My helimax cp jumps up for no reason.  
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All Forums >> RC Helicopters >> Electric RC Helis >> Helimax >> My helimax cp jumps up for no reason.
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My helimax cp jumps up for no reason. - 2/12/2008 12:18:52 PM   
Bradnplanes


 

Posts: 20
Joined: 2/10/2008
From: Minneapolis, MN, USA
Status: offline 		I am a new pilot and had a few minor crashes , but it jumps up about 3 feet in the air on
occasion , kinda makes me nervous and did crash a couple times because of it..
In addition it seems to be an all or no lift ,, I am going to look real close at all the head parts for
wear or damage...

Brad
       Post #: 1

RE: My helimax cp jumps up for no reason. - 2/12/2008 9:16:07 PM   
alienteabagger


 

Posts: 316
Joined: 2/28/2007
From: miami, FL, USA
Status: offline 		Check the ball ends on the head assembly and swash. Sometimes there is molding flash left on them and it causes what is called "Sticky collective".

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(in reply to Bradnplanes)
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RE: My helimax cp jumps up for no reason. - 2/13/2008 12:12:14 AM   
r_william


 

Posts: 102
Joined: 1/24/2008
From: Boynton Beach, FL, USA
Status: offline 		Yea,
or bent feather spindle, or too low head speed, or...

RW

(in reply to alienteabagger)
       Post #: 3

RE: My helimax cp jumps up for no reason. - 2/13/2008 1:49:33 AM   
PilotLight



Posts: 837
Joined: 8/15/2003
From: Benton Harbor, MI, USA
Status: offline 		I was just facing the same issue. I replaced the blades and found the tracking was a little off, so I raised the low blade. The next flight it was either going up or down. I couldn't get it to hover. Tried everything to make it quit, but I liked the fact the blades were tracking nicely. Finally, I decided to lower the same blade then to lower the original high blade . Tracking was nice and it hovered nicely. Check all the servos for stripped gears but couldn't find any. Guess it was just a spot where the swash didn't like to be in relation to the servos and throttle stick.

Keep at it, you'll eventually get a good flying heli. Balance the blades, balance the flybar, check for sticky swash or links.

(in reply to r_william)
       Post #: 4

RE: My helimax cp jumps up for no reason. - 2/13/2008 2:21:16 AM   
mensaboy


 

Posts: 65
Joined: 11/30/2007
From: Torrington, CT, USA
Status: offline 		this is from another thread


the "flip flop" from positive pitch to negative pitch due to slop in the rotor head is what causes this

if you have a high enough head speed to maintain a hover with very little pitch, as soon as you go near zero pitch, the linkages allow one of the blades to 'flop" over to negative and get that sudden, powered decent

the only way to alleviate this in a bird with the AXE's slop, is to increase the pitch at lower throttle, so you will descend well before zero pitch due to lack of head speed

or get rid of the slop with a metal center hub/flybar system, ala microheli

the other, less likely possibility, is that you have your flybar paddles on reversed

(in reply to PilotLight)
       Post #: 5

RE: My helimax cp jumps up for no reason. - 2/13/2008 4:22:07 AM   
Bradnplanes


 

Posts: 20
Joined: 2/10/2008
From: Minneapolis, MN, USA
Status: offline 		In addition when it pops up,, it seems like the main motor is getting a surge of power..
it happens when its hovering about as best as I can ,, seems like its in the sweet spot then up 6 feet and
big time pitch to the left..

i am going to try adjusting the pitch to start earlier in the rotor speed somehow...

thanks for the tips


Brad,,

(in reply to mensaboy)
       Post #: 6

RE: My helimax cp jumps up for no reason. - 2/13/2008 6:41:40 PM   
mensaboy


 

Posts: 65
Joined: 11/30/2007
From: Torrington, CT, USA
Status: offline
quote:

ORIGINAL: Bradnplanes

In addition when it pops up,, it seems like the main motor is getting a surge of power..



right, that would make sense, if you were hovering with one blade flopped to -1 pitch, and the other flopped to +4 or so, you would imagine there would be a fair degree of wind resistance since they are fighting each other, when you give enough pitch so the blade at - flops to positive, they are now both working for lift and not only does the heli pop up in the air, your headspeed will increase dramatically


the best way to confirm this is to hold the heli in your hand and pump the throttle slowly from 1/4 stick to 3/4 stick (roughly) the amount of lift from low stick to high should not jump dramatically from resting in your hand to pulling out of your fingers, if it does (this is like bending a card between your fingers and thumb, and popping it one way and the other, while keeping the card under pressure - you notice a distinct flop), then somethings flopping on the linkages

you can fix this by adjusting all 3 swash to servo links the same amount (move the swash down a bit) - the smallest change will likely fix it, just need to get that one low blade to flop up to + pitch before the heli lifts off

of course if your tracking is a good bit off this problem gets much worse, so that needs to be checked first

(in reply to Bradnplanes)
       Post #: 7

RE: My helimax cp jumps up for no reason. - 2/14/2008 4:17:17 AM   
blvdbuzzard



Posts: 1483
Joined: 6/16/2002
From: boulevard, CA, USA
Status: offline 		I am flying my AXE #2 now. Totally stock. I had a crash because it was doing to same thing. Jumps up then falls like a crazy leaf. Well the center hub popped and the blades flew up and away. I picked up the pieces and came home. I was putting it back together and found that there was some flash on the hub where it slides in the slide block. As I put my new parts on I feel the notch in the new parts. I found the flash was catching and making it stick then slide. I sanded it down and it slide free now. Maybe that was my problem.


