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Not sure if this is a start to a reliability issue?


911hillclimber
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FMS Kingfisher trainer, new this year, flown about 2.5 hours in sessions of about 4 mins, 3S batteries as per instructions.

Flies a dream, nose crashed about 5 times, one or two quite heavy, taken the undercarriage clean off.

So, that is the plane and I can actually fly it now solo so has been great.

 

Noticed on the last few take-offs that the speed control is changing.

 

The (Mode 2) throttle is north/south on the left stick (DX6) and moving it up from zero prop movement to full revs for take off seems to be getting sluggish but it does ramp up to max and off you go, flying is on stick vertical (I'm a leaner!).

Today (10 degC) is seemed particularly sluggish compared to how I remember it.

The speed controller is in the nose right by a cooling hole in the 'chin' of the plane, a FMS Predator 40A ESC

 

What could this mean (if anything) and should I be doing something about it? (ie replacing it)

 

Batteries are all 'new' from 4 Max, motor runs smoothly and flown by one-who-knows today flies really really well.

 

Any comments please. I do not want a dead-stick situation suddenly cropping up......

Thanks, Graham.

Edited by 911hillclimber
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First try recalibration the ESC from the TX as per instructions. If that doesn’t work fit an alternative ESC and see if it fixes the problem. If it does the issues is the ESC, if not is probably the motor (bent shaft or bearings most probably given it has been crashed a few times).

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Thanks for the speedy replies.

I'll have a go at both, Tx batteries charging at the moment.

I have been flying this plane buddied-up to another DX6 (wireless) if that has any relevance.

 

Motor rotates free and easy, BUT judders in reverse if you 'just' trickle the joy stick just off the Off to start-up, then rotates correctly.

Edited by 911hillclimber
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I am going to stick my neck out and say none of the above!

  • If its been running ok since the previous crashes then why would it change now?
  • If its been working ok with the TX why would it change unless you have been changing things in the TX?
  • Why would it be a timing issue if you haven't changed anything in the ESC or have you?

Ask yourself a question? Do you have the throttle fully shut at point of impact when crashing? Some people leave the throttle stick up for some time, that means the ESC is trying to drive the motor around, but the prop is buried in the ground, this causes massive current to flow and can damage ESC components in a very short time.  If you don't then its a possibility that you have damaged the ESC.

 

My money is on a loose motor connection to ESC, double check all ESC to motor connections, if there is nothing loose then cut the heat shrink sleeve off and visually check the bullet connections for poor solder joints. There is an outside chance that the motor is on the way out, but unlikely IMHO.

 

PS sound familiar? 

I had a model where once every ten or so throttle up's would result in the prop gently rotating backwards a small amount and then picking up as normal. All new kit and motor leads/bullets from the manufacturer + my soldered bullets on the ESC so all good there, right. Taxi tests and throttle up tests with no issues apart from the occasional low speed pick up issue, so on with the maiden. Take off didn't need WOT and flying about the model was trimmed in no time and hence a nice fast low pass was on the books until halfway through. Motor made a very odd noise and then dead sticked with more luck than anything else model landed ok. On closed inspection the motor lead bullet had become detached under the heat shrink sleeving (this was factory soldered).

Edited by Chris Walby
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The other thing here is that the temperature is falling, you note yourself that the last flying session was 10degC. LiPo batteries give out less power at lower temperature as the internal resistance of the battery cells increases. Higher resistance in the battery means less volts at the motor, less volts at the motor means lower current. Could this be the cause of the seeming lower pick up of power.

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 I had a motor that sometimes as you moved the stick up slowly it would judder, up some more and it would go but perhaps not quite the power it was giving before it had had a whoopsy . Checking it out of the model I found the outer casing [ outrunner ] had moved back a tad and was binding just a little with the rear plate. Just turning the prop by hand did not revile the problem.

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The judder on the prop clockwise (from the front) has been a recent observation, and I think followed a crunch where the motor was running on the buddy stick but the motor stalled as the prop was in the tall wet grass of the landing strip perimeter.

That is all a bit of faded memory.

 

I have changed nothing on the Tx from the start of the year before my first flying attempts.

 

Strikes me reading all these very useful comments a new ESC would be a good idea, only £20 so no great damage, and I would have peace of mind too.

Last thing I want is a dicky throttle control.

With the stick at WOT after about 3 seconds the motor will get there as if following an exponential curve, not a simple sloping line path on a graph.

This is on starting take off. The poor throttle response is noticeable and my buddy helper has commented on it several times too.

 

In the air, the throttle response is good, BUT when practicing my landings this morning the prop did not stop with throttle totally off....

 

A new ESC I think unless this last post give rise to more thought, but I'll check any mechanical rubbing first and report back.

Edited by 911hillclimber
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Many esc's have a helicopter mode which will slowly spool up when opening throttle. Can be changed by entering esc's programming mode. I did this once inadvertently and flew a model like this for yonks cause I couldn't be bothered figuring it out to change back. Likewise, was the lack of prop stopping because the brake was off? (Does it stop on the ground but keeps going in flight?) Again possible to be changed inadvertently.

