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Jan 02, 2016, 11:43 AM
I COLLECT flyaway&lost drones!
martin555's Avatar
Hello Joci!

I replaced KK board to NAZE32. my S500 flies now very well.

multistar elite 2216 920kv motors.

question:

what "cheap" but "good" prop do you recommend for 4S ?

are any plastic clones of this:

http://www.gothelirc.com/products/24...ormal-8mm-dji/

now I use plastic not-original DJI self locking 9,4x4,3 and I ordered cheap 9,4x5.

I have 20A afro. is it recommended to re-flash if yes with what firmware?

With KK board, and 3S (powerful 60C discharge) battery this motor was VERY BAD poor performance.

My friends fly with smaller:2212 motor 4S 5400mah battery DJI 1038 prop (naza controller) very well.

so I was wondering, with the bigger 2216 920 motor why is so poor performance.
Last edited by martin555; Jan 02, 2016 at 11:52 AM.
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Sep 29, 2016, 03:17 AM
Registered User
Hi..
I'm assembling x8 using e300 kit
My x8 specification roughly like this:
FC: APM 2.6
ESC: Dji e300 opto
Motorcycle: Dji e300
prop: 9443
Batrrey: Multistar 4S 10000mah
AUW: 2000 gr
rx: frsky x8r
Radio: Taranis x9d

Can someone give me information why my x8 can not hover at 50% throttle in stabilized mode? it s hover at 75% throttle, and the motor stay cool after 3-4 minute hover
Is my x8 too heavy?
or there are something wrong with my e300 kit?
Sep 29, 2016, 07:40 AM
Jack
jackerbes's Avatar
Thread OP
Did you read the testing data back in post #2?

Prop: DJI 9443 Self Locking prop (plastic blades)
4S (16.4V)
Throttle Volts Amps Watts RPM Thrust(g) Winding Temp (F/C)
25% 16.43 1.20 20 4202 139 78/26
50% 16.34 2.97 49 6162 357 78/26
75% 16.16 7.07 114 8175 705 83/28
100% 15.88 13.58 216 9596 1034 125/52

You need to have props that have a static thrust that is about 1.2 to 1.4 times the AUW of the multi to lift cleanly and and quickly and have stable hover. So for your 2000g AUW you want to have 2400g to 2800g thrust. And that would be 600 to 700g on each motor.

Here is my test data on static thrust, there is no free lunch, if you have the weight you need the thrust or it will not fly:

Multis - Static Thrust to Flying Weight Ratio Testing - 1.2:1 is the answer! - [url]www.rcgroups.com/forums/showthread.php?t=2186758

The test data for your prop back in post #2 shows 357g at 50% and 705g at 75% and that means that the test data is right on the money and everything is working normal. You need more thrust at 50% to hover there and that means a bigger or better prop. And to turn that bigger and better prop may require bigger and better motors.

If your motors are coming down so hot (on the base, not on the housing) that you can barely keep a finger on them you are pushing them as hard as it is safe to now.

Jack
Sep 29, 2016, 11:29 AM
Registered User
Quote:
Originally Posted by jackerbes
Did you read the testing data back in post #2?

Prop: DJI 9443 Self Locking prop (plastic blades)
4S (16.4V)
Throttle Volts Amps Watts RPM Thrust(g) Winding Temp (F/C)
25% 16.43 1.20 20 4202 139 78/26
50% 16.34 2.97 49 6162 357 78/26
75% 16.16 7.07 114 8175 705 83/28
100% 15.88 13.58 216 9596 1034 125/52

You need to have props that have a static thrust that is about 1.2 to 1.4 times the AUW of the multi to lift cleanly and and quickly and have stable hover. So for your 2000g AUW you want to have 2400g to 2800g thrust. And that would be 600 to 700g on each motor.

Here is my test data on static thrust, there is no free lunch, if you have the weight you need the thrust or it will not fly:

Multis - Static Thrust to Flying Weight Ratio Testing - 1.2:1 is the answer! - [url]www.rcgroups.com/forums/showthread.php?t=2186758

The test data for your prop back in post #2 shows 357g at 50% and 705g at 75% and that means that the test data is right on the money and everything is working normal. You need more thrust at 50% to hover there and that means a bigger or better prop. And to turn that bigger and better prop may require bigger and better motors.

