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S107 new...was fine, now it just wants to move backwards, unstable
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hc
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February 1, 2012 - 7:13 am
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I've been searching the post, havent seen anything really that covers this.  In our lab (yep..we have fun here) we have 3 heli's, my S107 and my boss has his S107.  Mine was flying fine, no big crashes or anything but now it won't take up straight it simply wants to move backwards...trying to control it to hover or take off just makes a mess of things.  My control works the other one just fine so its not that.  Tried both channels.  In looking it over, there isn't anything that seems out of place.  The shaft is straight, blades are in good shape (just had it a month).  Ground effects?  The other one flies perfect so that can be eliminated.  What should I look for as something damaged or?

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syma-guy
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February 1, 2012 - 7:41 am
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Not to sure if the shaft is ok. If it's only pulling backwards a little bit, you can try adding a bit of weight onto the nose, like adding some bluetac inside the cover ,may take a some messing to get the amount right tho.

someone may think of something to look for tho.

 

Syma-guy Wink

fly like you stole it

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Freeonthree
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February 1, 2012 - 5:54 pm
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Remove the canopy, your battery moved rearward Surprised  Move it back forward, then push it into the slot it came out of ?

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hc
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February 2, 2012 - 7:57 am
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Took a look...battery looks like its in the right place...it wants to take off and just fly off in one direction.  I hold it in my hand and run the rotors, and they look like its pretty "flat"

 

what would throw the stabilization off like this?

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hc
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February 2, 2012 - 9:09 am
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For $6 on ebay....ordered a spare parts kit..blades, shaft, etc

 

Shotgun it and replace things....seems like a valid thing to try at least

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Freeonthree
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February 3, 2012 - 6:17 am
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Other than drifting rearward, does it do anything else wrong ?  Does it steer ok ?  Will it go forward and backward still ?

If you hold slight forward stick, will it hover steady ?

If so, the battery moved rearward. Remember, even 1/4 gram added to the nose will change it drastically, so if the battery tilted upward in the front, or slid back, even 1/8 inch, it changed the CG (center of gravity).  Dennis 

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Freeonthree
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February 3, 2012 - 6:36 am
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The thing is, only two things can make it drift forward or backwards at neutral stick, and thats the angle of the blades, or CG (balance).  If the heli is tilted forward on take off, it will leave forward, and visa versa. Same goes for left and right.

Always take off from a level surface, or ya might be real busy for the first few seconds after take off  Surprised

If it wobbles in flight, look for damages blades or a bent shaft.

Always make sure that the two little dogbone links are still attached to the flybar and upper blade grips also, check those after every crash please. 

Also make sure there's no excessive slop between the movement of the upper blade grip and flybar. If one turns, the other should follow, without alot of freeplay. It's normal for the flybar to flop, but im talking about rotational slop between the two.

If your only problem is rearward drifting, either move the battery rearward, or turn off the ceiling fan Surprised   Dennis

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Freeonthree
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February 3, 2012 - 6:49 am
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OOPS !  One more thing I want to to check. Take er up and hover. Watch the tail rotor closely while hovering at neutral right stick. The tail rotor should not be turning at all. If it is, thats your problem. If thats the case, the tail rotor is turning at neutral stick, I have some research to do, as to wether that would be the heli's circuit board or a transmitter issue.  Dennis

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Freeonthree
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February 3, 2012 - 6:55 am
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If the tail rotor turns at neutral right stick, remember these are infra red (terahertz), so things like bright lights, sunlight, TV's, and other things can affect it. Make sure you don't have something turned on nearby that might be messing with it.

Hopefully, moving the battery slightly forward will fix er up.   Dennis 

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hc
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February 3, 2012 - 7:50 am
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All good suggestions.  Lets discount the effect of environment..breeze from the fans, lights, etc because others are flying correctly (even another S107).

It wont really hover and take off.   It wants to simply throw itself off the the left and not take off.  If we hold it up and let it take off from then hand, it veers off course immediately.  No hovering even trying to compensate with the controls.

Dogbones are intact, top blades follow the flybar...so everything looks OK there.  The shaft looks straight best as I can see.

Tail rotor is not spinning, but can be controlled.

It was mentioned it looked like it was vibrating alot....not excessive but maybe a lil more than it should be?

 

When i do try to take off...it starts....wobbles around pretty bad and then just sheers off

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Freeonthree
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February 3, 2012 - 8:52 am
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Something it off center, out of balance, or a shaft is bent, hense the wobble.

Look at the top blade grip, grab a blabe tip and push pull back and forth, The blade grip should only move maybe 1/16 inch max.

The flybar attachment should not have any slop, keeping the flybar centered to the shaft. Again, the upper blade grip is ok if it only moves back and forth about 1/16th inch, but the flybar should stay perfectly centered to the shaft.

