X5-lite tail driving me BONKERS

[Integrity Handywork]

Originally Posted by sp00fman

Thanks for all the input!

For the time being im completely broke. The >$50 CNC hub is just too much. I have seen plenty of hard 3d videos of the stock hurri with the plastic tailcase, I just cant imagine it is the cause of it all. It locks together tightly and is nice hard plastic.
Torque-tube is not an option on the plastic frame.

I'm just waiting out on my HK shipment of the CNC trex grips + trex550 tailblades. Its clone parts so at least no align logos on it

Shipped yesterday so 2 more weeks. In the meanwhile i will check all bearings again, and see if the thing does in fact still run smooth without tailblades.

I hear you man. It's hard to spend so much money on something like that. Verify the vibes with blades off and then try the new blades and stuff you ordered. I know how frustrating things like this can be. But i'm sure once you figure it out you'll slap yourself in the face and say "OHHHH". Then continue flying from then on, hopefully problem free.


Good luck! Hope the align parts work out for you.

[spykez]

Gee, I wonder if you're just better off converting the thing to TT. My vbar is happy as larry with the stock FES kit (ie plastic grips and not the full cnc tail case like I think the formula may ship with).

The TT is stronger than I thought. I landed on a patch of grass on monday (unpowered), missed the clearing I made in the field for it and I feared the worse but she was fine. Nevertheless I don't want to do it again.

I don't know what the belted tail case is like. Is it plastic like msh? Now, I found with the mini protos, you can clamp down on the tail case bolts till they are tight but on the protos, if too tight, somehow the tail shaft bearings in the tail case don't like that at all. Sometimes the idler pulley and/or bearing can get pinched as well. Causing tail vibes (I could see it on the vbar spectrum analyser). Could this be the source of your troubles?

I don't know if your grips or actual tail shaft is the issue - my sample of one (plastic) is very good indeed. Worked perfect from the get go, whereas I had to do a little bit of work to get my protos tail right. I am using the outer grub screw recesses.

edit: lol, did not see your pics. Sorry. So no TT option, eh? Maybe play around withe the tail case bolts and idler pulley there. Maybe snug is good enough vs clamped down. Worth a try I guess

[sp00fman]

Thanks, I will try to loosen up the bolts a little when i rebuild the tail part again.
I did some spoolups without the tailbub yesterday. I still have the belt too tight. it does not spin freely and have to force it over every belt teeth like turning a brushless motor by hand. Checked the pulley bearings and they are fine. Tail pulley gearmesh is good also, no tight spots..

Further examination showed the tailshaft spins off-center for its entire length. I touched a sharpie lightly to the spinning shaft at different spots, and the line it leaves is broken on the same side of the shaft. Seems a bearing is off center or the bearing not glued on the shaft evenly.... Rebuild time... here we go again!

Thank god i can fly my miniP in the meanwhile.


Edit: any harm in trying without the idler pulley?

[spykez]

I dunno sp00f, the idler pulley is there by design usually because without it, the belt will either rub against the tail case (tail shaft pulley size) or jump off the tail shaft pulley. X5 lite case specifically not sure about outcome. Could take a look I guess, there's always a chance it isn't needed.

[sp00fman]

So i took a few weeks break from tinkering on this heli and tried again today.

Turns out Trex500 grips wont fit, no biggy. It did not come with thrustbearings anyway and was cheap. Perhaps i misread a previous post and should have gotten the trex550 grips, or just got the wrong version?

Well, did away with the idler pulley, new shaft and new bearings and it at least runs true. No vibrations with tailgrips installed, so screwed on the tailblades ......and vibration is back. Tried the trex550 tailblades i ordered with it with same result.

Im completely puzzled again. Next focus is on rebuilding the tailhub&grip assembly again, perhaps playing around with a shim on one of the sides to see if it improves.

Worst case scenario is having to give up and keep it for spare parts for the almost duplicate 425mm bladed one that runs fine..... Will have to save up for some other heli kit to try again in the bigger heli class.

[sp00fman]

Another evening tinkering after a few packs on my 450 nightheli.

