Unstable Rotors

Tito3121 · Posted: Sun Feb 05, 2012 1:15 am Post subject: Unstable Rotors

I have a little Syma, electric infrared copter. I took it apart to replace a broken part on the fuselage. When I put it back together, it wouldn't hover. It wobbles and then blades A and B hit each other and it wipes out. So, what's causing this wobbeling? I read another post it it mentioned that it could be a bent shaft. Sad

tombo242 · Posted: Sun Feb 05, 2012 5:12 am Post subject: Re: Unstable Rotors

Tito3121 · Posted: Sun Feb 05, 2012 5:23 am Post subject:

Thanks tombo. I will do that. What about the Gyro? Think that could be broken and need replacing? Any way to check the Gyro?

tombo242 · Posted: Mon Feb 06, 2012 1:05 am Post subject:

Yep, the tail will wag like a happy dogs'. Spins are often caused by slipping gears, jammed gears or duff motors.

Tom.
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Tito3121 · Posted: Mon Feb 06, 2012 9:03 am Post subject:

No tail wagging here. I ordered a replacement shaft. Will see if that works. I took the shaft apart and rolled it on a glass cutting board. Could'nt see any jerking, but hopefully a new one works.

tombo242 · Posted: Tue Feb 07, 2012 3:48 am Post subject:

If there's no jerking Tito then it's got to be something else. Could be a bent flybar or a duff bade holder. Worth checking out the blade pitches but you may have to improvise on some sort of pitch gauge.

Tom.
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Tito3121 · Posted: Tue Feb 07, 2012 4:18 am Post subject:

This all started when I replaced one of the blades. Maybe its pitch is a little different? I could try putting a different blade on I suppose.

tombo242 · Posted: Tue Feb 07, 2012 8:52 am Post subject:

Always best to replace blades in pairs Tito, they don't always come out of the same mold and then they will not match up. That could just be your problem.

Tom.
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Tito3121 · Posted: Tue Feb 07, 2012 10:36 am Post subject:

Tombo,

I replaced all four blades with new ones. Still have the problem. Thanks for the suggestion though.

I don't know. I'm starting to get frustrated with this. I'm sure it's one thing, it's just that I'm new to this and don't know how to trouble shoot it. I hold it in my hand and fire it up and watch the rotors. If I tilt the heli a bit, the top blades seem to pitch back and forth, and continue even after I stop moving the heli. Mabey it's the balance bar on top? It looks fine. Hmmmmm. Confused

tombo242 · Posted: Tue Feb 07, 2012 8:18 pm Post subject:

Tito,

Can you make a video of this, it's not easy to diagnose a fault that you haven't seen. A 30sec run is probably enough. I would like to see just what it does.

The upper blade movement you describe sounds fairly normal, the flybar should try to stay horizontal and in doing so will move the top rotor. That's how it balances, any friction, slack or bends here will really upset it.

Tom.
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Tito3121 · Posted: Tue Feb 07, 2012 9:00 pm Post subject:

I was actually thinking the same thing. Yeah, I'll do that.

Thanks,

Tito[/GVideo]

Tito3121 · Posted: Tue Feb 07, 2012 11:03 pm Post subject:

O.k., check these out.

Link
http://www.youtube.com/watch?v=WR5jFojI4Fo

Tito3121 · Posted: Tue Feb 07, 2012 11:05 pm Post subject:

And, one more.

Link

admiral · Posted: Wed Feb 08, 2012 2:53 am Post subject:

Hi Tito3121,

Looking at the second video it appears that you have two upper linkages between the Flybar and the Upper blades, did you fit the second one ? or did it come like that ? I have only ever seen one used on coaxials before.
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Keep your rotors spinning

Keith

Tito3121 · Posted: Wed Feb 08, 2012 3:27 am Post subject:

Admiral,

Here's a closeup of the area you're talking about. It came like this. I did this apart and re-assembled when I took the shaft out for inspection. But, it was performing the same way even before I did this. So, I don't think I re-assembled it incorrectly.

I think I'm going to run this into my local hobby shop and see what the guys say there. I probably could buy another Heli for the amount of time I'm spending trying to figure this out, but now it's bugging me if you know what I mean.

I'll make a post if they help me to figure this out.

BTW, I do appreciate all the help you guys have been giving me. It's kinda nice to know that there are people out there who don't mind giving some free advice.

~Tito