Maiden Flight, ugh...

[Drew816]

Prior to the first flight above:

A Goober and his Gaui below:



So I got her airborne; barely, ugh. There's something screwy and I'm strongly suspecting that the mainshaft is bent, a ton of vibration in the head until you get her spun up and even then you can see the vibes translating. Bummer since it's BRAND NEW and was that way upon assembly but maybe that's not the issue. Well Hell, now that I think about it I HOPE it's something that simple because if it's not the mainshaft I'm lost as to what it might be!!! I had to adjust the blade tracking and that seemed to help the vibrations a little bit BUT the wobble is still there.

Keep in mind I noticed this wobble before I installed the paddles, let alone blades or anything; just spinning her up on the bench once the motor was installed I could see a wobble. And in installing the blades and paddles I balanced and weighed everything, checked and rechecked measurements on the fly and fly with paddles installed, etc...

In comparison to a T-Rex 450, that lower headspeed is noticeable in just the sound but response-wise she handles real similar as far as the throttle is concerned; you don't have to REALLY crank the throttle to get her moving despite the weight and size, that big ass blades are doing the job for sure. But this was my first 5 minute flight so many that impression will change, I can tell you that DAMN she's BIG in comparison, phew!

The motor and the ESC were extremely hot on landing, I think I'll recheck my gear mesh from the motor to the #1 as it seemed a just a tad loose.

I was getting a bit of right drift from the gyro, probably need to check my gain settings; what do you guys running Futaba 401's end up with normally?

So not a super successful maiden flight; wobbles, things to tweak but the bigger issue was we were racing to beat a Thunderstorm coming into the area (it's raining on and off now) and it was windy making me a bit nervous to boot!

[mysticmead]

don't look at the negatives... look at the positives... you had your Hurri in the air.. and it landed... not crashed!!

as far as the wobble.. you said it was there before attaching blades... that tells me it's either the main shaft OR... the swash isn't level.. I'd start with checking the swash first..if that is 100% level... then take the main shaft and roll it across a piece of glass to see if it's bent.

as far as the gyro gain... adjust it until the tail starts to wag... then reduce it until the wag stops.. it's going to be different for each heli

[JaggedEdge]

You're 550 looks AWESOME.

I know you're frustrated because you want and expect perfection but I'm 100% you'll get it figured out.

I really like the look of your Hurri! Nice job.

Edit: I hate to ask because I think I remember you mentioning you did.. but you did set your blades cg and then balanced them, right?

[kahn10]

hey drew good shit.... check that the two parts of your swash are pressed together properly and are true to each other,the balls are screwed in the upper ring of the swash straight,if their all good loosen the screws around the main shaft upper and lower bearings and spin the shaft round checking the bearings are located square in the frame

[Drew816]

I think it's the swash; I just replaced the mainshaft and the original unit seemed to be fine but I installed a new one just in case. I checked the mainshaft bearings in the main frame, that all looked ok. Spun her up with the swash disconnected and everything seemed ok, connect up the swash linkages and WOBBLE!

I can't see anything on the swash that would be a problem, as far as my 'eyes' can see all seems to be ok; but once you spin her up, WOBBLE!

CRAP! So now what, contact the dealer I bought it from and let them know what's up, is there an easy way to fix this or??? So close and yet so far, arrrrghhhhh....

And yes, she did get airborne, I flew it, hovered her around, very slow FF all while fighting the winds and the impending Thunderstorm and I landed her safely, ALWAYS something to celebrate. But she was hardly smooth and that's tough to swallow when you've put in all this time in the build and you're not sure what the problem is to boot!

[kahn10]

take a few pics close up all round your mast swash etc including the servo links and whack them on bro

[Drew816]

I need to get some video of this thing spinning, I'll try to get some on my better camera. Still shots don't show you anything, it 'looks' fine but once you start to spin you see it wobbling.

More to follow, but I think we've at least isolated the probable issue. Is this a known and somewhat common problem? How do you fix it, I don't have any way to push on bearing properly let alone to get them aligned to the necessary tolerances, AHAHAHH!!!!

