X5-lite tail driving me BONKERS

[sp00fman]

that is correct. i might need a drill rig/guide/chuck thingy. basically a metal block where i would stick the shaft in, and a hole in the side as a drill guide.

Still the problems of having no milling tools remains.

[galaxy_jason]

i'll second the pinon suggestion. It's been serveral years so I don't remember the details
but we found on the 550 that some pinion's would cause a resonance that would drive
the tail gyro crazy. Random tail kick on hover, etc. The ONLY thing that was changed
was the pinion. It's been too long to tell you what worked, I think I just went back to the
stock one and everything was fine.

[sp00fman]

I switched motor+pinion not that long ago. Does not make a difference.

Logo 400/500 tailshaft is on its way. I expect it is a direct fit.
Lets see what difference a real brand makes......

[sp00fman]

I need a stiff drink....

Logo shaft is nicer in the bearings, but the violent vibration remains. tried both my plastic grips and the metal assembly., took the metal one off and disassembled. had to hammer out the bigger diameter thrustbearing race to make sure it was seated properly. The anodizating on the part seems too thick. Filed the thrusbearing a bit so it would fit in again. Tolerances on the metal parts is lacking. One grip has the outer bearing rattling around making the grip wobbly, so had to put a piece of tape around it. 4 new bearings in the grips.
Did not fix anything. Flex of the plastic tailcase remains suspicious. , but wouldn't a well balanced tailshaft+ parts rotate smoothly in it even if it was very soft? Might try balancing the shaft with all the parts on a propbalancer again.

All in all another wasted evening.

[DL126]

I've installed new thrust bearings in main rotor, feathering shaft, main shaft, main gear, hub, and OWB.
Also pulled motor apart and oiled bearings.
The only thing I haven't replaced are the main shaft bearings. (But I have them to put in.)

As mentioned previously, the CNC tail rotor and the X gear box has installed.
Installed new KBDD tail blades last week.

Vertical tail fin still vibrates.
Might be a tad bit better but it's still there.

It might be worth mentioning that this is an aftermarket tail fin.
It's 1.5mm thick.
IDK what the thickness of the stocker is, as this was on the heli when I bought it.

[RedOctobyr]

Fiberglass or CF tail fin? They will resonate at different frequencies. A FG fin could vibrate visibly at a time that a CF version might not. I can't check the thickness of my stock CF one at the moment.

Sent using Tapatalk.

[DL126]

Originally Posted by RedOctobyr

Fiberglass or CF tail fin? They will resonate at different frequencies. A FG fin could vibrate visibly at a time that a CF version might not. I can't check the thickness of my stock CF one at the moment.

Sent using Tapatalk.

Fiber Glass

[sp00fman]

I tested if blade pitch was equal by locking the tailslider and measuring the distance between a folded blade and the tailboom. It turns out to be precicely equal, glued the bearings on the shaft again, and am sorry about that now it did not work. Pita to get it out again.


I went ahead and found an CNC intergrated tail case for a somewhat decent price. Does look super nice and stiff. No need stock up on flanged bearings like that are used in the CF plated design, it runs with the normal radial bearings.
Great thing about the design is that i can't possibly install it wrong or deform it in assembly.

[sp00fman]

Got the part in the mail today. Tried to sleep but could not put my mind off it, so i get the heli ready for a test spoolup tomorrow.

I must say i am impressed by the fit and finish of this Gaui part. Slots together tightly and looks super nice. The play on the shaft pushing it forward/back with some force is almost none compared to the plastic tailbox. Im getting my hopes up again.
I used the plastic tailgrips for now, as i got them to run smoother than the nicer looking cnc grips. Might change them out at some point, but first want to get flying a bit.

By the way, i ended up with the TT version of the part, but it is the same when i pushed all the gears and bearings out of the assembly. paid €62 shipped for it.

[sp00fman]

It works!
It has lost it's tendency to get in a resonate state and vibrate itself to death. It's smooth all the way to idle2 speeds. Next up is balancing the tailrotor further with the help of the V-bar vibration analyzer.


I ended up with using the logo400 tailshaft. its 4,96mm diameter compared to the 4,95mm of the Gaui shafts. Still would like to try a shaft made out of ejector-pin, but am happy for now,

[TimM]

Originally Posted by sp00fman

It works!

Great !
That was a long slog.
Good luck.

