Auto piro flip/chaos with 3G

[Globs]

The only other thing I can think of then is simple static - the 500 is well known for it's Van-der-Graaff tendencies - not sure of the 700.

Take the blades off and have the motor run up to headspeed while you try stuff out. Also try in a dark room to look for sparks, once your eyes have acclimatised. Look out for the tail blades however - or take them off too.

[ke6d]

Originally Posted by Globs

The only other thing I can think of then is simple static - the 500 is well known for it's Van-der-Graaff tendencies .

But the op's heli is a 500 ESP. The torque tube was not supposed to have Van-der-Graaff tendencies.

[Globs]

Originally Posted by ke6d

But the op's heli is a 500 ESP. The torque tube was not supposed to have Van-der-Graaff tendencies.

Oh - didn't realise the esp was a TT sorry. No static then.

[harryboe]

@CeeveeSiN

1st - I don't think the bench pitch pump is going to demonstrate anything. On a flybared heli the flybar will take the mechanical cyclic load from the blades and the servos only see the load from the paddles. If you use blades with a backward lateral CG - causing them to run forward - you will put a lot of load on the servos. Such blades appear to track bad and tend to be slow - in fact they make the servos slow due to the load! (Remark: I'm not an FBL expert nor a pro. That information is from some trusted sources that have been involved in FBL development for years - and it makes perfect sense)

2nd - What you describe looks like a "brownout" (blackout ?) of the 3G unit while the RX never registered a serious voltage drop. So this has nothing to do with your 10C LiFePO packs. They may well hold up with the current they are good for 20+ ampere. If you put that current on that tiny servo cable that has to hold up with the cyclic servos demand it's going to melt for sure!

3rd - the AR7100 will not solve your problem as it does not eliminate the 3G servo-bus problem.

The best solution will be a "power-box" setup that are connected to the power source and provides the current to the servos on one end and signal power for the RX and 3G unit on the other end. Here we can learn from our fixed wing colleagues!

Heli specific power boxes I'm aware off are the ReactorX or the Fromeco Kiwi Pass Through Regulator.

[MrMel]

I don't think the bench pitch pump is going to demonstrate anything. On a flybared heli the flybar will take the mechanical cyclic load from the blades and the servos only "c" the load from the paddles.

Pitch pump test is a really good test, its the fast start and stop of servos that generate high peaks, we have used that test to brownout BEC's and supplies which never browned out inflight. (Kontronik Jive controllers for electrics)

(Its a standard documented test by the VStabi team, test works for any setup)
http://www.vstabi.info/en/node/78

[Globs]

Makes sense (discussed in https://www.helifreak.com/showthread.php?t=190012 too).

The issue is one of voltage drop, for instance if you pull 10A down a cable/connectors of 0.4 Ohms you get V = IR = 4V. So 6.6V now becomes 2.6V.

[NTM]

Yup, pitch pump test for the win !
That's how all the cool kids are checking the bec output on the mikado logo's now.
Some of the latest kontronic jives have a slightly weaker bec than the older models, the pitch pump test can really show the difference between the two.

Also, I know that several years ago the v-bar's servo current draw was much higher, like double the amp draw.
It had something to do with the way the old software drove the servos.
Perhaps the same thing with the 3g ?

[OICU812]

Originally Posted by NTM

Yup, pitch pump test for the win !
That's how all the cool kids are checking the bec output on the mikado logo's now.
Some of the latest kontronic jives have a slightly weaker bec than the older models, the pitch pump test can really show the difference between the two.

Also, I know that several years ago the v-bar's servo current draw was much higher, like double the amp draw.
It had something to do with the way the old software drove the servos.
Perhaps the same thing with the 3g ?

Perhaps but to clarify, that was rectified long ago on Vstabi, there is (ZERO) issue on HV servos and systems with Vstabi now days, this may be a growing pain for Align, tough to say hope it gets sorted for you fellas is all, be well.

[thayghetucsb]

all rite, i did the bench test. Remove head (except for the swash) and tail. all 4 servos and motor are connected. power up, move both stick as fast as i can (pitch pump, etc) , then repeat with idle up there's no brown-out. held the heli up and shook it hard, everything seem fine. What symtoms would be shown if BEC is faulty (insufficient voltage/amp delivered)?

