TREX 500 Helicopter - 05 - Vibrations - Part II - Rotor Head Assembly

[vespira]

I have an EXI-250 that is almost a 100% Trex clone. I noticed the head button was wobbling even when turning the main gear by hand. I pulled the main rotor block and found that the shaft was straight as an arrow. I then put the main rotor block onto an appropriately sized drill bit and spun it up... wobbled like mad. :/ I replaced the main rotor block with one from align and the problem was resolved. Looks like you came to the same conclusion on a bigger bird. Seems to be a design flaw.

[surfgoof]

This is a great idea for solving vibrations, if you view it frame by frame. This will help me solve my shakey head, thanks.

[archienook]

it really looks like your upper head block its not straight enough the main shaft is straight enough u can see it on the video the wobbling just start from the main head. look like you have a defective head block from the factory if this is brand new, or maybe u can ask a replacement before you replace other parts,

[xkadet]

Thanks for the input. Looks like I have some work to do myself. Best regards,

[xkadet]

did you ever resolve the problem gary? It looks like the head is drilled off axis or the tip of the main shaft is slightly bent. I would replace the head sleeve and see if this solves the problem. It means setting up everything again, but I don't see the main shaft wobbleing, just the head, and that says head sleeve to me. Either damaged or machined poorly. If you did find the problem, please let us know.

[garypuppa]

@xkadet - I purchased a new main rotor head assembly last week. I'm going to install it this weekend and provide an update.

[garypuppa]

@xkadet I replaced the main rotor block and that solved it. Check out video #6 on my YouTube channel.

Thanks

Gary

[imprint2finished]

i think its your main rotor housing that is causing all the vibration... i had the same problem before, i landed a little bit too hard one time and thats were it all started, i tried everything to make it snug fit with the shaft but no success, sometimes the problem would go away at high rpm but i just got fed up with it and i bought a new main rotor housing... problem was solved....

[garypuppa]

@imprint2finished I replaced the main rotor block and that solved it. Check out video #6 on my YouTube channel.

Thanks

Gary

[garypuppa]

@imprint2finished I replaced the main rotor block and that solved it.  Check out video #6 on my YouTube channel.

Thanks

Gary

[trexinvert]

Hope you're getting some good feedback. A tip when doing testing. Re-program or create new model in the tx with a pitch curve that is 50-50-50-50-50%. Then you can throttle up and down without disturbing the swash plate. Then if you some swash movement then that will give you some additional clues. Good luck.

[inagerli]

Schaft des Rotorkopfes ist krumm. Welle ist scheinbar in Ordnung.

[leebethell]

have u replaced the main shaft??? if so looks like u need a new head

[garypuppa]

@leebethell - No I did not replace the main shaft. I did the "roll on a flat surface test" and it looked okay.

I thought it might be upper shaft bearing, so I also ran the motor with the existing shaft installed (head removed) and there was no wobbling. Thanks for replying.

Gary

[garypuppa]

@leebethell I replaced the main rotor block and that solved it. Check out video #6 on my YouTube channel.

Thanks

Gary

[trexinvert]

Ah...I think I know it is. It could be the head block. Specifically, the "split collet" feature of the block. Here's how to test. Grab the shaft and the head block only, and see if they wobble? I've had some problems with mine in the past.  I corrected this by pinching that area with a clamp to make it smaller and fit the shaft with a little bit of intereference. You will also see some scuffing on the shaft in one direction if this is the case. Good luck.

[SkinnyMcGeeSF]

normal, when you reach higher head speeds should go away, if your tail is bobbing the main problem is to low of head speed, make your head speed higher and it will go away. Good Luck!