Something is acting up...

[tptompkins]

I went flying today and one of my 550s was really acting up. It was warmer than usual today (about 31 deg) and there wasn't much wind. Perfect for flying! I brought it into a hover and the tail was twitching pretty bad. I thought that maybe it didn't have enough time to equalize with the outside temp so I brought it down and waited about 15 min. Put it in the air again and the twitching continued. A couple minutes into the flight it really started behaving erratically. It went from twitching to lightning fast scary 1/4 turn piros in both directions. I thought that maybe something in the tail was about to give and I would lose complete control so I tried to land it as quick as possible. Thankfully I got it on the ground without any damage.

I thought that maybe I had a loose belt. Checked and nope - super tight still. I loosened the boom block and readjusted it anyway just to be sure and made sure that it was tight. I spooled it up again but this time I didn't let it leave the ground. Even on the ground it started doing these wicked 1/4 turn piros in erratically in both directions. I checked it from the side view and the tail servo was definitely flipping out so I know it wasn't a loose belt issue.

I'm using the GP750 gyro. My gyro gain was set to 66% in HH and I lowered it to 60% to see if that would make a difference. I got a little better but not much. I switched it to rate mode at about 33% and it was no longer doing wicked 1/4 turns but it was still freaking out.

Any idea what's going on here? I've had a little twitching in the tail before but not like this. I don't think it's a static issue. I lube my belt and the air wasn't very very dry (91% humidity).

Tommy

[tptompkins]

BTW - I'm using a Phoenix 125 in governor mode with the governor gain set to 22. Could this have anything to do with the governor gain? I haven't changed my governor gain since I setup this heli and it was flying fine before today.

Tommy

[tptompkins]

I also have to add that I had my other FBL 550 sitting right there so I flew the rest of the day with that and it flew as smooth as silk! Boy I love that 550 and this is the first time that I can honestly say that I'm glad that I have two 550s ;)

Tommy

[Slyster]

Are both governors set the same in both helis? Tis strange. Sounds like gain but you did lower it. Gyro issue? Wish I could have flown today!

[tptompkins]

The governors are set the same on both helis. I didn't try lowering the governor gain today - just the gyro gain in the Tx. If I get out tomorrow I can bring the laptop and try to mess with governor gain settings.

Tommy

[Slyster]

For me.. every setting on one always is mirrored on the other.. never any difference needed. Of course you have one FBL and one not. Something must be up.. if not the gyro.. who knows... one way gear? Bearing somewhere? Actually.. I've had things like that happen on various helis.. and then next day it's gone! Weird.

[seemore74]

It could be the gyro even though the 750 is know to be the one that holds up compared to the 780, if you have another gyro on hand try it on.

[velocity90]

Set your lower and higher end points on the gyro again. Yesterday we had the same problem with a Quark. It just lost all the settings some how. It seems to happen to electronics. I had it with an Align esc.

You can check it easly by connecting your battery and see if you move the tail if the tailblades correct in both ways completly to the end(about a half to 1 mm before the total end offcource
:P)

Warmer weather would mean a tighter belt, thats only a problem with cold weather when the tube shrinks.

[freewheel510]

Just throwin an idea out here,

I had exactly that symptom on a Trex 500 once, it turned out to be a loose set screw in the tail assembly. That big a motion has to be something seriously wrong, not just a gain setting I think.

[lazor 22]

Sounds like the wag of death that I had on my 250. It was "flyable" in a hover but as soon as you start doing something its like it wants to kill itself. Can't say what I did though I sold it..

[Rob43]

Is it to a mechanical rhythm, or does it seem random in timing? If random, it could be elctrostatic discharge. Belt driven, without the humidity we'd otherwise have in warmer weather to help dissipate it. Just another suggestion. I know it's especially true for FBL systems combined with belt tails.

I've not had this happen personally on my 550, but I also considered maybe the gyro foam is stiffer in cold weather (not as cold as before, but not exactly warm). If so, I could not isolate vibrations it may otherwise absorb.

