Strange thing need some idea

[kaos]

OK, just finishing the build for my modified Super Falcon: (I have not decided I want a blonde, red head, brunette or black hair yet, so it is bald now )

I noticed something I am not quite sure why.
This one is equipped with a NTM 2700kv 4S, rated at 50A with 595W. HK gives a test data: with a 4.75x4.75 prop a 594W 40A
I tested the motor with a 55A ESC and a 4.74x4.75 prop running a watt meter and it reads at 460+W and 36A.
I figure that is enough thrust (by feeling how hard it is pulling), I changed to a lighter Mystery 40A ESC with burst of 60A.
but today when I ran it through the watt meter again and test the final set up. The 40A ESC only gives me 24.5 A and 340W or so with much less thrust of course.
I switch back to the 55A ESC right away and test it again, now it gives around 460W and 36A again with strong thrust.

What I could not figure out is if the 40A Mystery ESC is not capable of deliver >30A it probably should burn out, but instead it draws 24-25 A and gives a 300 something Watt.
Can any one explain this a little for me?

[Kilrah]

The 40A will have smaller power transistors, likely with a higher resistance. So more voltage loss, so less RPM, and less power draw from the (same) prop.

[kaos]

Wow that is fast reponse, Thx.
Isn't the power/amp draw is determined by the motor/prop? if the ESC won't give out that much A, shouldn't it just burn out?
If I understand you correctly, then I could put a bigger prop which makes the plane go faster/more thrust till it reaches the ESC limit? or the voltage drop just won't go that high which means the 40A ESC is just not efficient I should dump it?

by the way I did use fairly new 4S lipos rated 30-40C and I did recalibrate the 40A ESC after I found it did not give out much amp.

[pmullen503]

The timing may not be optimized for the motor on the smaller ESC. (Though running a 40A ESC at 38A means you are trusting the manufacturer's specs are not inflated!)

[jhsa]

yeah, specially a Mistery ESC

[kaos]

The timing may not be optimized for the motor on the smaller ESC. (Though running a 40A ESC at 38A means you are trusting the manufacturer's specs are not inflated!)

I will try to change the timing to test it again.
As for running 36A out of 40A ESC, my reasoning is it is rated at 40A with ability of a burst a 60A, if the spec is right then the time to run at 36A is really very short (100% throttle). That is the reason I end up getting a watt meter to see exactly how much amp is draw with a large ESC. Anohter reason is the 40A ESC is 30g vs the 55A's 53g. I have another 45A YEP is 63g.
The thing is the ESC was not hot at all. Just won't put out the amp/power. I don't know the ESC can limit its amp output by itself?? If so no ESC should ever burn out because overloading.
I will see how the timing change works. If I remember correctly both ESC were on 'medium' by default. the 55A is a Turnigy Trust. I will also test it with the YEP 45A next time.

yeah, specially a Mistery ESC

Mystery 40A ESC has been good when I used on 450 heli without any problem, and I am using 13T pinion with thatk so I have a few extra/spares. I only had one brand new Mystery 40A burned out on me while I was just testing servos without motor, just smoked on the 2nd usage.
I have 2 other Mystery 40A on 2 other planes without any issues but those 2 only draws 26-30 amp.

[Kilrah]

There could simply simply be differences in the ESC's software that makes it less efficient too.
And yes many ESC have some kind of overload protection.

But these setups with high Kv and small fast props are "unstable" by nature. I've seen the same with my Funjets some time ago, simply going from one battery to another can drastically change power, by nearly a factor of 2 for the reason explained higher. A little more voltage sag either due to battery internal resistance, thinner cable, higher resistance ESC etc quickly causes a drop in power (Kv is high so a small voltage loss means a higher loss of RPM, and power is a function of RPM squared).

[kaos]

The esc does have overload protection. But i was raising throttle slowly while reading watt meter, the amp never went up more than 25a.
Must be reason other than overload protection.
I will run a couple more tests like changing timing, switching frequence.....

[Spoogy]

Did you use same battery? Different batteries can affect by its efficiency to give the needed power.

I have the same Falcon Wing (for two years now) and I'm using Turnigy 3010B motor (http://www.hobbyking.com/hobbyking/stor ... arch=3010B) with Aeronaut 9x6 folding propeller. Gives plenty of thurst and speed.

Night flying video from our clubs autumn camp -> http://youtu.be/4PcMKpRIc68

-Spoogy

[kaos]

Yes, I was using the same battery.
that is a pretty night light set up you have there Spoogy!
I was trying to start a night flying group in my fly club, but was told 'avoid' going to that field at night 'alone'.
Have you done any mod to your Falcon? I basically add a pair new aileron and fixed the existing aileron as part of the wing to increase wing surface area in anticipation for FPV fly.
What is your CG location? I have read a lot people with this Falcon have CG issue, and the CG location is all over the chart. Currently I am balancing it at he location based on a flying wing CG calc and is ~1cm ahead of the main CF spar.
Wow, that 3010B motor gives 1650g of thrust with 3S at 420W . that is more thrust than my 2826 NTM motor 4S at 595W. May have to try that 3010B. that would shave off another 60g off the weight. Thx for the motor and prop combi info.