If your motors are coming down so hot (on the base, not on the housing) that you can barely keep a finger on them you are pushing them as hard as it is safe to now.

Jack
thanks for your respon
I think the existing data is correct
using propellers 9443 and 4s battery, at 50% will get a 357 thrust
But I use the 8 motor with x8 configuration
if I multiply by 8 motors, supposedly at 50% I will get 357x8 = 2856
but because it uses a x8 configuration might not get 100% efficiency.
Is octocopter efficiency with x8 configuration will reduce power by up to 50%?
Sep 29, 2016, 11:33 AM
Jack
jackerbes's Avatar
Thread OP
OK, if it is an octo I would expect to see it lift at 50% and 357g per motor and fly OK. Are you trying to fly a low energy type of flight? Not a lot of throttle activity and almost all level flight?

Jack
Sep 29, 2016, 11:38 AM
Jack
jackerbes's Avatar
Thread OP
A couple of the props tested got the thrust up over 400g at 50%, maybe a prop change would be enough to get the thrust you need.

Does your 2000g include the battery and everything? Ready to fly?

Jack
Sep 29, 2016, 09:14 PM
Registered User
Quote:
Originally Posted by jackerbes
OK, if it is an octo I would expect to see it lift at 50% and 357g per motor and fly OK. Are you trying to fly a low energy type of flight? Not a lot of throttle activity and almost all level flight?

Jack
yes, I will not play with the throttle a lot, I would not fly aggressively

Quote:
Originally Posted by jackerbes
A couple of the props tested got the thrust up over 400g at 50%, maybe a prop change would be enough to get the thrust you need.

Does your 2000g include the battery and everything? Ready to fly?

Jack
1900 grams is the weight of my x8 with battery, without gimbal and a set of FPV.
But I've calculated when gimbal and FPV mounted, weight x8 I will be around 2400/2500 gr.
Whether with such configuration will still be able to hover at 50%?
for now I'm waiting for new propeller with the size of 1045, hopefully will get more thrust
Sep 30, 2016, 12:23 AM
Registered User
BobbyC1's Avatar
What is the reason for 30a esc's when the motors peak at 12-14a?

I just bought a set of E300 motors and will be looking for escs soon. I was thinking of upgrading my smaller 200 class escs (20a) and using them for this build (Reptile 500)
Sep 30, 2016, 05:32 AM
Jack
jackerbes's Avatar
Thread OP
Quote:
Originally Posted by pramgeo
yes, I will not play with the throttle a lot, I would not fly aggressively



1900 grams is the weight of my x8 with battery, without gimbal and a set of FPV.
But I've calculated when gimbal and FPV mounted, weight x8 I will be around 2400/2500 gr.
Whether with such configuration will still be able to hover at 50%?
for now I'm waiting for new propeller with the size of 1045, hopefully will get more thrust
It will almost certainly do better than the 9443 props because of the increase in size and pitch. But you'll also have to consider what the additional load will do to the motors too. They will get warmer.

Jack
Sep 30, 2016, 05:33 AM
Jack
jackerbes's Avatar
Thread OP
Quote:
Originally Posted by BobbyC1
What is the reason for 30a esc's when the motors peak at 12-14a?

I just bought a set of E300 motors and will be looking for escs soon. I was thinking of upgrading my smaller 200 class escs (20a) and using them for this build (Reptile 500)
An ESC cannot really be too big for the motors, it just leaves you with some extra current capacity that you are not using. And the ESC should be working at a more relaxed pace and maybe not getting as warm too.

A good rule of thumb for ESCs is to use them at no more than 75% of their rated values. So if you only need about 15A a 20A ESC would be about right.

And a more important consideration for ESCs is the BEC, what type it is (linear or switching), what it's rating is, and how much of a load you are actually putting on it with servos and other accessories.

Jack
Sep 30, 2016, 07:44 AM
Registered User
BobbyC1's Avatar
Quote:
Originally Posted by jackerbes
An ESC cannot really be too big for the motors, it just leaves you with some extra current capacity that you are not using. And the ESC should be working at a more relaxed pace and maybe not getting as warm too.

A good rule of thumb for ESCs is to use them at no more than 75% of their rated values. So if you only need about 15A a 20A ESC would be about right.

And a more important consideration for ESCs is the BEC, what type it is (linear or switching), what it's rating is, and how much of a load you are actually putting on it with servos and other accessories.

