Thanks for the guidance. I guess this will be part of my learning experience.
Carbon blades can be very slightly more efficient especially when under load as plastic blades start flexing but this is so light that its just not an issue. carbon propellers can be stronger in a crash but in my experience that’s usually a bad thing because it just transfers the damage to the next component, usually the motor or frame thats far more expensive to repair.
Avoid cheap 3rd party plastic propellers as almost all arrive warped. I think genuine propellers have some filler in them to stop that like glass reenforced plastic GRP.
I was thinking, could a tune be optimised for power consumption?
Regular logic is you want its handling as tight as possible so you want your PID as high as you can without it shaking, but would that result in more power consumption keeping it in tighter tolerances ?
or would it lower power consumption using a less aggressively tuned PID allowing some more tolerance in its handling?
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All oscillation results in higher power consumption, especially high frequency oscillation.
So a bit relaxed PIDs are best for power consumption.
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I am interested in exploring the motor efficiency. You probably know more about this than me, but apart from the fundamental motor efficiency itself, I believe the matching of a motor to the “demanded” propeller torque / RPM for a propeller operating range is important. (I’m working towards making a simple test bench for this). Toyo Robotics has some good info, but most of the prop and motor data is for large sizes.
I agree with this, its one of the reasons I’m using OEM motors and propellers, as I assume someone has already spent some time and money matching them to a 250g airframe.
Yes and no. The OEM motors wil likely be a reasonable quality. However the OEM matching could have placed a high importance on achieving “maximum performance” (meaning speed and acceleration). If the matching is done with a high priority on endurance and efficiency, then a different motor / prop selection is likely.
If it’s from a camera quad like a DJI mavic then it will be all about efficiency.
your typical racing quad motors are much tougher and heavier, so you can’t get the efficiency purely because of the extra weight of the motors.
Yes that’s true. I do believe there is still scope for efficiency gain through “matching”.
For example a DJI Camera drome may be developed with a maximum thrust target of say 4x drone mass(?). If this target is reduced to say 2x mass (yes the flight performance is greatly changed) then a more efficient motor/prop combination can most likely be found. (need my test bench for that).
My expectation is that an appropriately selected smaller motor could realise increased efficiency and less motor mass. The research articles on BLDC (PMSM) motor performance seem to show that the efficiency for any particular motor is poor at low load. If I don’t want high output (like a racing drone) I expect to be able to select a small motor that “only just” produces enough output for my endurance quad. This should have the motor operating at its most efficient.
The worked example on the Toyo website shows the process. They gained a few % efficiency plus a 4gram motor weight save in this example.
This could help visualise the situation. The efficiency sweet spot for any motor is towards the “high load + high rpm” sectoin of the chart. If a motor is only operared well below its maximum output, then it will be running in the blue/green area of efficiency. By substituting a smaller motor that is operating as hard as it can (but with enough output to meet target thrust), then it should be operating up in the high efficiency part or its performance characteristic. Running a low Kv motor on 1S battery goes towards this. I have also read that ESC electrical efficiency is better with the lowest battery pack voltage (1S). It may be better to run a 1S2P battery than a 2S.
I know what you’re trying to say, I just think you are underestimating how much time and money DJI and other OEMs spend on making their quads efficient. I dont think there is not going to be much room for improvement unless you drastically change the weight of the vehicle from 250g,
I don’t underestimate the development effort that DJI put in, but have faith Geo! You have done an amazing job creating your V1 design doubling the flight time compared to a 250g DJI. The larger props will deliver a further significant gain. More gains are possible!
Now that the motors need to deliver less power due to the larger more efficient props, there are potential gains to be had by finding appropriate less powerful motors. This is especially true if the target for maximum thrust is reduced from the original DJI performance level. The new motors are most likely lower Kv (potentially with windings in star (wye) connection instead of the more usual delta). They should also be lighter weight.
Running 1S2P batteries may also help, as I read somewhere that ESC efficiency can be better with lower battery voltage (although I slightly doubt this as resistive losses in an ESC should be proportional to current squared). I would be interested to hear from anyone who has clear information on this.
You should play around with ecalc
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I’m interested in changing the camera to a DJI O4 Air Unit, considering the camera quality is great and the whole thing only weights 8.2g. I also want to use ELRS.
What parts of this list should I change to support my plan? I’m new to this, thanks!
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It uses a 20x20mm mount for the DJI vtx so It should just fit on top of the speedybee flight controller on the v1.
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Thanks. Just wanted to add, 6063 Aluminum screws are even better. They’re much cheaper than titanium and half the weight of titanium.
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I didn’t know you could get aluminium screws that size. It never occurred to me to look as I just assumed it was too soft. but when I think about it, this is so light that it should be fine, each screw is only holding around 20g so titanium is probably overkill.