400MX going up and down  
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All Forums >> RC Helicopters >> Electric RC Helis >> Helimax >> 400MX going up and down
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400MX going up and down - 6/24/2008 11:55:13 AM   
3 for 3


 

Posts: 34
Joined: 8/12/2004
From: Flint, MI, USA
Status: offline 		first, I'm a newbe to helis and only hover with nose out with lots of G2 sim time.

My MX400 will hover fine at eye level for about 30 secs and then it starts to go up and down needing alot of collective (left stick) adjustment. It will start to rise to about 20 feet with my collective stick moving down. then when the heli decides to descend I have to give up collective to compensate. So I have to start over-correcting because of this oscillating up and down. I have two 2100MaH lipos and the craft does the same oscillation on both batteries.
I have looked at the paddles and they are level (naked eye) and all the linkages and servos check ok.

Any ideas or suggestions?

thanks,
rcs
       Post #: 1

RE: 400MX going up and down - 6/24/2008 5:06:19 PM   
PilotLight



Posts: 837
Joined: 8/15/2003
From: Benton Harbor, MI, USA
Status: offline 		Is the main shaft moving up and down slightly? Slop in the collective servo or the linkage?

(in reply to 3 for 3)
       Post #: 2

RE: 400MX going up and down - 8/5/2008 6:33:14 PM   
3 for 3


 

Posts: 34
Joined: 8/12/2004
From: Flint, MI, USA
Status: offline 		Well i finally got the time to troubleshoot this up/down pogo action.
I discovered two items
1. the feathering spindle was slightly bent
2. there was a bind on the binding slide block as it moved up and down on the center hub pin.

I reassembled and it flies ok.
My next issue that I need to resolve is a constant pulsating of the heli while flying. People have asked me if I'm nervous and are my fingers trembling. No, I'm rock solid the heli is doing its own thing. Any ideas?

rcs

(in reply to PilotLight)
       Post #: 3

RE: 400MX going up and down - 8/6/2008 1:25:31 AM   
osterizer


 

Posts: 1548
Joined: 3/10/2007
From: Sykesville, MD, USA
Status: offline 		Soundslike there's some crash damage. What kind of pulsing?

(in reply to 3 for 3)
       Post #: 4

RE: 400MX going up and down - 8/6/2008 1:58:38 AM   
3 for 3


 

Posts: 34
Joined: 8/12/2004
From: Flint, MI, USA
Status: offline 		I flew the heli tonight and observed that it is intermittant. I checked the position of my antenna to the heli to cofirm that there was not a radio "hit" occuring. The pulsing is a slight shudder of the heli in all axis. It does not appear to be shuddering in the up/down axis. The four corners of the landing gear are oscillating up and down. No specific pattern. It's like some one is grabbing the heli and is shaking it.

This is like describing what chocolate tastes like. I suspect a video would shed large amounts of description to my problem. But I do not own a vid camera.

rcs


(in reply to osterizer)
       Post #: 5

RE: 400MX going up and down - 8/6/2008 2:43:37 AM   
osterizer


 

Posts: 1548
Joined: 3/10/2007
From: Sykesville, MD, USA
Status: offline 		I'd be checking the shafts that you didn't replace starting with the main, making sure nothing is binding up in the head, and making sure the autorotation bearing doesn't slip driving the mains. Also that the blades aren't binding in the grips (clamping and dragging, but not sticking), and that the head speed is up above 2300 RPM or so, to start. There are a lot of things that could be out of whack or sticking or broken- this is just the list I can come up with off the top of my head.

(in reply to 3 for 3)
       Post #: 6

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