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How to make Mini Arrow - Scream help

jdm85

New member
#1
I currently have the EMAX 2205 -2600kv on 4S 1300mah - 5x4.5prop

This setup has a high amp draw of about 50amps and full throttle with full charged battery

if I compared to say 2204 sized - 2300kv on 3s with 6x4 prop

the amp draw would be somewhere around 10amps. I would get much longer flight times with the smaller motor setup but would this increase my speed at all?

I'm trying to understand all of this.

What makes the plane move faster. grams of thrust or watts?
 

Wildthing

Well-known member
#2
For me the watts gives you an idea of how strong that motor is, I still to this day don't understand how guys figure out the thrust that way. Few years ago I bought a thrust stand plus which everyone should have is a watt/amp meter period. I test different combinations of props/motors , batteries and esc's. For me I deal with ounces of thrust, now I really know how strong the setup is. For example I can swap out a prop with a different pitch and right away know if it is better not only in thrust but amp and watt draw, or in some it is worse, makes a lot of noise but it's amp draw is higher and the thrust is less.
 

jdm85

New member
#3
Amps=Heat=Less efficiency

Scenerio 1: If a 2204 -2300kv on 3S 1300mah with 5x4.5 prop produces 600grams of thrust at 150watts of power pulling 10amps at full throttle

Scenerio 2: 2205-2700kv on 4s 1300mah with 5x4.5 prop producing 1500grams of thrust at 600watts of power pulling 50amps at full throttle


Results of Scenerio 1: Slower wing but longer flight time because of the 10amp draw
Results of Scenerio 2: Faster for short period of time as the 50amp draw will drain the battery much quicker. This is a much less effident setuop in my opinion.

Do I have this correct?
 

Wildthing

Well-known member
#4
Amps=Heat=Less efficiency

Scenerio 1: If a 2204 -2300kv on 3S 1300mah with 5x4.5 prop produces 600grams of thrust at 150watts of power pulling 10amps at full throttle

Scenerio 2: 2205-2700kv on 4s 1300mah with 5x4.5 prop producing 1500grams of thrust at 600watts of power pulling 50amps at full throttle


Results of Scenerio 1: Slower wing but longer flight time because of the 10amp draw
Results of Scenerio 2: Faster for short period of time as the 50amp draw will drain the battery much quicker. This is a much less effident setuop in my opinion.

Do I have this correct?
Yes, other then the size of the prop in scenario 1, you originally listed it as a 6X4.

It all comes down to what you want to have, speed or longevity? Also most don't fly at 100% throttle through the whole flight. You can fly slow on 4S also ;) .

Now where testing comes in as an example you could take your 2700kv motor and put it on 3S and see what size of prop/pitch would give the best results. You never know you could come up with a combo that is equal or better then the 2300kv setup. See I also like testing different brands of props, they may be the same size and pitch but they are never equal .
 

Arcfyre

Well-known member
#8
Remember that kv is a rating for RPM based on voltage, meaning RPM per volt.

That means your no-load RPM on the 2700kv motor on 4S would be (2700 * (4.2 * 4)) or 45,360 RPM. The 2300 kv motor on 3S no load RPM would be (2300 * (4.2 * 3)) or 28,980.

These are vastly different numbers, and obviously they don't take prop pitch or diameter into consideration at all, nor do they consider motor size or torque. But looking at just RPM, you can get an idea why the 4S setup is using so much more power.

Remember also that torque, RPM, and thrust are all interrelated as well. These numbers are tied to the prop pitch and diameter, as well as the amp draw of the system. A small, flat prop needs a lot less torque than a larger, coarser pitch prop. Which prop then makes more thrust depends on the power (watts) of the motor, which is determined by amps. It's all kind of a mess.

Looking at your setups, I think your 2700kv 4S is over the useful RPM limit for that motor. You'd probably get better performance by running the higher kv motor with the lower cell count (3S) battery. This will bring the no load RPM figure down while simultaneously increasing available torque. You would then be able to use a coarser prop to increase thrust, which will hopefully increase speed while not overly increasing amp draw.

Likewise, you could use the 2300 kv motor with the 4S battery. This will increase RPM and lower the torque available, necessitating a smaller prop. However, since the RPM would be 3.7 times higher, you'd likely get more speed out of that setup. Just watch your amp draw.

Hope this helps.
 

