Why is my MJ1200 with SureFlow mod doing this?

[Boomboy]

try turning it off and then back on, i did a mod on a 1200 not what you are doing and i found that plugging it in made it go one way and then unplugging and plugging back in made it go the other way. just a thought try that and see if it works. i could be totally wrong though.

[mike31154]

Sounds weird. As mentioned, AC powerheads will spin in either direction when plugged in and with the original impeller, it doesn't matter, since it's not directional, it pushes water through the volute either way. As noted, the tab is there to try and bounce it into the proper direction when fitted with a propeller.

It is possible that the propeller may be fitted on to the shaft the wrong way around though. When you look at the prop from the side, you should notice that the blade tines are sort of flat on one side and curved, or rounded on the opposite side. If I'm not mistaken, the flat part should be at the front, away from the powerhead body and the curved part at the back. Don't know if that description makes sense. If not, I'll try to come up with a pic or something.

Edit. Photos attached where the pen represents the driveshaft. Correct, Incorrect, and a moded Aquaclear impeller with prop in correct config.

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[Delphinus]

You'd almost think it wouldn't matter if the prop was upsidedown on the shaft though, since if its sucking water instead of pushing, it will pull out and hit the tab.

If it's happening every few minutes and the shaft is OK .. hmmm. I've never used the big props, mine are older and from the time they didn't give you the two. So I don't know if it's just something to do with the bigger one .. but it seems to me if it's hitting the tab and switching directions ... then hitting the tab again a few minutes later, then it must have switched directions in that time. Dodgy electricals? It's not running on a wavemaker is it (seems like an obvious question but I'll ask it anyhow).

(And if so, I found they really don't last when on wavemakers. Everytime they startup, there's a little vibration in the whole unit. This eventually distresses the little holder-arm thing that attaches the powerhead to the glass magnet, and it breaks at the socket point. I tried all manners of fixing it, but basically once this is gone, it's gone, nothing I could think of would keep it fixed longer than a week or so.)

[fkshiu]

The propellor is spinning the wrong way and is hitting the tab which is designed to make it spin the correct direction. What is probably happening to prevent this is the greater interial mass of the white (bigger) propellor is preventing the proper bounce back. The smaller (black) propellor does not have this problem on Sureflow kits. All the snapping against the tab puts extreme torque on the propellor which will eventually tear it apart. This is why you should NOT use these things on a wavemaker.

How do I know this? Numerous tries on building my own "maxi-streams" out of various bits and pieces before there were DIY kits available along with reading the monstrous thread on RC. The bottom line is that if you get too greedy and push the envelope (i.e. the bigger white propellor on a Maxijet 1200) you're going to run into trouble. Remember, this is - after all - a DIY project. One of my Franken-streams is now the dedicated salt mixer - a job it excels at but makes a big racket doing.

If you stay conservative and use the smaller black prop on a Maxijet 900 it shouldn't give you any problems. I've had my Sureflow going without issues for over a year now.

[mike31154]

Originally Posted by Delphinus

You'd almost think it wouldn't matter if the prop was upsidedown on the shaft though, since if its sucking water instead of pushing, it will pull out and hit the tab.

If it's happening every few minutes and the shaft is OK .. hmmm. I've never used the big props, mine are older and from the time they didn't give you the two. So I don't know if it's just something to do with the bigger one .. but it seems to me if it's hitting the tab and switching directions ... then hitting the tab again a few minutes later, then it must have switched directions in that time. Dodgy electricals? It's not running on a wavemaker is it (seems like an obvious question but I'll ask it anyhow).

I thought maybe an electrical problem as well, since once it hits the tab on initial start up and then starts spinning in the desired direction, it should continue to run smoothly until power is cut off and it is restarted. Myka did mention that it seems to be running in the wrong direction though. If the prop is mounted upside down, perhaps the curvature prevents it from properly engaging the kicker tab???

[Myka]

Originally Posted by mike31154

It is possible that the propeller may be fitted on to the shaft the wrong way around though.

