Electric flight query

[Erfolg]

I was yet again flying my "wing". All that have read, the Holtzflugel" will no this is a trilogy of crashes, some more mysterious than others.

 

All was well with the world, having flown for about 5 minutes, I heard a beep, from the model, but it kept on flying, then another.

 

At this point, i decided to land, on my way down, I decided on a loop. The model came out of the loop but was heading slightly down. I pulled in some elevator, nothing happened. It now had a slight bank, so I put in some opposite airolon. Yet again nothing happened. Allthogh the rate of sink had reduced as the speed increased. I decided to put some power onto the motor, nothing happened.

 

Shorly later the model impacted the ground.

 

It all took something like 5-10s.

 

On recovering the model, everything, seemed to work. The two servos. The motor did not initially, as all three, motor plugs had come out of the sockets. Re-plugging them, the motor now worked.

 

 

Could this be some form of radio failure?

 

Erfolg

[Erfolg]

I did a few checks this evening.

 

I suspected that the Rx had not "binded" to the Rx. I had a solid green light suggesting it was bound. I then decided to rebind. Which I did.

 

It then struck me that during this process no beeps are emmitted by the Rx. I then though that the beeps I heard must have come from the speed controller. Or the motor, I have been told it is the motor that makes the noise and not the controller?

 

If this is so what could be possibly be happening at about 5 minutes into a flight, as this appears to be the time frame in which the problems start.

 

It is noticable, that the plane(or wing) is rock solid in all aspects of handling before the crashes.

 

Erfolg

[Martin Harris - Moderator]

Are you using a separate rx battery or uBEC?  If it's working on the ESCs BEC you might have a faulty ESC.

 

The windings of the motor are used by the speed controller as a rudimentary loudspeaker so it sounds like the speed controller is doing something unusual and re-initialising - perhaps a bad connection from the flight battery, faulty connector to the rx or an internal ESC fault?

[Erfolg]

Martin

 

I think you may be right.

 

In the next few days I intend putting a watt meter on the motor. I will then compare the watts drawn with both the battery and the rating of the speed controller.

 

I will then run the mdel whilst weighted down, with power and actuating the controls to see what happens.

 

I was looking at the model this morning and noted that the heat shrink sleeve was only covering the front of the ESC, the case seeminly split and shrunk to havve it size. I do ask myself if this reasonable, as the heat required appears to be a lot. Or is it?

 

Previously i put down all the crashes to stalling and a CG to far back. There may be more to it than my incompitancy.

 

Erfolg

[Tim Mackey]

The important figure on the meter will be AMPS Erfolg - this is what kills motors and ESCs.

For example only

One could show 100 Watts being used with 50 volts and only 2A, or indeed 100 Watts with only 10 volts yet 10A current being drawn.   IYSWIM.

You really ought to use the wattmeter on every setup "on the bench" before any flight, this is the only sure way to check that all components are within spec. If you are using the ESCs built in BEC to power the radio, then its LVC should cut in and stop power to the motor well before it gets so low as to stop powering the radio. As you say, check all connections are good, as already suggested by Martin...especially the ones powering the radio.

[Erfolg]

Timbo

 

I hear what you say, I do believe I did a check, on completing the model. I am sure it was satisfactory.

 

Yet there is a problem, so may be I was not as careful as i should have been. I hope to find out.

 

I am reasonably confident, that the airframe is OK. The stall is now, a non event, high speed dives seem fine. Needs more up thrust, now as on full throttle it is wanting to loop (pusher).

 

I feel confident that the issues are not all me. As asome of  the crashes are long term events, where no amount of stick waggling and motor adjustment does anything.

 

I need information to help others, to help me.

