300X - the HOW TO GET RID OF VIBRATIONS tread

[SHYguy]

Originally Posted by Epoweredrc

Oh.. well that stinks, so if its able to move back and forth would that mean our belts are too loose?

Don't seem like it. I've tried with very tight, medium and loose belt. No difference.

It looks to me as it's coming from the belt moving up and down on the center gear (I use the Lynx alu with one-way).

I'll see if I can stop this behavior by making a new roller, maybe with a guide...

Then again my vibrations may not be from this... might be tail grip/rotor imbalance...

Anyone converted a 300X or 450X to torque tube btw???

[Uriah]

My belts wander around a little bit. They don't do it too much but it's enough to notice. When you think about it, the belt is twisted 90 degrees in the tail boom in order to go from the horizontal gear to the vertical gear, so I guess you could say a little wandering is expected. I never really paid much attention to it to care, since I do my tail vibe checks at full load without the main blades on. I tried grabbing some video but I couldn't get the camera to focus on it.



Regardless, if you feel it's wandering around too much, trying another belt certainly couldn't hurt anything.

[SHYguy]

Originally Posted by Uriah

My belts wander around a little bit. They don't do it too much but it's enough to notice. When you think about it, the belt is twisted 90 degrees in the tail boom in order to go from the horizontal gear to the vertical gear, so I guess you could say a little wandering is expected. I never really paid much attention to it to care, since I do my tail vibe checks at full load without the main blades on. I tried grabbing some video but I couldn't get the camera to focus on it.

Agreed, it's always been like that. But now on mine it just seems WAY too pronounced

AND I have some SERIOUS tail way to rid...

[Epoweredrc]

Don't know if i have tail wag or not, not been able to fly mine yet cause of a bad motor causing vibration on entire heli.

[zquez50]

Guys, I have been doing a lot of reading on this 300x vibes and I have fixed my vibes and no more roll of death.I have the lynx ultra dfc head and ultra tail system with the extended boom and 275 mm mains and the cf stiffner. I was getting bad vibes even after balancing both main and tail blades and with all the new upgrades.I have figured out that most of the issues have to do with the plastic frame, so instead of buying new bearings and other upgrades I decided to do the hot glue that was talked about at the beginning of this thread but took it a little further.I hot glued the inside of the frame all around even under and around the landing gear and I also used some of that lynx omicron pieces on the cf frame stiffner where it touches the plastic frame or very close to touching because I think that was also causing vibes.Once I did all that I lowered my throttle to no more than 78 % and my I also use double of that lynx omicron on my beastx and I have no more vibes at all! My carbon tail does not vibrate a bit, not even on spool up and no more death rolls.I did not mess with the settings on the beastx just made sure my blades were balanced and the hot glue and it solved my problems.I don't know how to upload a picture otherwise I would for everyone to see.I hope this helps some or all of you.I will be getting the Lynx cf frame next so I won't have to worry about any vibes period.

[thruster]

My heli hovers fine with no apparent vibrations. Even so, I wanted to see if I could improve the tail hub/blade balance. There is a minor short slow wag trying to fix. So I removed the main blades and ran the motor looking close at the tail hub for any sign of vibration while holding the heli steady on the bench. The tail spins very smooth at all speeds, can not see any vibrations. I would have tried a small amount of tape to balance......but not seeing any problem.

BUT.....when moving the tail from side to side, as the tail blade pitch increases near the limit with tail moving right (nose to left) there begins to be a harsh vibration as the pitch slider gets to within about 1/8th inch or so from the limit of travel. Then when moving the tail in the opposite direction...tail left (nose right) same thing except the vibration is much less but still some.

When I'm hovering and use the rudder I never experience this harshness or vibration. Does this sound normal? Maybe running with the main blades removed allows faster rotation speeds or some unusual dynamic?

[Nelsonisms]

Every time I've had tail wagging issues it's invariably boiled down to a problematic tail servo.

