Head problems

[MishuPtm]

Hey guys, i have my protos for a little over a year, bought it SH but it never flown properly... I've had like 10 flights with it and a couple of crashes. I finally found the cash to fix this amazing bird and after i replaced most of the bearings and broken parts it still won't fly properly.
I'm currently running 3s on it cuz i'm waiting for the serial adapter to arrive, but from my experience with this heli, 6s will only make my problem worse:
in hover, the pitch doesn't seem to be precise, basically it's impossible to keep a steady altitude; i slowly increase the pitch to take off and it eventually does, but i wanna fly a few feet above the ground, and it goes up, i lower the pitch very slowly, with no response until suddenly it rushes towards the ground, same thing again when i try to increase the pitch, no response until it goes really high.
The swashplate has some play, but i don't know if it's tolerable or if the links are not loose enough and put too much force on the servos (hks9257).
I've uploaded a clip on youtube showing the slop in the swashplate, and also how sturdy the flybar is.
Any ideas?
Thanks!

Swashplate slop and head friction? (0 min 44 sec)

[byHISgrace]

Sounds like the potentiometer(sp?) in the servos are bad. Disconnect the links from the swashplate to the servos and move the throttle stick on the transmiter(make sure your in throttle hold). Do the servos move as evenly as you move the stick? If so, do this again with slight pressure against the servos movement. The servos should move exactly as the throttle stick moves.

If they work correctly, leave the links off the swash and move it with your hand. The swash should move almost effortlessly up and down the main shaft in all points around the main shaft. Matt

[MishuPtm]

Thanks matt. The servos are fine, they work properly connected or disconnected from the swash.
The swash though does not move close to effortlessly, it is quite resistant...
I think that it gets even more resistant when i take it outside in the cold...


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[Jumna]

If there's no vertical play in the shaft from a loose/misplaced shaft collar, getting a new swash & maybe links if there are worn might help. You might also check the servos for a missing gear tooth or see if one has a lot of play too...

[MishuPtm]

I'm affraid it's the swash... Cuz there's no up and down play in the mainshaft, the servos have no play and neither the links... No need to buy new ones yet though, i need to make them move freely. If that doesn't solve the problem, i'll have to buy another swash...


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[byHISgrace]

Is the main shaft straight? Pull it and see if it rolls level on a plate of glass with no light between the glass and shaft when you roll it. The swash should slide with minimal resistance. Any rust? Do you have another one to try? Matt

[MishuPtm]

The shaft is straight, i already did that... There's no rust but the mainshaft has a strange color. That doesn't affect how the swashplate slides cuz i've tried all parts of the head to see if they bind without the links and they're very smooth. Then i add the links, not so much.

Where should i connect the grips on to the flybar spindle for a more stable flight? Closer to centre or further from the centre?


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[byHISgrace]

Originally Posted by MishuPtm

The shaft is straight, i already did that... There's no rust but the mainshaft has a strange color. That doesn't affect how the swashplate slides cuz i've tried all parts of the head to see if they bind without the links and they're very smooth. Then i add the links, not so much.

Where should i connect the grips on to the flybar spindle for a more stable flight? Closer to centre or further from the centre?


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Pull up the manual online and look at the tuning guide.

The linkage from the swash to the bell crank on the main grip is the "Bell" side and the link coming from the flybar to the main grip bell crank is the "Hillar" side. I think moving out on the Hillar side increases stability. Matt

[byHISgrace]

I finally watched the video. Remove the main shaft and polish off the discoloration with 1000 grit sand paper and test fly again. If it still has the same problem, I think the swash has too much play in it. The ball links could also be too stiff, you should be able to rotate a link with very little pressure. Matt

[MishuPtm]

I removed the servo links from the swash and tried to move it by hand. Cyclic had little resistance, but when i tried to move up and down the swash i had much more resistance. Just noticed today trying to find some vibrations that my shaft is slughtly bent, so i won't polish it. I have a spare shaft but i can't install it because i can't remove the lock ring from the old one...
Just ordered one now, after it arrives i'll have another test.
Can't wait!


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[BHChieftain]

FWIW I checked my swash and there is ZERO slop there...
Chief

[MishuPtm]

So i got this problem solved by making the links move free and changing the plastic slider right under the head cuz it was resisting alot, but just to find another problem... Pretty bad vibrations.
Without head assembly, or tail assembly and both shafts str8, i get vibrations. I have tried different belt tension but no difference. Bearings are new, motor is quite unbalanced, but the vibrations are alot worse when spinning the belt than with the belt off.


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[dr dremel]

Well first step would be then to fix the motor vibes. First check if the motor shaft has no runout. If you got the heli second hand I´d advice to replace motor bearings. Then add tape to the bell until it runs smoothly:

balancing motor rotor and open your ears... (2 min 31 sec)

If that all checks out ok and you have still vibes, on to the next components ...

[sp00fman]

I use that technique to balance my motors. Its best to start out with a new set of motor bearings. It can make quite some difference sometimes.

[MishuPtm]

Yes, i did buy it second hand, and the motor is a hobbyking one. Will look for bearings if i cand find replacements but i will give it a try to balance with tape...


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[dr dremel]

IIRC bearings should be the same as the stock Scorpion, but not sure. My motor required a good bit of tape (from new) to run smoothly, unbalanced it would make the whole frame buzz.

[MishuPtm]

What motor do you have?
My hk one has the bottom plate ofcentre, amd everybody has the same complaint about this motor.


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[dr dremel]

Same motor - the HK one, nothing to complain for the price. Depending on how much the bottom plate is off center you may well be able to balance it out

[banditpowdercoat]

I had this SAME prob with mine. Got used. What it was was the prev owner never put the .2mm shims in the head on the blade grips. All would seem smooth on bench. But in flight, was not stable on elevation. Slowly move stick, nothing nothing nothing, then bam shes rocketing upwards. Same with down. Check that those shims are in the head and make the swash move smooth too. Take head off, Work one piece at a time, from the servos. Swash, free. check, next piece in line, linkages, check, next part, etc etc. All must be smooth