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Can you help me fix a Christmas present...?
Tags: Syma X9
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awolter
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Guests
December 26, 2013 - 3:44 pm

Hello everyone,

 

I've been enjoying my 107 for a few hours but after (another) crash it won't lift off anymore. I don't think any of the crashes were very serious, so I'm at a bit of loss--maybe I got a dud.

Anyway, let me describe the problem. The bottom rotor is definitely spinning slower than the top, and too slow for the heli to gain lift. And it's spinning slowly, I think, because the large top gear that the lower blade is immediately connected to (the one that is spun by the motor via an intermediary gear) rides up and grinds on the the metal body above it. So, I can wiggle the lower rotor up and down, and I don't think that's supposed to happen. There's also a high-pitched whining noise which I take to be the top gear grinding on the body.

Does this sound familiar to anyone? I searched "whining" and "lower blades" and "lower rotor" and couldn't find anything quite like it so I though I'd start a new thread and ask. Am I supposed to be able to wiggle the wiggle the rotor up and down, or is that whole inner/outer shaft unit supposed to be stable?

Is there an easy fix for this?

 

Thanks for the advice!

 

Andrew

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CPD
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Guests
December 27, 2013 - 3:09 am

Classic gearslip---all you need is a small flathead screwdriver, and you're good. Just hold down the top shaft, and gently push the gear upward into it with the screwdriver. Just don't pry against any important electronics, and you should  be good to go! Good luck! Reply with the results!

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awolter
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Guests
December 27, 2013 - 3:55 am

Thanks for the response!

 

I might just be confused, but I don't think it's a gear slip problem... To be more clear, it's not just the gear that can be wiggled up and down, as if the gear is slipping up and down on its shaft. The whole gear+shaft unit wiggles up and down. If I push down on the lower rotor, all the gears are in place and nothing moves. If I push down on the top rotor, I can wiggle the bottom rotor+shaft+top gear up and down. If I wiggle the top rotor (without holding the bottom down) the whole shaft, upper and lower blades and respective two large gears move up and down.

 

To describe it another way, if I pick up the heli by the top rotor, the whole shaft/blades/large gears assembly lifts up about 1/8 inch. If I pick up the heli by the lower rotor, the main/external shaft stays in place, but the rotor and the top large gear it is connected to (via an internal shaft, I guess?) lift up about 1/8 inch.

 

Maybe the inside shaft is broken?

 

Is that more clear? I might try to make a video but no promises there...

 

EDIT: Making a video was easier than I thought it'd be...

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Syma Freak
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December 27, 2013 - 11:13 am
Member Since: November 26, 2010
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It could be a broken shaft, take the black bottom part off and try to push the gears more up the shaft

"Fly like a butterfly sting like a Syma" http://syma107.com

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awolter
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Guests
December 27, 2013 - 2:41 pm

Hi!

 

I'm trying but I can't get the gears to budge. I took the main shaft out to see what I was dealing with; I'm pushing up on the gear hard enough to nearly bend the main shaft and it's not moving. I'm afraid I'll break the shaft... Any other pointers?

 

I appreciate the help!

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CPD
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Guests
December 27, 2013 - 3:16 pm

Well, this seems to be a major issue, and I haven't heard of it before. Either there's something binding it all up, or there's a motor that's locked up. I would have thought from the bladesets being able to go up and down that a gear would be loose and slipping. They do go up/down a little normally, but I'm not sure about that much.

If something broke apart in a motor, or a brushholder melted, and then ground it to be stuck, then that might cause the motor to cease and create a buzzing noise from it trying to turn when it can't. Personally, if I was Syma, I'd make a BL model, (s107BL and s800BL) which is a little more expensive to cover the cost of BrushLess motors, (Thus BL) since they last a lot longer and work better than their cheap brushed motors.

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awolter
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Guests
December 27, 2013 - 3:46 pm

I'm pretty sure the motors are fine and the lower rotor was spinning more slowly than the top because its gear (i.e., the lower rotor's gear) was being pulled up into metal body body/engine housing frame by the lift force of the blades. The whining, then, was either the lower rotor gear (the top gear in the gear set) rubbing on the metal body, or was the sound of that gear not being properly aligned with the intermediary gear that connects it to the motor. I'm obviously no expert, but it just seems wrong that that top gear should be in contact with the body / motor housing frame.

 

I should have done a video of the motors/blades running before I took the heli apart, but if you can imagine, when the blades/shaft "pull" the heli into the air, it also pulls the gears (the two large, shaft gears) up into the body/motor frame, slowing them enough to keep the heli from taking it off. It just sort of dances lightly in a little circle, not quite able to lift off.

CPD, when you pull up on the shaft, does it move enough to put the top gear / lower rotor gear in contact with the body/frame?