Arcfyre

Well-known member
#9
Yes 4S 1300mah

What motor/prop size are you using?
I have tried several different setups. Most recently was a Turnigy 2826-2200 with a 7x6 prop on 3S. That moved really well until a control horn failed and it spiraled into the dirt.

I've also flown the same arrow with an 1806-2700kv and a 5x4 prop. It moved pretty good and was much lighter and more efficient.

I haven't found out what I really like yet. I'm still experimenting, but as my previous post tried to cover, there are a lot of variables to consider.
 
#10
I'm going to try 3s with higher pitch 3 blade prop tonight and see what happens. 5x5 3 blade and then 6x4 2 blade

I will setup my watt meter before to see what kind of amperage I'm drawing
 

Arcfyre

Well-known member
#11
I'm going to try 3s with higher pitch 3 blade prop tonight and see what happens. 5x5 3 blade and then 6x4 2 blade

I will setup my watt meter before to see what kind of amperage I'm drawing
I assume you mean 3S on the 2700 kv?

I need you to tell me every spec when we're talking about this otherwise it just isn't enough information.

That should work. I have a fast versa wing that runs a 6x4 CF prop with a 2836-3000kv. That setup draws about 70 amps, but it moves pretty good.
 

Arcfyre

Well-known member
#13
Got it. Keep an eye on your watt meter, especially with that 6x4 prop.

Post your results if you done mind. I'm a nerd and I'd like to see the data. :cool:
 

Wildthing

Well-known member
#15
I have tried several different setups. Most recently was a Turnigy 2826-2200 with a 7x6 prop on 3S. That moved really well until a control horn failed and it spiraled into the dirt.

I've also flown the same arrow with an 1806-2700kv and a 5x4 prop. It moved pretty good and was much lighter and more efficient.

I haven't found out what I really like yet. I'm still experimenting, but as my previous post tried to cover, there are a lot of variables to consider.
Try that little Turnigy if it is the 6T one on 4S and a 6X4 APC prop plus a 40A esc. super torque out of it . It gets warm but it keeps on going.
 
#17
Test Results for Emax 2205 -2600kv

4S DAL prop 5045 2 blade- 32a/480w - "This was the original config and still the quickest"
3s APC 6x4 - 30a/387w- "Even though the amps and watts are lower than previous test I would say the flying speed was close to same"
4S DAL prop 4045 3 blade - 38a/588w - "Wing barely held altitude after launching and flew extremely slow"
3s Master AirScrew 5045 3 blade - 46a/644w - "Slow flyer"
4s APC 6x4 2 blade 55a/836w "It was time for this little motor to take a dirt nap. Cooked her pretty good "

I knew there was a great possibility of melting the motor at 55a so that's what I did. Time to move on and find something better.

What are your thought about any one of these motors

Test32w.jpg
 

Arcfyre

Well-known member
#18
Your results to me seem a little incongruous. Obviously I wasn't there, but it surprised me that on 3S a 5x4.5x3 would pull that many more amps than a 6x4. Especially odd to me is that the higher amp, higher wattage setup yields lower speed.

You stated that the 6x4 on 3S flew about as fast as the 4S with the 5045. Too bad you didn't have a 6x5 or 6x6 to try on 3S. Both of those props would have increased amp draw, but it looks like you had a little headroom to play with. I wonder if that would have been the needed ingredient to up your speed.

As for choosing a new motor, I'd say that while experimenting like this, get something cheap. There are plenty of motors in this size class for under $20 so if you cook one, it's not the end of the world. I would advise though that as you continue testing, you change as few parameters a possible. You're swapping between 3S and 4S and different props right now, and you're also in need of a new motor. That's a lot of changes and it's easy to lose track of what setup is working right at the moment.
 
#19
I made a mistake
It was 4s and not 3s on the 5045 three blade pulling that many amps


I’d like to stick to 4s as I have plenty of batteries

I’ve been looking at the 2216 2000kv that comes stock on the sonic models F1 wing
On 4s with 6045 prop that things a rocket
 

Arcfyre

Well-known member
#20
I made a mistake
It was 4s and not 3s on the 5045 three blade pulling that many amps


I’d like to stick to 4s as I have plenty of batteries

I’ve been looking at the 2216 2000kv that comes stock on the sonic models F1 wing
On 4s with 6045 prop that things a rocket
Yeah that makes more sense.

That 2000kv motor will work well I think because it will allow you to use a larger prop. Give it a shot and let us know how it goes!