eCalc accuracy?

N

nemorov

Member
Hi Guys,
Posted a longer post yesterday about Axi motors and eCalc but didnt get any replies so I'll make this simpler.
What are peoples experiences with eCalc ?

Its telling me my motors are running over current ( and we have had one fail ) but I'm finding it hard to find any setting for these motors that will work.
I'm reticent to change my motors until I'm sure that the figures from eCalc are actually making sense.
The only other option for me is to find a way to measure my motor current draw in the real world.

So what are other peoples experiences with eCalc ?

Thanks

gavin


www.gavinnewman.com
 

P

PaNt

Member
it is very accurate ..! what is your problem?? tell us your setup or show us a pic of your settings on ecalc..!
 

N

nemorov

Member
Hi there,
Thanks for the reply.

So heres our situation.
Following a recent motor failure on our custom built HEX I started looking at the figures on Ecalc.

Until recently we were running our copter on 2x 3s 5000mah batteries without any problems.
After installing a DJI Z15 Gimbal we uprated our cells to 4s cells to accommodate the Gimbal power requirements.
Several test flights in the UK ( 20degree ambient temperature ) went fine without any flight issues apart from some drifting of the Gimbal.
On location in Borneo (35-40degree ambient air temp) on the first flight the copter flipped on landing and appears to have blown one of the AXI motors. Visual damage to the windings inside the motor.

Trying to diagnose the problem I put all the figures into eCalc.
Using our current 13 x 7 props, 4s batteries and the 2814/22 motors with our TOW of 6.2kg I get over current warnings for the motors. This would account for our motor failure, especially given the high ambient temperatures experienced in Borneo.

However when I started playing around with other figures I find it hard to get any combination using the 2814/22 on a 'heavy' copter that will work so I'm interested in other peoples experiences of using these motors on heavy lift copters...
If you're flying these motors on a HEX whats your battery and prop configurations and Take Off Weight?
I contacted AXI and they confirm that their motors are OK up to 5S cells and they also commented that they don't recommend eCalc as they don't consider it to simulate real world situations very well at all.
Any other observations also welcome.

My eCalc settings are attached.View attachment 7565

Its looking like my only option to get something that is within tolerance according to eCalc is to change motors to a low Kv rated motor such as the Tiger MT3515/15 (400Kv) and use 6s batteries.
This interestingly is very similar to the setup used in the DJI S800 which uses 320Kv motors and 6s batteries.

Anyone have experience or thoughts on the Tiger motors?

Thanks,

gavin


www.gavinnewman.com
 

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S

Stacky

Member
My experiences are very mixed, some accurate, some wildly off when i tested against real world measuring. One i had was within a minute of the ecalc and another was 4 minutes out. I use it as a guideline as it does a good job of giving a rough idea most of the time. the problem is that there are now so many different esc's, motors and props etc that it can no longer cover them all.
 

nicwilke

nicwilke

Active Member
I have had good results up till they introduced some new Tiger Motors. There is actually 2 2814-10 (770), with my setup, old ones work, new ones don't, but no difference in specs on those motors.
 
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R

RotorFilms

Member
Hi Gavin,

I also run a hex with AXI 2814/22 motors, TOW on my setup is about 5.5kg. I can tell you one thing you are over propping your motors, I use to run APC slow fly 14 x 4.7" and the motors got so hot that I could not even touch them. This is using a 4 cell battery. I then started doing some tests, first by adjusting the timing on the ESC's as I saw on AXI's website that they recommend their motors be used with high timing. I tried High and low with the 14 x 4.7" props but still no success motors kept on getting hot even after short 1 minute flights. I eventually gave into the notion that I'm over propping the motors. So I did a test again, set up a load test where I compared the thrust between the 14 x 4.7" and 12 x 3.8" props, to my surprise not a massive difference, yes My throttle stick was maybe just above half for 1kg of thrust on the 12 x 3.8" APC slow fly but the motors was cool to the touch. So now I'm running medium timing 15deg I think, 12 x 3.8" APC slow fly and 4cell batteries and I have never looked back. I have enough power to gain altitude real quick and the craft is very responsive still. To tell you the truth it is actually less affected by wind now that I'm running the smaller props.

I hope all this helps as I know how frustrating it can get and I just did not want to admit to myself that I bought a crazy amount of 14" props which I can't use.

Regards,

Andre
 
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N

nemorov

Member
Hi Andre,

Thanks for that feedback its really useful to find someone with a similar setup.
I've got some APC 12x3.8 props so I'll give those a try. I also have Xoar 12 x 6's which I'll also try.
I've just invested in the Telemetry system for my Hitec Aurora 9 radio with temperature and current sensors so hopefully that should allow me to see what the motors are really doing during flight and hopefully find out what caused my motor failure.
Not sure if I can adjust the timing on my ESC's ( Hobbywing 40amp Opto's )but I'll take a look at the manual.
What capacity batteries do you fly and what sort of flight time are you getting with 5.5kg TOW.
My current setup runs 2 x 6100mah 4s batts and gives me around 8-9 mins useful flight time.

