Hey guys. I built a quadcopter. One of the motors stops before the others when i pull down the throttle. I have zeroed on the problem and found out that its being caused by the esc. i have decided to change the esc. But i have a doubt. Will i have to change my motor also? Could the esc have damaged my motor?

Have you calibrated the ESC's yet?

No. The motor gets tighter than the others if I'm connecting battery to the ESC. I am using emax 4 X 25 amps ESC. The motor number 3 is faulty. It gets tighter.

Can you please elaborate "Motor gets Tighter"?
Maybe a video?

Do you mean that motor #3 rotates freely when battery not connected, but gets hard to rotate as soon as you connect the battery to the ESC (at 0 throttle)?

Yes. It gets tighter to rotate as soon as i connect the battery. Do you think this could've damaged my motor? Or will it be sufficient if i just change my esc?

help

It sounds lime the brake is on for that ESC. That doesn't mean the ESC is bad. If the quad fly's ok , then I wouldn't  worry about it. You could turn the brake off by looking up the procedure for that brand of ESC.
I could be wrong so perhaps someone with more knoledge could chip in.

+1 ,Ashimda.
@rameshgoud, emax 25 amps ESC, Is it SimonK? If not , ashimda's opinion is correct & you have to deactivate the brake function of ESC.

It's not Simon K. The quad flips while taking off and falls.

You have to deactivate the break feature of your ESC, you ca use the Tx for that, refer to your ESC manual. For Quad copters , it is better to use simonK ESC One best option is to re flash your ESC to SimonK

I don't have my manual.. And I'm a bit new to this. Don't know how to reflash..

Motors do get 'tighter' after you power it and run it. It loosens up after sometime if you let it sit. I dont know why but thats the way it works. Its not a defect because all my motors exhibit similar behavior since I began using them. For the rest just try to rotate the prop before and after the flight you will know the difference.

What you can do is switch the esc to different motor and see what happens?

Your issue is primarily related to esc calibration or acc calibration on your fc.

For ex,
1. if you calibrated the esc one at a time, there may be chance that they were not calibrated equally.

2. Similarly if your frame or fc is tilted to a side, the motor on that side may spin up before the rest or viceversa.

Its a 4 in 1 ESC. And it gets a lot tighter. Not a bit. It happens as soon as I connect the power source.

My frame is not tilted to one side. This motor gets too tight.

Can I assume that the motor getting tight is always the same one?, If so , connect that motor to another ESC channel (in your 4in 1 ESC), and check whether the motor rotates correctly, Then the other motor which is connected to the Faulty ESC should behave as the previous tight motor,

If this is not the case and the Motor is still tight after changing ESC, We have to conclude that ESC is good and either motor is faulty or your flight controller accelerometer need to be calibrated.

     For checking Flight controller, Remove the tight motor from its current place to the another side and put the motor on that side to replaced motor's side, and check again, If problem is with FC, The new motor should also behave as tight as previous one, And if problem is with the motor itself, The motor which is replaced to other side will still behave tight.

If you cant understand any thing, pls feel free to ask

Refer this guide (page 5) to calibrate and disable brake

http://www.verticalhobby.com/kauppa/pdf/EMAX_ESC.pdf

Yes. It is always the same one. I bought new motors and connected them. They're tight too. And I'm afraid if they're damaging my motors..

Please connect the tight motor to another ESC, And check whether is still tight.

try without connecting kk board to esc and still its getting tight?

Ramesh as I said earlier,motors do get tighter when you run them even for a minute. If its getting stuck, making noise,not running at all or you can observe burnt windings/smoke or something then its a problem, otherwise everything looks fine.

If brake is enabled it would try to stop the motor when throttle is completely closed(you can still turn the prop by hand), used in planes to stop windmill/freewheeling prop.First try to spin the prop by hand before powering it, then connect it to esc(power it) and try to spin it by hand(dont use throttle). If its tighter then brake is enabled, if its the same as before powering then its not. If its a simon K esc only throttle calibration is programmable, nothing else last time I checked(brakes are disabled by default).

As for flipping quad have you selected correct orientation in kk 2 and fixed the props accordingly? If there is a very huge difference in esc calibration then it may cause flips otherwise its related to fc/props.

Can you put up the details of which brand motors and esc(probably emax 4 in 1) you are using,possibly with a pic of your setup/connections?

Dont be brief, and if you can get in touch with a member who has worked with quads from hyd, he may be able to help you out.