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Jan 13, 2016, 06:38 AM
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Power consumption in F3F, F3B and similar models

For over three years I'm doing various electrical measurements on models on the fly. I am doing it for my pleasure and expand knowledge about models . On this basis we can draw many interesting conclusions (even what and where which servo is suitable) and can refute many myths that have arisen by the years. For us, the most reliable is power consumption.
The first measurement done on a model of electro-glider Toxic. This is a 3m model with tail V. At the beginning I measured current only for the receiver and V-tail servos. Then came ailerons and flaps, and many more attempts.
My database includes various models F3F (Toxic, Respect, Freestyler) flying in different conditions (from empty models flying in thermals for models weighing 4,5-5kg) with different control systems for the flap and aileron (classic and LDS - no RDS). Servos - these was mainly MKS and KST. I was checking the batteries NiMh, LiFe and LiOn. Last year I've started to fly F3B so the first, preliminary measurements for this class of models are also available.
In subsequent posts, as far as I have free time, I'll be placed with further information. I hope this serves you in the daily flying and building models.

Jurek Mataczyno
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Jan 13, 2016, 06:39 AM
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The origins of measurements: electro-glider, V-tail and classic Links & Control Horns

As I wrote above, the first model in which I installed a current measurement system, was electro-glider Toxic. Facilities at the beginning it was like: MKS6100 servos for the V-tail and Hyperion and some Chinese in the wings. Classical drive system for flaps and ailerons with a fairly long arms and horns. Power supply for avionics - Eneloop batteries. Weight of model: about 2800g.
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Description: My first Toxic

At the beginning of the measurement system was hooked only to receiver and V-tail servos. It allowed me to verify the theory and the effectiveness of the V-tail. By the way, I checked as during the real flight behave NiMh batteries. So the first result was:
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Description: Power consumption: V-tail (2xMKS6100) and 2.4GHz receiver
A we can see, power consumption of receiver is ca 100mAh and... two servos on V-tail consume only 200mA in peaks! I made a lot of sharp and fast flights an was not possible to exceed 200mA! I think it is good info

But the NiMh batteries dissappointing me:
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Description: Eneloop accus - not so perfect!

After less than two months, I made some changes in the model. Power swapped for LiFe 2100mAh. In the wings I used a MKS 6125 mini and glide servos.
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Description: My first flight on the slope with electro-glider
As we can see the average power usage is ca. 400 but it grows to average 600mA when model was flies faster (in turns). But during the flight there are peaks up to 1.6A (in fast maneuvers and turns). Higher power consumption is only when Buterfly is open but it not exceed 2.1A

And I made my first flight on the slope:
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Description: Life voltage and power consumption
As we can see, the average power consumption is higher then in standard electro-glider flights and 1-1.2A peaks are "permanent" in turns. Also Life works much better then NiMh

After several months, the new Toxic glider came to me . It was fitted in MKS6100 and MKS 6125 servos. And LiFe of course. I used much shorter arms and horns.
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Description: Shorten horns and arms in second Toxic

So it was model only for slope flights:
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Description: Power consumption: flying on the slope
Shortness of arms and horns resulted in an increase in the average power consumption to 0.7-0.8A (and also in peaks during turns).

And now at the end there is power consumption for measured flight. Weight of model was 4800-4900g, the wins was 17-18mps and time was ca. 40s.
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Description: Current consumption during measured flight (about 40s) - the weight of model 4900g, wind 18m/s we can see the average consumption after start (speed up and flight) increased to 1-1.1A.
But not too much and not too little as it may seem. Is not it?

end of part 1 Next models were equpied with LDS system
Last edited by czyno; Jan 13, 2016 at 03:14 PM.
Jan 13, 2016, 06:40 AM
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Next step: LDS system

LDS system - I love it! Below I will describe some of my insights about this system.

In all my next gliders almost exclusively I have been using LDS. In the beginning were the DIY systems then others (ie from RCsolutions and TUD).
LDS is an ideal solution for such gliders - allows high precision control of models.
But it has also several disadvantages:
- Higher current consumption (prejudices here's what I will write tomorrow)
- Requires precise servos
- If you're flying on a slope, requires precise and expensive servos.
I used/use in models MKS 6125, Graupner 3288 and those servos are correct. I also used KST 135 servos. 135 servos have too soft gears and were very quickly wore out. I gave them. But MKS 6125 also have disadvantage - engines that have delicate brush. If dozen times servo blocked (eg. By any object that falls between the aileron and flap or after landing), there is a high probability that the engine breaking down (or its brushes) and servo will inoperable. And it's happened to me several times already, and with two - three times during the flight on competitions. So be careful and be ready
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Description: DIY LDS system
I tested two systems LDS - with Stainless puch rod and with solid push rod (like from TUD). The advantage of sysyem wit clasic Stainless puch rod is its flexibility, which is its advantage when you catch ie. a bad landing. Instead damage servo gears, simply push rod bends or breaks. This is an advantage when you are flying F3F. In normal use, the stiffness of both systems is almost the same. Only during the start of the winch, system with classic push rod does not provide the same rigidity as systems with solid push rod. So in F3B solid push rod is better.

