Midas D.

This is way to stupid and freak's me out…….

Did an air leakage test on the gears cause i changed out an spring.
So left the whole lot connected and fired up with the gears up to see if i lost some air.

Guess what, came back father +/- 20 min. all good
Switched the whole lot off, did some more fiddling about, fired the whole lot up again, both Flap servo's burned out?????????????????
Worked all fine during the gear leak test, worked all fine on previous flight's no humming or any strange things going on, and out of the blue they burn both to bits, not even under load?????

Anyone?

Really flabbergasted here...

Dave Wilshere

What servos? With the linkage off the servo end, holding the ball link at roughly the same height as when connected to the servo, does the ball link rub on the top skin as it closes? does the flat close with no resistance? Often the wing skin to moulded cover (closes the opening) needs the resin cleaning off or the flap top skin lower front edge needs chamfering to allow total clean closing.
Some Digital servos don't buzz under load...

D

BlueBus320

My Feedback: (57)

I always test my servos through an amp meter during the rigging, & final testing (before flight) stage. I find it to be a good way to know the stresses on each servo. Especially when all servos are the same (8411) it's easy to tell which are working too hard.
Jay

Midas D.

Dave,

i use Graupner servo's. 707's

Nothing is touching or rubbing any thing, and as said it all worked flawless until i left the system fired up for about 20 min. (+/- 6hrs total flight time)

It really freaks me out….

BaldEagel

Do you have these servo's paired in some way, i.e. separate signal wires but combined power through say a multiplex connector, I have found in the past if you only connect one servo into the Rx from a combined multiplex connector both will burn out, just a thought.

Mike

Midas D.

Mike,

I'm using an multiplex 6 pin connector. But the aileron and flap go on one connector other side of the wing the same.
So 2 multiplex conectors in total for 4 servo's.
Basically all the servo's have their one leads from servo in to the RX using slot 1 and 5 for Ail. and 7 and 8 for Flap (futaba)
The multiplex connectors are only there for separate the wing from the fuse.

Again??????

I'm about to start do an amp's check, building in the new servo's as we speak.

BaldEagel

That is what I meant, but do you combine the negative and positive from the servo's onto the twin pins in the centre of the plug? or have you connected the servo's independently to the pins on the plug? this is where I have had trouble in the past when one of the Rx leads from the combined Multiplex plug was not connected.

Mike

Midas D.

Mike,

Each wire has it's one pin, nothing combined.
So 2 servo's on one connector, all 6 pins in use.


Cheers,

Ed

BaldEagel

Ed, OK it was just a thought, but do keep investigating I am intrigued.

Mike

Midas D.

It's getting more and more interesting, my powerbox sensor switch is giving 6.1 volt output……….
As i think it should be 5.9 as per manual...

Dave Wilshere

Ed

I was test flying customers model Sunday when a Graupner 800 series servo stopped working on ailerons. No obvious problem, just stopped. Its why I only use JR servos!

Dave

cbooth1979

My Feedback: (22)

My Powerbox sensor switch reads 5.7V at the reciever. I thought it was strange as well, as the manual states 5.9. Are you on the correct battery chemistry?

Midas D.

cbooth,

Jep on the right chemistry.

Dave,

I had JR servo's burn out that's why i swapped to Graupner ;-)

Dave Wilshere

Must be you then, as the common factor ;-) I have 100's of JR servos in my fleet and never burned one. 5.8-5.9-6.0-6.1 tiny difference as its a fixed figure, not like a 5 cell Ni pack which starts at 7+ and reduces to 6.0v.

Did you have the flaps up during the 20 minute air system test?
Sensor switch.
Chemistry setting has no influence on the out put voltage, you can set it to Li-Po and fly with Li-Fe and it works just fine, it just won't tell you when the voltage is crashing.

phantom_najd

My Feedback: (2)

I'm almost sure your flaps servos are binding somehow on the position you had them on for 20 minutes. However, I also think the binding is not severe and the servos draw slightly higher than normal Amps that they needed 20 minutes to burn out. I don't think it's the issue of powerbox delivering 6.1v as servos rated for 6v usually tolerate more than 6.6v (2 cell LiFe 7.2v fully charged) or in some cases 7+ (as Dave pointed) for short period of time which makes 6.1v normal.

