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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 07-15-2007, 12:41 AM   #1
garfro
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Default Heli spins hard on takeoff

I have 450sa and am just about hovering but the last few times i have taken it out to practice it gets a few inches off the ground and starts spinning (cant remember left or right) 1st time the belt looked slack so tightened and it still does it ......took it apart and looked for broken teeth and belt wear but can see none, tail rotor seems to spin up ok

Ant ideas????
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Old 07-15-2007, 12:45 AM   #2
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after your in the air dose it still do it. if not before you take off putt a little right rudder into it and it will stop it. my se v2 was doing the same thing at the first time youd take off on a new pack so i took off then landed measured the tail pitch then set the center of the servo at that.
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Old 07-15-2007, 12:49 AM   #3
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More than likely, you've got the gyro working backwards. I strongly suggest you checkout Finless's gyro video HERE
and pay particular attention to the final direction checks towards the end. Almost everyone who mentions this issue has the gyro direction reversed and has neglected to verify the proper operation of the gyro prior to spooling up the heli.

Good luck!
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Old 07-15-2007, 12:55 AM   #4
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Do you use to be ablle to hover ok, whit out this problem?
if so what changed? di you replace some stuff?

what gyro have you got?
Are the tail blades spining the correct way, are they on the correct way.
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Old 07-15-2007, 12:57 AM   #5
garfro
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Quote:
Originally Posted by Skiddz
More than likely, you've got the gyro working backwards. I strongly suggest you checkout Finless's gyro video HERE
and pay particular attention to the final direction checks towards the end. Almost everyone who mentions this issue has the gyro direction reversed and has neglected to verify the proper operation of the gyro prior to spooling up the heli.

Good luck!
I was thinking that myself.........after checking the mechanical side Ithought it must be in the electrics.....funny it was ok before


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Old 07-15-2007, 01:00 AM   #6
garfro
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Quote:
Originally Posted by Brent@paradise
Do you use to be ablle to hover ok, whit out this problem?
if so what changed? di you replace some stuff?

what gyro have you got?
Are the tail blades spining the correct way, are they on the correct way.
Yeah it flew (well hovered) before then one time i took it out and the problem started

keep it up guys we will fix this together

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Old 07-15-2007, 01:01 AM   #7
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So, you've been able to hover this thing before?? Or at least spool it up? Did the skids ever leave the ground before without it spinning? What kind of surface are you flying from?
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Old 07-15-2007, 01:06 AM   #8
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Quote:
Originally Posted by Skiddz
So, you've been able to hover this thing before?? Or at least spool it up? Did the skids ever leave the ground before without it spinning? What kind of surface are you flying from?
It has hovered before and i have been hovering over grass that is maybe a bit too long and then one day it just started doing this and i am doing the obvios things to rectify but with no results

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Old 07-15-2007, 01:11 AM   #9
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Grass has a LOT of surface friction and I was thinking you'd never actually got the skids clear of the grass and therefor never seen the spinning problem...

I'd certainly take a good look at the gyro setup and make sure you've got everything centered up mechanically (gyro in rate mode - or even better - completely out of the loop) and make sure the gyro initializes in HH mode *AND* is operating the proper direction..

Which gyro/servo are you running?
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Old 07-15-2007, 01:15 AM   #10
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the gyro is a GY401 with JR 3400 digital .....I am going to check the gyro but like i said it was ok before then started doing it ..no repairs/crashes etc

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Old 07-15-2007, 03:45 AM   #11
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reverse the gro direction
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Old 07-15-2007, 03:32 PM   #12
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check the gear that holds your tail belt on inside the block. if it is plastic it could be starting to frey off the top part that holds the belt on. mine started doin the same thing one day and just looking from above while the heli was spinning up i could see it shaking a bit. then i discovered it was just about to break and of course i have the metal gear one now and no prob since. if u allready have the metal belt gear then i guess this wont help you. I am shure you will figure it out with all us frieks on here
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Old 07-15-2007, 04:21 PM   #13
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I'm wondering if you haven't got some binding in the tail rotor control rod, pitch slider, or perhaps the tail servo itself isn't working. Just because the tail rotor spins up doesn't mean that it's working properly.

Check your linkage and tail pitch slider for proper operation.
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Old 07-16-2007, 06:42 AM   #14
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If you changed the belt, did you check to make sure you twisted it hte right way the tail blades are turning the correect direction (front blade turns UP intothe rotor wash)?
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Old 07-16-2007, 03:16 PM   #15
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I have just had the exact same situation as nwtampaguy34,- the gear didn't follow the shaft when the RPM's increased. I tried to CA it on the shaft and it worked fine, but I have now ordered the HS1216 for replacement. It seems that plastic parts in this position is unreliable.

I was hard to tell because at low speed it all looked okay, but immediately at takeoff it began spinning left.

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Old 07-16-2007, 04:52 PM   #16
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Garfro:
I had something similar happen. When I was learning I hover one morning didn't do anything to the heli that afternoon it did what is happening to you. Suggestion. spool it up on cement or tile, put left and right rudder to see if it respond. then take it out side and see if it does it when you take it airborne. If you have a good rudder and goes out of control piro of the ground then is the Gyro reversing switch on the gyro it self. Can't explain why but it happen to me.
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Old 07-16-2007, 11:56 PM   #17
NINJA RICK
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I have now seen three new 450sa with the slipping tail belt drive gear

problem.

the birds all did strange things at takeoff and would kick in hover

intermittently. simply replace the tail drive gear assembly with the metal

one and get the high quality tail belt from tech-mp.com. :wink:
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Old 07-17-2007, 04:33 AM   #18
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Have you set the GY401 to digital? better set it to analog since you are using a JR servo.. they are not 100% compatible...
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Old 07-17-2007, 07:41 AM   #19
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Quote:
Originally Posted by soneebee
Have you set the GY401 to digital? better set it to analog since you are using a JR servo.. they are not 100% compatible...
Where did you get this info? I've never seen anything that even remotely implies a problem using the 3400 in digital mode on a 401. I've never had a problem either
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Old 07-17-2007, 12:47 PM   #20
garfro
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OK guys......i am convinced it is slippage on the belt or plastic gears so have got new gears (metal) and a new belt,

any tips on replacing the front gear (easist way to dismantle)
Tail I can do

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