Dru.

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       Post #: 8

RE: My helimax cp jumps up for no reason. - 2/14/2008 11:37:59 PM   
Shadow99


 

Posts: 385
Joined: 8/23/2007
From: Southwick, MA, USA
Status: offline 		Be sure to lubricate all your sliding points on the rotor head, swahplate, ball links, etc. Plastic parts need lube too. I use a silicone grease for all my componets, but some use Tri-flow grease as well.

Shadow


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(in reply to blvdbuzzard)
       Post #: 9

RE: My helimax cp jumps up for no reason. - 2/17/2008 7:37:19 PM   
besthobbie


 

Posts: 32
Joined: 1/26/2008
From: Buffalo, NY, USA
Status: offline 		I had the same problem but what i found was my transmitter wasnt working properly when my cell was close by. My cell phone was messing with my signal. Make sure you do not have it close to any other electronic devices..Im going to change my reciever to a digital one and run it off my dx6i that would help...

(in reply to Shadow99)
       Post #: 10

RE: My helimax cp jumps up for no reason. - 2/18/2008 10:00:33 PM   
PilotLight



Posts: 837
Joined: 8/15/2003
From: Benton Harbor, MI, USA
Status: offline 		Something I tried today was to add a little up or down pitch to the flybar paddles. Seems a little negative pitch smoothed things out a little. If you went too much negative pitch with the throttle stick, it would "jump" downwards instead of up, but it hovered much better. I starting to think its a sloppy servo gear set.

(in reply to besthobbie)
       Post #: 11

RE: My helimax cp jumps up for no reason. - 2/18/2008 11:40:23 PM   
blvdbuzzard



Posts: 1483
Joined: 6/16/2002
From: boulevard, CA, USA
Status: offline 		Mine started to jump real bad. It was all over. No real pattern to the jumps, just up down left right. I had it on the bench and my left hand servo was real sloppy. I could move the arm up or down over an 1/8". I swapped out the servo for a real HS-55 and it flew much better. I also saw the "Z" bends were sliding from side to side. I have ordered a set of links and ball joints so I can put a ball link on each end of the rods and get rid of the "Z" bends. I am replacing the stock arms with the Dubro heavy duty arms. For the stock location, it is the second hole out. There is a lot of arm to cut off, but they are stiffer then the stock ones. After I have it all setup I will give a flight report.


I am looking for a better servo then the HS-55. There are some Airtronics micros 94761, HS65's. I would like to have them have a lot less slop. I can still get a lot of movement out of the new HS-55's. They are about 1/3 as sloppy as the stock servos. If I twist the blades, I can get 3 or more degrees out of the blades and not move the servo gears. If I hold the links there is not much slop in the ball links. Is any one running better servos out there? If so, what are they?


Dru.

(in reply to PilotLight)
       Post #: 12

RE: My helimax cp jumps up for no reason. - 2/20/2008 9:33:32 PM   
PilotLight



Posts: 837
Joined: 8/15/2003
From: Benton Harbor, MI, USA
Status: offline 		Flew again two flight so far today and it has not had any problems with the paddles set with just a little negative pitch.

Could somebody here with the "jumping up and down problem" try this and verify it's a possible fix?

(in reply to blvdbuzzard)
       Post #: 13

RE: My helimax cp jumps up for no reason. - 2/21/2008 12:22:04 AM   
r_william


 

Posts: 102
Joined: 1/24/2008
From: Boynton Beach, FL, USA
Status: offline 		Hey PilotLight,

I'll be sure and try it as soon as the S. Fla. weather will allow.
It's been too windy to fly outdoors for the past 5 days and the jumping makes it too risky to fly in my garage.
I got my Axe about 6-7 weeks ago and this [jumping] has lowered my confidence and flattened my learning curve.
I'm still trying to hover a full battery pack in a 20' x 20' area.

RWW

(in reply to PilotLight)
       Post #: 14

RE: My helimax cp jumps up for no reason. - 2/21/2008 3:34:19 AM   
PilotLight



Posts: 837
Joined: 8/15/2003
From: Benton Harbor, MI, USA
Status: offline 		That's actually a pretty tight area for learning to fly. The air flowing down under the heli will go out and hit the walls and begin to create airflow around the room. Airflow is ok as long as it is constant and from the same direction. In a small room it will change in intensity and direction.

Let me know if the jumping settles down, though.

(in reply to r_william)
       Post #: 15

RE: My helimax cp jumps up for no reason. - 2/26/2008 1:27:38 AM   
Bradnplanes


 

Posts: 20
Joined: 2/10/2008
From: Minneapolis, MN, USA
Status: offline 		(
I gave it a bit more pitch from stock , then a bit more pitch ,(recomended by helimax tech} just to get the jumping to stop, the shaft was smooth with no binding and i even got new ball links without the Z links.... In frustration I took it back to the LHS ,, they took a look at it and said the main shaft was bent but he was going to send it in under warrenty,,, I kinda find it hard to belive the shaft is bent because the blades tracked perfectly and it is very smooth with little or no vibration.. oh well I would guess he knows better than I do...LOL