Took a new tailhub and replaced the bearings in the X5 pastic grips. made sure the grips are solid on the hub without making the bearings crunchy. It is tighter than before so not as free moving as it was, but still feels the grips turn on smooth bearings. The small amount of friction is minimal compared to the forces on the spinning tail. The slider does jump to center when spooled up.

I dare not say it out loud, but i think i nailed it.

I can spool up to 100% throttle and no vibes to be found. There is one resonance area when spooling up but does not feel that bad. The bearings i removed feel smooth, but perhaps there is a weight difference between them messing up my heli.

To top off my build i made the trex 550 extended tailfin to size and put it on. Now have 4cm ground clearance instead of 1cm. Dont feel like accidentaly bumping the tailrotor on the ground when i go for a test flight.

AUW with 3000 6s lipo = 2180g.
Hopefully pretty close to the X5 i actually want this heli to mimic

[mverhorst]

[sp00fman]

Bleh , test flight not so good. Vertical tailfin showing the vibrations still present on the tail.

One grip has a really small play around the outer bearing while the other has the bearing seated more tight.

Ordered X5 metal tailgrips to try......

[tolenca]

Sp00fman, I think the problem I had with my hurricane is the same you have. I changed everything, even the motor, and for some reason I never could get rid off high tail vibration after 1800-1900 rpm main head speed. I was so frustrated.
The only way I found to enjoy my hurricane was upgrading to 550 main blades. Of course i had to upgrade the tail boom and belt. Head speed governed to 1800 rpm and bingo.

Tolenca.

[sp00fman]

Darn, that's not so good to hear.
Already have the longest boom but with 520mm blades. I expect i wont like 1800rpm that much. The tail is mushy at that speed and even with 550mm blades i expect it to fly way to mellow for my taste. The other one i have with 425 blades is a powermonster at 2800 rpm, but heavy for its bladesize. If the 550 just lacks power compared to it i wont enjoy it.

I really hope the tailbelt is not causing all this. Could it start vibrating like a guitar string?, or perhaps ride up on the pulley sides when loaded up? The belt does move to one side on the pulley bucause there are no guides except for the pulley flanges.


Oh well, tail parts will arrive tomorrow.
After this i'm done pouring money in it. .... well, perhaps. The heli just looks too darn cool to keep hanging on the wall.

[tolenca]

Part of the sound when I had the vibration was the belt touching the boom. However I think that was induced by the vibration and not the source of the problem. I changed the belt two times and also related parts
I really hope you find the problem when new parts arrive.

I love the Hurricane 425 concept.

[DL126]

I have the same thing going on with a FES TT version guys.

I've even installed the X version tail box and the CNC rotor.
Vertical fin still vibrates like the aforementioned guitar string.
I dunno what to try next but I'll keep plugging away at it.

P.S.
I'm using a red main gear.
I have 3 of them, and every damn one of them wobble when installed.
What's up with that???

[Luvmyhelis]

Hmm, lets back up here and take a closer look at what you are playing with. My guess is that it is in the grip assy.

Here are some of the basics of clearing out tail issues. Those not already mentioned. After of coarse making sure the tail hub itself is supporting the tail shaft at a true 90deg.

1. Tail shaft play. This comes from quite a few different areas. One, you already covered but it is worth mentioning. Making sure the OD of the tail shaft matches the ID of the support bearings and there is very little to no side to side or shaft wobble.

2. Make sure the slider hub doesn't have sketchy bearings in it also. I have seen some that wobble and are grainy. Even a few that have the bearings seated at an angle.

3. The tail gear itself has to rotate concentrically (not out of round or wobble) on the tail shaft itself.

4. The tail shaft support bearings have to have very little play, and also be tight in the frame/tail hub. Higher abec quality really helps here, especially on the inside support bearing closest to the slider assy. Anything even slightly grainy feeling or one having too much shaft play when you hold it on a tight fitting ID/OD shaft fitting. Meaning the shaft can still wag axially when you have the bearing installed on a spare tail shaft without it being installed into the frame. So if you hold a tail shaft by itself. Then slide the tail shaft support bearing over it. You want to see almost no tail shaft wag, either from the mating surfaces or the actual bearing play.