The question I would ask is if the vibration is being caused by something mechanical or is it the servo struggling to fight against the torque of you moving the tail by hand. I guess I haven't done that (spool up with just the tail blades attached) with a BeastX equipped heli in a while so I'm not sure how normal that is. I'd say if the mechanics move smoothly without any binding by hand it's probably not a big deal.

[thruster]

Originally Posted by Nelsonisms

Every time I've had tail wagging issues it's invariably boiled down to a problematic tail servo.

The question I would ask is if the vibration is being caused by something mechanical or is it the servo struggling to fight against the torque of you moving the tail by hand. I guess I haven't done that (spool up with just the tail blades attached) with a BeastX equipped heli in a while so I'm not sure how normal that is. I'd say if the mechanics move smoothly without any binding by hand it's probably not a big deal.

Reading your response made me realize I was really forcing the tail movement against the push of the tail blade thrust, probably in a forceful way that would not happen while flying, because the heli would follow easily into line with the thrust and not fight it like I was doing. Yes I think that's it. There is no binding.

[bobbygz]

I was seriously hoping I wouldn't be here again but here I am! Just spent 4 hours trying to troubleshoot this dang wicked tail vibe. Without tail blades, she runs as smooth as a 300 can run. With tail blades (and I've tried 3 different sets, two cf and one plastic) from about 25-30% throttle, you can see the vertical fin going crazy and it gets worse up the throttle curve as it actually bogs down the motor. Motor mesh is also spot on.. I've always been able to fix with electrical tape on one blade through trial/error but after 4 hours I'm calling it a night. Everything is straight from tail shaft to hub to the main shaft......belt is just the right tension and I even tried loosening it all the way till it skipped with a little force......no differnce. Thank God for the 450 otherwise I'd really be hating it. Also have the Lynx frame brace and she's as rigid as heck. Can't work tomorrow due to 8-12 inches of snow forcasted so hopefully with a fresh start and a whole day to look over it.....this gets really frustrating to the point I can only laugh about it to keep from throwing it against a brick wall

[thruster]

Bobby, I had really bad tail vibes a year ago with my original 300x. Ended up getting a Tarot 450 alloy tail hub which helped greatly. But I also had to replace the tail shaft and both bearings with a new stock shaft and some other brand of bearings. I may have replaced the pitch slider as well. Mine has been great ever since that major overhaul.

Maybe take a close look and see if the gaps between the grip and hub is exactly the same on both. Sometimes a thin shim between one grip and the hub can help. Just an idea......best of luck buddy!

[bobbygz]

Originally Posted by thruster

Bobby, I had really bad tail vibes a year ago with my original 300x. Ended up getting a Tarot 450 alloy tail hub which helped greatly. But I also had to replace the tail shaft and both bearings with a new stock shaft and some other brand of bearings. I may have replaced the pitch slider as well. Mine has been great ever since that major overhaul.

Maybe take a close look and see if the gaps between the grip and hub is exactly the same on both. Sometimes a thin shim between one grip and the hub can help. Just an idea......best of luck buddy!

Funny you should mention the grip to hub gap as I did notice on one grip there is the tiniest amount of space whereas the other grip has no play whatsoever. I was afraid of adding any weight to only one side but tape can balance it out if that comes into play. Thanks Thruster, I'll check that out tomorrow. I really don't want to throw any more money into it without knowing for sure if it will fix it or not....

[bobbygz]

So after another 2 hours messing with the tail (yesterday turned out to be impossible as per working on it) I finally got it so that I have a slight resonance at about 20-30% throttle, then it smoothes out and at 85%, which is my flat TC in idle up, she's smoothe and the BX is stable with no movement. Now to take her and the 450 to the field and see what she does. What a PITA! I got it to this stage just by the smallest amount of elec. tape on one tail blade up near the grip....wish there was a "fingers crossed" icon. This is the closest.....

[DoubleCH]

Originally Posted by bobbygz

Funny you should mention the grip to hub gap as I did notice on one grip there is the tiniest amount of space whereas the other grip has no play whatsoever. I was afraid of adding any weight to only one side but tape can balance it out if that comes into play. Thanks Thruster, I'll check that out tomorrow. I really don't want to throw any more money into it without knowing for sure if it will fix it or not....