 

Erfolg 

[YakMad]

Erflog,

 

 

      It does sound like you had a power failure of some kind, I have found the Futaba 2.4 can be slow to recover from "brown outs" could be 6 to 8 seconds and i found it varies between rx's I use Futaba 607 and 617 rx's. I have Spectrum and JR 2.4 gear as well but as I was always a Futaba person I converted all my Futaba gear to 2.4 first but since then I have only bought Spectrum and JR gear, mainly because it's better priced and the more extensive types of RX's. I will not be buying Futaba anymore.

[Erfolg]

Do Futaba 2.4 sets suffer Brown Outs (If I only had PM Brown receiver, they are never wrong).

 

Can they be prevented?

 

Erfolg

[Tim Mackey]

Apparantly ...Yes  - I just read a posting somewhere else to that efffect.... IE: above yours !!

Edited By Timbo - Moderator on 03/07/2009 17:02:38

[Erfolg]

Welllllllllllllllllllllllllllllllllllllllllllllllllllllllllllll, I have started my tests.

 

Seems I was right in the Brownian sence, the current draw was.........................

 

In the real world, seems I have pushed everything to the limit if not beyond.

 

The motor draws 362 watts on 10.5 volts. The issue is it is rated at 250 watt!!!!!

 

The GC speed controller is rated at 45amp. So I have been a little to near to the max, than I would like.

 

The battery "Flightmax 2200" is rated at 25c, so I will have pushed that also.

 

Seems I could not have used my Wattmeter on the set up, as I have had to make some conversion leads from Plug and sockets to Deans. So I feel quite, chastened.

 

The propeller used is a 9*5, as per the recomendations. A 8*4 is also recommended.

Does anyone have any clue if this will drop current draw to about 200w?

 

The motor is  2217-6T Hi-model, without the sticker. It also says the same motor is marketed as Towerpro,Dimension, Strongpower

[Tim Mackey]

Erfolg, as previously stated to you - forget the Watts for a minute its Amps that matter.

I assume from your description its THIS motor?

This motor is only rated for 18A continuous, and if your figures are showing 360+watts on a 10.5V battery thats a whopping 34A. You are very lucky not to have burnt out the motor.

However the odd thing is they recommend 3 or 4 s battery and a 10 X 5 up to an  11 X 5 and this usually menas  that the big prop is on the 3s and the small one on the 4s.

Your battery will be OK as @ 25C rating a 2.2A pack is good for up to 55A and at 34 thats only 15C.

[Erfolg]

In essence it is a very similar motor, just the turns are different.

 

This permits 28 amps for 60s. 22 amp continous. A number of the other parameters do differ, slightly. It is the same case etc, with a different wind.

 

With the amount of power available, i have only used it for approx 10-20s, because it is very high in this time frame.

 

Your assement is almost certainly correct, and is very similar to my own.

 

I have a suspicision that this high current, is a clue to the crashes. I think all of the crashes were immediatly after a burst of power. Either to roll, gain height, or even loop.

All the crashes were quite drawn our affairs. Where I pondered what to do, try it, then resign myself to an eventual crash, whilsy wondering if it could be rebuilt.

 

I want to reduce current draw and an considering a different ESC.

 

What would you do?

 

Erfolg

 

 

[Tim Mackey]

Another ESC will not affect current draw. Either reduce the battery to 2s, or more simply... use a smaller prop combined with the wattmeter to bring the current to acceptable levels.

[Erfolg]

I do intend reducing the current draw by using a smaller propeller. 8*4 being recommended.

 

What really puzzles me is that the 9 inch prop, is drawing approaching 400w, whereas the data sheet is indicating this would be about 180w.

 

What is causing additional concern, is that, perhaps, either, the receiver is suffering so called "Brown-outs" for some time, or maybe the ESC is switching off, due to the current draw. I think it is being pushed hard. Very near to the rated 45 amp. The shrinking heat shrink, seems to point at a lot of heat.

 

So will an 8*4 do the trick? as i do not want to do any more tests on the 9 inch prop. It seems a lot to ask from 1 inch in prop dia. to reduce watts by 200w. I feel uncomfortable that my results are at such a variance with the data sheet

 

Erfolg

[Tim Mackey]

An Inch will make a difference, but unlikely to be quite that much. Something does seem wrong here as there is a big difference between your results and the supplied Data. 

