Author Topic: Motor Efficiency (Read 7377 times)

Peter Germann · « **on:** June 03, 2016, 03:53:15 AM »

When comparing published motor efficiency at approx. 9’500 RPM, I have found the AXI 2816/12 760 being rated at 76% motor efficiency while the Hacker A40-14S-14p-V2 530 reaches 90%.
Run in governed constant speed for a lap time of 5.3 sec and from a 5S/2700 battery, this translates into flight test results of:

AXI 2826/12 760 (183 Gr.)
APC E 13 x 5.5 at 9’278 RPM (33 Gr.)
Battery charge for 5’20 run time: 1’950 mAh (72%)

Hacker A40-14S-14p-V2 530 (216 Gr.)
Aeronaut Cam Carbon light 13 x 6 at 9’570 RPM (27 Gr.)
Battery charge for 5’20 run time: 1’788 mAh (66%)

From this, the gain in efficiency of the Hacker A40 / Aeronaut drive train might allow the use of a 60 Grams (2.2 oz) lighter 5S/2250 battery (TP Magna 70C), thus over-compensating the Hacker’s weight penalty.

What I have so far noted, too, is that both the Hacker motor and the (Castle Edge) ESC remain significantly cooler as the AXI.(45°C as opposed to 65°C)

Igor Burger · « **Reply #1 on:** June 03, 2016, 05:22:03 AM »

Few comments:

1/ You probably compare "maximal" and "average" efficiency. I guess because you say Axi has rated efficiency 75%. I am absolutely sure AXI 2816/12 has MAXIMAL efficiency much higher. I guess 85% or so. AXI 2816/13 has even some percent higher, 88% or so. Maximall efficiency is efficiecy which can be reached at best load. The average efficiency is efficiency which the motor can reach at some specified range of loads stated by maker. For example maker can say efficiency is better then 75% at current between 10 and 30A. And I am ambsolutely sure hacker does not keep efficiency more then 90% in the same range. So I am for 99% sure you are comparing diffenent values :- )) It is typical that maker states current range from-to where motor reaches 75% efficincy, so it is typically not property of motor, it is chice of maker - if they state it for 90% it will be VERY narrow (if even possible).

2/ It is not only efficiency what gives motor temperature. It is also size and thus radiation. It will be for sure that 30g heavier motor will run colder, if not, something is wrong :- ))

3/ It is hard to compare motor with KV=760 and another with KV=530 in the same model with the same prop and battery. I would say that while AXI runs at deep PWM (RPM limited by ESC) and therefore motor current is much higher compared to Hacker which probably runs most of time at full power, what will certainly lead to colder run. The difference is what happens if battery goes flat, or you will fly at higher altitude when you need add some RPM. The key for proper run is to design powertrain to have proper headroom giving safe run at end of battery but still good enough to prevent overheating. I would say neither are good, the proper solution will be "something between", for example motor with kv 680 or so. AXI 2826/12 with 5s is good choice with active timers when you need boost to 11 000 uphill, but flying at constant RPM close to 9000 is wasting of battery you will do better if you test that axi with 4 cells, you will get better efficiency (with minimal or nill head room).

Peter Germann · « **Reply #2 on:** June 03, 2016, 08:28:36 AM »

Quote from: Igor Burger on June 03, 2016, 05:22:03 AM

1/ You probably compare "maximal" and "average" efficiency.

I have found the partial load efficiency numbers in http://ecalc.ch/motorcalc.php?eflight&lang=de

However, as the Hacker/Aeronaut combo uses less energy, I thought it would be safe to assume its efficiency being better.
When usiing batteries with approx. 60 cycles on them, the min. in-flight under load voltage logged is 18.1V which leads to 97% power-out in the clover.

Trying to bring down RPM, I now fly the Aeronaut 14 x 6" prop at 8'976 RPM (consuming 1'950 mAh). It shows 18.3 V min. in-flight voltage and 92% power-out in the clover, hoping that this will work until the under load voltage will be down at 17 V. (see attach)

Igor Burger · « **Reply #3 on:** June 03, 2016, 02:01:13 PM »

Quote from: Peter Germann on June 03, 2016, 08:28:36 AM

I have found the partial load efficiency numbers in http://ecalc.ch/motorcalc.php?eflight&lang=de

However, as the Hacker/Aeronaut combo uses less energy, I thought it would be safe to assume its efficiency being better.

