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450 Class Electric Helicopters 450 Class Electric Helicopters manufactured by Align, Tarot, SYMA, Airhog, Chaos, HK and similar.


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Old 07-15-2014, 12:25 AM   #1
mqowen
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Default 450L wanting to roll slightly to left in air

I have a 450L, and today I kept correcting a slight left roll.

I set it down, pulled power, and let gyro reset and all seemed fine.

Then last flight same; slight roll to left.

Nothing uncontrollable, but not what I was expecting. Its as if trim was off a couple of notches except this system has you keep trim all at zero.

I notice one blade grip had play in it. Would that possibly cause something like that?

I have a 450L 3GX with futaba 6208sb rx and futaba t8fg tx.

Thoughts?
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Old 07-15-2014, 07:23 AM   #2
DavisBladeWorks
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Which FBL unit? And am I understanding correctly that after resetting your FBL unit you had a flight where you DIDN'T see the issue, then on your last flight it came back?


If the issue is intermittent, I would look to a vibration as the cause before anything else. I'd check your TT shaft first. Take the mains blades off and run the heli with your hand on the boom; what do you feel?


ETA: Sorry, read this before my coffee, so didn't see the 3gx part. All of the above still remains the same.
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Old 07-15-2014, 07:28 AM   #3
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I run BeastX on all my helis and last time i had this exact issue it was caused by a bent
torque tube. A good hard landing can cause this..
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Old 07-15-2014, 09:35 AM   #4
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Quote:
Originally Posted by DavisBladeWorks View Post
Which FBL unit? And am I understanding correctly that after resetting your FBL unit you had a flight where you DIDN'T see the issue, then on your last flight it came back?


If the issue is intermittent, I would look to a vibration as the cause before anything else. I'd check your TT shaft first. Take the mains blades off and run the heli with your hand on the boom; what do you feel?
I tightened one of the main blade grips. It had become loose and had some play in it. I could move the blade along the feathering shaft about 1 mm or so.


Quote:
Originally Posted by Sirolf View Post
I run BeastX on all my helis and last time i had this exact issue it was caused by a bent
torque tube. A good hard landing can cause this..
I will take I a look at TT. I put two bearings boom so as to better support the TT. Hopefully all good.

I didn't mention it but I dug the blades into the ground a few days back. I hit T-hold about 12 in off ground and somehow rolled it. Didn't appear to be any damage that I could see. Test flight after seemed ok. Anyway... Could be related.
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Old 07-15-2014, 07:10 PM   #5
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Did you take the blades off and stick a wrench on one of the feathering shaft bolts and turn it to see if there is any wobble. This will tell you if you have a bent feathering shaft.
If you do vibration from that could be messing with your FBL system.

Also a bent feathering shaft could potentially snap the head off the bolt letting the blades go so definitely check that if you haven't.


If it was a mild tip over the main shaft only might be bent.
If its not bent enough to see it wobble with the head on take the head off and hold the heli very steady and spin the shaft and see if there is a wobble. A small amount shows up as vibration at 3000 RMP.
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Old 07-15-2014, 08:00 PM   #6
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Not that the cause of your problem is the same as mine, but it sounds very similar. You can see my thread here:
http://www.helifreak.com/showthread.php?t=636542

I give more information about the odd behavior in my second post of the thread. I haven't found out what is causing it yet. I have been wondering if the wind has been causing it. I am leaning towards this possibility but am waiting for a still day for a control. If it were caused by the wind, the question would then be, why now?

Going to check for vibrations again. I know my TT is not as straight as they come, but I have three bearings supporting it.

I'll get back if I find anything else out.

Question: Which 3GX version are you running? I'm running 5.0. Trying to figure out if this could be one of those quirks of a version.
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Old 07-15-2014, 09:03 PM   #7
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Default Problem found - missing tooth on pitch servo main gear

Quote:
Originally Posted by Bladecpnitro View Post
Did you take the blades off and stick a wrench on one of the feathering shaft bolts and turn it to see if there is any wobble. This will tell you if you have a bent feathering shaft.
If you do vibration from that could be messing with your FBL system.

Also a bent feathering shaft could potentially snap the head off the bolt letting the blades go so definitely check that if you haven't.
I took feathering shaft completely out and roll tested on granite counter top. Checked ok.

Quote:
Originally Posted by Sefrez View Post
Not that the cause of your problem is the same as mine, but it sounds very similar. You can see my thread here:
http://www.helifreak.com/showthread.php?t=636542

I'll get back if I find anything else out.

Question: Which 3GX version are you running? I'm running 5.0. Trying to figure out if this could be one of those quirks of a version.
I think my 3GX is version 4, I know it's not 5.

Thanks for the link as it could be useful in the future.

Now for what I found. I went to fly today. Most beautiful weather of 2014 with a dead calm flag on flag pole. Never this calm ever since I've been flying. Anyway, first flight smooth and I flew entire flight upright just getting warmed up. No problems. I pulled in close. No vibrations visible. IU2 entire flight.

Second flight I get up to IU2; bam, aggressive left roll worse than before. Still able to control with sticks, but some back and forth hard twitchy movement I had to keep compensating for. Got it on ground safely. I thought gyro needed to be reset as I have caused gyro to be off before by moving heli during initialization. I even swapped batteries after only 1 min flight. Third flight, up and away; IU2 again and bam. Same thing. Back down to landing spot.

Simply, it is a missing tooth on pitch servo. I moved servo up and down by hand and I felt a very slight bump or notch. Quite a chore to get servo out and break open case but found problem.

This is a picture of the missing tooth. Hope you can see it. Its on main servo gear that has the splines for the horn. It is about the 9 o'clock position relative to the picture. A missing tooth.