I suggest that you use Amp meter ( I recommend http://www.horizonhobby.com/products...t-meter-HAN172 ) to check all servos amp draw at center and both end points.

I hope you'll find the real cause of the flaps servos burn out so that you regain your trust in your plane, I know how hard it is to trust a system when something goes wrong without you knowing why.

Azzam

Dave Wilshere

Sensor switches are brilliant, you don't need an amp meter (Although I have the Hanger 9 unit) Put the aeroplane in flying state, gear up and clean, leave it 2 minutes, put your finger under the sensor switch to the heat sink, (caution it could be V hot!) If you can put your finger on it and hold it, the current is acceptable, if you can't something is working it hard!
Generally its hot, but not burning. I do this on all my models during building and occasionally after a flight to monitor servo condition/linkages.

Dave

Midas D.

Dave,

Had the flap's in up position during test, plane on it's stand supported under the fuselage.

What phantom say's it's such an nasty one cause it rips the faith in the system to bits. Think it does not matter witch servo's used, something got **** and is for now not traceable and that add's an scary feeling to the show……
Specially cause i also installed an new turbine in the bird and are about to go for an second maiden so to speak

I will give the finger thing an shot then and see if it becomes hot.
Otherwise i will try an multimeter test on the amps.

So the 6.1V should not be an issue then here?

Received the paint by the way, thanks for the quick response on that one!!

Cheers,

Ed

phantom_najd

My Feedback: (2)

Having the flaps in the up position about says it all. I know it takes 1 or two clicks in the end point settings for the flaps up position for the servo to jump between drawing 0.4 Amp to 1.2 Amp. So I think the servos were actively pulling the link to retract the flaps further for the whole 20 minutes while the flaps can not physically retract more. I strongly suggest that you use an Amp meter on the new flaps servos while you set their end points. I also suggest that you always leave the flaps on take off position while taxing and setting up in the workshop (that is the way I always do). Don't forget that you have 5 more servos on the plane that didn't burn which could boost your confidence again in your setup. Good luck.

Azzam

afterburner

My Feedback: (18)

Yes, I always leave my flaps in takeoff position when the plane is powered up to do some work. Least current pull than up or full.

Bravo77

Just want to share my experience with the UF flaps , During my set up I struggled with the flaps not closing properly and the servos buzzing when it tries to pull the flaps close .I wrote to Dave and he explained the glue on the flaps joint and when I looked he was right , there was a lot of the white glue and it was preventing the flaps from closing , this I did not know although I have been on the jet scene for years. Dave's advice helped me and just want to share that if it can help some one . I took a small file and some sand paper and after some work I was able to have it close nicely and all the buzzing went away , without any further adjustment , so my adjustment was good , the glue need to be removed . The secret is to operate and play with the flaps without powering the servos , When you get it right then power up and if all is well , there should be no problems .

Dave Wilshere

Ed 6.1v does not worry me. No problem on the paint, they said sorry for the mix up.

I've just grabbed an UF wing off the rack I'm due to build. The arrows show where the glue builds up on the flap and the wing skin lip I sand on the underside edge-its cut square in the factory-to allow for the glue fillet left on the flap. Also at one end this has some glue ripples on the fairing, I clean all of this off. Also under the skin it has glass vacuum bagged onto the lower surface, this can have ripples of resin, so I run a sanding board under that lip too.
Same sort of thing on the CARF Hawk flaps is needed.


Like Afterburner I leave my flaps in the take off position except when in flight. All the time I'm setting it up and start up taxi etc.

Midas D.

Thanks for all the tips, bona look in to the edges!

Midas D.

Edges are as clean as they can be and did an amp. measurement, both servo's pull 0.00amp's when full retracted………..

Must be an ghost in there i think

Midas D.

Got her up there today again.
Kinda re-maiden after i buried her nose in a ditch
Did 8 flights and again absolutely flabbergasted on the performance and the ease of flight!
What an superb airframe!!!!

I really like this bird!!!!

ps. not an single hick up on the flap servo's so you can shoot me in an bucket i would say…….

Bravo77

Post a video please