That is definitelly true, but you do not compare the same ... hacker is almost at 100% throttle (so it shows its maximal efficiency) while AXI is deeply limited, so it is bad for its efficiency, so it is true that AXI has lower efficiency, but it is not cause but its properties, it is cause by operating point. if you want compare the same, you must compare it with apropriat voltage, and you will get its effectivity back :- ))

I can easily find operating point where effectivity of hacker will lower then Axi :- )))

Peter Germann · « **Reply #4 on:** June 12, 2016, 07:10:52 AM »

Quote from: Peter Germann on June 03, 2016, 08:28:36 AM

Trying to bring down RPM, I now fly the Aeronaut 14 x 6" prop at 8'976 RPM (consuming 1'950 mAh). It shows 18.3 V min. in-flight voltage and 92% power-out in the clover, hoping that this will work until the under load voltage will be down at 17 V.

That was not really a brilliant idea as the almost new 14 in. prop just lost a blade in flight. Which means I need to build a new nose now...
As I have quite a couple of 5S batteries in use, I might replace the (damaged) 530 RPM motor with a 610 RM/V type.

Tim Wescott · « **Reply #5 on:** June 12, 2016, 08:46:06 AM »

Hey Igor!

I know that any given motor/amplifier combination (amplifier is part of the ESC) will have an optimal switching speed for part-throttle efficiency -- but just what it is depends not only on the construction of the motor, but on the design & construction of the amplifier. So I absolutely positively don't know enough to know what's good in real life.

Do you know of any experiments with different switching speeds with a given ESC? I seem to recall that some ESCs let you dink with switching speeds. (If I were to sell ESCs I'm not sure that I'd let the user diddle with switching speeds, BTW -- it's one of those things that would be great for a very few experts, and likely disastrous for the Great Unwashed.)

Igor Burger · « **Reply #6 on:** June 12, 2016, 09:37:27 AM »

We tried to do some tests, but it looks veeery flat. Means outrunners with iron core are not sensitive to PWM - 8 or 16 or 6 does not matter too much. The only real need for higher PWM is coreless motor like inrunner with gearbox running at at 50 or so, but that is I think more problem of commutation speed in combination with PWM. I think Jeti Spin has only 2 modes, one is 32khz for coreless inrunners and 8khz for rest of the world. They have also different spin up mode, I think if you try 32khz with outrunner it will even not start rotation. May be you can try castle which has more PWM frequencies and put it with prop at the same settings (advance, rpm, etc) and try different PWM, measured current can tell more.

The reason could be magnets strength, and apropriate coils, because magnets are so strong, that inductance of coil is so small (to make proper back EMF) that the current in coils does not look like classic saw, they are just small peaks. So it is very different from classic commutator motors (where fly wheel current goes without back voltage) in large coil. On BLDC we have batterry back voltage and small inductance so it stops the current very soon. So if you have higher or smaller frequency, it does not change situation too much, they are still only peaks and not "almost contiguose" current.

Dean Pappas · « **Reply #7 on:** June 13, 2016, 09:49:03 PM »

Hi Gang,
Peter's observations are interesting, and as Igor has noted running a motor at higher "throttle percentages" to achieve the governed RPM will lead to higher efficiency just because the peak currents are closer to the average current ... but
he important variable not mentioned in that discussion is how much voltage overhead is available for those brief moments where some punch is required to maintain RPM during maneuvers that pose brief high loads to the system. I prefer to bias the system to run at an RPM that is fairly close to 75% of Kv times the nominal battery voltage.

Efficiency is a second-level consideration ... unless you are right on the cusp of a battery weight reduction!

So much experimentation and fun.
take care, Friends
Dean P

P.S. I had an embedded firmware writing co-worker show me a copy of Tim Werscott's article about control systems entitled "PID without a PHD" just the other day. He called it his control systems bible

Peter Germann · « **Reply #8 on:** June 14, 2016, 05:05:55 AM »

Quote from: Dean Pappas on June 13, 2016, 09:49:03 PM

I prefer to bias the system to run at an RPM that is fairly close to 75% of Kv times the nominal battery voltage.

Here is a further question for the experts:

IF, in the last manoeuvre (clover) the in-flight voltage logged of my 5S battery indicates 17 Volt and the power-out (to motor) percentage logged at the same time shows less then 100%, do I then still need more headroom to drive my 530 RPM/V motor at 8'000 RPM in governed constant speed mode?