 

Again, I appreciate help and I'm hoping someone here has run into this before so I get this thing up and flying again--having it up for maybe three flights was just a tease! Worst case scenario, I've got two more coming in the mail in a few days and then I compare my broken one to a operational one and see if that makes the issue clear (during recharge times of course!).

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CPD
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Guests
December 28, 2013 - 4:24 am

I'm trying to think... my helis are in my dorm room right now, so I can't reference one of them offhand, but I do want to say that they move both gear sets when you pull the top rotor. (Top rotors=bottom gears, bottom rotors=top gears)

That could be some level of grinding, or they're pulling up into the top of the corpus, and friction could be grinding it to a halt.

Do you have any sewing machine non-oil or other non-oil lubricant, or a Teflon lubricant laying around? There might be friction building up between the gears when they push together, and that could be causing the binding and thus slow speeds. A quick way to determine this would be to simply lubricate right there between them, and see if there is an improvement. If the problem goes away, then the solution is to keep lubricating it every now and then, and if it doesn't go all the way away, we at least know the issue and somebody can probably figure out a more permanent solution.

There should also be a bearing of some sort at the point on the board where the gear would com in contact with it. That might also need a little bit of non-oil, electrically safe lubricant.

--Just a note: petroleum oils will degrade plastics, and are generally considered to not be electronics safe. Ideally, a hobby-grade plastics and electronics safe, non-volatile synthetic non-oil should be used, such as model train lubricant, or a specialized RC non-oil. Just don't use the lithium/white grease they try to sell for that--all it does (at least for me) is dry into what appears to be a giant bird dropping stuck to your gears forever.

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awolter
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December 28, 2013 - 5:23 am

I don't have any suitable lubricant, but I'll likely invest in some soon here.

 

What I'm stuck on is that the top gear rides up high enough to come out of contact with the intermediary gear that connects it to the motor. So it's like the whole lower rotor / lower roto shaft assembly is "loose", and it appears that everything would be fine if there just wasn't so much movement on that lower rotor shaft unit.

 

The reason the main shaft / main shaft gear comes into the picture is because if that is pulled up, it pushes the lower rotor gear up and out of contact with its intermediary gear.

 

If the main shaft is held stable the lower rotor shaft is still free to move. If the lower shaft is held stable, nothing moves. My video was basically an illustration of this.

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CPD
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Guests
December 30, 2013 - 2:29 am

Now you've got me thinking... I don't think there's a bushing between the top and the top gear, but I wonder if adding one might fix your issue--if it's a matter of it moving higher than the gear on the motor, then logic would say that stopping it from going above the gear would solve the problem.

The other thing might be, are the gears on the motors at the same height? The one for the top gear should be higher than the one for the lower gear, (Thus A/B motors) and if they accidentally put two lower gear motors, then it'd cause it to not be at the proper height.

When you said in your video that the top rotor/bottom gear didn't move when you held down the top one, I thought you meant that it wouldn't rotate--that one's on me.

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awolter
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Guests
December 30, 2013 - 5:58 am

It does seem like a brushing would help... but why would I need it?--I mean, I ought not to, of course. Unless there is a brushing which has broken and fallen off--but I don't think there was one to begin with. In other words, while the brushing would perhaps help it wouldn't solve the mystery of why the thing is malfunctioning in the first place.

 

The motors--they appear to be at the same height, but I can't see how this would be a problem since they are both in good contact with the intermediary gears (they're at the appropriate height relative to the gear they turn).

 

Another possible explanation: There's a main shaft sheath between the rotors, and if that was about 1/8 longer, it would stop the up/down movement that is causing the top gear / lower rotor gear to come out of alignment. Maybe I wound up with a short one?

Also, I'm pretty sure the whirring / whining noise is the misaligned gears (top gear and its intermediary) and not the top gear spinning on the metal body.

 

I should be getting another in the mail tomorrow, and I'll see if anything comes out of comparing them.

As always, I appreciate the help and feedback.

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awolter
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Guests
December 31, 2013 - 8:53 am

Well, I compared it to a new one, and came up with nothing. There's just too much up and down on the lower rotor shaft and I'm not sure why. Anyway, I ended up returning the unit today.

 

I appreciate the help from all who responded!

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lew803
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Guests
February 22, 2014 - 3:34 am

OKawolter,What has happened since you returned the unit?Everything back in order?

I had the same problem that you described and after tearing everything down and redoing it I found that the forward motor was bad and there was a slipping gear on the shaft of the intermediate gear for that motor.Also an 1/8th of an inch play is toooo much.

Have fun with the 107.Good plane.

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Syma Freak
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February 28, 2014 - 9:03 pm
Member Since: November 26, 2010
Forum Posts: 1429
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@awolter our pleasure to help-great guys like Lew and CPD  are always here with great help  and info-keep posting dude we love the action on that

"Fly like a butterfly sting like a Syma" http://syma107.com

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