Need Help: Vibration, Head Speed, and Collective Pitch

[iceman_215]

Greetings everyone!

About a month ago, I finally decided to jump into the world of RC. And not just any RC, I opted to start with RC Heli, which is (as most say) quite a challenging genre of RC.

I just had my first crash. Hehehe. Not a bad crash, but it was enough to break the landing skid, bend the main shaft and broke the main rotor blade (woodies). I thought that was it. But when I replaced the broken/bent parts, I got this crazy vibration. I tried the best I can, check the screws and balanced everything. I managed to reduce the vibration to an acceptable level, but still a bit noticeable while flying and the gyro wanders away. It’s driving me nuts. Luckily I love challenges, so I’m not going to give up on this. I realized that in the world of RC Aircraft, we have to master two professions--- being an aircraft engineer/mechanic and pilot. Sweet! Challenging!

Any of you experienced pilots out there have any kind advice to this newbie? Anyone had the same experience with the MT? Please...

I’ve been wondering about the effective steps in order to track down the sources of vibrations. I also have questions on the effects of Head Speed and Pitch Angle (throttle and pitch curves). Will it affect stability and handling? Any of you guys have something to say on this? Any advice would definitely help.

My setup:
Since I’m a newbie, I’ve been flying on entirely stock parts.
Heli: TT miniTitan E325 (stock)
Gyro: TG6100M (stock) --- should I get a better gyro?
Servo: Hitec HS65HB (cyclic)
Radio: JR Propo DSX7 & RD721

Thank you very much! Good Luck to me…

[misato]

Since you mentioned broken blades and bent main shaft.

Its like the feathering shaft damaged and usually it will induce low speed vibration, the most visible effect would be chicken dancing (violent enough a vibration to cause the heli to jump around on its skid) on spool up/down.

On your tail not holding well (gyro wandering away?), have you check that the boom is straight and not bent slightly? Is the auto-rotation gear (the smaller main gear) or the tail gear in good condition with no visible damage? A slightly bent tail rotor shaft, thought not visible to the naked eye can cause such unwanted vibrations as well. The last item is to recheck on the centering of the tail rotor to ensure the pitch of the tail rotor is at the manual recommended angle.

Another question: Are you still on the training skid? If yes, that can also induce unwanted vibration as it will resonate with your heli own vibration and amplify it.

On the gyro... if you can afford a better one.. why not. Meanwhile, I believe your current one is still sufficient for beginner training.

[erwinseow]

Did you replace the spindle shaft? Normally, when the main shaft gets bent, so does the spindle shaft. Some also call this the feathering shaft. Also check you tail whether its been damaged. Hope this helps.

[iceman_215]

Yup! On training skid...

I replaced...

1. Main Shaft... its was visibly bent.
2. Feathering Shaft and the dampeners... Yup, it was chiken dancing...
3. Main Rotor Head... Some kinda deformed..
4. Tail Boom... its was slightly bent...
5. Main rotor gear... its was kinda wobbling... is this normal...???
6. Tail autorotate gear...
7. Landing Skid... well, evidently it was broken...

So far, I haven't touched the tail rotor... as the vibration was low frequency, during spool up around 20% throttle...
Hmm...

Maybe I'm missing out the tail rotor... I'll recheck.

Do I need to balance the training skid...? as it does amplify the vibration when in flight...

[Niven]

For your case... check in order...

1) tail rotor shaft
2) did any of your servo gear strip?
3) ensure the blades are tracking
4) flybar straight?
5) did you turn your belt correctly? meaning it should be 90 degress onli... u turn 270 it will cause binding...

still got vibration?
1) balance your blade
2) turn ur heli blades with your hands... everything should be smooth and not binding...
3) remove ur blades and paddles.... power your ur heli slowly and carefully...
4) no vibration? add paddles... no vibration? then u add blades confirm no vibration... provided your blades are well-balanced...
5) all else fail... go down to funfly and ask ppl to check for you... sometimes its easier to spot the faults by a pair of experienced eyes...

hope that helps... dun worry... it takes time to learn how to tune a heli...

[feudallordcult]

ah, the MT, my all-time fave 450 bird other than the beam

well, appears from yr writing that the crash was pretty bad. insofar that I can recall, causes of chicken dance can be many. main culprit as listed by all the senior brothers. if yr budget allows it, upgrade gyro to gy401(outdated but still good) and main rotorhead to cnc. although the stock plastic ones are of good quality, there is just no telling what others part could have been damaged from the crash.

Instead of looking crashes as a waste of money, take it as an opportunity to upgrade...from the wise words of ken.

[iceman_215]

Thank you Bro's...

Thank you very much for the replies Bro's...

Daddy Hobby is the best...

Now I have a much clearer insight what to do next... This is very helpful!
I may have to prepare my wallet for this... hehehehe...

[DK Yong]

ah, the MT, my all-time fave 450 bird other than the beam

well, appears from yr writing that the crash was pretty bad. insofar that I can recall, causes of chicken dance can be many. main culprit as listed by all the senior brothers. if yr budget allows it, upgrade gyro to gy401(outdated but still good) and main rotorhead to cnc. although the stock plastic ones are of good quality, there is just no telling what others part could have been damaged from the crash.

Instead of looking crashes as a waste of money, take it as an opportunity to upgrade...from the wise words of ken.

bro i miss my mt ;x minititan is really gd !

[misato]

I replaced...

1. Main Shaft... its was visibly bent.
2. Feathering Shaft and the dampeners... Yup, it was chiken dancing...
3. Main Rotor Head... Some kinda deformed..
4. Tail Boom... its was slightly bent...
5. Main rotor gear... its was kinda wobbling... is this normal...???
6. Tail autorotate gear...
7. Landing Skid... well, evidently it was broken...

