Vibration Woes

[lawrenmd]

I have a tail vibration that I cannot get rid of no matter what I do. The vibration is up and down at about the frequency of the head. The main blades balance perfectly, tail blades as well and I have tried three different types of blades, stock, 58mm carbon, and 68mm plastic full length and trimmed to 62mm. I have successfully built over a dozen machines with zero visible vibration but this thing has me stumped. I have done all the reccomended fixes to correct the problem including new carbon boom supports, tail push rod, tightening the belt, ect. If I hold the tail of the machine at zero pitch on the mains. I can feel the machine vibrate very slightly while on the ground. Based on this I adjusted the main blade tracking until there was no vibration felt, took off no vibration and tracking looked spot on, did a few flips, rolls brought it back and guess what, vibes are back. Could this be caused by these wonderful high quality main blades? I ask this because I had similar issues with my T-Rex with cheap blades and a head speed over 2800. My set up is below, any help is appreciated.

5S Set-Up

Evo 5S3700 Bats
Hacker A30-10XL
19 Tooth Pinion from Kovi, 70% thorttle @ 2700 RPM
Stock Lepton including blades.
Tail Blades as described above
Airtronics servos
GY401 W/9254
MJP carbon Vertical and Horiz fins, lower frame support, tail lift.

Thanks

[Finless]

I am going to throw this up and I have been through this myself as well as helped a few others that had the EXACT same problem.

BLADES my friend.

My first Lepton flight I had this problem. After doing EVERYTHING I could think of I finally swapped out the main blades with a firends Lepton and BAM..... Problem gone! I put my blades on another Lepton and it had vibes... I contacted MRC and sent the blades back. They sent me a new set and they were fine.

A month ago I was out at the "Buzzin the border" fun fly and another Lepton flyer had the EXACT same problem. I loaned him my blades and viola! Vibes gone!

Two weeks ago a guy came out to my local field with a new Lepton with the same problem... Gave him my set of blades... PROBLEM GONE!

Now I like you balanced and DOUBLE CHECKED balance of my blades. I was CERTAIN it was not the blades but in fact it was. To this day I still have no idea why some of the Hirobo FP blades do this and some do not. I am guessing it is CORD wise CG issues but since I sent my blades back I dont know. Jeff Green never got back to me and confirmed if they had some problem and I talked to him personally :(

Anyway after seeing this myself on 4 different Lepton and solving it with blades, I am going to reccomend trying another set of known good blades.

Bob

[lawrenmd]

Thanks Bob! This machine is brand new and never even been set down hard. It started to hit me about the blades because the first hover of the day it had no vibes, as soon as I flew some 3D, Bam, the thing shakes like crazy. I will not try another set of new Hirobo blades and take a chance of another bum set, and no one else around here is flying one so I'll have to wait (again) for some MAH or SAB's to become available.

Dave

[Finless]

Dave... MAN... this is EXCATLY the symptom.... You can go into the hover and NO vibes.... Go fly around and do some stuff and come back into the hover and BAD vibes.... Also when your flying around you know the vibes started up as you can start to hear the belt ringing in the boom.

I am not going to tell you 100% that it is the blades but what you just described is EXACTLY what I had and the others I talked about....


Bob

[lawrenmd]

Yes this very frustrating!! I hate a machine that vibrates that is why I fly high end machines. Also this vibration plays havoc on the gyro, I havent been able to get one ejoyable flight in yet because of this issue! Thanks again for your feedback I feel a little better now.

[Finless]

Dave... BTW after my last crash I got to see what is inside these blades. I am not slamming the design but inside they are mostly hollow with 2 lengths of music wire epoxied inside just ahead of the cord CG... Nothing wrong with that but I bet dollars to dognuts that the problem lies in the fact that both blades dont have the music wire running parallel up the blade thus causing lead lag issues and cord CG problems.... Just a guess but these blades are made pretty darn CHEAP for the $70 they charge for them!

As you see on this forum there are carbons coming out for this heli. At this point I highly reccomend investing in a set rather than these FP blades.... I am sure some people will FLAME me for posting that the Hirobo FP blades suck but maybe not :)

This is one of the BEST E-helis in this size range and it needs good blades!

Bob

[TMoore]

It's not just the Hirobo blades. The MS blades that I got needed correction too.

I've been using the Koll rotor Pro for years and it never lies. The MS Blades were right on chordwise but were off in the spanwise direction and this was enough to do the deed. They were shakers on the first flight but I made the correction and all is right with the force.

TM

[nogod]

i had the same problem with my lepton blades and someone suggested I losen up the blades in the grips problem gone. I think the stock shims are to soft and in flight the get pinched and don't move freely.

[Nick J]

I actually cracked lepton blades on the trailing edge because they are so weak. I pushed it pretty hard but theres no reason the blades should crack.

[hoverhobbies]

I seem to be having the same problem...
I have a new lepton just assembled, I have the ikarus cf tail blades on it, 12 turn hyperion with a 5S 3700 on the 24T pinion.
With the heli completely RTF minus main blades I can spool it up and hold it at any rpm all the way to 100% and its smooth as silk. no visible vibes and none can be felt on the tail case or boom, the head speed without main blades is over 3400 rpm and everthing is smooth.
So I bolt on the stock main blades and at almost 100% the tail vibrates so bad you would think its about to self destruct, it even spun the boom about 15 degrees or so.
I am in the same boat, I dont have an extra set of blades that size to try but it seems strange to me.....very frustrating.

[lawrenmd]

Ok maybe some new information. I installed new MAH blades (They fly great) and the vibe seemed to have gone away, wrong. What I noticed today was that there was no vibe at the beginning of the flight. Normal mild 3D stuff, still good to go. If I invert the heli and apply full pitch -11 degrees of pitch the vibration starts. After landing I moved the spindle in the head by pushing up and down on the grips, this fixed it for a few manuevers. I then took out the spindle and lubricated the heck out of it and the dampers with silicone grease. Few again with no problems. Maybe this will help? I will post more when I get few more flights in.

Dave

[hoverhobbies]

OK, I just insatlled a set of ms blades and I am getting the same results, no main blades = no vibes up to 100%, I bolt on the blades and at about 60% throttle the tail starts a low frequency up-down vibe that gets worse as I increase headspeed. I guess I will disassemble the head and lube the feathering shaft really well to see if it improves any...I was really hoping the new blades would solve the problem.