tassos p

Thanks Dave,

The fact is that when I disconnect the FLAP servos ONLY on the ground the consumption reduces. The servos are making noise but they are NOT screaming. And I have carefully grinded again and again all the binding points in the flaps. It seems that the flap servos just on the ground just on the FLAP's weight is causing this.

And if there was binding wouldn't the max current draw of all servos much exceed the 2.7 Amps that is measured?

Are you using the PB Royal Dave and you measure the current draw or by other means?

Tassos

Carsten Groen

Somethings not right here.
The Royal says max current of 2.7 Amp and a combined consumption of 2 Amp/H for one flight.
Now, if we forget the decimals, and go by rough numbers, each flight should last something like 45 minutes IF the entire flight used the 2.7 Amp "max current" all the time....
So, either the max current is wrong (which I think it is, 2.7 in max is very low!) or the consumption meter is wrong.
I have 16 digital servos (Aileron: 8 x 8511, Elevator: 4 x 8911, Rudder: 4 x 8511) on a comp-arf Pitts S12, and I see way higher max currents after a flight, and I use around 1300 ma/H pr flight (depends on the flying style)
I also have the Royal in that plane, and as a note, the max current on the servo adjustment page shows the total current of the module, not just the servo you have selected "now"

PS: You say the consumption of 2 amp/h is read from the Royal, how much current is your charger actually putting into the batteries after one flight ??

jeanfi

Hello Tassos,

I have a CARF Lightning with 7 DS8911 servos.
The consumption per flight is about 220mAh for one battery (I have two batteries).

Check your flaps servos.
Something could be wrong....

Jean-Philippe

Dave Wilshere

Tassos

No I use a std Powerbox. I have a H 9 meter and also the Graupner Amp Clamp. But I do it by ear and total battery consumption. I charge new models batteries before setting up the model, set it up which usually takes me not much more than 10min inc mixes etc...so about a flight time, plus any other testing on gear etc.
Before I test fly I charge the batteries again and always note mAh used..as during the life of the model this tells you so much. I have an expected consumption. So if I was doing your Lightning and I guessed 20min total on time I would expect on 5-600mAh use from each battery.

I then fly it and monitor battery use.

Dave

Didier

Hello Tassos.

I have a Ultra Lightning with a AMT NL Olympus HP.
I have 7 JR8911 and 1 JR8611A in the UL.
I use a powebox Champion with 2x 2350 mAh Lipo batteries.
With a flight time of 7 mininutes, (10 minutes runtime per flight) I can easely make 6 or 7 flights without charging and still have about 50% in the batteries.
Is it possible that your flap servo geometry in relation to your flaps is not correct?
Try to use the most innerhole on your flap servo arm to get the best resolution (more precise) and the servo will be stronger as well so consumption should be less.

Andrew Bird

I monitor the what goes back into the packs after each flying session.

Once I had unusual inputs back into the packs after a days flying (took way more MAH). Sure enough, after some checking I found a servo that was on its last legs and it failed...........

tassos p

I agree with you something is wrong here and the data on the PB Royal could be misleading. Last night after 3 flights (with the same more or less consumption per flight per battery) each battery got 4 hours of charge at 400mAh = 1600mAH. I use 2 Duralite 3800mAh batteries on the Royal.

Could it be an issue of the Royal and its software?? 2.7Amp means for 1 hour 2.7 Amps. For a 14 min period of on to off time the system recorded 2 Ah consumption. Something is definetely wrong here.

Still the servos are not screaming.

However I will check once more my flaps.

Tassos

tassos p

I will try this. However look at what the manual suggests to use. This is what I've done.

Thanks Didier

Tassos

KC36330

your powerbox is screwed up, if the max current was 2.7 amps, then it would take 40 min of flight time at a constant max current to draw 2000 mAh..........so if you are getting a 40 min flight, the cause of the high current drain is the weight of the fuel load

tassos p

KC,

As you can see in the pic the flight time was 14.48mins for the recordings you see.

