3dhehe

Hi all,

I have recently built a foam 3d plane using some of my left overs from old planes, and it seems to be cutting out on ocasions, and making a grinding sound like gear grinding (but its an outrunner motor?) After several second its ok again provided i dont give it to much throttle, this happens regardless of how charged the battery is also.

I undestand ive gone wrong somewhere in the compatibility department, and was hoping some one may be able to lend a helping hand. The set up is as follows.

plane: ultrafly furious
battery: 11.1v 730 mah 14c lipo
esc: 15a (18 for 5 seconds) brushless
motor: dualsky xm300b
prop: 10 x 4.7

The problem occured after just 2 flights, both flights were ok and landing were fine (so no physical damage) im guessing ive overloaded something? am am looking to change the problem part, so any ideas much appreiated.


Thanks in advance.

jdetray

In my experience, the "grinding" noise is a symptom of too large a prop.

The recommended prop for your motor on a 3-cell lipo is a 8x4. With a 10x4.7, you may be drawing more than the recommended 12A.

- Jeff

3dhehe

Thanks Jeff, great advice. Propped down to an 8 x 4 and the problem has gone, though ive lost all 3d capability. So its the motor letting me down in this case?

Thanks again

jdetray

I don't know that the motor is letting you down. You are simply asking it to do more than it was designed to do. I've never used that motor; I'm just telling you what its spec sheet says.

In my own experience with building motors, I've encountered the "grinding" effect, which is often accompanied by excessive heating. A smaller prop always cures the problem.

- Jeff

Matt Kirsch

My Feedback: (21)

I think the grinding may actually be the magnets grinding against the stator inside the motor. There isn't much clearance in there, and it would make perfect sense because heat causes things to expand in all directions. Motor expands, clearances close up, grind grind grind

jdetray is spot on. You're simply asking too much from the motor. The bigger the prop, the more Amps the motor will draw. You've got to pay careful attention to Amps, because if you draw too many, the motor will burn up. You might be able to get away with a prop that's slightly larger than an 8x4, but you really should have a meter to check the Amps and make sure they don't exceed the specifications of the battery, ESC, or motor.

3dhehe

Thanks matt, i may have to try a 9 inch prop, and think ill invest in a meter to measure the amps.

Thanks again for your input.

perttime

Somebody just mentioned ... somewhere ... that outrunners demand well balanced props, or at least they are a bit more sensitive to inbalance than some other systems.