I'm hoping someone can help me out here! I've just started working on a long planned project and I've already hit my first snag. I've bought a 4 x Sharkoon SE 200 80mm fans, and I've got to say the quality is amazing, really happy with them, they're perfect except for one slight oversight on my part. When facing the front (i.e. the dressed face, not the mounting side) these fans are working as impellers. i.e. they suck! (figuratively speaking), for the application I need them for I need the fans to be the exact opposite. I know most of you will be saying "just turn the sodding things round idiot!" well again application specific I can't spin them round, I need the mounting side to be the intake. I've even took one apart to see if I can re mount the motor or extend the drive shaft but sadly none of this is feasible (well without a disproportionate amount of work). Also reversing the polarity going in (i.e. switching wires) won't work so that's a no go. Now for the question: does anybody know of any fans that are set up in such away that the dressed face is on the output side and not the intake? (they'd spin counter-clockwise if that helps and would probably be exhaust fan specific!). Any help would be greatly appreciated!
All fans are blowing into the direction of the struts that hold the fan/motor as far as I know tbh. I looked for some 15 minutes now at all pictures of fans being sold by my etailer and they all are blowing into the same direction. You can tell this by looking at the blades of the fan.
Reversing the polarity on a brushless motor won't work. There are some possibilities to reverse it, though. I'm not 100% sure about the construction of fan motors, but you could probably reverse it by either reversing the hall sensor or changing the phase direction. (If there are sets of 3 coils, two of the coils on each set must be electrically interchanged.) Try researching a bit on how brush less motors work. Designs will vary slightly, so having the PCB will help you to figure out the construction. Just remember that the fan blades isn't necessarily symmetrical. The fan may be slightly less effective or have different noise characteristics in the reverse direction.
I'd expect the fan to be weaker, but it might be a little quieter, unless it's one of those fans that has ~45 degree non curved blades, then I'd expect things to be very similar in reverse. I'm thinking that removing and flipping the motor electromagnet/stator assembly would be doable
This is very intriguing. I really need to see some diagrams of what you want to do. Fans are designed to rotate in one direction, performance would be crap spinning the other way. Mounting side? Most fans are designed to be mounted from either side. Taking the motor off and mounting it the other way around is the same as turning the whole thing around ie., a waste of time. It's quite simple to cut the motor away and make a new mount if you want to, there are examples of this in the project logs.
I put normal as there are exceptions to this, I think delta make a fan that goes the opposite way to spread the air, and looking at the riffling on this fan it could as well(that riffling would be beyond pointless if it spun the normal way as it would push air out to the intake side.) Bgears makes a cheap fan that blows blade to frame(this is what your after if I understand), but I don't know where you live so finding a source is up to you. Most cases I'm all for hacking something apart, but in this instance I think it would be a lot of work for little gain. Good luck whatever you decide. Think he's thinking about aesthetics for a visible fan, so reversing would mean mounting the frame side visible.
Firstly thanks for all the responses. By mounting side i mean the side of the blades that attaches to the housing. (What I'd call the back of the fan). I know my explanation isn't too clear but I'm finding it difficult to get my point across. Reversing the rotation of the fan (which ever way) wouldn't work as the blades are specifically designed to turn one direction so I ruled that out. The reason it's slightly more difficult than just flipping the fan and bolting it on the other way is because I intend to add spinners to the fans, the nose part on an aircraft propeller, to keep in-line with the rest of the build. Now these spinners have to be on the exhaust side of the fan and fixed to the front. Hence my dilemma! Thanks again to everyone so far... muchly appreciated!
Attila: I've reviewed some of the work logs and actually what I'm aiming for is something similar to what you've achieved (and demonstrated in your forum avatar). Basically I want a bank of fans with spinners attached so they look like traditional propellers.. however where yours is set drawing air in I need mine the exact opposite, expelling air. If I just switched my fans round (mounted opposite round) the spinner would be attached to the stationary housing and not the moving fan. Does that clear it up a little?
100% clear to me. Only counter rotating fan I've ever seen really are... counter rotating fans: http://www2.electronicproducts.com/...low_pressure-article-inrc03-jul2007-html.aspx http://www.jmcproducts.com/products/dc_fans/40x50x38mm.shtml ^sort of things- you may be able to split the 'tunnel' so that you are only using the single counter-rotating fan that would face outwards & also act as an exhaust fan when mounted facing outwards. Then again, you may be stuck with a rather large fan assembly, but it would work & look how you want it too, assuming you have enough space in your case..
