Hi Chris,
First, I commend you on doing your homework and much of what you wrote is true. You might should have done your homework before making your first statement and it would have been even better if you had done your homework on the Inspire motors in particular and not just RC electric motors in general. Theses are much different than sport helicopter and airplane motor/ESC combinations.
To begin with, the electronic gyros and accelerometers in the IMU are worked much harder during flight than they are while the copter is sitting on a table, this is particularly true while flying in windy and gusty conditions. I made people aware that they should run the motors while in the atti mode vs GPS mode which prevents the sensors from needless output signals from the IMU to the aircraft's computer and finally to the ESC and motors..
The current firmware will not allow the motors to spool up close to what the rpms that these motors are designed for. See the document below that points out that the firmware prevents the motors from achieving fast climb rates and prevent fast forward flight in an effort to prevent the motors from drawing too much current from the battery and thereby preventing the battery's overload protection circuitry from shutting down while in flight. It's kind of like an electronic governor that is controlled by the firmware and aircraft computer rather than the ESCs governor (not even sure if the Inspire's ESCs have a governor, probably not since the motor speed is controlled primarily by the aircraft's computer and firmware).
The 3510H motors are rated at 420KV which means that they will turn 420 rpms for every volt applied to the motor. Not getting into wattage, torque and number of coil wire turns since the kv rating is tested and rated under a No Load condition by the manufacturer.
Before telling people here that they could run their motors without the props on, I tested the rpms at full speed with the battery at 25.7 volts. (Which I just replicated because I didn't take photos of my first test).
25.7 volts at 420 rpms per volt comes to 10,794 rpms which is what these motors are designed to turn at based on the current battery voltage, diameter of the motor, height of the motor and the the number of coil wire turns.
I measured the rpms using a photo type tachometer which uses a strip of reflective tape placed on the motor housing to determine the motor speed. (See document below that shows and explains the type of tach I used). I've had this tach for a few years and I primarily use it to test industrial motors. When compared to other higher end tachs, this one was found to be highly accurate and reliable.
As you can see in one of the photos below, the maximum rpms were 8,499. That is only 78% of the rpms this motor was designed to run at so there IS NO overrunning of the motors going on with the Inspire copters while on the table with no props. This also means that there are no high feedback voltage signals feeding back into the ESCs or the aircraft's computer.
Hall effect sensors are placed on the motor's outer edge inside of the motor and feed motor speed information back to the ESC and to the aircraft's computer.
I don't know it the Inspires have hall effect sensors or not but when they are used, that's where they are placed (I didn't have the need to research whether or not Inspires use hall effect sensors).
Another photo shows where and how I put the reflective tape on the motor housing. Another document below shows that placing the reflective tape on the outside of the motor housing is a standard and acceptable method.
I'm not asking anyone to just believe my photos or my words but I do challenge anyone to do their own test to prove to themselves that they will get very close to the same results that I did.
Please, go ahead, test it yourself, don't take my word for it!
As far as overrunning an electric motor goes, you would have to have an external force applied to it to overrun the motors.
Example: While flying one of my electric competition 700 class single rotor helicopters and while in a competition one day, I put the helicopter in a high altitude nose down dive at midstick and when I flared it out, the rotor rpms shot up to over 800 rpms higher than it was designed for, again, that was rotor rpms, the motor went much higher than that considering the 7:1 gear ratio. Not good AT ALL so I had to be sure not to do that again (I used the data from an in flight data logger that is built into the ESC to gather that information).
Note: RC single rotor helicopters are highly capable of landing safely by performing an autorotation without power. An autorotation is where you lose power and when that happens, you put the helicopter in a steep dive (but not straight down), the rotor will lose a considerable amount of head speed during that dive. As soon as you flare the helicopter near the ground, the rotor rpms will very quickly increase to produce the needed lift to be able to land it under control. During the autorotation, the motor is not engaged because of a one way bearing that disengages the motor from the rotor which also prevents drag on the rotor by the motor and gearing.
Another example: A friend of mine put his electric airplane in a nose dive without reducing the throttle and seriously overrun the motor. He lost power in that stunt and we think it was because he fried the electronics (not sure if it was the ESC or something else, I didn't follow up with him to learn exactly what happened but I do suspect it was the ESC). He really should have throttled back during that nose dive!
I wish there were a way to autorotate a multirotor but there isn't because they don't have collective pitch props. The only solution for multirotors is to use an emergency parachute (which I have).
In case you didn't know this and I'm not saying that you don't but if the motor is not being controlled and run by a battery and an ESC, you can connect a drill to the output shaft of the motor, I'm not referring to the Inspire motors because there's no place to connect the drill, I'm referring to a standard outrunner or inrunner with a straight output shaft that's configured to add a pinion gear, then hook up a volt meter to the wires. Turn the drill on and you will see that voltage is being produced by the motor itself which means that these motors also act as a generator (that's the principle behind gas powered electric generators). "IF" you overrun a motor while connected to a battery and ESC, it will start producing excessive voltage that will feed back into the ESC and immediately conflict with the electronics in the ESC, in many cases to the point where it can and likely will fry the ESC.
I am
"SERIOUSLY OFFENDED" by your statement of
"give a general "ah no problem!"-advice to the people". YOU DON'T KNOW ME!
DO NOT assume that you know what I did or didn't do "OR" what was in my mind! You have no clue what trouble I went through to make sure that it was in fact OK to run theses motors with no props!!!
You just "Attacked my Character" "WITHOUT ANY" basis "Or" evidence so I will NOT apologize for what I just wrote this time!!!
I know you wanted to defend yourself but you really should know exactly what you're talking about first, and know what I did (backed up by evidence) before attacking me (or anyone else for that matter).
I don't normally write like this. I pride myself on treating people with respect and kindness and I always try my best to be helpful, BUT, I DO have the right to defend my character when it's being attacked like this!
You stepped over the line, sir when you attacked my character by stating that I blindly and carelessly advised people that it was safe to run the motors without the props!
If this gets me kicked off of here, then so be it. I try to help people and this is what I get.
This has happened before on another forum a few years ago while trying to help other people that were stumped on something, I wasn't kicked off but the other person was! I chose to quit because I don't need this C**P!
I should have known better than to get involved again. It seems to never fail that "someone" in the crowd wants to attack me with no evidence or probable cause.
I was very polite and even apologized deeply to you but you still attacked my character. WHY did you do that? (That's a rhetorical question, meaning I don't expect a response)
I'm done with this discussion with you.
I do still wish you all the best and I do pray that all of your flights are safe ones!!
Joe