Are you certain of the data - EG: Could it be that the data is based on using nickel cells, or perhaps 2s not 3s?

I could really do with knowing the exact motor, as there seems to be some uncertainty, and I feel this could be the root of the problem. How do you know the wind of the motor?

Edited By Timbo - Moderator on 04/07/2009 14:57:21

[Erfolg]

The information sheet, aka GC, which is not as structured as BRC, contains the following

 

Type A2217/6

No. Off cells 3-4 li-poly/8-12 ni-mh/no-cad

rpm/v:1500kv

max. efficiency 78%

no load current/10v,1.6 A

Current capaciy: 28A/60s

 Recommended working curent: 8-22 A (efficint 70%)

Internal resistance: 100 Mohm

dimensions 28 * 35 mm

shaft dia 4 mm

 

Recommended prop 8 *4 to 9 * 5

 

I normally find that it is difficult to get the power into the motor, as I use folders, which seem to draw less. In this case I am using a normal prop, mounted normally,  that is a s a tractor, but reversing the motor rotation so it works as usual ( and is therfore rotaing as usual).

 

I will try again, probably on Tuesday, using partial throttle to make sure I did not read the meter incorrectly. Although it is a very ordinary Tornado watt meter.

 

Something does not seem right at all, I find it difficult to imagine the data sheet being wrong, as so many others will have used the same data, and the motor is one in a seriese, using the same frame/armature.

 

If what I measured is correct, it would explain why the model is a rocket, initially put the climb rate down to, an exceptionaly brilliant clean design, by me. Being honest, just thought that the drag must have been very low in the climb.

 

What I did not note, was how much energy had been taken out of the battery. Although the re-charge was not that long. In rectospect, this may have shed light on if it really is drawing as much as I think I saw.

Yet with the excetionaly high climb rate, and short power on,  I possibly only used power 2-3 times in the 5 minutes of flight.

 

Seems I could have gathered a lot more information, If I had my wits about me.

 

Erfolg

 

[kiwi g]

ERFOLG

If its crashing because of no response , that means no power, that means bad connection or youve got a esc with no bec. . not all have bec technology.

I have a stryker that would overheat the ecs. The esc would stop, as to the motor but full flight control was kept every time.

I suggest you set your motor /controller ect up as in the crashed model but try it with a small flight pack to see if the controller /motor was the original problem.if it doesnt cut you know it is esc. instead of testing everything separately. 

I still think no power is just that. bad connection /no bec.

One more thing, was the loop the first one done with that model.....

 

[Erfolg]

Graeme

 

The ESC has a BEC.

 

To verify if it is working satisfactary manner, I intended running the model a about 70-80% throttle. To simulate in flight current  draw.

 

The high current relative to the motor data, has taken me by suprise. So verifying that it is drawing the current I think it is will be step 1.

 

Simulated operation step 2.

 

Again I will state, that the model seemed realy easy to fly, on all occaisions. Until 5 minutes or thereabouts into the flight. When after putting power onto the model for a few seconds, control was lost. The last was the most revealing in some respects, in that, I just climbed to a high altitude, and the crash, started in slow motion. Going into a shallow dive, which acquired a gentle bank. There was no responce from my increasingly frantic stick waggling, finally I applied power, seeking altitude, and no change. Yet on recovering the model it was all working.

 

I am really puzzled and do not really know, if the issues are me, the model, the electric bits or all.

 

It is times like this, when all the other peoples expeirences are worth considering.

 

Erfolg

 

[Martin Harris - Moderator]

You'll only find out by following Kiwi's advice and adding a receiver pack or by substituting the ESC.  Intermittent faults are the bane of a diagnostic engineer's life and unless you can reproduce the fault at will, can only be cured by substitution. It's unlikely that anyone on the group will be able to help any further remotely the  - perhaps you have a clubmate that can assist if you're intimidated by Kiwi's suggestion?