[mverhorst]

[FailureToFly]

I've been following this thread and am really happy that you sorted it! I really felt for you as it would drive me absolutely crazy not being able to fix something like this.

The Formula tail case really is nice compared to the original FES unit IMHO. Hopefully it is also really crash proof as it's simple to get at the bearings (no presses or hamming etc).

[DL126]

Originally Posted by sp00fman

It works!
It has lost it's tendency to get in a resonate state and vibrate itself to death. It's smooth all the way to idle2 speeds. Next up is balancing the tailrotor further with the help of the V-bar vibration analyzer.


I ended up with using the logo400 tailshaft. its 4,96mm diameter compared to the 4,95mm of the Gaui shafts. Still would like to try a shaft made out of ejector-pin, but am happy for now,

[sp00fman]

Strange stuff on the bench while ironing out the last vibes. If i start to vary how tight the tailblades are in the grips the vibration comes back, or goes away when i get the balance between the two grips right again. Perhaps there lays the main cause. Im still not sure what changes when i tighten stuff up. Really loose blades do give huge vibes.

Oh well, ill just do some test flights soon and keep an eye on the vibration log.

[sp00fman]

In flight the problem reoccurred when i went to idle1. The vibration messed with he gyro and starting to tilt to the left. Would have crashed it if i didn't reacted as quickly. It made a loud deep buzzing sound. Sounded like a tail blade disconnected from its pitch link, but the vibe went away when i backed up to idle0 (1800rpm) and coached it back to the pavement.

Flight lasted just a minute, back to the workbench now. Did get a slight sense of what this heli is capable of with its 520mm blades. At 2,2kg with lipo it feels really light even at 1800rpm.


What the hell is wrong with this thing?

[mverhorst]

Darn...

I can't help you, you have done, checked and re-checked everything I could think of...

[sp00fman]

Reading up a little on balancing.

What is the effect of unbalance on a rotating part? At one extreme, if the rotor mounts are
rigid, the forces exerted at the bearing supports can be very high and potentially damaging.
The forces are a function of the unbalance. They are the centrifugal forces described
earlier. At the other extreme, with flexible mounts, the part is loosely constrained and may
exhibit large amplitudes of displacement.

Yup... thats my heli alright.

http://www.balancetechnology.com/pdf..._basics202.pdf


I hope i only have a quasi-static unbalance. Dont have a rotating-balancer with computer attached, but perhaps i could make it better with some trial and error.

Im going back to the Gaui shafts and use the inner hole to make the distance between hub and tail-case as close as possible. I dont think i really need 45 degrees of pitch on the tailblades


Edit; got an idea. have a spare 1300kv motor with 5mm axis. Might directly mount the tailrotor on to make sure the belt drive of the heli is not the cause. Also, a direct-drive tailrotor might not be a half bad idea,

add: The PDF gave some insight. The plastic tailbox is flexy, so acts a bit like a spring holding the shaft. It will have its own resonate frequency. If that matches the rotation frequency and there is an unbalance, it gives the huge vibes. Changing to the metal tailbox just changed my stiffness/ups the resonate frequency. .
If i get the system in a resonate state and touch the shaft with a sharpie i would get a mark and get a clue about the direction my vibration originates from.

Using a spinning balancer is out of the question. Needs electronic sensors/computer program for it and needs to be specially calibrated for this particular project.

[tazcat]

Not sure what you're running for ESC and Gov, but just wanted to pass along info about a related problem.

I have the standard FES package, had never used the HW Gov but ran a flat TC. Heli was rock solid, even in the wind. Decided to try the Gov, and now the tail is wagging and no amount of tweaking the gains or anything else will help. Heli flew fine, rpms sounded consistant, but the tail would not settle down. Looked at in-flight amps and they were bouncing around at the same rate as the tail wag. Got rid of the Gov and everything is fine again, amps steady.

I never would have suspected the Gov could cause that kind of problem in a steady hover, but it did. Maybe that helps....

[Jerrymac]

This might be totally unrelated to your problem, but since you said it was a Hurricane I thought I would mention it.
I am aware of several cases that people were having vibs at higher head speeds, but not lower ones. They too spent lots of time fooling with the tail, but that wasn't the problem. What they found was that the screws that hold the front gear/hub together, and in a couple cases the rear gear/ hub became slightly loose, and caused some pretty bad vibs at higher head speeds. Might be worth checking if all the work you are doing on the tail doesn't solve the problem.