General Help with forward movement

zenmetsu

zenmetsu

Member
I am noticing that my heli wants to move forwards while hovering. I have adjusted trim to provide rear-cyclic to counter it, but I cannot find the cause of the motion. COG is about as perfect as I can get it, and I cannot detect any nose-heaviness while balancing the heli on the flybar while the blades are inline with the body.

With the amount of rear cyclic trim that I have applied, the swash is visibly tilted rearward. I suspect that something else is out of whack. Should I add mass to the tail to try to counter the tendency to move forward, or is there something else that could be causing this behavior?
 
Tony

Tony

Staff member
You can try to add some ballast to the tail, but if it's flying fine with the cyclic, you should be fine. How much tilt are we talking about?
 
zenmetsu

zenmetsu

Member
I removed the head button and put a bubble level across the blade grips while suspending the heli from the flybar. Fore/aft tilt was nonexistent according to the bubble level, so my COG should be fine. Swash is currently tilted to the rear about 3° to zero out the movement.

I have a suspicion that it is a weight issue and the fact that the COG is so far below the flybar it is difficult to detect an imbalance by balancing on the flybar. I'm going to try rolling the heli on a dowel (on it's skids) and see where the COG is that way. Any idea how to add ballast to the tail in a sane way?
 
zenmetsu

zenmetsu

Member
I am using one of those Hyperion 850mAh packs, ya know, the ones that are about 3.5 miles long. :/ Not really much way to move it backwards.

What gets me is that I wasn't having this problem earlier. I played around a bit at a friend's house, hovering in his yard (at night, and in gusty conditions) and eventually lady luck decided to leave me for a better man and I ended up doing some grass mowing. Nothing major, but I did end up replacing a feathering shaft and one of my linkages since it split open (the one going from the flybar seesaw up to the blade grip). Ever since then, I have noticed this issue.

On the plus side, I did discover a fix for the one-way bearing issue that I was having. Turns out that tightening the screw and washer at the base of the main shaft too much causes binding since the metal that the washer butts against will not rotate in relation to the main gear. My solution was to use a slightly longer screw so that it ends up binding inside the main shaft just as the washer is being pressed against the base of the bearing housing. It was a standard screw in the kit, i'll measure it and maybe put up a post on the topic once i've tested this fix for a while. My blades now rotate freely for a good 20 seconds after I kill the motor, as long as there is no pitch on the blades.

As for my balance issue, I'm just going to throw my HSG-5084MG back on the tail and see if it helps. It might work better with this quark; it was not working well with my GY401 gyro.
 
zenmetsu

zenmetsu

Member
I put my other servo on the tail and that almost balanced the heli. I ended up taking out the horizontal screws that secure the aft part of the tail boom supports and used slightly longer screws so that I could slip a flybar weight over the screw. That fixed her right up.

I talked my fiancé into recording my hovering this afternoon, so I'll post a link in the video section once the video is done uploading to youtube. It was overcast and gusty, so it was a good test of my gyro and tail servo. :)

*ugh, youtube only pulling down 95KB/sec from my connection. 2 hour wait for video :(*
 
Last edited:
S

scott17818

Member
thats why I use my iphone as a network connection when uploading big vids... faster than my cable modem.. capped at around 50k/sec..
 
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