Jack
I thought there might be some other benefit to using higher amp escs with bigger motors. I have 30a escs on a Vtail 400 with 2208 1800kv motors (18a max pull with 8045) but that's more of an acro quad that often sees 75% throttle or more. The E300's are going on a TBS Discovery knock off frame and will be flown more for AP than aggressive flying.

The 20a escs are Opto. I plan to use a separate BEC for 5v 1.5a or 3a depending on accessories I'll be installing.
Sep 30, 2016, 10:28 AM
Jack
jackerbes's Avatar
Thread OP
There is no advantage, as far as flying power, to using a larger ESC. lt sounds like what you are doing or planning is good.

On the external BEC for the opto ESCs make sure it is a switching mode BEC (if they do not say it is switching mode assume it is a linear mode one). And make sure that it is rated for a higher amperage than you will be drawing. I would almost always use a 5A or larger external BEC simply because there is virtually no weight penalty between a 3A and a 5A.

Jack
Oct 31, 2016, 11:15 PM
Registered User

battery choice


so i have 2212/920kv motors, for the dji f550 so what battery should i get for longest flight. its a film drone and peak power wont be used as in flying fast or crazy maneuvers, mainly hovering or slow movement. Please help thanks
Nov 01, 2016, 07:24 AM
Jack
jackerbes's Avatar
Thread OP
Quote:
Originally Posted by raptor4184
so i have 2212/920kv motors, for the dji f550 so what battery should i get for longest flight. its a film drone and peak power wont be used as in flying fast or crazy maneuvers, mainly hovering or slow movement. Please help thanks
This is not a easily answered question. If you look back at the prop testing data I posted earlier, you can work out an intelligent guess as to what might work and then you could fly it and adjust the the size of the battery if it did not meet your needs.

Here is how to do that for one of the prop and motor combos I tested 2212/920 motor:

Prop: DJI 9443 Self Locking prop (plastic blades)
3S (12.3V)
Throttle Volts Amps Watts RPM Thrust(g) Winding Temp (F/C)
25% 12.42 0.93 12 3375 78 71/22
50% 12.36 2.05 25 4892 210 72/22
75% 12.25 4.65 57 6661 428 74/23
100% 12.05 9.18 111 8220 701 78/26

The primary consideration is that the ready to fly weight of your quad is what decides the input power and throttle setting you need to attain slow, level, and controlled flight. As you can see there, at 50% the thrust is 210 grams and at 75% it is 428 grams.

You need to see a static thrust that is about 1.2 to 1.4 times the AUW of your quad to lift cleanly and hover. So at 50% throttle with 210g of thrust from each of four motors you would have 840g of thrust and that would be good for a quad that weighs about 650 grams. I say that because 650g x 1.3 = 845g.

As you can see there is a major increase in the thrust at 75% as it goes up to 428g per motor for a total of 1712g and that would fly a quad that weighs about 1320g because 1320g x 1.3 = 1712g.

And if you look at the test data, you can see that the current the motor was drawing was 2.05A at 50% and 4.65A at 75%. And it is that continuous current draw that really decides what size the battery has to be to give you a specific flight duration.

If you have four motors drawing 2.05A that would be 8.20A, if they are drawing 4.65A that would be 18.6A. And you can use that info to do some more calculations to consider battery sizes:

Let's consider a 4000 mAH battery. For starters, you will get about 80% of the rated capacity as useable capacity. So you really only get 3200 mAH out of the 4000 mAH pack.

3200 mAH = 3.20A

3.20A x 60 minutes - 192 Amp/Minutes

And if you are drawing 8.20A your duration will be about this:

192 Amp/Minutes / 8.20A = 23.4 minutes of flight duration

If you need 75% throttle to maintain the level hover your duration would about this:

192 Amp/Minutes / 18.6A = 10.3 minutes of flight duration

So if you can find some test data for the prop and motor combo you intend to use you can get pretty good estimates as to what you can get out of a battery of a given size or what battery size you need to get a specific flight duration.

Jack
Jun 25, 2017, 03:54 AM
Registered User

Some questions


Dear Jackerbes,

The current amps draw in your post is all about one motor or Total Amps in 4 props?
This is such kind of a stupid question, but I wondered.

And How can 3s li-po battery draw maximum Amps?
Can it feed 4 motors for 20A drawn battery?

Thanks!


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