Mike, you are BRILLIANT!!

The prop when it spins one way rams right into the tab, but if it goes the other way because the prop is slanted if it hits the tab it just slides up it.

I think it's actually messed up and spinning the wrong way because it took some serious efforts to get the propeller off which makes me think that no one turned it around. BUT, it worked!!! Well, it's been running for about 5 mins and hasn't messed up yet. So...fingers crossed. I'll see how it runs, but it's doing ok now. Has a bit of a vibrating hum to it though...but I think once my MH setup gets here and the fans are going I wouldn't hear the hum of this powerhead. Every once in awhile it puts out a fairly loud buzz. This is my first try at these SureFlow kits...so far, thumbs down. Noisy! (even at the best of times...maybe better when they are new though)

I didn't get the smaller black propeller, which I am a bit disappointed because I wanted to put the smaller one in a 900 and use the bigger one in the 1200. Extra greedy.

[Delphinus]

Glad you've figured it out but boy that doesn't make sense. The powerhead can spin either way, so if the prop was upside down it just needs to spin the other direction if it's going backwards at startup.

Oh well, apparently I'll just hurt myself if I think about it any longer ... so I'm not going to. Either way I'm glad you figured it out. But yeah, these kits are good for giving you flow in a hurry without spending gobs of cash, but that's about it. Like anything I guess ya gets what you pays for.

[mike31154]

Great, glad it's working for you... so far. Dunno about brilliant though, I'm not filthy rich, call it logical, although I don't have pointy ears, har har. Probably all the good training for my tech. career fixing aircraft instrument electrical systems. And yes, I did have the opportunity to work on some old prop jobs there, as well as the jets.

It was a long shot, but lucky I guess. I've never seen the Maxi Jet mod up close, but I tried to mod a couple of AquaClear power heads with propellers I purchased at hobby shops. The smaller ones seemed to work better, fkshiu's theory on mass of the larger prop has merit, I'm sure. When I fitted a prop to an AquaClear 802 and finally got it to spin in the right direction, the thing went nuts! So much power I could have emptied my tank in a few minutes with the water slopping over the rim!

Now with respect to the vibrating hum, I suspect that may be due to a slight imbalance and the fact that you're working with a longer shaft than the original design of the Maxi Jet. A minor misalignment of either the prop or the shaft will contribute to this excess vibration & noise. You almost need a secondary bearing farther up the shaft to minimize or eliminate any misalignment or flex. My fellow mechanical type techs had some pretty sophisticated equipment to balance props on aircraft & track rotors on helicopters. It doesn't take much to make equipment rotating at high speed self destruct. Even a few grams of difference can be huge and alignment is crucial as well. If it gets out of hand, or before it does, it might be worthwhile to ensure the prop is fitted as straight as possible on the shaft and that the shaft itself is not off at a slight angle. Then again, every time the prop hits the tab, it may mess up any effort you make to keep things straight.

Great mods for the money, but I'm glad I have my VorTech, it's designed with a prop in the first place and has a controllable DC motor, too bad the price is so hard to take. Wonder how the previous owner of the Maxi Jet dealt with the issue you experienced??

Live long and prosper.

[Myka]

Ya, I don't understand why it's spinning backwards, and ALWAYS spins backwards, not just on startup. I can't even get it to spin the right way if I stick my finger in it (which hurts btw).

The only reason I bought it is because I was in need of some cheap water movement for now until I buy a Wavebox and/or VorTech or...?

Oh, and no it's not on a wavemaker.

[mike31154]

Ok, now you've got me confused. Always spins backwards? So it is currently drawing water through the front and pushing it out the sides/cage? I can't conceive of how that would work without the prop continually hitting the tab since the shaft & prop would be moving towards the front of the cage & tab? Where exactly is this tab located, at the front end of the cage, perimeter?? Should be a 50/50 chance that the thing will spin in either direction at start up and half the time not even hit the tab on start up. Just too difficult to visualize what you're describing.