Why is my MJ1200 with SureFlow mod doing this?

mike31154 · #1 05-25-2009, 04:50 PM

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 · #2 05-25-2009, 05:01 PM

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 · #3 05-25-2009, 05:17 PM

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.

Delphinus · #4 05-25-2009, 05:18 PM

Clearly, she's plugged it in upsidedown. I'll refrain some making any blonde references now.

mike31154 · #5 05-25-2009, 05:23 PM

That's it, her stunning good looks are making the electrons run backwards.

Myka · #6 05-26-2009, 04:26 AM

Well, it was freakin difficult to get that propeller off the shaft and turn it around, so I'm assuming that no one took it off and put it back on backwards, so that makes me think that the propeller is spinning in the opposite way that is was intended. If you look at the propeller from the front it is spinning counter-clockwise. It spins the same way every time I plug it in.

Oh, and the frickin thing is going to be banned to salt mixing as soon as I find a replacement. It is obnoxiously loud. Grr.

fkshiu · #7 05-26-2009, 05:18 AM

Quote:

Originally Posted by Myka

Well, it was freakin difficult to get that propeller off the shaft and turn it around, so I'm assuming that no one took it off and put it back on backwards, so that makes me think that the propeller is spinning in the opposite way that is was intended. If you look at the propeller from the front it is spinning counter-clockwise. It spins the same way every time I plug it in.

Oh, and the frickin thing is going to be banned to salt mixing as soon as I find a replacement. It is obnoxiously loud. Grr.

The flat side of the propellor should be in front.

If it is facing correctly, then you should try shaving the propellor down a bit with a dremel tool to make it smaller.

mike31154 · #8 05-26-2009, 03:45 PM

Quote:

Originally Posted by Myka

Well, it was freakin difficult to get that propeller off the shaft and turn it around, so I'm assuming that no one took it off and put it back on backwards, so that makes me think that the propeller is spinning in the opposite way that is was intended. If you look at the propeller from the front it is spinning counter-clockwise. It spins the same way every time I plug it in.

Oh, and the frickin thing is going to be banned to salt mixing as soon as I find a replacement. It is obnoxiously loud. Grr.

OK Myka, going by your current description, it's working as intended, pushing the water through the front of the cage. Looking at the spare hobby propeller I have in front of me, if it's built the same way as yours, counter-clockwise is the way you want it to spin since that will push the water which is what you want. I'm not sure what makes you think this is the opposite way as intended. How about taking a quick close up photo of the shaft & prop to show us what it's looking like?