[Globs]

Originally Posted by thayghetucsb

all rite, i did the bench test. Remove head (except for the swash) and tail. all 4 servos and motor are connected. power up, move both stick as fast as i can (pitch pump, etc) , then repeat with idle up there's no brown-out. held the heli up and shook it hard, everything seem fine. What symtoms would be shown if BEC is faulty (insufficient voltage/amp delivered)?

You need to load up the cyclic servos - and possible the tail one too to replicate what happens in the air. On the bench they just sit idle (unless you have the main blades on!) so you are better disconnecting the motor, and pushing against the servo arms like the rods would in flight, while moving the sticks.. keep a check on wire temperature while you do this however.

I very much suspect the voltage drop to the 3G is the issue. If you have a Y-lead and a safe (do not short!) means of measuring the 3G's output voltage do so while loading the cyclic servos. I.e a Y lead going from 3G to elev servo and meter - measure voltage ground to supply (ignore signal wire).

[ShuNut]

And when they say move sticks fast they mean faaast like this guy does. [ame]http://vimeo.com/2983063[/ame]

[blade strike]

jesus

[123mvd321]

A friend of mine had the same problem, after spinup his T700 dit a auto pyroflip into the dirt.
After rebuilding the heli we found the error what caused this,
With his heli turned on we secured the 3G unit in place into the frame and suddenly the unit re-started itself and servo's acted weird.
wow this was scarry, the problem occured when we jerked with the sensor cable.
if we pulled out the sensor cable nothing happened, but with the cable plugged in and some jerking with it the unit restarted.
so we took the cable apart and noticed the following:

one connector was open and made a bad contact with the unit.
probably from the engine's vibrations it caused the unit to restart and mess up the heli.
after the cable was repaired the unit worked correctly.

Hope this helps.

[panzlflyer]

How easy is it to take the connector apart?

[rubbersoul]

I had the same problem with my long cable. But luckily, my 3G unit didn't want to initialize with it. One pin looked similar to yours, open. I just crimped it a little bit with a nose pliers and everything is good.

[OnTheSnap]

Crud. So I put my 600 3g-eezus about a week ago. I was hammering it in an inverted rainbow, and it suddenly started spinning out of control about 50 feet up. I'm pretty sure I had no cyclic control, but the tail was spinning so hard it was difficult to tell before I hit throttle hold. My 600 created a nice creator along with $200 in damage. More important is my time to repair it. Picking up the debris, I found that the front TT gear was mostly stripped all around. I figured this was the cause of the failure. But now I think that it just somehow got stripped in the crash (even though I was in TH) or by the 3G going nuts.

I'd venture to guess that I had a 3g brown-out. I was in a hard collective maneuver when it happened. Guess I need to build my own own servo power bus and then try again.

Sometimes it sucks being an early adopter.

[Globs]

Originally Posted by OnTheSnap

3g-eezus

Classic!

[thayghetucsb]

well, i did a whole bunch of bench tests today after rebuilding my T500. I found that approximately 20% of the times, the main receiver light was oscillating its intensity. i'm not using the word "blinking" because blinking requires the light to go off and on. all this was when i moved the sticks fast. 8 out of 10 tests, the light remained solid no matter how hard i tried. BEC or insufficien power bus?

[thayghetucsb]

also i'm running DS510s on cyclic and ds650 for tail. would these be power hungry enough and in turn caused hands-off piro flip to meet mother earth?

[Globs]

Originally Posted by thayghetucsb

well, i did a whole bunch of bench tests today after rebuilding my T500. I found that approximately 20% of the times, the main receiver light was oscillating its intensity. i'm not using the word "blinking" because blinking requires the light to go off and on. all this was when i moved the sticks fast. 8 out of 10 tests, the light remained solid no matter how hard i tried. BEC or insufficien power bus?

Do not strip the gears, but I suspect you just need to push on the servo horns a bit with your fingers while slowly moving it. For a proper answer rig up one servo with a Y lead and multimeter and measure the voltage coming out of the 3G unit while you do this.

Also try wiggling the plug with the 4 wires on it - and inspect the plug visually of course too - the little connectors in the end. I suspect this is the main culprit..