower efficiency.

Would you agree with that Hahn?

Thank you both.

T

I dont agree. Making the volute larger in diameter is the #1 way to increase performance, while even leaving the impeller the same diameter. What you are doing with this is changing the pump to be more flow biased... which if you are using it as a needlewheel... well... thats pretty much a given anyways (converting to a needlewheel kills the pump's pressure handling). The best needlewheel pumps are heavily flow biased (large volute thickness/diameter, large diameter outlet... impeller not so large usually). What this means is that the pump will be more sensitive to height and back-pressure... sure, but that goes with the territory considering its a needlewheel.

Tarzan, for the MJ's... the reason I skipped them (I did have my sights on them years ago until I noticed the few Aquaclear 802's I had laying around and with that fixed shaft were just sooo much easier to mod) and went for the Aquaclear instead was because the MJ has that pesky shaft support on the inlet... which kills the intake and is a PITA have to try to DIY into another volute. An MJ900 is about 10 watts, and the 1200 is about 12 if I remember correctly (its nowhere near as high as the 22 that the mfg claims, oddly enough). The Aquaclear 70/802 as a needle wheel has gotten up to 850lph of air for a meager 12 watts. IMO, MJ's arent worth modding. The AC has a huge magnet which makes for a better startup, where the MJ has a dinky little one. The power factor of MJ's is rather horrid to start with, and I would imagine is even worse as a needlewheel... so it is more likely there would be startup sputter problems, calcium buildup/breakdown, etc. So its on my list of pumps 'not to bother with'.

That would include:

Gen-X
Sedra
Maxi-Jet

I keep getting PM's on Sedras and Gen-X pumps, but my response is always the same: go online, buy a Quiet One 3000 for $40, use the Sedra for something else. The work you would have to do to make it a good asperating pump is just more than the motor is worth.

Now, eheims and aquabees aren't that much greater, but at least they make the volutes that are moulded onto the motorblock able to be chopped off all together, and then you can do a Laguna-style mod on them. You still have that shaft support in the center though.

Those new Maxi-Jets... those might have some potential. They look like they have more flow bias (a few sizes).

I think its fine that you posted here about the MJ's. I think we talked about them in the AC802 'pimp my pump' thread, but if you want some help in that other thread, Ill stop by. I would say the first thing to do is to make the impeller well/volute larger by about another 1/2", and maybe thicker too if you can... to 1/2" would be good. This means you likely need a new longer shaft though... PITA, and a new inlet... PITA. If you mod up the impeller a bit though, that should help though too.

 

[hahnmeister]

<a href=showthread.php?s=&postid=13634288#post13634288 target=_blank>Originally posted</a> by Young Frankenstein
hahn what I am saying .and this is after experimenting with my pumps...you can have a low rpm pump give the same results as high rpm pump..it all depends on the design of the volute and the needlewheel. Size makes a diffrence.

Ill give you this... the rotational velocity of a 2" diameter impeller at 2000 rpm is the same as the rotational velocity of a 4" diameter impeller at 1000rpm. So in that way... it is all 'relative'.

What we were tossing around before was how the 'ideal speed' might also be a function of the 'interface planes' on the impeller... if you have fewer, larger impeller vanes/pins,etc... or many more smaller pins/mesh. Something I have been wondering more about is why more makers dont make hybrid needlewheels. There are some, dont get me wrong... but I mean something like this... from the axis to about 1/2 the radius of the needlewheel, you have your finest and tallest pins... but as the water moves outwards, the air is more blended (a relative thing though, IMO, most of the 'blending' happens around the outer edge of the volute as bubbles smash into each other and the outside wall of the impeller well), and the speed of the impeller increases... you could start using larger pins, or even parts of impeller vanes pop up again because at the higher speeds, a larger contact area can be used.

 

[hahnmeister]

<a href=showthread.php?s=&postid=13634715#post13634715 target=_blank>Originally posted</a> by alpine
Ok so how did this thread go from diy red dragons to maxijets volutes?

Also I thought the sole purpose of creating smaller bubbles,was for more surface area and better foam production.Now Hahn is saying that making bubbles to small can cause problems?

IIRC I could swear before the dc red dragons came out that Klaus had posted in a thread saying the pumps would be capable of 10k rpm.

Now you guys are saying that spinning the pump to fast can cause problems.I dont see how rpm is relevant in this thread since the pumps we are suppose to be talking about do not spin that fast.When will the shananigans end and we all get back to the original thread?

Bean & Hahn,while your debates are very informative.You guys need to realize when your debates have become a whos right and whos wrong discussion,and just call it a draw.After a while you two really start to derail some threads .

Sorry for the infighting. Bean always likes to correct people though and say whats right and wrong, and I just find it annoying (as well as the lack of any corrective information) so I throw it right back as useless jibber-jabber. To me, it seems he is more interested in telling the person they are wrong than actually contributing anything of value (very dismissive), and that burns my gord.

As for DC pumps and skimmers... its just my opinion, but something I will add to my response to YF just before this one is that once again 'its all relative'... the actual speed of the OD of the impeller is relative to its diameter... so perhaps tossing around rpm values is a bad idea, since a 6500rpm pump with a 1" diameter pinwheel is going to hit 28.3 ft/s at the OD, and a 3" diameter pinwheel going 1800 rpm is only 23.55 ft/s at the OD. So talking about rpm's itself is the error... as its all relative to the size of the pump. Smaller impellers would benefit from a higher rpm, where larger pumps are going to hit a wall with rpm's that is much lower. I think everyone can agree to that.

My own 'rpm tinkering' is with a smaller pump. I see larger DC pumps are more of a liability than advantage... it depends on the waveform of the power going to the pump, but one of the major advantages of a DC pump is that the torque is constant (if you have a square wave input). The problem is that then you are using a higher RMS wattage (RMS power = peak power with many DC pumps), and so you might have awesome startup power, but you are burning up wattage. So then you turn back to a sinewave input like regular AC power, and gain back the efficiency. But most DC motor controls wont let you startup with square wave, and then switch over to sinewave for operation... not to mention, you just nullified a major reason for going with DC then (all thats left is higher rpm's... but past a certain diameter * rpm, you see a decline in efficiency anyways).

So IMO, the best application for DC pumps is something small. I have been tinkering with that 6500rpm DC motor that is only 24v/48watts max with promising results... but my impeller diameter is only about 1.25"... so at 6500rpm, its OD is only at 35.4 ft/second. But on a 5000rpm motor with a 3" diameter impeller... thats 65.4 ft/s at the outside of the impeller! So Im sure that factors into why you aren't going to see any huge DC motors pulling down massive rpm's in skimmer applications. I would submit that its not the rpm's, but a figure of rpm's * impeller diameter that is what we should be comparing. And thats cool because you can get some great quality small Ti shaft pumps made in Hong Kong on the cheap these days...

 

[JohnL]

This thread was automatically split due to performance issues. You can find the rest of the thread here: http://reefcentral.com/forums/showthread.php?threadid=1499727