Discussions

HI all,

A question regarding Centre of Gravity, vs Centre of Thrust.

Basically, I attempted to fly my prototype tonight, but it failed dismally - it flipped over on it's nose. Now, I do think there's a problem with the Turnigy multistars that are in there - the throttle response is utterly brutal, even after setting the end points.

They also do something weird...if you arm and just add enough throttle to start spinning them, they slowly start to get faster and faster, and you can hear one or other of the motors pulsing. It will continue until it either flips forward or you cut the throttle. If you do cut the throttle, the brake appears to be on (even though I supposedly turned it off).

Do compassmot (9%), throttle end point etc...no problem - linear response, and no braking. Anyone seen this before?

But more fundamental is the frame design (see below). Put simply - my CoG is around 4cm forward of the CoT (the point directly at the intersect between all 4 motors.). My CoG is exactly halfway between a line joining the front motors and the line joining the two rear motors.

Even with the V frame config, I do believe this is too much, even for a big quad like this, and serious design cock-up on my behalf.

Thoughts? I can kick the front legs back to a 45% angle, which will fix this, but then we're back to "prop intrusion" on the video (though maybe not with some nex5 lens options, but I'd rather not have to rely on that).

One thing I am doing is chucking the multistars, and putting my old T-motor 30A opto pro's on, and will see how it flies then. If at all.