Gavin.

www.gavinnewman.com
 

R

R_Lefebvre

Arducopter Developer
I find it is pretty accurate for many typical setups. However, it seems to not be able to predict some setups well at all. For example, we've seen people fly for over 1 hour, but I find it is impossible to build a theoretical quad which can fly for more than 30 minutes, even if I make it a "flying battery" with zero frame weight, and the most efficient props possible.
 

R

RotorFilms

Member
Hi Gavin,

Currently I only fly 1 x 4cell packs, 5000 mah. I stop flying at 4 min's that equates to about 80% of my battery capacity. Must tell you though I flew today and the motors got hot again but I suspect my gains are too high as I adjusted them for windy conditions on my last flight. So I'm going to go down on the gains again and see what happens. As a rule now though I feel my motors after each flight just to make sure everything is in order.

Let me know how it goes with you're testing.

Cheers....
Andre

nemorov said:
Hi Andre,

Thanks for that feedback its really useful to find someone with a similar setup.
I've got some APC 12x3.8 props so I'll give those a try. I also have Xoar 12 x 6's which I'll also try.
I've just invested in the Telemetry system for my Hitec Aurora 9 radio with temperature and current sensors so hopefully that should allow me to see what the motors are really doing during flight and hopefully find out what caused my motor failure.
Not sure if I can adjust the timing on my ESC's ( Hobbywing 40amp Opto's )but I'll take a look at the manual.
What capacity batteries do you fly and what sort of flight time are you getting with 5.5kg TOW.
My current setup runs 2 x 6100mah 4s batts and gives me around 8-9 mins useful flight time.

Gavin.

www.gavinnewman.com
Click to expand...
 

N

nemorov

Member
Tested the motors today with a current meter on the telemetry with the copter strapped down to a bench.
Different readings on CW & CCW props. CCW motors are pulling up to 38amps and the CW 16amps on 4s batteries.
38 is way over the AXI recommended 25amps and also about the 29amps predicted by eCalc for my setup although the average of CW & CCW equates to not far off that figure.

Anyway 38amps is way to high. 3s batteries give me 24amps, still to near the max for my liking so I'll be trying the Tiger 400kv motors next on 4s batteries.
eCalc suggests this as a much more efficient setup for my machine.

So watch this space...
 

S

Stacky

Member
Are you measuring the total amps for 4 motors?. Have you remembered to divide the total amp draw by 4 so that you get the correct per motor draw?.
 


R

RotorFilms

Member
nemorov said:
Tested the motors today with a current meter on the telemetry with the copter strapped down to a bench.
Different readings on CW & CCW props. CCW motors are pulling up to 38amps and the CW 16amps on 4s batteries.
38 is way over the AXI recommended 25amps and also about the 29amps predicted by eCalc for my setup although the average of CW & CCW equates to not far off that figure.

Anyway 38amps is way to high. 3s batteries give me 24amps, still to near the max for my liking so I'll be trying the Tiger 400kv motors next on 4s batteries.
eCalc suggests this as a much more efficient setup for my machine.

So watch this space...
Click to expand...

Hi Gavin,

That is truly interesting. Can you tell me what size props you did the test with and also how exactly you conducted it. Did you run full throtle during these tests? As mentioned previously I got 1kg of thrust on a APC12x3.8" SF prop, must admit I did not test the current bu the motor was running much cooler than before. Still have heating problems currently but I'm trying to get too the bottom of it.

Regards,

Andre
 

N

nemorov

Member
Hi Andre,
I used 13x7 props and also tried 12x6 props. I setup the copter as for normal flight but then strapped it down to an external bench so it couldnt take off. I have the current sensor loop from the Hitec telemetry system attached to one of the ESC power cables. I then run up the copter briefly to full power to see what the maximum current draw is with that motor/battery/prop combination.
I've now tried the same copter but with Tiger 3515 motors ( 400Kv ) with interesting results.
With 4s batteries and 13x7 props the copter doesnt generate enough power to lift off ( using a dummy load of 1.7kg to simulate the Zenmuze mount and GH2 camera combination ) Current draw at maximum thrust was around 6amps on the measured ESC.
I then ran it with two 3s batteries twinned together to give a 6s pack ( I dont have any real 6s packs available ). This gave plenty of power and the current draw at hover was around 8-9amps. I havent tried the strapped down maximum current draw test yet but will do that later today.
The 3s packs I tested with are quite low C rating (20) and the voltage dropped quite quickly using two 3s 5000mah packs so I'm just making up some more twinning cables and will do a further test using 4 x 3s packs twinned to give a total supply of 6s 10000mah and see what duration we get with that.
Assuming that gives a good result we will be investing in some proper 6s packs.

More results later...
gavin.
 

R

RotorFilms

Member
Hi Gavin,

I look forward to seeing the results you come up with.

Where did you purchase the Tiger 3515 400kv motors? They seem pretty good, but I'd like to do a little bit more research.

Regards,

Andre
 

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