Igor Burger · « **Reply #9 on:** June 14, 2016, 05:42:28 AM »

No, if it keeps proper RPM with high load and low battery, then you not need more voltage. Only if you need reserve for high altitude or high temperature - means if you tested low in cold.

in case of CONSTANT rpm setup.

Igor Burger · « **Reply #10 on:** June 14, 2016, 05:45:33 AM »

Quote from: Dean Pappas on June 13, 2016, 09:49:03 PM

he important variable not mentioned in that discussion is how much voltage overhead is available for those brief moments where some punch is required to maintain RPM during maneuvers that pose brief high loads to the system. I prefer to bias the system to run at an RPM that is fairly close to 75% of Kv times the nominal battery voltage.

and if governor acts quickly ... and we know that not all does :- ))

Mark Scarborough · « **Reply #11 on:** June 14, 2016, 08:05:08 AM »

Quote from: Igor Burger on June 14, 2016, 05:42:28 AM

No, if it keeps proper RPM with high load and low battery, then you not need more voltage. Only if you need reserve for high altitude or high temperature - means if you tested low in cold.

in case of CONSTANT rpm setup.

Igor
resp[ectfully, I find I need reserve for LOWER altitude and COLDER temperatures.
I use significantly less voltage at home, 2600 feet elevation than I do at contests at 400 foot elevation
am I misreading your intent?

Igor Burger · « **Reply #12 on:** June 14, 2016, 08:18:55 AM »

I am not sure what you mean "use less voltage" ... do you use 4s instead of 5s? Do not you mean battery CAPACITY? That is another storry.

However my experience shows that I need (and I do) to set higher RPM in thinner air compared to thicker. So that means in thin air and without reserve you can run out of max RPM determined by motor and battery voltage.

Mark Scarborough · « **Reply #13 on:** June 14, 2016, 08:29:23 AM »

I must apologize, I allowed myself to become distracted in the midst of my typing,
I intended to say I use less CURRENT, or less capacity at home
but when I go to a contest at a lower elevation, I run out of capacity/voltage at some points.
IOW I loose the ability to generate the rpm because the capacity falls short and the ability to generate the rpm is no longer available.

I know better than to type and think at the same time, or not think, or something

BOttom line, I have several of my batteries that will now not be usable at contests ( 400 foot elevation) but for the time being at least, they will work at home for practice flights.

and at least with my setup ( Hubin timer in govenor mode) at lower, and or , more dense conditions I must increase my rpm to maintain flight speed, in the thinner air I can decrease my rpm and still have all the drive and airspeed.

Igor Burger · « **Reply #14 on:** June 14, 2016, 08:40:10 AM »

Quote from: Mark Scarborough on June 14, 2016, 08:29:23 AM

I intended to say I use less CURRENT, or less capacity at home
but when I go to a contest at a lower elevation, I run out of capacity/voltage at some points.
IOW I loose the ability to generate the rpm because the capacity falls short and the ability to generate the rpm is no longer available.

Yes, clear, thicker air needs more power and thus current and thus capacity.

Quote from: Mark Scarborough on June 14, 2016, 08:29:23 AM

and at least with my setup ( Hubin timer in govenor mode) at lower, and or , more dense conditions I must increase my rpm to maintain flight speed, in the thinner air I can decrease my rpm and still have all the drive and airspeed.

Well this I have just reversed, thicker air needs lower RPM and thin (hot for exmpale) needs to add little bit.

Tim Wescott · « **Reply #15 on:** June 14, 2016, 09:17:10 AM »

Quote from: Igor Burger on June 14, 2016, 08:40:10 AM

Well this I have just reversed, thicker air needs lower RPM and thin (hot for exmpale) needs to add little bit.

I could see this being a function of propeller size. I was going to pontificate on HOW, but then I realized that I wasn't sure. It may also be a function of Igor's regulating setup vs. the Hubin.

Mark Scarborough · « **Reply #16 on:** June 14, 2016, 09:21:35 AM »

I am not sure either, but I know what I have to do, I believe that overall drag of the airframe has a much larger part in the equation than does propellor size.
I believe that the other non Igor system people face the same situation I do, and if I am not totally mistaken, even our local Igor system fliers also must increase rpm baseline at lower altitudes .

