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Old 01-06-2018, 03:56 AM   #1 (permalink)
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Default v977 tail doesn't hold. Any suggestions?

Hey guys I am new to v977. this bird arrived our door a few days ago. Had some flights, despite some mild tail wag up and down out of box, it flies nicely and fast, flip and invert with no problems.

But things went wrong after a few crashes, the tail won't hold any more! pitch pump or hard cyclic will make its tail swing to the right. I replaced the entire tail boom set and the stripped main gear but the same problem remains, now it's not safe to fly (

Anyone experienced this same problem before?
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Old 01-06-2018, 07:53 AM   #2 (permalink)
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Originally Posted by koopa137 View Post
Hey guys I am new to v977. this bird arrived our door a few days ago. Had some flights, despite some mild tail wag up and down out of box, it flies nicely and fast, flip and invert with no problems.

But things went wrong after a few crashes, the tail won't hold any more! pitch pump or hard cyclic will make its tail swing to the right. I replaced the entire tail boom set and the stripped main gear but the same problem remains, now it's not safe to fly (

Anyone experienced this same problem before?
Tail hold is pretty amazing on these for what they are, so you definitely have a problem. If you replaced the whole boom with a new motor, that should resolve any issues there. Have you taken a look at the wiring and especially the board itself. Maybe there is a crack in the solder or actual board, and the latest crash made it worse. Getting a new board is really going to be your next step unless someone else has a better idea.
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Old 01-06-2018, 08:20 AM   #3 (permalink)
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Check that you don't have any up/down play on the mainshaft - the main gear could have slipped down giving you much more positive pitch...
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Old 01-06-2018, 08:22 AM   #4 (permalink)
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If all else fails pick up a second bnf k110 and use the first one for parts. Ive done that for other micros if it is a board issue.

either your tail motor is over-revving or your headspeed is dropping. Either way sounds like an esc issue imo if you put a new motor on tail. I doubt it is a main motor issue unless you main gear or pinion is slipping a tiny bit. it doesnt sound like your headspeed is an issue tho which means tail issues. might double check the connections there.
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Old 01-06-2018, 07:41 PM   #5 (permalink)
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Thank you guys.

After every crash first thing i checked is whether main gear has slipped. it is well in correct position.

I replaced the whole tail boom set including the tail motor, which would point right back at the ESC board as you suggested. Have looked at the wiring and the board itself couldn't detect any physical damage. I will order another ESC to see if it fixes the problem.

Cheers
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Old 01-08-2018, 01:51 PM   #6 (permalink)
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Feathering shaft........ I know it seems completely unrelated to the tail but I have seen this many times. Last year my V977 developed tail issues, particularly not holding on pitch pumps, I thought oh.... the tail motor Is dying so popped a new one in confident it would fix the issue but the problem remained Replaced the feathering shaft and the tail was rock solid.

With these little micros, when I see tail issues, the motor is last on my suspect list. First thing I do is pop a new feathering shaft in, especially if it's had a few hard knocks in recent flights. Bent main shaft and warped or poorly balanced main blades can also affect the tail. It plays havoc with the flight controller.

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Old 01-11-2018, 10:29 PM   #7 (permalink)
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Today I checked both its main shaft and spindle shaft, they are not bent and in good condition. Charged up the battery and give it another try, tail still doesn't hold well when flying hard. However at reduced pitch range it flies fine. i will include a new esc board in my next shipment. cheers
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Old 01-31-2018, 03:24 AM   #8 (permalink)
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The tail blades can crack through the motor spindle hole , hard to see but slips like crazy under load...... Try a new tail blade.


Most guys upgrade to the k110 motor and tail blade or the k110 motor / K120 tail blade
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Old 04-18-2018, 11:15 AM   #9 (permalink)
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I'm having the exact same problem OP describes with my K110. It happened after a few crashes. The main shaft isn't bent, and neither is the feathering shaft. Based on this thread, it sounds like the issue is either the main board or the ESC - if the OP is still here, which one did you order, and did it solve the problem? The ESC is cheaper - I'm debating ordering another ESC, or do I need a whole new main board?
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Old 04-18-2018, 05:35 PM   #10 (permalink)
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Obviously I can't say 100% it's a shaft or blade balance but I can say this..... testing them using the rolling method is far from foolproof with these tiny little parts. I've had shafts that looked ok visually but we're out by a hair and that's enough to cause issues on these nano class models.

I just don't understand why you would start with two of the most expensive parts on the model. New feathering shaft and blades are cheap as chips, infact they're cheaper than a bag of chips

A worn/damaged main gear is another potential cause for tail issues.
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Old 11-17-2018, 04:15 AM   #11 (permalink)
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lol it's been for a long while.. over the year I have learnt many many things about this hobby and just recently I decided to have a look at my v977 again in hope to figure out what went wrong, then I found the root cause of its TBO. ie. collective pitch range was set too high..

I remember when I was a newbie after a few crash with my v977, it didn't have enough negative pitch even the gear didn't slip. So I simply used trim to increase the negative collective range to the desired level, which would cause the positive pitch range become even higher. No wonder the tail couldn't keep up with the massive positive reactional torque.

So I leveled the swash, re-center the swash at mid stick by adjusting the length of servo linkages, let both positive and negative pitch range are roughly equal and docile (10 degrees or less). Also made sure no collective trim is used. TBO is gone! my old v977 is flying again.
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