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If you've changed nothing, it sounds like a loose connection somewhere, or possibly some binding caused by heavy landing.

 

Try rotating the motor slowly be hand - should be silent; if not, it's either rubbing on the airframe, or internally (crud inside it from 'landing'), and that needs rectifying.

If motor OK, check soldered connections and fix as necessary.

 

If both OK, and you haven't changed anything, ESC probably damaged and needs replacing.  Easiest to get one with same connectors for battery and motor that you have - probably meaning an FMS spare.  Or if you're happy soldering the old connectors to the new ESC, and generic ESC will do.  Soldering is a 'must have' skill for electric flight IMO.

 

Please let us know

 

GG 

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Sounds like the ESC as above, but I would just try putting the ESC back to its default settings before you do. You might not think you have changed anything, but ESC's work in mysterious ways, so its got to be worth a go. Other than that, it is possible that you have either slightly bent the prop shaft and / or damaged the bearings. The bearings in the smaller electric motors are tiny, and it does not take much to damage them. The good news is, they a very easy to replace, and not silly money. If in doubt replace, as you rightly said you have come a long way and don't want a dead stick which could potentially destroy the model!.

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3 hours ago, Dale Bradly said:

Many esc's have a helicopter mode which will slowly spool up when opening throttle. Can be changed by entering esc's programming mode. I did this once inadvertently and flew a model like this for yonks cause I couldn't be bothered figuring it out to change back. Likewise, was the lack of prop stopping because the brake was off? (Does it stop on the ground but keeps going in flight?) Again possible to be changed inadvertently.

Been there and done that. Strange behaviour pushing the stick forward and waiting for the motor to 'spool' up alerted me but flew anyway, just the once as I really did not like it. It was the first ESC I bought that came set up in Heli mode all the others came in fixed wing. Yes the strange behaviour @911hillclimberis experiencing does tie in.

 

BTW Graham well done going solo so quickly. 

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All good info gents, and I thank you all.

 

The motor is stationary on the groung just before take off checks.

All checks good and this is where if I just move the stick the motor ill judder backwards, then it will speed up slowly as I progress the stick to WOT.

 

I flew again yesterday and it consistently does this trick.

On landings (all successful yesterday I'm pleased to boast) dropped the throttle to 'off' but the motor kept going slowly but the prop was still spinning but nowhere near enough to prevent the landings.

Found the FMS manual last night, so this afternoon will try to reset it all to fixed wing assuming it is not already sett to that, can't hurt.

 

I'll post when I've done that.

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7 hours ago, 911hillclimber said:

All good info gents, and I thank you all.

 

The motor is stationary on the groung just before take off checks.

All checks good and this is where if I just move the stick the motor ill judder backwards, then it will speed up slowly as I progress the stick to WOT.

 

I flew again yesterday and it consistently does this trick.

On landings (all successful yesterday I'm pleased to boast) dropped the throttle to 'off' but the motor kept going slowly but the prop was still spinning but nowhere near enough to prevent the landings.

Found the FMS manual last night, so this afternoon will try to reset it all to fixed wing assuming it is not already sett to that, can't hurt.

 

I'll post when I've done that.

Try and work your way through the "beeps", it may take a few times until it becomes clear!. Look for "Return to default" or similar, once that is set you will be back to square one. Good luck, its all a bit confusing until you have messed with a ESC'S for a while! 

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None of this is simple!

 

At the moment I've changed nothing.

Tx on

Battery connected (100% charged) and the plane goes through it's set up routine.

 

All control surfaces pulsed.

Motor beeps are 3 short ones (for the 3S cell batt) and then a short pause,  one then follows and then no more, which according to the FMS ESC manual (page 27) is the motor braking is ON.

 

2 beeps after the 3 and the motor braking is OFF.

 

I don't think the motor should be braked for a fixed wing, but possibly no big deal either.

 

Am I getting hot-n-bothered about nothing?

 

There is a lag between throttle off to WOT but the motor sure revs when is up there and is totally adjustable through the rev range by the stick.

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If you have motor braking on at closed throttle the ESC will stop the motor, this is useful on an electric glider as if the prop windmills then the blades won't fold and you have more drag. Brake off and the propeller will windmill on a closed throttle, on a power model this can be quite useful on landing as it adds some drag and allows you to do a steeper approach and shorter landing. As you say it is no big deal either way on a regular powered model.

 

 

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The sluggish throttle response is on the model tonight, no buddy link, but since linking his Tx some months ago when I switch my Tx on the screen says No Slave, and if I touch am

nd move , say, the rudder movement the screen immediately changes to normal.

Connect the battery in the plane and it goes through its check, twitching the surfaces.

the motor jolts and beeps 3 times, pause, and a final beep and silence.

If I then just touch and slightly move the throttle stick the motor will judder backwards, move it further and it stops that and revs correctly and has a short delay to rev in unison with stick movement to wot.

 

The motor responds to stick movement from wot to stop and never faulters.

 

On the field, pre flight checks all ok, move throttle to advance to take off speed and that is when you notice the delay.

Within 10 feet or so the motor picks up to wot and the plane takes off a dream and flies really well.