I can only guess, Igor perhaps you can clarify, you stated that you just reversed and now you use lower rpm in thicker air and higher rpm for thinner air.
are you basing this on airspeed or some other variable?

Igor Burger · « **Reply #17 on:** June 14, 2016, 09:51:01 AM »

Prop can play role, but not so much as I found ... in any case, the drag equals the thrust ... physics.

Prop thrust and frame drag is linear to air density. Means if we fly at lower air density (higher altitude), the drag is smaller and thrust also by the same magnitude. So theoretically speed should not change.

But we have also something called kinematic viscosity. Thinner air has lower viscosity and thus reynolds nuber is lower on both the air frame and also prop in higher altitude. And that makes difference - while air frame has little higher drag then expected with altitude change in the same RE, the prop has lower thrust. That makes airplane slower in higher altitude.

And well for sure, it is better to fly little quicker in thinn air as well :- ))

I ADD 20 rpm (it is "one click" on my system) per 0.01 kg/m^3 air density (does not matter if higher or warmer) ... MORE in thinner air. I have calculator for settings, so I simply check before every flight and problem solved. It works well for all my props, 11" and also 12".

Dean Pappas · « **Reply #18 on:** June 15, 2016, 09:58:51 PM »

Quote from: Peter Germann on June 14, 2016, 05:05:55 AM

Here is a further question for the experts:

IF, in the last manoeuvre (clover) the in-flight voltage logged of my 5S battery indicates 17 Volt and the power-out (to motor) percentage logged at the same time shows less then 100%, do I then still need more headroom to drive my 530 RPM/V motor at 8'000 RPM in governed constant speed mode?

Hello Peter,
I looked at your plot, and the peak motor power (really drive voltage as a percent of maximum) is at 92% in the last peak loading moment. I would say that you do not need more headroom: 7% of voltage could easily generate several Amperes of peak current to fix a momentary RPM deficit when the peak load is applied to the system.
On the other hand, if I had seen 95 ~ 97%, I would say you need more headroom. If I saw 98 or 99% I would strongly suggest you pitch-up and lower the RPM 10%.

Since you showed hard data, it is easier to give a real answer!

Regards,
Dean

Chris Cox · « **Reply #19 on:** June 16, 2016, 12:51:06 PM »

Hey Mark

FWIW - both Alan and I, using Igor's system, have to reduce RPM for cooler weather, and increase RPM for warmer weather. Or another way of looking at it, as air density decreases (density altitude increases), we must increase RPM. That said, even though the RPM is higher in warmer, less dense air, the actual battery power used is less due to the decease in airframe drag. This would explain why your battery maintains power throughout your flight at home (thinner air), but is lacking on the coast.

I would have thought you would need to decrease your RPM when flying on the coast vs. your home flying site. Unless (there is always an unless) it happened to be very cool at home, and then you went to much warmer conditions on the coast?

Hope I got that right! No doubt Igor will correct me if I'm wrong. 😄

Cheers, Chris

Mark Scarborough · « **Reply #20 on:** June 16, 2016, 01:43:14 PM »

Quote from: Chris Cox on June 16, 2016, 12:51:06 PM

Hey Mark

FWIW - both Alan and I, using Igor's system, have to reduce RPM for cooler weather, and increase RPM for warmer weather. Or another way of looking at it, as air density decreases (density altitude increases), we must increase RPM. That said, even though the RPM is higher in warmer, less dense air, the actual battery power used is less due to the decease in airframe drag. This would explain why your battery maintains power throughout your flight at home (thinner air), but is lacking on the coast.

I would have thought you would need to decrease your RPM when flying on the coast vs. your home flying site. Unless (there is always an unless) it happened to be very cool at home, and then you went to much warmer conditions on the coast?

Hope I got that right! No doubt Igor will correct me if I'm wrong. 😄

Cheers, Chris

.

Thanks Chris,
it appears that I need to log more information.
I had a brief email exchange with Paul and it appears that there is a piece of information lacking in my records.