[Spoogy]

Yes, I was using the same battery.
that is a pretty night light set up you have there Spoogy!
I was trying to start a night flying group in my fly club, but was told 'avoid' going to that field at night 'alone'.
Have you done any mod to your Falcon? I basically add a pair new aileron and fixed the existing aileron as part of the wing to increase wing surface area in anticipation for FPV fly.
What is your CG location? I have read a lot people with this Falcon have CG issue, and the CG location is all over the chart. Currently I am balancing it at he location based on a flying wing CG calc and is ~1cm ahead of the main CF spar.
Wow, that 3010B motor gives 1650g of thrust with 3S at 420W . that is more thrust than my 2826 NTM motor 4S at 595W. May have to try that 3010B. that would shave off another 60g off the weight. Thx for the motor and prop combi info.

That video is captured at one of our camps which we keep every spring and autumn at the Jämi (civilian) airport in here Finland. There are hotel, restaurants, etc... and cottages which we usually rent for the weekend to keep these camps.

But I do not have any special mods. Just invented better holding mechanism for the cockpit. Added 3mm CF tube through cockpit nose and CF rod to the hull, sticking out towards to cabin, which will be inserted into the CF tube of the cockpit when it's attached on the plane. I Also added 4 neodyms to rear end of the cockpit (two for hull and two for cockpit. One on each side) for better holding. And then I just added some GF tape over the CF spar. Ouh, and I also added some small CF rods inside of wingtip joints before I glued them on place, just for better hold. As you could see on the video above, I hit the tree and plane was still intact.

CG is 12 inch. from the tip of the nose and I too fly with 4S battery. I also have small (800mAh) 3S and brushed ESC on the plane for the lights. With brushed ESC I can adjust brightnes of the LEDs from Taranis potentiometer. I have had 40A Corona ESC, 40A Turnigy Plush ESC and now I have 60A YEP ESC in there. All has been given similar kind of thurst and power output, but the YEP esc has been best for the throttle response. Very smooth and very responsive. Turnigy Plush did have best brake (as I use folding prop). Corona was one piece of c**p. Kept terrible noise.

-Spoogy

[kaos]

Thx Spoogy for the info. I heard YEP is pretty good. so after my last purchase of the Mystery 40A of 3. I got myself a few YEPs as spare too. but it is a little heavy for my current build main purpose, lighter weight and longer fly time. You are running the 3010B with 4S without problem, that is good to know. HK list it as a 3S motor. Just to be sure, this is the one you are talking right? http://www.hobbyking.com/hobbyking/stor ... ouse_.html

and yes, most of these foam canopy won't hold at high spd with stock mechanism, I glued a tongue blade tip at the bottom tip of the canopy tip and cut a groove in the nose to lock the front. if you read my pic there is a transparent cellophene/plastic strip across the canopy to hold the canopy with 2 red dots each side. those are nylon 3mm screws with a 1cm riser glued into the foam body. no magnets in mine. under canopy I glued 3 trip of cellophene strip (those used for packaging that cuts your fingers all the time ) strategically to reenforce the canopy. With the balsa flat top together, it needs a crash to break the canopy. I did the enforcement because the flat top is where the FPV equipment is going to be, that canopy has to be able to hold them and stay put.

Now I think I figure out where the problem is. MY OWN stupidity and some battery issue.
I think I did not calibrate the ESC correctly. twice in a roll. I reread the instruction on the Mystery ESC. I need to wait until the motor beeps before I pull the throttle stick down. But I was doing a little too early and the ESC was calibrated some what lower than the full throttle. This motor and this ESC seems to take longer for the beeps to come out and I normally just wait a couple second and pull the stick down. Last night I recalibrated the ESC, following the instruction, and test it today. it does go up to 560 watts and at 40.5 amp draw.

so I went ahead to test 5 of my 4S lipo and I found out there is a big difference among them too. the 3 Zippy 2200 mah 4S 40C gives me the full power at 540-560W drawing 39-40amp. I did test it with full power 5-10 sec burst, the Mystery 40A ESC survived. It is getting hot but no shutdown or burning up. But outside temp is only 36degree, in the summer it may be different. But temperature in the fly may be OK with more air flow. The test is a static run.
But my 2 Turnigy 2200 mah 4S 30-40C only can give out 400+ w and draws about 26-30 amps. So, no more Turnigy 4S, zippy lives.
I did not realize these lipo can vary THAT much.
Never run a watt meter till recently, I think it is going to be one of my daily equipment for these planes from now on. What a difference seeing those numbers pop up.