Well this is the end of a good thing, because I write not about.

First my model with LDS was Toxic. Here is some datas (I don't remember weight of the model in this flight):
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Description: Toxic with LDS

As we see, in comparison with the data presented in the previous thread, the average power consumption (in this case) is slightly higher. But more interesting are much higher current peaks during turns. Quick movement of the control surfaces (ailerons mostly) causes a significant increase in current up to 2.2A

On another picture we can find some inetersting:
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Description: After landing something found between aileron and flap

Where the model starts to go really fast, doing flat turns, average current consumption begins to increase significantly (to 1.1-1.2). Also they increase power peaks (up to 3A!).
And what happened after the landing? Between the aileron and flap was a hard grass (or twig). The current increased to 3.8A. I suppose that if I had not had individual BEC for each servo, servos would have burned completely. If this situation has become with brushless servos, there was a high probability of damage to the electrical system through a very high power consumption.

On another picture wa have also very fast flight, with flat turns. The weight of model was over 4kg. Average current > 1.2A and peaks up to 3A
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Description: Flight as flight

Next model with LDS was FS4. Here is some datas from mesured flights. Weight of model 3,8kg, wind 14-15m/s, time ca. 40s
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Description: Freestyler 4 - time ca. 40s
Nothing very important has happened, not counting higher current while landing after opening BF. It was quite a sharp approach to landing. After landing the model fell into a hole and electricity remained on powiomie 1.3-1.4A, generated mainly by servo valves.

And the last picture:
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Description: When you make to short control horns in wings
In another Toxic I made to short control horns for ailerons. And as we can se avarage current consumption increases to 1.4A during moderate flight.

And it would be enough when it comes to power consumption by models running with LDS system on typical servos (MKS6125). As I wrote, the average power consumption is slightly increasing , and significantly increase current peaks during turns.
And watch the landing! Rigid drive system can geneate a huge current after blocking it.
Last edited by czyno; Jan 17, 2016 at 06:50 AM.
Jan 13, 2016, 06:40 AM
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First F3B flights and LDS System and brushless HV servos
Last edited by czyno; Jan 13, 2016 at 03:21 PM.
Jan 13, 2016, 12:57 PM
Pure soaring - no motor
Between 300 and 400mAh per hour. F3B plane at the slope and F3J xplorers. All with non-HV gear.


PS: servos 3150; 3155; Rx Jeti
Last edited by Bernd Brunner; Jan 13, 2016 at 01:31 PM.
Jan 13, 2016, 12:59 PM
satinet's Avatar
Agree about 300 to 400 for models with say s3150s.

I find mks are a little more power hungry. Maybe 700 or more. I look forward to the data.

Also modern 2.4ghz telemetry receivers can use up to 100mah or so per hour
Jan 13, 2016, 03:17 PM
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I'm using Graupner Hott receivers. And 100mAh is true
And after part 1 there is the question: it is neccesary to use 4-5-6-7-8 or 10kg/cm servos in our models?
Jan 13, 2016, 03:51 PM
cityevader's Avatar
FWIW, with a "fixed load" like a motor in a servo, if you apply more voltage the amperage ALSO increases.
Therefore, it's inadequate to say that Nimh don't put out enough power, because the electrical conditions are so vastly different.
Give it a 7 cell Nimh and retest? Kinda sorta lipo voltage at least.
Jan 13, 2016, 04:38 PM
satinet's Avatar
Originally Posted by czyno
I'm using Graupner Hott receivers. And 100mAh is true
And after part 1 there is the question: it is neccesary to use 4-5-6-7-8 or 10kg/cm servos in our models?
I think a lot of servos are far more powerful than is necessary.
Jan 13, 2016, 04:43 PM
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Yes cityevader you are right. Larger voltage it is mean larger current. But ... I forgot to write that each servo has its own independent BEC. So when I am using LiFe , the voltage at the servo and is only 5V.

Current output by Sanyo Eneloops is too small for this type of application (large voltage drop under load). High power NiMh batteries will work better probably. I didn't test them.

And to be clear this is not some single readings. I have more than 11GB of data read a variety of models, including more than 6,5GB from 3m glider. The results are repeated.
Last edited by czyno; Jan 13, 2016 at 04:56 PM.
Jan 14, 2016, 04:49 AM
Pisaneli's Avatar
This is very interesting thread, thanks. May I ask what power analyzer you're using?

From the servos I tested I've noticed that Blu Bird BMS-A55H have the biggest current consumption.
Jan 16, 2016, 04:51 PM
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Sorry - I was very busy and had no opportunity to finish thread. I hope that tomorrow I can continue
I use modules from Graupner (GAM) and from SM-modelbau (UniSens-E)
Jan 17, 2016, 06:54 AM
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Small update is redy to read
Last edited by czyno; Jan 17, 2016 at 04:36 PM.

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