Actually, if you look at the fan pic posted by NES, the fan would actually push a bit more air spinning in reverse, than normal. The downside would be increased noise - the curvature of the blades in that fan, as it is in many pc fans, is engineered to trade off some airflow for low noise operation. You can compare it to rowing a boat. Digging/scooping in to the water will push more water but with more noise and splashing, but rowing with the oar angled towards the front of the boat, will push less water, but create much less noise and splashing. You know, I think I might have a look at reversing an old brushless fan sometime this weekend, I'll let you know how it goes
If you are able to make a very precise cut you could actually turn the fanblades around. If you cut out the entire "label disc" in the fan blade piece and move the magnet to the correct position you could glue the fan on backwards. It would be very difficult to get everything balanced, though. Another way of doing it could be to extend the axle of the fan somehow and mount the "cone" on that axle (on the strut-side of the fan). That won't look as good, but is probably the easiest way out.
OK, so am I right that you want the spinners on the back of the fan, and spinning with the fan? If so, then the fans I modded (and this design is common to many brands) Have a metal shaft that goes through the motor body and is fixed with a 'split nylon circlip'. Remove the shaft and replace with a longer one and fit the spinner so it rotates with fan. This solution has many problems though. Getting the shaft out of the fan will be difficult. A new, longer shaft with a machined fixing groove in the right place will need to be custom made. a new plastic base for the spinner will need to be made so that it can be press fitted to the shaft. And getting the spinner to spin true will be difficult. I think just fitting a stationary spinner to the back could be made to look pretty cool if done right.
It does seem to be weaker but it still works in reverse. As for noise level, I cant tell because of the noise of the drill in my test set up. First we need some smoke. I used mozzie coils as I don't smoke any more. Then a fan was mounted to a drill which in turn was clamped into the vice. Ignition. First photo is taken with ambient light, fan spinning in normal (cc) direction. Second photo is taken with flash. The next two photos are taken with the fan spinning in reverse. Natural light and flash. The fan actually works in both directions but 'appears' to be less efficient in reverse. My opinion: Don't run the fan in reverse. All the fans below have more or less the same basic design for the fan blades, a leading edge to 'scoop up' the air and a trailing edge to direct it rearwards. Running them in reverse aint going to give you good performance. If the OP wants to make the back of the fan assembly look better, there are ways. Here is a fan with a nose cone at the back (wrong size cone but you can get em all different sizes). This is what the fan looks like mounted 'behind' the motor. But to do this requires some heavy duty modding. And if you are using multiple fans, then that's a lot of work indeed. But it can be done.
I did a little fan modding, and realised I had a bit of a brainfart b4 and had forgotten which way typical fans blow So the curvature of many pc fans is such to boost airflow at low rpm, where wind noise is not a signifcant issue. So reversing the fan proved to lower airflow, by what felt like about half. The noise didn't change much, at 12v the fan was only a tiny bit quieter. Anyway, here's the victim, an old 60mm fan i'm probably never going to use: peeled the sticker off and unclipped the fan: now the damned stator assembly seemes to be press fit and glued in aswell, because the mofo does not want to come off!!! I cut the motor away from the fan shroud to get better access, but trying to force the stator off started to tear the plastic behind the stator But then I saw an easier solution, rip off part of the stator backing, and just swap the wiring of the stators So yes, there was no need to cut the motor away from the shroud, only part of the backing The red arrow is pointing out a track I cut, and you can see two exposed tracks of the pcb where I've scratched the paint off: I've rotated the stator a little, and done the same to the other end of the pcb, and soldered a little red wire on. You can see the cut track right on the left where the wire is soldered: Rotated back to the other end of the pcb, and made the connections for swapping the power connections to the stators: used a little blob of sticky tak to secure the motor backing, whilst I melted it back in place with the soldering iron: and melted the motor back into the shroud: Again, there was no need to cut the motor out of the shroud, but it's no biggie, since the damaged and repaired sections can't be seen from the front, and melting the plastic back together is just as strong as original when melted well. I do it by poking/mushing the plastic into each other with the iron, and then use the iron to gently smooth out the lumps. You can see the evenly spaced layers of paper I used to center the fan, and the fan is untouched, so there are no balance issues. Check out the raw power of the 60mm showing a business card who's boss: yeah, it's about half the standard airflow, but if that's enough, then pop on a cone and all's good. Otherwise, mod some fans that don't have curved blades!
Thanks to everyone for the input.. you've given me plenty to toy with! Anything I try out I'll document and hopefully find a good enough solution that looks the part. Thanks again to everyone!
I HAVE FOUND IT riotharmus Check out MSI's Nightblade series they have a fan at the back which is designed exactly the way you wanted. I think. Also have a look at this which is a video specifically on it, I have made it start at the time when he talks about it. Now, I'm not suggesting you buy a whole computer just for the fan, but maybe try email MSI and ask very nicely? I don't know.. Hope this helps
