Thrust/Power Data for Power Pack A/H / others

[JasonK]

NOTE: I found a calibration issue in my tests, jump to this message to get the data that has the updated methodology/calibrations.

Attached is my initial data for thrust/power for a power pack A motor (1806, 2280kv) with 2 different props and 2 different lipos.
Lipos were at storage charge.

Current is an approximation as I haven't calibrated the sensor and just used the center and range vs the ADC range on the Arduino.

I will follow up with some additional graphs/etc once I have time to work over the data.

of quick note, max thrust by prop/cell count:

	6x3	5x3apc
2s	220g	181g
3s	403g	324g

Let me know if there is anything specific you would like to see out of the data.

 

[JasonK]

Quick look at the data, and I might need to give a longer delay between setting the PWM value and reading the sensors, at least for current, or do multiple reads for each PWM value, as there are a few current dips, which doesn't make sense.

 

[JasonK]

Got some charts setup and I definitely want to look at the sampling process, with the power usage and efficiency so noisy, I am fairly sure there was to much noise in the voltage and/or current measurements (based on looking at the data, I think the noise is in the current measurements).

 

[JasonK]

I reran the tests for the APC prop (It is what was mounted) with a 1/2 delay between the PWM change and the sampling of everything. I also did 10 samples of voltage and current and returned the average value of each, this got my data to be significantly less noisy.

For the 3s, it looks like the peak efficiency is around 1200ms, but your getting sub 50g of thrust at that point, so not very useful.


For the 2s, it looks like the peak efficiency is around 1300ms, but again with under 50g of thrust at that point, so not very useful. it might be as high as 1500ms, but that is still only around 50g of thrust (less then 1/3 max thrust). The 'hump' on this batter is less pronounce, so harder to ID were the efficiency maxes with how noisy the data is.

 

[JasonK]

and for the 6x3 prop:

3s looks like efficiency peaks around 1300 ms, which would be 50-60g of thrust.


2s looks like efficiency peaks around 1400ms, which is about 50g of thrust.

 

[JasonK]

Let me know if your interested in my testing anything else or any other data from this.

 

[JasonK]

2s 6x4.5 and this accounts for all the prop size/pitches I have for my power pack A motor. I didn't run this on a 3s as my experience is that 3s gets to warm on this prop... or at least did in a southern US summer when I tried it out.

Efficiency peaked around 1350ms with about 50g of thrust (this seems to be a fairly constent amount of thrust for best efficiency). Unmentioned before, this is all 'static', I am sure all of these curves would change at speed.

 

[JasonK]

looking at all the data, it looks like generally a larger prop spinning slower gets better efficiency. It would be useful to compare equal thrust points, this is me just looking over the curves.

I still have an h-pack motor and 2 different prop styles I can test on it, I am definitely curious how it compares out in the efficiency tests (as I like the H-pack as it gives the ability to make a sub-250g twin fairly easy, if a touch under powered in some cases).

 

[JasonK]

I got my Power pack H motor on the stand today and ran it with both the 3x3.5x3 props that came with it and some 2.5x3.5x3 props that I picked up, hoping I could get it running on 3s without overheating. 3s gets to hot to the touch on the test bench even with the smaller prop, the only way I could see 3s working with these motors is in free flight, where the forward movement of the craft lowers the power draw sufficient to not overheat the motor at full throttle.

2s 3x3.5x3 H-Pack
Eff maxes out around 4.5, but doesn't seem to run much drop off.


2s 2.5x3.5x3 H-Pack
Eff maxes out around 3.5, again without a significant down turn.


3s 2.5x3.5x3 H-Pack
Note: this was to hot to touch immediately after the test, probably not a good idea to run at this on the bench
Eff maxes out around 2.5 and max power consumption goes _way_ up (both 2s maxed out around 25w, this maxed out around 60w)

 

[JasonK]

Looks like, if the goal is efficient (IE long flight time), using a single power pack A motor wins out.
This chart is just me eyeballing the graphs above.
The highlighted point is were my PfP plane cruses well.
Comparable thrust points are highlighted.
The one thing to consider is thrust drop off with airspeed.
looking at this break down, the 6x3 at 2s is a better option, if I was good with having a less then 1:1 max thrust to weight. If I was good with about a 1:1 max thrust to weight, the 6x4.5 on 3s is probably the best option as the thrust drop off with airspeed would be less, meaning 50% throttle would probably still hold the cruse needs, yet keeps what appears to be the same or better eff then the 6x3 as 3s.

The ultimate test would be to work out an airspeed sensor (and on board monitoring of the same things and black box recording of everything), to figure out the power draws at various speeds (and what throttle levels they take to hold), to see how much actual flight characteristics impact all of this.

Power Pack	Prop	Lipo	50% Eff	50% Thrust	75% Eff	75% Thrust	100% Eff	100% Thrust
A	5x3	3s	7	100	6	210	5.5	310
A	5x3	2s	9	50	8	110	7.5	175
A	6x3	3s	8	125	7	260	6	380
A	6x3	2s	10	75	9	140	8	210
A	6x4.5	2s	9	100	7.5	175	6.5	275
H	3x3.5x3	2s	4.75	40	4.75	70	4.75	115
H	2.5x3.5x3	2s	3.5	30	3.5	60	3.5	90
H	2.5x3.5x3	3s	2.5	60	2.5	110	2.5	150

 

[JasonK]

Ran a 1306 3100kv motor through the bench test on 2s with a 5x3 prop, was warm/hot to the touch at the end of the run. Store page rates it for Max Continuous Power: 75W and suggests LiPo Cell: 2S Recommended Prop(inch): 5043 which is bit more aggressive of a prop then what I put on. My max power calculation was about half of the rated max continuous power - so either I have my current sensor calibration way off, my definition of 'to hot' is low, or the motor I got is under performing the store.

I did some extra heat testing with a no-touch IR thermometer... 10s at 100% got up to about 109F, 30s got up to 135-140F, So I suspect it could handle it in cooler weather or in many use cases (in flight, forward speed should reduce the effective load some, which would reduce the power needed to maintain that speed).

Max current draw was around 5-5.5A

 

[FoamyDM]

Great work sir! I'm loving this.

 

[JasonK]

Great work sir! I'm loving this.

Thanks!

 

[TheFlyingBrit]

That takes me back to the old days when I started off my working life in science, doing experiments and analysing data I love it nice work.

 

[JasonK]

NOTE: I found a calibration issue in my tests... while the relative efficiencies based observations should still be valid, the exact numbers are off.

Posts after this message have the updated calibration and testing methodology.

I also put in an RC low pass filter from the current sensor to the ADC input - which got my current readings be much cleaner and removed a bunch of noise (which is noticeable in the charts except at very low inputs - which is caused by the resolution of the ADC [<1024 bits for -30 to +30A based on the setup] in the device I am using.

 

[JasonK]

I ran all my setups other then the H-pack motor again after my calibrations, these were all ran with a freshly fully charged battery, swapping batteries for each test... all of them were 650mAh 75C Tattu batteries at 2s or 3s depending on the test.

Here are all of the A pack motor tests and a test of a 1306 motor:
the 1306 motor is a 3100kv motor
the 1806 [an A-pack motor] is a 2280kv motor.

 

[JasonK]

H-pack motor on 2s with the included 3x3.5x3 prop

 

[JasonK]

A pack motor with 5.5x4.5 on 2s