Good luck,

[tptompkins]

I went flying yesterday with Pete and the tail acted up again. I put it down before it could get too bad but at least Pete and Matt could see what was going on. After I got it home I sprayed the belt with a fresh coating a silicone / teflon spray and spun it up in the driveway. I let it idle on the ground at 1900 rpm for a few minutes and none of the symptoms occurred again. It seems that maybe it was a static issue after all.

I've heard that the Phoenix 125 is more susceptible to static so maybe that's contributing. I have the same Phoenix 125 on my other machine (mounted in the same exact spot) and that has not experienced any of these problems but I am running a different belt in there so maybe that's part of it. I'll have to take a look at those static discharge mod threads more closely and possibly implement one of those.

Tommy

[Slyster]

Very interesting. Glad it was a quick fix. Maybe since that heli appears to be susceptible to static you probably should do one of the static mods. Here's one from Capi http://www.helifreak.com/showpost.php?p=1149419&postcount=88

[signal7]

I found I had to do the static mod. I have a custom metal belt pulley on a G10 kit. The metal pulley may be the cause, not sure.

When I originally maidened without the mod my tail servo went crazy too, so I think it was indeed static related.

Here are some tests I did, and this is with a lubed belt:

My OR550 without static mod:
http://www.youtube.com/watch?v=LNaZxOWQq3Y

My OR550 with static mod:
http://www.youtube.com/watch?v=-NQvuViRs10

[tptompkins]

I definitely think mine is static related too and I was going to try to find some time today to do a boom grounding mod. Which method did you use to ground your boom?

Thanks for posting. Those vids are very helpful!

Tommy

[tptompkins]

BTW - my 550 that is having static issues is also a G10 kit. My other 550 which doesn't appear to have any static issues is a CF kit. Coincidence? Or is there something about G10 that is more prone to static issues?

Tommy

[Slyster]

Interesting. CF is conductive you know.. and G10 isn't. Although... one of mine is G10 as well and I've never had static issues. But I keep my belts maintained well with silicone.

[signal7]

Usually it's the other way around I think, but who knows. If nothing else by doing the static mod you'll be able to eliminate it from the equation.

I grounded my boom to a screw that screws into the motor mount, and tested for conductivity. If I recall there was a spot or two where I had to use a file to expose bare metal to make it all conductive.

[tptompkins]

I drilled a hole into the underside of the boom and ran a wire from there to a bolt on the motor mount. Connectivity tests out good with my meter and it still looks clean so I'm happy with this mod if it works. I guess we'll see if I can find some flying time this weekend.

http://redcart.com/images/random/helifreak/550-boom-ground/2011-02-11-0001.jpg

http://redcart.com/images/random/helifreak/550-boom-ground/2011-02-11-0002.jpg

Tommy

[signal7]

Yeah that's basically how mine is wired up too. Nice job :thumbup:

[lazor 22]

Looks great! I have been meaning to ground mine. How did you get the screw to stay in the tail boom?

[DominicD]

Why such a thick wire ??

[gregg25]

capi ya can always slide the battery forward

[freewheel510]

I drilled a hole into the underside of the boom and ran a wire from there to a bolt on the motor mount. Connectivity tests out good with my meter and it still looks clean so I'm happy with this mod if it works. I guess we'll see if I can find some flying time this weekend.

http://redcart.com/images/random/helifreak/550-boom-ground/2011-02-11-0001.jpg

http://redcart.com/images/random/helifreak/550-boom-ground/2011-02-11-0002.jpg

Tommy


I just lube my belt and pulley with silicone spray, but geez Tommy, that orange gear and pulley look seriously hot!! Nice work!

It appears from the photo you have the boom supports that are *not* pinned -- there is a little hole in the side. If that's true, you may consider replacing them. Mine came adrift in a very mild crash, and the newer ones I got from HD are pinned with a little black pin through that same hole. I'm pretty sure these won't do anything until they completely fracture.

Chris

[tptompkins]

Looks great! I have been meaning to ground mine. How did you get the screw to stay in the tail boom?

I just drilled a hole that was slightly smaller than the bolt and let the bolt thread itself into the boom. I cut the bolt down with my dremel so that it doesn't stick up inside the boom too far. There isn't much metal there for it to bite so I added some locktite and just snugged it up without much pressure.

Tommy