5. I mic out my tail grip bearings. Each one has to exactly match the one on the opposite grip in thickness. As do the thrust bearings. In cases where I am chasing vibes I also weigh both grips bearing sets against each other. Also the grips themselves, bare then assembled.

6. On plastic molded grips there occurs from time to time what they call core shift. Where the bearing seats aren't even from grip to grip. If you have a mic, inside depth check each tail grip to insure the bearings on each are seated identically. Or one grip will be seated out farther than the other on the tail hub. Throwing the grip assy off balance.

7. Grip wag. This is critical. And why I use Abec 7 bearings in all my tail grips myself when I run into problems. If one grip wags out against the farthest grip slop angle than the other. It will produce more thrust than the tighter one on the opposite side. Pushing the tail shaft into a wag. HUGE vibes will result. This is my response to idiots telling me grip slop isn't a big deal.

8. Next, check the assembled tail grip assy. off your tail shaft. Remove the tail blades. And rotate the center hub by using an allen driver on one end through the grip mount bolt itself. Hold the grips themselves so the grip arms are even to each other while doing this. This tells you if the hub is rotating true and it isn't bent. If one grip wags while spinning the hub. The hub has one of its grip pins bent.

9. Now, for the grip hub itself. I use my mic and make sure each grip pin is equal from the tail shaft hole. I have run across quite a few that have been machined incorrectly. So one grip seats out farther than the other. If this measurement is off at all. Either file down the hub to equal each side or toss it. Keep in mind, some manufacturers also drill the tail shaft hole off center! Align is famous for this. It also has to have the correct OD on the pins and ID on the tail shaft hole or they will have a sloppy fit.
If all this looks good, then the hub is ok.

10. Now check the grip hub bolts! They have to be identical to each other. Same weight, size and length.

11. Next, lets take a look at the slider Y arm. If one side of the Y is not equal to the other, it will also throw off the grip angles. Producing the same effect as a sloppy grip! Both Y arms must be exactly equal and at the same angle off the shaft. I have also seen the slider hole drilled off angle that the brass slider itself threads into, and Y arms bent or plastics have shifted. Making the Y arm produce horrid grip tracking.

12. Look at the grip bolt assemblies that hold the blades in the grips. They too must be identical.

13. Next, hang your blades! Find a small tail shaft or bolt and make sure each grip is identical to the other from the grip hole to the end. I just had a Sab tail blade that had its grip hole off by a full 2.5mm. Weigh the blades, they must be identical. And they must balance identically. Plastic blades also have to have the same identical profile. I have seen core shift on factory blades that produce blades with unequal profiles.

14. Then balance the grip assy after it is assembled. No blades yet. If it balances (I use a Dubro here) then add the blades and balance it again if the blades have passed muster. I also Koll balance my tail blades on anything over a 550. It makes a difference.

These are just the additional basics for making sure the tail assy is good. I could post a very in depth tail novel here, but I am trying to hit the basics so you can find whatever it is quickly.

Hope this helps! LMH

[sp00fman]

Thanks for the input!
Shame i have to do with digital calipers. Dont have a micro.

I have done a lot of testing with the new CNC grip assembly. Neighbors must be getting annoyed by now, me spinning up the thing all the time.

#8 is a really good one and been using that before. None of my Gaui tailhubs seem to be off, nor prone to get bend. Its hard to say if the hole is drilled correctly. Can overtightening the grubscrews cause it to get bend? Just asking.

I think i have to take a step back again. i have some play on the tailshaft now, but only in the lengthwise direction of the tailboom (not sure i make sense now). If i take the tip of the shaft between my fingers and push it to the front of the heli and back, it rocks. I can feel the belt tension giving a bit of resistance one way. The up/down movement is zero... mush be the bearing holders in the tailcase being a bit oval. cant explain otherwise why there is no up.down play.