I dont know the temperature, but I know the altitude. I did not think the temperature would have been enough different to swing the density but I cannot say for sure
I had my setup dialed in at 5.3 second lap times at home, at 2600 feet.
In Roseburg with the same setup I was at 5.43 laps at 600 foot elevation so I had to speed up to get some of my air speed back.
So there is something I am missing on this topic
Thanks for the feedback,, now I have more work to do to figure this out, Starting with adding a line to my log to track weather and temperature, ,sigh

Igor Burger · « **Reply #21 on:** June 16, 2016, 01:50:12 PM »

Mark, if you have hot and humid air in 600ft and cold and dry air at 2600 it could be easily more dense :- ))

Mark Scarborough · « **Reply #22 on:** June 16, 2016, 01:58:47 PM »

Quote from: Igor Burger on June 16, 2016, 01:50:12 PM

Mark, if you have hot and humid air in 600ft and cold and dry air at 2600 it could be easily more dense :- ))

which absolutely matches the possible conditions, we had been having fairly nice weather at home, probably in the 55 to 65 degree Fahrenheit range and at Roseburg it was possiblly in the 75 degree or up temperature, but it is closer to the ocean so I pretty sure the humidity is MUCH higher than home. Our normal humidity is in the 20% range.
I need to set some time aside to actually get a feel for the relationship of temp, humidity and altitude which is something I have never paid attention to. However I am finally getting to a point where I could tell the difference in the way my plane was flying so its becoming important now.
Thanks for the feedback, Hopefully Paul isnt sitting back shaking his head at me,, LOL

Tim Wescott · « **Reply #23 on:** June 16, 2016, 02:05:16 PM »

Quote from: Mark Scarborough on June 16, 2016, 01:58:47 PM

which absolutely matches the possible conditions, we had been having fairly nice weather at home, probably in the 55 to 65 degree Fahrenheit range and at Roseburg it was possiblly in the 75 degree or up temperature, but it is closer to the ocean so I pretty sure the humidity is MUCH higher than home. Our normal humidity is in the 20% range.
I need to set some time aside to actually get a feel for the relationship of temp, humidity and altitude which is something I have never paid attention to. However I am finally getting to a point where I could tell the difference in the way my plane was flying so its becoming important now.
Thanks for the feedback, Hopefully Paul isnt sitting back shaking his head at me,, LOL

Have a smart phone? I'm sure that there are density altitude calculators that you can use if you know the altitude, humidity and temperature. Alternately, wouldn't the density altitude be listed for any airport with a tower, as part of the meteorological report (pilots of real aircraft please correct me here...)?

I'd look up or calculate the density altitude, say to myself "I'm flying at XXX feet today", and go fly. The way my brain works, I'll just start unconsciously working on the problem until I have a feel for things.

Igor Burger · « **Reply #24 on:** June 16, 2016, 02:05:41 PM »

You must take care about sea air pressure, altitude, humidity and temperature - that determines air density and that determines RPM for proper lap time :- ))

May be I should add a calculator to my timers :- ))))))))))))

Mark Scarborough · « **Reply #25 on:** June 16, 2016, 10:08:29 PM »

I understand the interaction of altitude and such, the thing that caught me off gaurd was more the proportion, or significance of each element, so yeah, I need to aquire or at the least research it enough to have a feel for the proportions.
yes a monitoring of the relevant information is warranted,,

Tim, how much elevation change do you deal with>?
Maybe the TUT timer could incorporate a pressure sensing transducer and algorythm to compensate automaticaly

Tim Wescott · « **Reply #26 on:** June 16, 2016, 11:59:35 PM »

Quote from: Mark Scarborough on June 16, 2016, 10:08:29 PM

Tim, how much elevation change do you deal with>?

Not much, although I think I noticed the difference in Roseburg.

Quote from: Mark Scarborough on June 16, 2016, 10:08:29 PM

Maybe the TUT timer could incorporate a pressure sensing transducer and algorythm to compensate automaticaly

Still need accurate temperature and humidity readings -- best to do the math. https://en.wikipedia.org/wiki/Density_altitude

David Hoover · « **Reply #27 on:** June 17, 2016, 05:59:52 AM »

Or you get a Kestrel 5000 weather meter and you don't have to do any math.

https://kestrelmeters.com/products/kestrel-5000-environmental-meter

Tim Wescott · « **Reply #28 on:** June 17, 2016, 10:40:05 AM »

Searching on "Android density altitude app" gets about a bazillion hits. The top one will work off of METAR data from the airport of your choice.

Igor Burger · « **Reply #29 on:** June 17, 2016, 11:05:47 AM »

I tried several such things, but none of them are precise enough.

