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All Forums >> RC Helicopters >> Electric RC Helis >> E-Flite Helicopters >> Hard Time Holding Altitude
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Hard Time Holding Altitude - 8/10/2006 2:52:57 AM   
BLBncsu


 

Posts: 204
Joined: 5/17/2004
From: Raleigh, NC, USA
Status: offline 		Just upgraded to a 3S Lipo from helidirect and went with a 8T main motor on my BCP. I've rebuild the entire heli recently but it seems now that it has a hard time holding a constant altitude like it used to with stock setup. All it takes is one click up or down on the throttle (around 55% throttle) to send the heli up really quick or bring it down to the ground.
Not sure if there is too much pitch or too little pitch in the blades to where I may be stalling the blades at a certain head speed or what? Blades are balanced and track good. Any thoughts or advice here? Makes flying a bit tougher when it doesn't maintain altitude and bounces around the sky!

_____________________________

Car: RS4 3SS O.S .18 & More
Heli: Blade CP
       Post #: 1

RE: Hard Time Holding Altitude - 8/10/2006 3:08:01 AM   
Psikelly



Posts: 1024
Joined: 2/19/2006
From: Ottawa, ON, CANADA
Status: offline 		Its possible your main hub is slightly bent. You can look at it and say its not but it takes such a slight bend not noticable to the eye to make it stick. When it does release if you happen to be idled up itll rocket to the ceiling. This is what mine did and now that Ive replaced the hub it hovers amazing again. And oil wont help either. If it really is your hub then you should just replave it for the 8 or 10 bucks it costs

_____________________________

NO I did not just crash!! Im making it flop around on the ground like that on purpose. Its a new stunt.

(in reply to BLBncsu)
       Post #: 2

RE: Hard Time Holding Altitude - 8/10/2006 3:16:28 AM   
Psikelly



Posts: 1024
Joined: 2/19/2006
From: Ottawa, ON, CANADA
Status: offline 		oops... The best way to test this is to disconnect all linkages etc from the main hub. Taking off the flybar is helpful but I dont think necessary. If you do remove it then also remove that top screw. Then slide the top of the hub up and down on the shaft. Youll immediately notice if its too sticky



_____________________________

NO I did not just crash!! Im making it flop around on the ground like that on purpose. Its a new stunt.

(in reply to Psikelly)
       Post #: 3

RE: Hard Time Holding Altitude - 8/10/2006 5:40:00 AM   
ct420


 

Posts: 1177
Joined: 3/26/2006
From: mansfield, TX, USA
Status: offline 		Do you have good blade tracking throughout the throttle range, or does the tracking vary a bit based on throttle position?

If it varies with throttle input, and NOTHING is bent (spindle, rotor shaft, whatever...) then it is likely bad O-rings or too loose blade dampening.

I had this problem once, and found that I had to put 2 shims behind the o-rings to stiffen the dampening. This gave me solid blade tracking throughtout the throttle range, and also cured the problem.

When it was happening to me, I found it impossible to hover at a steady altitude, but if I flew in any direction, even quite slowly, then it 'smoothed out', and held altitude well. If this is happening to you, then take a look at the dampening.

Be careful not to get it too tight, though... If the nose of the heli starts to 'nod' up and down, you have it too tight, and need to remove 1 shim...

(in reply to Psikelly)
       Post #: 4

RE: Hard Time Holding Altitude - 8/10/2006 8:52:46 AM   
twistercp


 

Posts: 219
Joined: 6/13/2005
From: UK, UNITED KINGDOM
Status: offline 		try disconnectng the motors from the 4in1 and move the throttle up and down
see if the collective is smooth

(in reply to ct420)
       Post #: 5

RE: Hard Time Holding Altitude - 8/10/2006 1:07:16 PM   
Psikelly



Posts: 1024
Joined: 2/19/2006
From: Ottawa, ON, CANADA
Status: offline
quote:

ORIGINAL: twistercp

try disconnectng the motors from the 4in1 and move the throttle up and down
see if the collective is smooth


That doesnt really work. Your servos can provide enough torque with the blades not spinning to move it quite easily. I did that test with mine and I was positive it was fine but when I took it apart and tested it manually it was sticking. It doesnt take a lot of stickyness to bind the collective especially when its in motion.


_____________________________

NO I did not just crash!! Im making it flop around on the ground like that on purpose. Its a new stunt.

(in reply to twistercp)
       Post #: 6

RE: Hard Time Holding Altitude - 8/11/2006 1:09:25 AM   
BLBncsu


 

Posts: 204
Joined: 5/17/2004
From: Raleigh, NC, USA
Status: offline 		The main hub (center spindle with gear on it) is brand new. I'll check the dampening perhaps. Odd thing was though that it flew very nicely with the stock setup and once I switced to the lipo and 8t motor the problem developed. Everything as far as I can tell is straight and not bend, etc....
What size are the shims and where do you get them at? Thanks for the input.

_____________________________

Car: RS4 3SS O.S .18 & More
Heli: Blade CP

(in reply to Psikelly)
       Post #: 7

RE: Hard Time Holding Altitude - 8/11/2006 1:17:15 AM   
ct420


 

Posts: 1177
Joined: 3/26/2006
From: mansfield, TX, USA
Status: offline 		That is strange. Perhaps the higher rotor speed makes the problem more noticeable or something... Not sure...

Anyway, here are the shims:

http://www.horizonhobby.com/Products/Default.aspx?ProdID=EFLH1144

(in reply to BLBncsu)
       Post #: 8

RE: Hard Time Holding Altitude - 8/11/2006 1:51:14 AM   
rawvoodoo


 

Posts: 232
Joined: 7/1/2006
From: Canton, OH, USA
Status: offline 		My Cp Pro bounces too. When It loses alt the prop sound goes up a bit. I have a new main gear/shaft and just added 2 shims to either side of my rotor head. I still have some minor left/right slop when holding the gear and twisting the head. Im thinking that the problem might just be that the heli has such a small rotor plane and such fast response with the bell/hiller that its going into FF and losing some lift... If I manage to get a stable hover it holds better when I lose the hover and start chasing it around the garage the alt drops until I gain the hover back. These things are so twitchy its easy to tilt the rotor plane enough to lose lift.

(in reply to ct420)
       Post #: 9

RE: Hard Time Holding Altitude - 8/12/2006 11:16:55 AM   
rawvoodoo


 

Posts: 232
Joined: 7/1/2006
From: Canton, OH, USA
Status: offline 		OK my buddy has a cp with a brushless main. Its hard to judge the slop in his head because he has a oneway bearing in his gear. His doesnt bounce hardly at all though. MIne has about 5 teeth of slop if I hold the main gear and twist the head and thats with a brand new main gear/shaft Is there supposed to be some slopin that pin/hole that holds the head on?

(in reply to rawvoodoo)
       Post #: 10

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