- Joined
- Mar 3, 2018
- Messages
- 43
- Reaction score
- 17
- Age
- 71
Do battery side motors spin faster?
- Thread starter shegeek72
- Start date
That's actually a very good question and something that's never occurred to me. So, that being the case, if I'm in a situation trying to get home on low battery, would it help to fly backwards and use the rear weight to help tilt the AC thus using less power?
Wow thats some good smoke! Great question. Never thought about that. Never noticed the offset battery even
The simple answer is no. All 4 motors spin at varying rates. Initially on takeoff, in a perfect world condition, which is basically impossible to achieve, all 4 motors, when at idle would spin at the exact same speed. In calculations from the IMU and the FC, the aircraft tries to perfectly level itself before takeoff, which being on the ground eliminates the weight bearing factor. After takeoff, it is the same thing, the aircraft attempts to level itself at hover. This is not 100% effective, hence the difference in the motor RPM's. The weight has little to no bearing on any of the motor's. This is by design that the rear motors do tend to be a little faster. But not always so in flight. A normal takeoff is exampled below:
Oso
Premium Pilot
I was reminded of this thread which I found to be interesting back in the day:
P3 is heavier on rear end ( battery side )
P3 is heavier on rear end ( battery side )
My understanding of aviation physics is that there is no difference in thrust/energy required to fly a quad backwards, or forwards. A quad requires a certain amount of thrust from each motor to hover at a constant height. So, to all intent and purpose the quad becomes theoretically weightless.
So, in order to fly forward or backwards either the front, or rear two motors need to increase their thrust to overcome the hover, or theoretical weightless condition. The same amount of thrust would now be required to tilt the quad forward, or backward as both are acting on a hovering quad. Neither the front, or rear motors, to my understanding, can reduce thrust to achieve the required tilt as that would cause the quad to lose its hover thrust and head towards the ground, as it has no wings to assist in lift.
I accept that I may be completely wrong in my understanding.
So, in order to fly forward or backwards either the front, or rear two motors need to increase their thrust to overcome the hover, or theoretical weightless condition. The same amount of thrust would now be required to tilt the quad forward, or backward as both are acting on a hovering quad. Neither the front, or rear motors, to my understanding, can reduce thrust to achieve the required tilt as that would cause the quad to lose its hover thrust and head towards the ground, as it has no wings to assist in lift.
I accept that I may be completely wrong in my understanding.
Makes sense, so if the P3 was perfectly balanced the front motors would spin abit faster and the rear abit slower during hover (compared to what they do now) but ultimately the 4 combined are still generating the same amount of thrust and drawing the same amount of energy to maintain a level hover. So the weight imbalance does not come into the equation at all if I understand correctly.
Close, but just using the right rear as an example during hover, you are looking at an estimated average of around 100 Watts or there abouts.
So are you saying by "close" that a more evenly balanced P3 would be slightly more power efficient?
That is such a fine line that due to the subtle differences in weight of the various parts, you are only talking about a few grams of difference between each aircraft and it would be virtually impossible to achieve "perfect" balance. These are not MIL spec parts we are talking about here. The tolerances are quite variable. And even with MIL spec parts there is a tolerance factor but much smaller than the commercial versions. Basically a mute point.
It could be tested tho. Using 2 small weights (that have been determined to be the right amount to compensate for the extra rear weight) and first attach them dead center on ghe side lower landing skids to not upset the original balance, do a ten minute hover in a controlled environment and then again move them to where the AC is perfectly balanced and duplicate the hover and compare flight logs. Interesting...
Possibly, yes but you would get different results each time, so you would have no baseline to work with. Waste of time and quite honestly useless information that would be gained.
I
Information is never useless if it satisfies curiosity lol
That would depend on what the curiosity is. Many a curious person has regretted finding the information they sought.
It's splitting hairs but if all other things are equal the FC will either give the rear motors a few extras ZOOMS or reduce a few on the front two.
Do battery side motors have to spin faster to maintain level flight? Newton's third law says yes. The motor under a heavier load will have to work harder to maintain equilibrium between weight and lift than a motor under a lighter load.
Very good question - I honestly never thought about it before now. I suppose if you just took your bird and hovered for the entire time every time then yes, you are probably correct. But who does that? So I side with the folks that say it is splitting hairs - really depends on your flying habits. Good question though!
Similar threads