The biggest problem is that altitude is usually measured by GPS. That is nice, but it needs to settle, not used first measured value as most of them use (because they are designed for real time use). The other problem that most GPS receives give elipsoid altitude and only some of them are corrected and that can give error up to 100m (300ft) error what is completaly off for precision we need for competitive use. So I had to make own program for smartphone which works as necessary.

The other problem is that thermometers are usually in nice black case - what makes terrible errors in summer - not only on sun, also thighs around radiates and few degrees can already change lap time.

I do it simple - if I go somewhere I will check real altitude of field by global maps, for example https://www.daftlogic.com/sandbox-google-maps-find-altitude.htm
I found air pressure does not make too much difference, so usage 1013 is good way. Humidity changes it also only in extremes, so 50% is not bad. However it is good to check extremes, high pressure make air thicker and high umidity make air thinner but only little bit.

Then I prepare table for setting on that place and print.

Then on place I check only air temperature by good thermometer. I strongy recomend thermometer with metalic shiny senzor (such type with long stick). Absolute precision is not so important, but colored or plastic surface is wrong way :- )) Let the air blow to sensor to remove accumulated heat.

I see I must really make standard program :- ))

Howard Rush · « **Reply #30 on:** June 18, 2016, 08:58:49 PM »

I don't think density altitude is particularly useful. You can't calculate anything from it unless you convert it back to density. I think it was invented to give pilots something intuitive to go by. It sounds scientific, and lots of people are used to looking at it and have a general feel for what it's telling them. I prefer density ratio, the ratio of density to density of a sea-level standard day.

Two ways I've used to determine density ratio (or density altitude) are by Web sites or by iPhone. Before I got the phone, I noted what time I flew, then looked later at http://www.wrh.noaa.gov/mesowest/getobext.php?wfo=sew&sid=KAWO&num=72&raw=0 (pick your location) and https://wahiduddin.net/calc/calc_da.htm . I entered the elevation of where I was flying in the Wahiduddin calculator. Then I interpolated temperature, altimeter setting, and dewpoint from the NOAA site (pick a nearby airport) for the times I flew and entered them into the Wahiduddin calculator. With the iPhone I use https://itunes.apple.com/us/app/air-density-meter-relative/id838893833?mt=8 . It calculates relative density (same as density ratio) and density altitude from data from a nearby weather station or from numbers you enter yourself. It is handier than the after-the-fact Web method, and it gives you real-time data on how tight you can turn a corner.

Mark Scarborough · « **Reply #31 on:** June 18, 2016, 09:11:25 PM »

Quote from: Howard Rush on June 18, 2016, 08:58:49 PM

I don't think density altitude is particularly useful. You can't calculate anything from it unless you convert it back to density. I think it was invented to give pilots something intuitive to go by. It sounds scientific, and lots of people are used to looking at it and have a general feel for what it's telling them. I prefer density ratio, the ratio of density to density of a sea-level standard day.

Two ways I've used to determine density ratio (or density altitude) are by Web sites or by iPhone. Before I got the phone, I noted what time I flew, then looked later at http://www.wrh.noaa.gov/mesowest/getobext.php?wfo=sew&sid=KAWO&num=72&raw=0 (pick your location) and https://wahiduddin.net/calc/calc_da.htm . I entered the elevation of where I was flying in the Wahiduddin calculator. Then I interpolated temperature, altimeter setting, and dewpoint from the NOAA site (pick a nearby airport) for the times I flew and entered them into the Wahiduddin calculator. With the iPhone I use https://itunes.apple.com/us/app/air-density-meter-relative/id838893833?mt=8 . It calculates relative density (same as density ratio) and density altitude from data from a nearby weather station or from numbers you enter yourself. It is handier than the after-the-fact Web method, and it gives you real-time data on how tight you can turn a corner.

we talked about this in ROseburg for a moment right? so the real number that matters( by your cipherin) is the relative density. Does it go out and find the info for you, or do you have to populate the calculator your self from data gathered elsewhere manualy?
Not that ultimatly that is relevant to me since I am an Android abuser, I shall go look for a density calculator poste haste

Howard Rush · « **Reply #32 on:** June 19, 2016, 12:01:43 AM »

Quote from: Mark Scarborough on June 18, 2016, 09:11:25 PM

Does it go out and find the info for you, or do you have to populate the calculator your self from data gathered elsewhere manualy?