[mjdee14]

Congrats on the maiden...looks cool...I like the colors....


when you say wobble, does that mean that if you are at zero pitch, the swash wobbles?

I'm assuming as you say you have checked each linkage is correct, the smae length each side, blades in track, etc. then the servos must not be centered and the swash level to begin with....

As mentioned, post some pics of the swash, head,etc, maybe something will stand out.

I would say yu had a very successful maiden......"it lives to fly again"

[Drew816]

It wobbles with nothing connected, let alone once you've connected her all up. To me it looked like a bent mainshaft from my T-Rex flying experience, but the odd thing is that she'd wobbled with just the swash held in place (no servo arms connected) and the motor spun up. If you connect the servo linkages the wobble translates down into them as well.

When I first saw this while in build mode I thought "...hum, something isn't quite seated, let's hope it gets sorted out in the final assembly" but it's not gone away. On spin up with the blades attached it's pretty pronounced until you get the head speed up and then the whole bird is rocking slightly but it becomes more stable (as the vibration translates throughout).

Will a T-Rex 450 swash work, maybe a little hacking here and there but...

As for the colours, I'll be adding ORANGE here shortly to help keep orientation but I was in a rush to get her airborne so that fine tuning can wait if you know what I mean. Plus I learned my lesson about spending a lot of time on painting a canopy and parts with my T-Rex 450; one good THUMP and it's all gone so I'm sticking with the Canopy KISS Painting method from here on out! Thanks for the compliment regardless...

Is swash screwyness a known problem with Gaui's?

[kahn10]

bro the biggest initial cause of strange head behavior with hurri,s is not getting the servo links spot on. try dropping one link off each servo and spinning up the head.when these things first came out guys were getting the frames to walk by having one ball out by half a mill to a mill.the offsets accentuate very slight inaccuracies.worth throwing up some stills as well as vids.swash bearing should be retained by 3 screws on the bottom.make sure all three are pressing lip of bearing flat with outer swash ring
roll your main shaft on a sheet of clean glass.you can see but also hear if its not true.if it doesn't make sure its not lumps where the holes and chamffer(how the hell do you spell that)s are they can trick you

[mjdee14]

Originally Posted by Drew816

It wobbles with nothing connected, let alone once you've connected her all up. To me it looked like a bent mainshaft from my T-Rex flying experience, but the odd thing is that she'd wobbled with just the swash held in place (no servo arms connected) and the motor spun up. If you connect the servo linkages the wobble translates down into them as well.


?

something sounds fishy when yu say you have wobble before hooking up the servos...

I would take the head and everything off....spin up with just the shaft...then add swash, then add washout arms, etc, and see if I could see what is inducing the wobble. if the shaft wobbles with nothing on it.....then it might be one of the bearing blocks off center or a bad bearing.

start with nothing and keep adding parts back on.

[JaggedEdge]

Originally Posted by Drew816

It wobbles with nothing connected, let alone once you've connected her all up.

I knew I remembered you saying something about that. Sorry. :o
I'm sure you'll get it figured out.

[Drew816]

Thanks for the suggestions guys, I'll start by removing one linkage at at time and then adding them back and see if that changes anything. Followed by the complete tear down and build back up routine until this gets isolated.

The link lengths are all the same, measured them on calipers and checked and recheck and rechecked over and over. With no trim on take off she went right straight up, no trim necessary (besides maybe a bit of forward bias as she seems a bit tail heavy with the long boom and small T-Rex sized batteries). I'll recheck them all again as well just to be sure but I'd think you'd hear the servos screaming as it was fighting the two off-sized links if that was the case?? Maybe not but...

I don't have a swash leveling tool but I think the straight-up take off kind of answers that; maybe not...

I did install a brand new shaft that I checked rolling it, it was perfect, installed it and the wobble remains. The original shaft looks fine as well.

You guys are the pros so I'll follow the advice, so much for this being an easy build; time to get my T-Rex's back flying and stop working on the Gaui Gremlins so I can fly SOMETHING!

