i brought Avionic C2830 KV850 QUAD brushless motor(http://www.rcbazaar.com/products/1905-avionic-c2830-kv850-quad-brushless-motor.aspx) but when i connect it to an ESC and just throttle up the motor does not spin but instead it is jumping around and making beeping noise can you please suggest a fix ? esc calibration was already done and it spun for one time ESC is 30A simoK firmware EMAX
video link to the problem -

@ anis jayaram
Check for break or bad solder joint in the motor's 3 wires.
Regards

I agree with Iyer sir. This behavior is typical of two-phasing

Yeah, this probably could be only a loose joint, either in battery side or on the motor side.

Are you using connectors, or just twisted the cables up for testing it ?

i just twisted it to check whether it is working it worked one time but didnt so the next

i just twisted it to check whether it is working it worked one time but didnt so the next but i used insulation take to hold it in place

It should be just connection problem, try after soldering proper connectors.

I agree. This looks like a case where only two of the three phases of the motor are being supplied, causing this 'twitching'. Solder on some bullet connectors (male on the motor and female on the ESC) and try again. BTW, you can remove the 's' from https in the YouTube link and it will automatically be embedded in your post.

@SK, hey, you have had same problem right ?

Yup, I hadn't soldered the bullet connector on properly in one case and in the other case, the connection between the male and female connector was loose (sliding). Compressing it slightly with pliers helped. A couple of hours ago, another bullet connector came off my ESC after an ugly crash (hit a tree). I have run out of props and need to buy more 

is that the first crash ?

No way. On Friday, a prop broke in mid air and the quad flipped, breaking the other 3 props. I have a had several rough landings and a few prop strikes. In fact, I hit another tree a bit earlier but managed to compensate with higher throttle to avoid crashing since the branch was thin. I also had a few flips when I tried flying with old firmware.

well, the list goes on ..
You  should seriously consider tuning the FC and transmitter again for problems, Usually, if correctly set up and flew in self level, It should not lose control.
I don't think it's merely manual errors.

You're right. I have tuned the self-level and PI settings though PI needs some more work. Self level gains were too high for me causing oscillation. My quadcopter tends to climb and dip excessively, even with some expo. I will turn up the expo and try again once I get more props. I have run out  . Luckily RCBazaar is only 20 minutes away for me   

I forgot I am hijacking Anis jayaram's thread, sorry for that.
@SK1701, reach via PM