You can do it either way. If you fly near an airport with a weather station, it can get good data automatically. At Auburn, I'd enter the field elevation, take the local school station's word for temperature, and use the iPhone's barometer via another app to get altimeter setting.

Igor Burger · « **Reply #33 on:** June 19, 2016, 02:38:11 AM »

Quote from: Howard Rush on June 18, 2016, 08:58:49 PM

I don't think density altitude is particularly useful.

Not for any calculations, but if you need compensations, fo example +/- throttle like we spoke above, does not matter what number you have, you need only proper table of corrections to "something".

I have table regarding air density and I know I need change throttle by 1 per every 0.01 kg/m^3 ... similar solution can be per m of density altitude or by % of sea level density or whatever. But that is right, density altitude will really not tell you anything about minimal corner radius :- ))

Crist Rigotti · « **Reply #34 on:** June 19, 2016, 07:00:49 AM »

Quote from: Igor Burger on June 19, 2016, 02:38:11 AM

Not for any calculations, but if you need compensations, fo example +/- throttle like we spoke above, does not matter what number you have, you need only proper table of corrections to "something".

I have table regarding air density and I know I need change throttle by 1 per every 0.01 kg/m^3 ... similar solution can be per m of density altitude or by % of sea level density or whatever. But that is right, density altitude will really not tell you anything about minimal corner radius :- ))

Igor,
I have a question. On the day of the contest,when you change the RPM because of air density, do you do another calibration flight before an official flight?

Mark Scarborough · « **Reply #35 on:** June 19, 2016, 09:01:26 AM »

Quote from: Howard Rush on June 19, 2016, 12:01:43 AM

You can do it either way. If you fly near an airport with a weather station, it can get good data automatically. At Auburn, I'd enter the field elevation, take the local school station's word for temperature, and use the iPhone's barometer via another app to get altimeter setting.

so I found an Android ap for my phone, it works either way, it goes out and finds the closest airport and steals the information from there, or It says I can input my own data, more to follow,,
but it does Air Density and RAD as well as a bunch of other stuff,,

Igor Burger · « **Reply #36 on:** June 20, 2016, 02:42:07 AM »

Quote from: Crist Rigotti on June 19, 2016, 07:00:49 AM

Igor,
I have a question. On the day of the contest,when you change the RPM because of air density, do you do another calibration flight before an official flight?

I check before every flight, so answer is no :- )))

But to make the thing clear - calibration is to store "level" centrifugal force. You not need to do calibration if you do not change the level lap time. Managing proper throttle is just to keep constnat lap time, so it really not needs calibration.

Beside that, I do not do calibration at all (never). Timer has some default value, it will work with that OK. You will need to do it if you see that lap time changes with checnge of sensitivity. If you are OK with that, you not need to do it. I do not change chenge sensitivity if it is once OK, so I am OK with that :- )))

However the default value is for standard line length and lap time, if you have smaller model or short lines , it is better to do it.

Igor Burger · « **Reply #37 on:** June 20, 2016, 02:45:47 AM »

Guys, lap can be different also on grass and concrete on the same field (in calm). So it is better to measure then believe those "remote" sources. Air density on closest airport can be something different then on your field.

Crist Rigotti · « **Reply #38 on:** June 20, 2016, 06:08:39 AM »

Thanks Igor, that makes sense.

Igor Burger · « **Reply #39 on:** July 08, 2016, 10:21:25 AM »

If anyone wants to try, here is a program for android :- )) ... I hope you understand

http://maxbee.net/download/AirDensityThrottle.apk

the default settings are just as I use it with my actve timer and standard Jeti ESC settings and with mine 11x5 or 12x5 props. on my Max Bee

Igor Burger · « **Reply #40 on:** July 24, 2016, 01:09:00 PM »

Does anyone uses that program? Any comments? wishes? errors?

New version is already available, 2 wishes are implemented 1/ Wind correction 2/ another 2 trimming paramaters (whatever you need e.q. sensitivity, pipe length, LO guides, rudder, xxx ? ? ? ... etc)

another 2 wishes are waiting, I am too lazy and they look like lot of work.

Igor Burger · « **Reply #41 on:** July 26, 2016, 08:17:06 AM »

And one of wishes also already fulfilled ... android gps altimeter with geoid correction:

http://maxbee.net/download/Altimeter.apk