I thought about the unevenness of blade pitch and perhaps the slider causing it, so i ran the assembly without the slider. With and without tailblades. Once spooled up the blades just track in 0-pitch, because of the tennis racket effect. Still vibes occur once i reach target RPM. Attempted to put shims on one side of the hub before installing the grip, but not found a solution there. Played around with tracking tape but did not find a balance point.


I have not found a bearing that is really snug on any of my tailshafts. If anyone knows a technique to fix the shaft exactly in the bearing center i would love to know. Loctite will just not fill the gap between bearing and shaft evenly enough, causing the shaft to spin off-center.


By the way, something to note about switching from plastic to metal tailgrips, the metal ones dont have offset grip arms for build in counter-torque blade pitch. Also the heavier material makes the force needed to change the bladepitch a lot more(it is not binding!). The metal grips are a few mm shorter also, giving a smaller disksize.
-just details, not really problems

Ill reassemble my spare tailcase and will try everything again later.

Things to sort out:
1 - a way to see if the tailpulley is spinning centerted / and a way too see of the belt is behaving on the pulley when spooled up and under some force

2- see if i can figure out which direction my vibrations are going. I plan to glue a little mirror on the tailcase and shine a laserpointer on it. Perhaps the reflected beam shining on a wall further away will give some clues. perhaps the vibration is rotational, or mostly in one direction in one of the 3 axis.

[cafediablo_30]

This may or may not be a solution to ur particular problem..but after trouble shooting endlesly for vibes i was experirncing i came across this.

The pinion on th motor had play and was slipping ...not much at all...just a tiny back and forth movement...almost un noticeable.

Red main gear...16t pinion..i tried red locktight and tightening as much as posible...but didnt work.

Switched to the slant gear(which is bigger in diameter) and slant pinion...also bigger...and had no slack.

Now ir flys smooth..

Good luck with ur fix....take care stay safe.

[DL126]

Yesterday, I installed a new boom/TT assembly.
Pulled the bearing from the old TT and installed it on the new one to have 2 inside the boom.
Vertical fin vibes still there. (Although maybe not quite as bad as before.)

At one point, I pulled the tail boom out far enough to disengage the drive gears.
Spooled it up with no main blades, and TT not turning.
Vertical fin was still shaking a bit.
Obviously at least part of it is coming from the head as cafediablo_30 mentions above.

Edit: For future reading of this thread, I should mention that the heli flies with no problems considering my limited skills. It's just annoying to see that tail fin vibrating to point of looking like it's 1/2" thick.

[sp00fman]

One thing i learned from my cheap clones over the years is not to fly with hard vibrations like you have on your tailfin. It will quickly wear out certain parts and something will eventually fail prematurely.

[DL126]

Originally Posted by sp00fman

One thing i learned from my cheap clones over the years is not to fly with hard vibrations like you have on your tailfin. It will quickly wear out certain parts and something will eventually fail prematurely.

You ever make any progress with yours?

Yesterday I removed the motor, oiled bearings, and adjusted gear mesh.
Seemed to have helped a bit on the bench with no blades.
Raining so I can't take it outside for a good check.

[sp00fman]

Still working on it. Just got the other tailbox installed again with the glued on bearings on the shaft. Now with the metal tailgrips and t550 tailblades. LowRPM spoolup did seem workable, but wife and kid were asleep so did not continue with ID1 and ID2 speeds.
The sound of this thing just travels through concrete somehow.

I have constructed a backup plan. I am sourcing some 5mm dia nitrated ejector pins. These are supposed to be precise diameter and super straight, and the coating low friction and wear resistant (perfect for the tailslider).
My only tools being a dremel and a hacksaw, i have to find someone willing to risk his drill-bits to drill me some holes for cheap. That gotta be the hard part. (finding that person)

[RedOctobyr]

Wow, cool plan I *believe* that the nitriding would be just a surface hardness treatment; that is, that beyond the nitriding, the steel wouldn't be as hard.

You might try Dremeling a flat where you want the hole (and maybe where it would exit?). That would get through the coating, and would also provide a flat for the drill, so it wouldn't want to just walk off the cylindrical surface.