Tassos

KC36330

That's why i say your PowerBox is having some software issues computing the mAh consumption. if it were mine, i'd send it back to have it looked at/updated.


even if you somehow drew the full 2.7A load per battery the entire flight it would only be roughly 650 mAh draw per battery on that flight.

olnico

Tassos, do yourself a favor. Buy a Hangar 9 amp meter.
By the way, why do you need so many 8911/8711 on this plane ? Is this a manufacturer recommendation ?

If you're interested I could compute the flight controls power requirements. I strongly doubt that the plane needs so many strong servos...

tassos p

I'm leaning against this version of what is happening. I think its a sw bug but I wanted to check with anyone else is having the same setup in their planes and getting the same measurements.

I will talk to Mr Deutsch from Powerbox to see if they have identified this issue.

Thanks alot,

Tassos

tassos p

Thanks Oliver that would be nice. Why I chose those servos? Because I thought the stronger the better, but I guess here I find the side effects of my choise..... The manufacturer suggests 8511 all around which are I think 15kg cm (260oz in) each while the 8911s are 25kg cm (400 oz in).

I was just about to read also your article on RCJI of this month on the pre-maiden procedures for the Phoenix. Maybe I can get something out of there.

Tassos

Didier

No let the 8911 stay in your Lightning!!
Yes they are overrated but the advantage is when the servo's don't have to work hard, they will not draw as much Amps compared to servo's that have to work harder! Ofcourse if you have jammed servo's then it will be a differnet story.
What I use for a couple of years, is a simple cheap Lipo battery checker (plug it to the balancer connector). It will tell me EXACTLY how much percent is still in the Lipo battery's. I use it for all my electric models as well and it it is never wrong!
My advice, buy such a cheap checker (about 30 euro's), fly and check after the flight how much you have left in the battery's.

olnico

Hi Tassos. You will certainly get something out the article. Especially since I explain how to compute the equivalent weight ballast for the intended aerodynamic load.
This wil enable you to do a proper electrical system test under realistic flight load and check the validity of your system and battery sizing as well as thermal endurance of the Powerbox regulators ( something to consider as well when having such a big electrical load )

What we could do here is go on the practical side of the article and make a proper simulation together.
Have a look at the article and at the RC calc software:
http://www.geohei.lu/olin/data/model...calculator.xls

Then give me all the flight control dimensions: average cord and span.
Then I'll need the control horn arm and maximum speed as well as average aerobatic speed ( I assume that you don't go full blast all the time )

KC36330

that is incorrect. if both servos are capable of doing the job they'll both use the same power to do the same job, you don't gain efficiency by using over rated servos and in most cases the higher power servos will actually use more power because of their motor design.

Didier

In practice I think the efficiency of the recommended 8511/8611 compared to the 8911 under NORMAL load will not be very different.
At least this is NOT the problem of Tassos as I have the same jet with the same servo's and I can easely manage 6 flights with 2x 2350 mAh batt with still 50 percent of the charge.

Tassos, just saw your video of your UL with the onboard camere (nice ) and I hear your servo's buzzing a lot compared to mine, maybe its just the video but it sound like a couple of servo's working hard statically already

KC36330

that was my point and why your previous statement was incorrect.

olnico

I agree with you KC and this is partly the purpose of my latest article: compute the power requirement and choose the appropriate servo.
That saves money ( on adequate servo, batteries and regulators ) and weight ( on the same elements ) .
Additionally the method is very accurate to test the electrical system in realistic flight condition simulation.
I'll show you how to do it here, when Tassos comes back with the data.

Didier

This debate about the energy used compared between 8611/8911 will not be different and it will not help Tassos problem.
Fact 1:It is not servo choice problem as we have couple of UL/8911 flying in the Netherland and nobody have this problem. Ofcourse there can be 1 servo that's not very healty.
Fact 2: Composite-ARF recommends the 8911 servo, in fact they use them in all there planes according to them.

