Strange vibration on a particular RPM when I do blade tracking.

[Kostya]

Hi,

I was trying to adjust blade tracking on Esky Belt CP v2. So I was holding a heli with my hand on the desk. The I started to spin it up.
When it reaches particular RPM (about 30% of the throttle, i.e. 1/3 of the throttle stick) the whole heli started to shake.
If add some more throttle (probably up to 1/2 of the stick or a bit more) it's starting to spin smoothly.

I did it 3 times (I mean spin up, then spin down and stop, then spin up again and etc.) And it does the same every time.

So I am not sure if it's normal or it's a problem.

I haven't tried to fly it yet. I am going to make sure everything is fine before.
Thank you for your help.

[arbilab]

It's a resonant imbalance. Car tires do the same thing, shake at a certain speed but not much below or above that. Most likely blades, as little else on the rotor has the moment (distance from center) to do that. Flybar is also suspect.

See 'blade and flybar balancing' for a better discussion of how to do that than I could give you.

[grnbrg]

Hi,

I was trying to adjust blade tracking on Esky Belt CP v2. So I was holding a heli with my hand on the desk. The I started to spin it up.
When it reaches particular RPM (about 30% of the throttle, i.e. 1/3 of the throttle stick) the whole heli started to shake.
If add some more throttle (probably up to 1/2 of the stick or a bit more) it's starting to spin smoothly.

I did it 3 times (I mean spin up, then spin down and stop, then spin up again and etc.) And it does the same every time.

So I am not sure if it's normal or it's a problem.

I haven't tried to fly it yet. I am going to make sure everything is fine before.
Thank you for your help.That's not unusual.

If you're as new as the question suggests, you should probably put in a couple of hours with a flight simulator before you go any farther with the Belt. CP helis are crazy-difficult to fly....

(It's normal for it to want to scoot left as you take off, too.)


grnbrg.

[jasmine2501]

Yup, always balance before working on tracking - poor balance can throw off the tracking.

http://vimeo.com/1815691

[bwalt822]

you when the revs per second of the blades reach the natural frequency of the helicopter you will get these vibrations. This is true for any object.

Something is slightly unbalanced.

[Kostya]

See 'blade and flybar balancing' for a better discussion of how to do that than I could give you.

Thanks. I will have a look.

[Kostya]

If you're as new as the question suggests, you should probably put in a couple of hours with a flight simulator before you go any farther with the Belt. CP helis are crazy-difficult to fly....

(It's normal for it to want to scoot left as you take off, too.)


I would say I am not just new - I am brand brand new. :) That's why I am posting into Beginner Training Area. :)
So I am sorry if my questions is sort of "everyone know it"...
Esky manual is just a parts catalog. :) Looks like they are interested in our crashes only. :)
I spent some time reading forums. But I still have some questions left.

I did spend some time with a simulator as well. I know it's hard. Even simulator is not simple. :)
And I know about drifting left at the take off.

Thank you for the warnings.

[Kostya]

Yup, always balance before working on tracking - poor balance can throw off the tracking.

Thank you for the link.

[Kostya]

you when the revs per second of the blades reach the natural frequency of the helicopter you will get these vibrations. This is true for any object.

Something is slightly unbalanced.

That's what I am wondering about...
I know I need to try to get a maximum balance. But is it possible to get a vibration free heli? :) I know it's not a ideal steel ball in a vacuum. :)
Where is the point at which I should stop trying to tweak it...?

[grnbrg]

I would say I am not just new - I am brand brand new. :) That's why I am posting into Beginner Training Area. :)
So I am sorry if my questions is sort of "everyone know it"...
Esky manual is just a parts catalog. :) Looks like they are interested in our crashes only. :)
I spent some time reading forums. But I still have some questions left.

I did spend some time with a simulator as well. I know it's hard. Even simulator is not simple. :)
And I know about drifting left at the take off.Sorry if I was a little cranky this morning... :o

What sim are you using? If it's FMS, it won't be helping much, and there are better (free) alternatives.


grnbrg.

[jasmine2501]

It's not an "everyone knows this" question - I just didn't feel like boring you with physics and a long explanation, when it's a simple answer you need. Just follow the balancing procedure and see if that helps. If not, then you have eliminated one variable, and we can look at other things. I don't think it's possible to completely eliminate all vibrations, but you can get it pretty smooth.

[arbilab]

'Real' helicopters vibrate. They go to extensive design solutions to minimize it, but it still happens. One thing they do is put resonances away from the nominal rotor speed, so the vibration speed never happens except maybe during runup. You don't have that exotic option with a model.

About the only 'dumb' question here would be, "will it work underwater?". All the literature is deliberately misleading and vague. Most of the manuals are vague, if not almost blank. It helps to know the outline of heli physics going in, just to know the terms if nothing else. Models of course, are nowhere near as thoroughly engineered as 'real' ones though, and they're left with rough edges both from design and from haphazard manufacturing.

In a way, RTF means "ready to futz with". None of these gizmos works perfectly out of the box, not for long anyway. And you've already found, the vendor's documentation won't help worth a fart in a hurricane. Might be why this is one of the most active product-user's forum on the net.

[Kostya]

Thank you guys for your great support.

I have read that people saying about vibration caused by flybar ...
Well... I took my off and try to roll it over the glass (like I did for the main shaft).
And my flybar is a bit bent. It's quite weak (2 mm rod) so I was trying to make it straight. But didn't make much progress there. :) It looks straight. But when you try to roll it over the glass it's still a bit bent.

Probably I am worrying to much. :)
Probably I just need to stop worrying and start flying. :)

[Balr14]

A bent flybar is something that should be addressed.

[nasukaren]

And my flybar is a bit bent. It's quite weak (2 mm rod) so I was trying to make it straight. But didn't make much progress there. :) It looks straight. But when you try to roll it over the glass it's still a bit bent.

Definitely fix this.

Have you thought about the CopterX head + tail mod? It's only USD $50 + shipping and in my experience, gives you much much better performance and stability. For me, it was night and day difference with my Belt CP (and I'm just a n0000b). The added benefit is that replacement parts are all Trex 450 SE V2 compatible, which means tougher flybars and feathering shafts.

Here's my modded bird:

http://www.youtube.com/watch?v=hj-ytpMzksc

I usually hang out on the beltcp forum on h?l?freak, so find me there!

karen

[Kostya]

I will try.
Thank you for the advice, I will check Copter X head.