Since you notice the gap difference, that's where you need to fix it and you don't need to throw money at it. First check if the extra gap results in extra radial slop on the grip. If so, reducing the gap is the way to go. Dismantle the grip assembly to see if something has worn out or bearings in wrong order. Failing that, a piece of aluminum tape on the washer will add 0.05mm thickness to reduce the gap, which will result in needing about 1/4x1/2" clear tape to dynamic-balance. And yes, 1/4" makes a big difference. If you've tried everything and there's still slight resonance at low throttle, loosen tail case bolts including tail fin bolts a bit and see if it improves.

[bobbygz]

So what I noticed today before taking her to the field was that I wasn't pulling the grip that I thought had no slop in it hard enough. Both grips have identical slop, which I'm not crazy about. I had one identical bolt washer that I added to one side, just to see how much it would improve the slop.....I would still need one more washer to completely get rid of it, and having only one and needing 2 for each grip, I just figured if they each have identical slop all would be ok. That, and I desperately wanted to get her in the air. However, when I got to the field and spooled it up and saw the vibration (same amount I had at home just around 20-30% throttle, but now we're talking putting her in the air!!) I got a sudden case of the chicken sh*ts and decided to just fly the 450. It takes every ounce of skill I can muster just to switch back to normal mode during a roll right episode... The order of what's inside the grips from the hub out is bearing, brass spacer, bearing, wide outside race washer, thrust bearing set, small bolt washer, bolt. And I double checked when I got home that all of the thrust bearing caps were correct which they were. Am I missing something? I never had that amount of slop before I'm pretty sure. Is that aluminum tape you mention heating and air duct tape? I have a roll of that. But with the amount of slop I have I'd probably be better off just ordering 4 washers. Or save the aggravation and just order the lynx, Align or Tarot hub.

[bobbygz]

Now that I think about it, is it the small bolt washer or the larger inner race washer you need to add thickness to?

[bobbygz]

I noticed on Lynx webpage with the 300x hub/grip assembly, Luca says they determined a good deal of the vibrations come from the thrust bearings, which they have completely eliminated on theirs...

[bobbygz]

Got the tail vibes to a minimum, just at 40% throttle without the mains on. At the field spooling up with the mains, which are perfectly balanced and tracked, I had so much vibration it was unbelievable. Running a Lynx main shaft/owb assembly. Guess I'll be doing a complete tear down and rebuild and see if anything is obvious. I had loosened the tail case as per suggestions so I don't know what else to do but tear it down including the head assembly. If I can't find anything and it still vibrates afterwards, I'm gonna order the lynx tail hub assembly and go from there. This sucks. At least the 450 is flying great so I'll just be grateful for that. I'll let you guys know the minute I find the problem.

[bobbygz]

As soon as I disassembled the Lynx frame brace I found the frame was split almost in two . Well, I am half Polish Impossible to see with the brace attached and the frame seemed rigid when twisting so I completely overlooked it. Totally split behind the front servo and cracked halfway on the other side. Now it makes perfect sense as to the amount of vibration I was getting as soon as the mains were attached and spinning. Thanks to all for the support and thanks Shy for this thread. Instant stress relief!!!!

[Murph_d]

Great that you found it, what a relief. I use the stock plastic frame because I' m obsessed with keeping the weight down and I don't crash much anymore, but every crash I've ever had has broken the frame somewhere. The rebuild will give you something to do while the snow melts.

[bobbygz]

So I got the main frame and rebuilt everything and lo and behold.......same wicked tail vibrations. So I break the complete tail down again and this time I noticed the spacers between the two bearings in each grip were different. One was a beveled spacer while the other one was flat. It not only made the grip not sit as tight to the hub but also possibly have a different weight......I'm curious so I'll weigh them both later and see. I had some old grip parts and found another beveled spacer and slapped it together and now I'm flying without any tape on the tail blades. The only thing I can think of is that they were from different grip lots and at one time they used the square bevel??? I have just replaced one grip in the past........