If it's having trouble lifting off, and wants to rotate, look at the gear teeth for wear (slippage), and also alignment with other gears teeth. Check alighment with the heli verticle, and make sure the shaft moves up/dn freely maybe 1/16 th inch.

Now hold the heli up by the flybar, and check all that again, for proper alignment.

At no time, should any meshing teeth of the gears, ever be NOT fully on the teeth it's meshing with, no hang over of teeth.

Now look in the side of the chassis, and see the two big gears on the main shaft.

The top gear is for the lower blade. Hold that gear from turning, and make sure you can't rotate the lower blade without that upper gear turning. Is anything slipping beside the gear in your fingers ?  If so, BINGO !

Now do the same with the lower big gear and the upper blade grip. Don't twist it by the flybar for that test please.

If nothing is slipping, how old are the motors ?  Have they been subjected to crashing and leaving the throttle on  Surprised

You may have a motor going out, loosing rpm, or getting erratic due to poor contact between the commutator and the brushes. 

If one of these tiny motors gets too hot, or the brushes have arc'ed alot from excessive load, the delicate brush springs can loose their strength to push.   Are we getting close ?   Wink   Dennis 

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Heliman
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February 3, 2012 - 10:24 am
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I had a similar thing happen to mine, it was so unstable you really couldn't fly the thing.  I discovered in the end that the buckles (the dog bone things mentioned above) can get pushed too far in causing instability.  It's like a tiny ball and socket joint and the socket should only just pop over the ball.  If you can see the ball clearly sticking almost through socket then you need to pull it back into the correct position with a thumbnail.  You will hear a slight click. 

Any one of the four joints can cause the problem.  It can vary from a slight wobble in the hover to being vitually un-flyable.     

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hc
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February 3, 2012 - 10:30 am
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Comparing to the other S107 in our lab....it appears that the top rotor assembly and stabilizer bar is....lack of a better term...floppy.  Its sitting at rest around a 45 angle where the other is maybe 10 degrees down.  Im guessing its something in that top assembly, so gonna take it apart tomorrow and see what I can see...

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hc
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February 3, 2012 - 10:40 am
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So who can wait till tomorrow when you have  a bench with magnifiers, microscopes and tools!

 

Believe I found the problem...the yoke for the top rotor was sheared off....so the blades wont stay stable.  Gonna see if it glues else wait for my spare parts...unless Dennis has a spare he wants to throw in the mail? 🙂

 

I'll see if that fixes it....but...many thanks to all of you that replied with great things to check!

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Freeonthree
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February 3, 2012 - 12:08 pm
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Heliman said:

I had a similar thing happen to mine, it was so unstable you really couldn't fly the thing.  I discovered in the end that the buckles (the dog bone things mentioned above) can get pushed too far in causing instability.  It's like a tiny ball and socket joint and the socket should only just pop over the ball.  If you can see the ball clearly sticking almost through socket then you need to pull it back into the correct position with a thumbnail.  You will hear a slight click. 

Any one of the four joints can cause the problem.  It can vary from a slight wobble in the hover to being vitually un-flyable.     

Good one !   Thanks !   I just added that to my notes. I completely overlooked that posibility, and thats a darn good one.

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Freeonthree
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February 3, 2012 - 12:18 pm
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hc said:

So who can wait till tomorrow when you have  a bench with magnifiers, microscopes and tools!

 

Believe I found the problem…the yoke for the top rotor was sheared off….so the blades wont stay stable.  Gonna see if it glues else wait for my spare parts…unless Dennis has a spare he wants to throw in the mail? 🙂

 

I'll see if that fixes it….but…many thanks to all of you that replied with great things to check!

Are you saying the splines on the shaft are slipping inside the upper yoke ?  Yoke is stripped inside ?

Sorry, all my parts are on Yellow and Blue, unless ya need a tail rotor blade, I still have both spares of those.

 Hmmm… 11 and 12  ?  Hmmm...  Oh !  23 !   here goes !   lol

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Freeonthree
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February 3, 2012 - 12:23 pm
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Looks like we have another successful S107G resurection in the works  :>)  Ya just can't keep a good S107G down  Wink

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Freeonthree
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February 3, 2012 - 12:38 pm
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I believe Super Nova did a help video about repairing that joint up there.  Dennis

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Heliman
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February 3, 2012 - 8:06 pm
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On mine at least nothing was stripped.  Not even any wear on anything.  It was simply that the pop joints had got pushed in too far. 

 

I've just done a test on mine and with one upper joint set wrong it doesn't hover as well, sort of weaves about a little.  With both upper joints wrong it gets much worse.  Three joints set wrong and you really can't keep it in the air! 

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Freeonthree
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February 3, 2012 - 10:17 pm
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Are you talking about the dogbone links ?  Thats good info there. I havn't experienced that yet with mine, but im glad you described the symtoms of one or both being past the balls (after crash issue). That would be alot better than losing one.

I hope thats the worst thing that ever happens to mine. lol 

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