Esky Belt CP Vibration headache

[Strofio]

Hello everyone,

Recently I had a crash with my Belt CP (v1), that resulted to the usual damage: main gear was stripped, feathering shaft and flybar were bent, and the main rotor blades were destroyed. The problem is that after repairing the heli, I still have significant vibrations.

I changed all the broken parts, and I balanced both blades and flybar very accurately. I am always very precise when balancing the blades, as it is the main reason for vibrations on the rotor.

The assembly of the flybar was also done very precisely, using measuring gauge and electronic scales.

All the above said to underline that it is not possible that the blades, nor the flayer, cause the vibrations.

After careful examination, I found out than there was a very small crack on the head block housing, right where the housing of the main shaft meets the main part of the block.

After replacing the fractured head block with a new one, I was very surprised to find out that the heli was still vibrating like hell.

I then tore the hole system down, and I begun reassembling it step by step, part by part, and every time testing it out. I started by installing only the main gear and main shaft, and putting it into spin. Everything was perfect, as expected. No vibrations at all. No need to mention that during the hole process of rebuilding the rotor, the tail rotor belt was removed, to be sure that during the tests there wouldn't be any vibrations coming from the tail.

When I added the new headlock, and put the main shaft into spin, it resulted in a minor vibration. When I eyeballed it, during low speed spin, it was obvious that the top part of the head block, where the feathering shaft joint is housed, was not just spinning, but also moving in the sense of the horizontal plane.

The low amount of vibration produced was normal, due to the low spinning mass combined with the small eccentricity.

As I was adding more parts to the rotor, the vibration, as expected, was getting worse every time.

A careful examination of the new head block, lead to the conclusion that the block's eccentricity was due to the not-so-tight fit of the main shaft into the head block. It seamed like the inner diameter of the hole where the main shaft is inserted, was slightly larger than the diameter of the main shaft, resulting in a very small angular movement of the block, in accordance with the main shaft's axis.

I then decided to repair the old head block, by glueing the crack, using a very strong glue with no elasticity, because the old head block had a significantly tighter fit on the main shaft.

No luck with that either…

My conclusion is that I was very unlucky with the new head block, as it seems that I bought a faulty part. And it may be that when I tried to repair the old one, some very tiny part of the glue that entered the main shaft;w housing on the head block, causes the head block to fit on the main shaft with a slight angle.

I am thinking of buying a main rotor upgrade set, to avoid future problems with faulty - low quality - plastic parts, although I am not yet 100% sure that the head block is faulty, as I haven't yet bought a new part and repaired the helicopter.

Anyone had any similar experiences before?

Is it that common that those parts are faulty?

I have to note that I have already replaced all the parts of the rotor with new ones, except from the swash plate, that doesn't seem to have any problems at all.

Thank you for your time, and I'm looking forward to your replies.

[pizzano]

Hmmmmm....

No mention of replacing the bearings along with the new "headblock".....?

Here ya go.... try replacing all the main rotor head shaft bearings along with all bearing blocks:

http://www.xheli.com/esbeve2.html

Then if that dosen't work the next step is the checking the swashplate, belt gear assembly and motor mount for wear and fit.

Then if that dosen't do it, work your way back to the tail rotor assembly and check for wear and fit.....bearings back there wear as well and could be another source of vibration.......

If that dosen't work.....time to go to an all metal head and tail assembly......

and finally......If that dosen't work....time to get yourself a newer CCP heli...an Align (Trex) or clone will do until you stay in the air longer and off the ground replacing parts.

Edit: probably the first thing you should check...........

Forgot to mention the main shaft could be bent as well.......replace, do not try to straighten!