[Erfolg]

Graeme

 

The loop was the first, with the model, Which was started under power.

 

The flat spin, was a steepish climb, from about 150 feet

 

All these were with power, after switching of the power, immediatly, control ceased.

 

The third incident with the non crash outcome, was a servo running to the extreme movement and stalling in that position. Lucky to recover from that one.

 

I will bear in mind all that has been said by all. I have no intention of dismissing or ignoring ant suggestion. But will start simply.

 

I will now carefully try and record as many checks as I can.

 

I would be suprised if the feed to tha battery is a problem. I use Deans connectors, the cables are now, all as supplied with battery and ESC. Though I will be examining these components.

 

Erfolg

 

[kiwi g]

Erfolg   more questions . was the controller set to soft start. and was power applied slowly or just not much power to full power.

I have found that with power gliders and flying wings the transition to power has to be gentle to allow for air flow over control surfaces. for example if you were in a slight turn or correction when power is applied this can give extreme results and very often catch the pilot out , he then over compensates on his control and then the same the otherway buy which time the aircraft is out of control and giving the illusion of power loss . eg  No response.

you do say that the crash happened quick so sometimes things may not be as they seem,  hence lack of control /no control

You have to relise I do not know you flying experience so do not be affended by my comments.

Cheers

Kiwi G

 

[kiwi g]

oh , sorry I just read your first post again......

And it doesnt sound like pilot.

power went off after the beeps.

could the motor have drawn all the power from a battery going flat and not left enough for the servos although leaving enough for the receiver but not servos. turning off motor would have restored control.,or was the loop too fast and loaded the servos so they wouldnt pull up/.

the mini servos in my stryker will not pull on high speed runs , meaning I have to be level when close to the ground, . most servos work hard at 150 mph.....

[Erfolg]

I have done my first test

 

on a 9*6 normal stick type prop, 389w @ 12 .38v 36amp

 

changed to a folder

 

8*4.5 folder 265W @ 12v @ 23 amp

 

With the change of propeller, it is now marginaly above the recommended 22 amp, yet below the 28 amp for 60s.

 

I think I can now try the prolonged simulation, without to much danger. What do others think?

 

I was thinking of 15s full throttle, 3 minutes of , repeating. As I think this is something like a typical flight pattern. Again any thoughts.

 

[Tim Mackey]

Not sure why the smaller prop test showed the battery at 12V - lower than when using the bigger 9X6... I guess you didnt re-charge inbetween ?

Anyway.... once it unloads in the air, I think that shold be safe enough, all but the cheapest of motors usually have a little margin for overcooking. 

When I do bench testing, my normal sequence is...

WOT for 1 minute.

50% for 30 secs

WOT 1 minute

50%, 30 secs

3 minutes WOT. 

6 minutes in all, as can be seen in the attached JPG  from eagle tree logger in "live mode "

...........which is about average flight time for most of my leccy stuff.

Edited By Timbo - Moderator on 09/07/2009 18:31:34

[Erfolg]

The 12v, was nominal, I did not bother with the decimal points, although it did drop.

 

I have considered an eagle tree logger, it is the cost, of the latest that deters me. Particularly when I see that schultz, Multiplex amd Graupmer are pushing the concept of the down linking of data, as part of the 2.4 radio. Yet Eagle Tree are hear today, the rest could be pie in the sky.

 

Eagle tree does appear to offer the data that I crave, how high, when, relative to motor usage. On Wednesday,deperatly diving to get out of wide spread lift, it did cross my mind how fast was it going, something I would have liked to known in real time, as I was really worried  me that the model was about to explode into a myriad of parts (which i have had happen). It is scary to hear the scream of  a GRP and 1lb of lead fusalarge, descending and wondering where it is going to impact. 

 

Erfolg