 

Landing is all good, throttle to no revs and flare the plane down. The prop still rotates, but at a speed you would expect as the planes speed keeps it turning.

When stationary, the prop has stopped.

Hope that lot might help.

 

Again, am I worried about nothing?

the motor delay has 3 steps, very soft, soft, and none.

The instructions say default is soft, a one second period to control the motor speed front nil to max, plane without prop fitted.

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Hi,

 

You don’t really want the soft start feature enabled at all for a ‘normal’ fixed wing model. Not sure why FMS set that ‘on’ as a default.

 

I’m not sure if I am interpreting your description correctly, are you saying that the ‘delay’ only happens on the first throttle opening after powering up, and subsequent to that the throttle is more or less instantaneous? Having just looked at the manual for the Predator ESC I see there is also a governor setting for helicopter use. That produces a throttle delay on the first increase only. Perhaps that has somehow got inadvertently set?

 

Lastly, if the problem only showed up since you stopped using the buddy box system, could you try using that again? That would perhaps prove or disprove differences in the transmitter settings.

 

Brian.

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You have just made me think Brian.

My Tx has the B switch set to enable Buddy when I got to the field. The instructor used this to link the Tx to his so converting my Tx to Master, his to Slave and we would swop Tx's before flights so he could take over at any time he touched any control.

My Tx is still switched that way as I was testing last night, prob why the Tx comes up with ;No Slave' when i switch it on!

 

Yes, the motor responds in the air fine, so i get the delay just as I start the take off, 10 feet of slow moving over the gound on what feels like 10% throttle and then the speed of the motor increases over the next 2 secs to full speed and the plane moves forwards quickly and in 20 feet I'm climbing off the field nice and progressivly to height and turn (etc).

Once up there, throttle back to 'vertical stick' giving enough speed to maintain the trimmed height 'hands off'. If a bit windy, ie 5 to 8 mph it will need a bit more motor to keep the flight speed up against that breeze.

Landing is get aligned to the field and start decent, 1/4 motor down to about 15 feet up and drop the stick to zero. The prop will then free wheel (I presume it is) and it lands with some flaring by elevator.

On the ground the prop has stopped.

 

As to motor function, the defalt is soft delay, but later in the instructions it say to run the motor on hard start. When I first had the plane I'm sure the motor had no delay.

 

Should have some quality time today to try to get this all sorted.

Could be good flying weather locally tomorrow, so want to get this right for tomorrow.

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Hi,

 

What would happen if you were to ‘pretend’ to take off, ie do everything that you would normally do during take off but get someone to hold the model still on the ground for the whole time, then reduce power back to low.

 

If you then repeated the process would you then get full power straight away or still the couple of seconds delay?

 

If straight away then it suggests that the ESC is set to helicopter mode (accidentally).

 

If you find it difficult to follow the sounds that the ESC uses during the programming process you can buy a programming card which makes it much easier. Do a web search for the ZTW programming card as it suggests that this is suitable for FMS ESCs. Cost is under £10.

 

Brian.

 

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Thanks Brian, but...

 

Got myself ready for the Battle of the Beeps but first moved the B (buddy enabling) switch from the usual buddy position to off.

On switch on the Tx now goes straight to normal screen, ie batter level, pic of a fixed wing plane etc.

Switched off.

Switched the B switch on (3 posn switch) and restarted the Tx, and the No Slave signal is on the screen, reverts to normal after a touch/movement to any stick.

Switch Tx off.

 

Took the prop and nose cowl moulding off to expose the motor completely and allow almost total extraction of the ESC.

Nothing catching on the motor case or it's mountings, esc insulation sleeve is intact and no signs of heat bubbles, all smooth. Wires all good, and outside all clean of mud or corrosion.

So, switched the Tx on, buddy switch off and the check sequence was completed as per usual. Motor gave 3 beeps for the 3S cells and a pause and a single beep which indicates braked motor.

Screen was normal showing battery level etc.

'just' touched the throttle stick up (0.5 mm?) and the motor case rotated correctly!! No judders or clockwise rotation. Typical.

Miffed almost, (or relieved) tried it again from 'off' and same again, just turning anti clock and advance to WOT with a snap stick movement was about 1.5 secs which is helicopter mode.

 

Motor will rev from off (no motor case movement) to WOT to mid way etc etc totally easy and keen to regulate motor speed to stick position. No sluggishness, no delay.

 

The climb of the motor speed certainly follows an exponential curve, not a straight line.

 

Where are we then?

 

I'm not going to 'fix' anything. nothing seems broken, the characteristics are manageable, so I will hope to do 4 x batteries tomorrow and lots of landings, so take off, a few circuits and come down I hope smoothly. Should get 4 of those to a battery.

The grass length on the field is a bit high and when dew/wet is quite a drag on the plane but takes about 15 feet to come to a halt. Prop is stationary before stopping on the ground.

 

One thought before I almost leave you all in peace is, if the motor is braked with the throttle off how come the prop free wheels coming in to land or is the braking really quite weak just to allow the prop blades to collapse?

 

_DSC0037.JPG

Edited by 911hillclimber
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