[kahn10]

hey drew......when i said wrote posted......just before......about a half a mill blah blah i meant more about the balls.i can't see whether you've used predrilled holes or made your own but if one of them is slightly out of alignment - when you set up at mid stick all good but as soon as you turn your servos each link has slightly different geometry which leads to torque twisting the frame from the servos and pitch and roll arms.ages back a guy called ozace? got about to where you are and just about ended up biffing it then found out a couple of months later he had slightly misaligned the balls on his servo arms.dropping one link should negate this to check

[Drew816]

AAHHH, the balls on the JR Big Wheels, got ya. So I'll drop one of these each as well in my 'isolation sequence' to attempt to find the wobble. Hell I HOPE I screwed one of these things up as that would answer the question and make life easier, happy to admit I'm wrong if it resolves the problem, just FLY RIGHT already!!!

I did measure all the servo arms, checked them Center to Center with the Servo pivot point versus the upper arms, popped them on and off one at a time when assembling and of course used the calipers to measure them all off one another too. I wonder if the Rocket City's/Linco's on Servo #2 versus the stockers (there's one of each) are slightly out? That would make some sense but they were completely inter-changable when I was assembling, no out of the ordinary binding of fight to put them on but I know which servo I'll be starting with tomorrow!!! Let's hope that's it only I can't go back to the Gaui arms since I had to cut up the stockers to make the Linco's work; THANKS Finless Bob, little did I know that this wasn't necessary anymore. Update your flipping videos!!! Oh, and ahh, thanks again for doing all those to begin with eh... :o

Thanks for taking the time to walk me thru all this...

[Mikej]

One thing to look for Drew is that occasionally (though I don't think I've heard of it on a 550) the hole in the ball in the swash plate is drilled off-centre, this would explain what you are seeing.

[skigolfmike]

I wouldn't wait for Finless to update his videos on the 550.

I got a bunch of Raptor 30 ball links and used them where needed; however, since the links were lengthened, it was only a few places.

If the main shaft is straight and spinning OK in the bearing blocks, it has to be something from the swash up. I had a lot of vibration problems in the tail on my 550. Turned out to be the see-saw and flybar. I had the upgraded see-saw cage, but there was some play that was corrected when I got the CNC seesaw.

I saw the vibration in the tail of my 550. The fin would start vibrating and would wear out the locating pin in the stock tail case. I busted at least 3 tail cases. What worked the best was using CA to keep the tail case from twisting on the boom. I finally got a CNC tail case from HeliDirect.

[Drew816]

Ok, the wobble is coming from the head down OR the swash itself; it's not coming up from the servo arms. I'll still measure all this stuff out but by removing the linkages to the swash and holding it with my fingers and slowly spinning up the motor the WOBBLE is there instantly.

The arms coming down from the upper mixing lever were different lengths, this IS how you adjust blade tracking after all, right? So I made them the same length, reattached, spun her up, WOBBLE!

How could anything in the upper head be screwed up, the flybar holding arms are straight (head lined up with the flybar cage phillips head behind it), the see-saw arms look about the same, etc, etc...

UPDATE: OK, screw all that, it's the swash for sure. I dis-conneted all linkages to the swash, held it in place and spun her up and WOBBLE! Something in the swash is messed up for sure. My wife has 'misplaced' our good camera so I can't get any video today (I'll look around again this evening for that bugger!!) but trust me, disconnected the swash is wobbling around a brand new, true as I can tell mainshaft.

Thoughts?

[mjdee14]

Originally Posted by Drew816

Thoughts?

The swash bearing might not be pressed all the way in....look at the bottom and see if it has the same amount of bearing sticking out on all sides....

There were problems with some earlier swash bearings.

[kahn10]

the earlier probs were seperation issues hence the screws.drew try removing the screws eyeball the hell out of your swash to see if it has a machining error....if not lie it upside down on a flat piece of wood and find something like a socket that contacts on the bearing outer race without touching the outer swash and give it a couple of gentle taps.tho maybe contact the supplier first and check doing this won't cause any issues if they need to replace the swash.also before giving it a tap hold it at eye level line upside down and give the inner swash a spin to check the bearing itself hasn't got a machining error.if it has you should see a wobble between the inner and outer bearing races.luck bro