From this I know now that a bad pitch servo can at least cause a left roll problem. Thinking back on this now I wonder if the 3GX didn't help save the heli by trying to compensate.

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Old 07-15-2014, 11:26 PM   #8
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I did have a slight mystery as to what caused the missing tooth. The other part of the mystery is why it would seeming fly perfectly fine one flight and be ok for a few more flights.

I thought sure it was the 3GX and my mind immediately went into hate mode for 3GX because so many people despise them it seems. However, I can't really say i have had any issues myself.

I recently ran the blades into the ground. No apparent damage, and no issues with flying until yesterday when that first slight roll came in.
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Old 07-16-2014, 07:31 AM   #9
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You know you can get gear sets for these servos? I only ask because your other thread says you replaced the servo, just wanted you to know you can get gear sets to save you some money down the road.

On the missing tooth, any hit your blades take can transfer forces down to the servos. It could have weakened that tooth and in time it snapped off.

The other possibility is you are being too rough with the servos when moving the blades around. I've seen people really man handle their helicopters when putting blades in the blade holders and such, which can't be good. Not accusing you of this, just saying it's something to watch out for.
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Old 07-16-2014, 07:38 PM   #10
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Quote:
Originally Posted by DavisBladeWorks View Post
You know you can get gear sets for these servos? I only ask because your other thread says you replaced the servo, just wanted you to know you can get gear sets to save you some money down the road.

On the missing tooth, any hit your blades take can transfer forces down to the servos. It could have weakened that tooth and in time it snapped off.

The other possibility is you are being too rough with the servos when moving the blades around. I've seen people really man handle their helicopters when putting blades in the blade holders and such, which can't be good. Not accusing you of this, just saying it's something to watch out for.
Thanks. I did have a set for my 250 but not 450. I have a couple of spare servo's and I will keep all the good gears for possible future use.

I try to handle my blades as gently as possible. In this particular case I dug the blades into the dirt accidentally hover about 1 foot about the ground. Another story. But anyway I didn't see any damage at the time and then not long after a control problem showed up.
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Old 07-20-2014, 10:21 PM   #11
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Problem was not corrected.

Turned out the roll left problem still exists.

Servo was definitely broken and it seems to exasperbated the roll left resulting in a hard roll. Roll left issue is still there but softer. A mystery. Remains unsolved.
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Old 07-21-2014, 01:09 AM   #12
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I was going to say, my servo's seemed to be fine, but the issue was there. Let me ask you this. If you let the heli tilt and begin to drift does it eventually swing back? You might have to get the heli up to let it drift any reasonable amount without crashing it.

This is what I observed. Essentially the 3gx would correct eventually, but stick inputs had me fighting continously.

Other than it being some odd 3gx behavior, I could only guess the swash wasn't level. It certainly made sense anyway. Because, if we assume the swash returns to this neutral position after the sticks are released back to neutral after input, the heli will begin to roll. Only then will the 3gx begin to correct. Give some stick input again and release back to neutral, and the cycle starts again, the tilt comes back. This is exactly the behavior I have seen.

The problem was, I had leveled the swash. I used a swash leveler for one method, and I also used a magnet with a needle that leveled the flat part of the swash itself (as opposed to leveling out at the linkages). Neither of these methods fixed the issue.

Continuing to assume it was a swash issue I said screw it as far as to leveling. If a level swash plate corresponds to a non tilting heli, and a non tilting heli corresponds to a level swash, and my heli is tilting to the right, I'll just adjust it tick by tick (sub trim in setup mode) to the left.

It seems I have reduced the tilt quite a bit now with a few sub trim clicks. You may try this also.

Perhaps for me, the swash is slightly out of alignment. I guess if I rotated it through 120 degrees and leveled again to see the tilt change 120 degrees I would have my answer.

Longer post I know.

Last edited by Sefrez; 07-21-2014 at 02:45 AM..
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Old 07-24-2014, 04:11 PM   #13
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Quote:
Originally Posted by Sefrez View Post
I was going to say, my servo's seemed to be fine, but the issue was there. Let me ask you this. If you let the heli tilt and begin to drift does it eventually swing back? You might have to get the heli up to let it drift any reasonable amount without crashing it.
I don't think I can let it drift. It is or pretty fast. With the broken servo tooth it was almost at 90 in a half sec. Now it is tamed down but will roll pretty fast. I can play with it and see what it does.

Quote:
Originally Posted by Sefrez View Post
This is what I observed. Essentially the 3gx would correct eventually, but stick inputs had me fighting continously.

Other than it being some odd 3gx behavior, I could only the swash wasn't level. It certainly made sense anyway. Because, if we assume the swash returns to this neutral position after the sticks are released back to neutral after input, the heli will begin to roll. Only then will the 3gx begin to correct. Give some stick input again and release back to neutral, and the cycle starts again, the tilt comes back. This is exactly the behavior I have seen.

The problem was, I had leveled the swash. I used a swash leveler for one method, and I also used a magnet with a needle that leveled the flat part of the swash itself (as opposed to leveling out at the linkages). Neither of these methods fixed the issue.

Continuing to assume it was a swash issue I said screw it as far as to leveling. If a level swash plate corresponds to a non tilting heli, and a non tilting heli corresponds to a level swash, and my heli is tilting to the right, I'll just adjust it tick by tick (sub trim in setup mode) to the left.

It seems I have reduced the tilt quite a bit now with a few sub trim clicks. You may try this also.

Interesting about the sub trims. I would think the heli would level according to the gyro versus if the swash was perfectly level. I'm not sure I understand how all of that works. In fact I'm sure I don't.

I will try and keep you posted of anything I learn. And thanks for your thoughts. I'm a little slow in my response last few days, but I read every single post to anything I have asked about.
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