Runaway Motor

[toryander]

I took my FT P-51 Flat flyer out today. I actually landed him (dead stick) in one piece. He had the following power specs: 2207 radial motor 1750Kv, 25amp esc, 9" 4.5 prop, 850 mAH 80c 3s battery. He took off like a rocket. When I throttled back half the engine stopped. When I throttle forward to keep him from falling out of the sky it went full throttle. I had no throttle control. After a minute the motor burned out and I glided him back in. I thought it was the esc, but I tested later and the esc controls a different motor just fine. It appears that the motor simply malfunctioned (it has been in a few crashes)? Am I getting this right?

I'm looking at buying a new 2207 1800KV and two 800 mAH 2s 120c (I can't find the recommended 45c on Amazon). The 120c worries me. Batteries still confuse me. Anyone have some wisdom to impart? I'm ready to learn.

 

[Houndpup Rc]

I'm looking at buying a new 2207 1800KV and two 800 mAH 2s 120c (I can't find the recommended 45c on Amazon). The 120c worries me. Batteries still confuse me. Anyone have some wisdom to impart? I'm ready to learn.

120c is perfectly fine, all it means is that you can draw more amps from the battery, but it won't force more down. (A motor always only draws as much as it needs) You can actually use a battery with less "C", you just won't have as much punch. (Usually only matters when stunt flying or when going for high speeds)

 

[Houndpup Rc]

I took my FT P-51 Flat flyer out today. I actually landed him (dead stick) in one piece. He had the following power specs: 2207 radial motor 1750Kv, 25amp esc, 9" 4.5 prop, 850 mAH 80c 3s battery. He took off like a rocket. When I throttled back half the engine stopped. When I throttle forward to keep him from falling out of the sky it went full throttle. I had no throttle control. After a minute the motor burned out and I glided him back in. I thought it was the esc, but I tested later and the esc controls a different motor just fine. It appears that the motor simply malfunctioned (it has been in a few crashes)? Am I getting this right?

I'm looking at buying a new 2207 1800KV and two 800 mAH 2s 120c (I can't find the recommended 45c on Amazon). The 120c worries me. Batteries still confuse me. Anyone have some wisdom to impart? I'm ready to learn.

Where you possibly out of range 9Or getting close to it) when it punched to full throttle? Your TX or sometimes the ESC has a failsafe where if it goes out of range, it will do whatever its programmed to do (I have a ESC that is known to punch to full throttle when it loses signal, and has more then once failsafe on the bench with the prop on😬)

 

[Houndpup Rc]

I took my FT P-51 Flat flyer out today. I actually landed him (dead stick) in one piece. He had the following power specs: 2207 radial motor 1750Kv, 25amp esc, 9" 4.5 prop, 850 mAH 80c 3s battery. He took off like a rocket. When I throttled back half the engine stopped. When I throttle forward to keep him from falling out of the sky it went full throttle. I had no throttle control. After a minute the motor burned out and I glided him back in. I thought it was the esc, but I tested later and the esc controls a different motor just fine. It appears that the motor simply malfunctioned (it has been in a few crashes)? Am I getting this right?

Oh, I think I figured out what happened! (Had to check the motor specs) You had a too big a prop on (Recommended size is 6") it so the motor probably overheated and went out of sync, resulting in lose of motor control.. I did a similar thing when I first started..I put a 10" prop on a 6" prop motor and it totally smoked the ESC and the motor!😆😆

 

[toryander]

Oh, I think I figured out what happened! (Had to check the motor specs) You had a too big a prop on (Recommended size is 6") it so the motor probably overheated and went out of sync, resulting in lose of motor control.. I did a similar thing when I first started..I put a 10" prop on a 6" prop motor and it totally smoked the ESC and the motor!😆😆

This makes sense to me as to what happened. I just wonder why FT ships the 9" prop in the kit for the flat flyer? I'll try a 6" next time.

 

[Merv]

...Anyone have some wisdom to impart? ...

ALL of the ratings in the RC world are do not exceed.
If a motor has a 40 amp rating, don't use a prop & battery that will cause it to draw more amps. A higher voltage battery makes a motor spin faster. So a prop that works on 2S is likely too much on a 4S battery.

Start with a prop & motor, will this prop cause this motor to draw more amps than it is rated for at the voltage I intend to use. Next, pick an ESC and battery that can supply that many amps. With batteries, you have to calculate their amp capacity. The formula is mah x 1000 x c. Example: a 2,200 mah 30C battery can supply 66 amps (2,200 x 1000 x 30 = 66).

If at any point, motor, ESC or battery, you EXCEED the amp rating, that is what is going to burn out.