So far, I haven't touched the tail rotor... as the vibration was low frequency, during spool up around 20% throttle...
Hmm...

Maybe I'm missing out the tail rotor... I'll recheck.

Do I need to balance the training skid...? as it does amplify the vibration when in flight...

Since yours is the full plastic rotor head assembly, the main rotor hub, flybar seesaw hub and flybar rod are usual suspects for being distorted after a crash. Check the main rotor grip as well for damages.

While your at it, if you can weight your main blades and make sure their weight is not off by too much as a unbalanced blade can cause vibrations as well.

One of the last detail to take note of is the tightness of the main blades when assembled onto the grips. It should be just tight enough that it does not move under its own weight and lose enough that to move on the grip. This applies to the tail blade as well. Needless to say, both blades must be of equal tightness, else bad vibration will occurs as well.

[feudallordcult]

Since yours is the full plastic rotor head assembly, the main rotor hub, flybar seesaw hub and flybar rod are usual suspects for being distorted after a crash. Check the main rotor grip as well for damages.

While your at it, if you can weight your main blades and make sure their weight is not off by too much as a unbalanced blade can cause vibrations as well.

One of the last detail to take note of is the tightness of the main blades when assembled onto the grips. It should be just tight enough that it does not move under its own weight and lose enough that to move on the grip. This applies to the tail blade as well. Needless to say, both blades must be of equal tightness, else bad vibration will occurs as well.

+1. most well-said.

[iceman_215]

Since yours is the full plastic rotor head assembly, the main rotor hub, flybar seesaw hub and flybar rod are usual suspects for being distorted after a crash. Check the main rotor grip as well for damages.

While your at it, if you can weight your main blades and make sure their weight is not off by too much as a unbalanced blade can cause vibrations as well.

One of the last detail to take note of is the tightness of the main blades when assembled onto the grips. It should be just tight enough that it does not move under its own weight and lose enough that to move on the grip. This applies to the tail blade as well. Needless to say, both blades must be of equal tightness, else bad vibration will occurs as well.

I replaced almost all the parts in the main rotor, except the flybar seesaw hub... hmm... I'll check if its deformed or something.

Do I need to replace the blade grip as well...? Do they have the tendency to deform after a crash? hm... I have doubts they don't rotate on the same plane anymore. I can observe the blades are out of track even with just very slow rotation... say 100 rpm. Hehe... sounds odd... I believe out of tracking blades shows up when spooled up to say 1500 rpm, when the heli gets light on the skid...

Thanks again for the info... good stuff... very helpful... now it seems i'm on the right track.

[misato]

I replaced almost all the parts in the main rotor, except the flybar seesaw hub... hmm... I'll check if its deformed or something.

Do I need to replace the blade grip as well...? Do they have the tendency to deform after a crash? hm... I have doubts they don't rotate on the same plane anymore. I can observe the blades are out of track even with just very slow rotation... say 100 rpm. Hehe... sounds odd... I believe out of tracking blades shows up when spooled up to say 1500 rpm, when the heli gets light on the skid...

Thanks again for the info... good stuff... very helpful... now it seems i'm on the right track.

You don't need 1500 rpm to have blades out of track. Re-check on your pitch of both blades to ensure they are the same at 0 degree pitch, from what you says... it does seems to be out. A quick tip on catching the pitch tuning, one turn on the lower long link rod gives (the ones that connects from seesaw to swashplate) +/- 0.5 degree pitch, one turn on the upper short link rod (the one that connects to the blade grip) gives +/- 1 degree pitch. Always try to measure pitch from the same point on the blade.

[iceman_215]

You don't need 1500 rpm to have blades out of track. Re-check on your pitch of both blades to ensure they are the same at 0 degree pitch, from what you says... it does seems to be out. A quick tip on catching the pitch tuning, one turn on the lower long link rod gives (the ones that connects from seesaw to swashplate) +/- 0.5 degree pitch, one turn on the upper short link rod (the one that connects to the blade grip) gives +/- 1 degree pitch. Always try to measure pitch from the same point on the blade.

This is very helpful...

Turn upper link gives +/- 1 degree.
Turn the lower link gives +/- 0.5 degree.

you won't find this in the manual... it's straight out from experts' experience.

thanks bro!
I'll try this one...
I'll try and update as soon as I've sorted out the cause of the vibe.

[misato]

This is very helpful...

Turn upper link gives +/- 1 degree.
Turn the lower link gives +/- 0.5 degree.

you won't find this in the manual... it's straight out from experts' experience.

thanks bro!
I'll try this one...
I'll try and update as soon as I've sorted out the cause of the vibe.

Not expert... but crashed too many times.. sorta learn all the shortcut ways of hastening the rebuild of my MT. :X

[iceman_215]

Still no Luck... hehehehe

I have already tried my best... still no luck on sorting out the vibe...

I have balanced everything... Blades, pitch (tracking ok now), made sure all screws and bolts tight, etc... replaced the gyro...

But anyway... I'll keep trying.

I have a few suspects though...

The main drive gear... there's some significant wobble in it. will this cause a vibe..?

The main shaft ball bearing... there's some little microscopic horizontal play on it. Took out the whole rotor head assembly and let it spin. It has some very small vibe in it, like its some sort of bent in the microscopic scale. Putting on the whole rotor assembly and putting in the paddles and the blades, is this vibe amplified...?

Its unforgiving... but i'm not ready to give up yet... the cost of my repairs so far have reached the price of a new kit... hehehehe

I'll try replacing the bearings... if still no luck, then I'll get a new kit.