Anyway Tassos hope you find your problem, its a matter of isolation the problem.

olnico

Tassos already knows how to isolate his problem.

However this thread is also about battery consumption on one complete flight. One very important factor on that matter is the servo idle consumption. The 9711/8911 consumes about 30% more current at idle than the 8611/8511.
Multiply the figure by 7 and you'll soon realize that sizing the servo correctly for the purpose is extremely important. Otherwise you enter a vicious circle: powerful servos = more current drain on one flight = bigger batteries = bigger regulators = bigger cables = possibly need for higher spec connectors etc...

My purpose is just to show you guys how to compute flight controls power requirements for a given airframe and how to chose your servos.
It is also a matter of saving money and weight on an airframe while being 100% safe.
This method also enables you to check the hinging momentum and thus verify that the hinges and servo mounting systems are sufficient for the purpose...

i3dm

My Feedback: (51)

Is the Gangar 9 any different than a regular watt meter, such as this one ?

http://www.hobbycity.com/hobbycity/s...dProduct=10080

gooseF22

Make sure your servo arms of this type are not binding against the servo case. It should move freely unpowered.

What I would do:
Start unpowered.. move all surfaces full range and feel for mechanical issues. Flap setups are usually the first place to start HOWEVER... what I have found...

It doest take alot of binding to create an idle current flow, and you cannot trust your ears.. the ammeter is a must.. so no new news here.. but..

Not long ago we had the same thing happen. upon recharging the batt after 1 flight and ground setup on a rookie, the batt took 1900 MAH in a 2300 A123.. we would have lost the plane if flown again.

The ammeter ended up at 2.4 amps.. culprit in the rookie was the servos on the landing gear valve and the brake valve. Its easy to find this stuff, just move the surfaces and unload them and take the stress off the servo and watch.. it will tell you.

If you have Hitec programmables, you can open the deadband and that will help... On the JR's, they have minimal deadband, so they try to hold it tightly, so the bigger servos will use more power in general at even low loads.. (thats a very general term...dont shoot me)..

My opinion on the smaller jets, like flash/rookie, the average servo setup should be less than .5 amps idle, and .3 preferable. the bigger jets, (depending on design), should have less than one amp. On another jet, I found a binding rudder linkage. It would show good idle current, but it was binding.. we found that with the power off test..

I also found one on a nose gear and another on flaps..

So. using an ammeter and your PB, you should be able to get a 10 min runtime down into the range of 200-400 MAH per battery per flight. My ELAN with 11 servos, (6 8611A), was .25mah at idle for example.. but if you set the flaps by ear, it was over .700. I just had to live with the flaps being not perfect..

You have to solve this or it could very likely cost you a plane.. I lost my favorite glow / pattern bird this summer on the same issue. I had a bind and a battery issue I didn't catch and depleted the battery in flight... It was an A123, so I didn't notice the performance degrade until it locked me out.

Any ammeter will do. I use my Astro and wire it in between the battery and the receiver using a Deans adapter.. doesnt matter which as long as it will register amps in .1 or better

good luck..

tassos p

Just saw your video with your new engine, very good.

I don't need the checker because on the PB Royal you can see the exact battery voltage. I use 2x3800mAh Li-Mg batteries for the PB and when fully charged they go up to 8.3V (nominal is 7.4V and stop fly voltage is 6.9V). Now in the pic I took of the Royal display you see that at that point the batteries were reading 7.89V each after flight No 3 of the day with roughly the same illustrated consumption each flight. This means that after flight 3 the consumed mAh should be roughly 3000mAh per battery according to the PB display. However the voltage remains 7.89V.

This is not right so I'm beggining to guess my PB is measuring misleading consumptions. That's why I asked if anyone out there is using the same setup as I am and reading off their Royal Display the same data.

Tassos