Trex 450 Vibration issue

[Zander]

Hi to all at RC Heliaddicts

Im having some issues with my Trex 450 sport
when i get to around 30% throttle it starts to shudder real bad i also have a trex 500 and a raptor 50 & they spool up fine no vibration at all.
but the 450 looks like its going to shake its self to bits.
i bought it off a chum so im not sure if it was ever crashed but as it was shuddering so bad i went and replaced the main shaft and the fethering shaft along with the main gaear and one way bearing.
i have not replaced the swash and the main bearings yet.
please have a look at this video and let me know if you spot anything.

https://www.youtube.com/watch?v=Pd5ZzkmLQwU

Regards
Zander.

[cloudrider]

Hi Zander.
There is something out of balance.
Check for concentricity of the main shaft and rotor housing assembly.
Check for correct thrust bearing assembly in the blade holders.

You also need to inspect the main blades.
Check weight of both blades they should be within 0.01grm of each other. Check their individual centres of gravity, should be identical.
Check blade tracking and that the blades are not held too tightly in the blade holders.

[adrianMS]

I'd check how tight the blades are in the grips, if too tight vibration on spool up/down is common.
Even when correct you will get some vibration caused by the hell rocking on its flexing skids. EG I have Gorilla skids fitted which are more flexible than std Align so the 'wobble' is even worse.
Once the head is up to speed your Heli seems fine.

[Jez N]

Take off the blades and run it without. Are the vibes still there? Are the blades balanced? Could still be a bent rotor head or blade grip?

May be worth asking your mate for an honest crash report. At least then you will know if bent bits are likely.

[PorscheBoy]

+1 on how tight (or probably too tight) the main blade grips are, also tail grips need to be correct grip level. As said, it looks ok once up to speed

[Jez N]

Think I must be watching a different vid as it shakes pretty bad when it gets off the ground. I agree a loose grip can cause vibes but not sure it will be causing those shakes. Go back to basics and take off the main and tail blades and spool it up. You may need to take off the tail and boom as well in order to find the problem. Could be any number of issues I'm afraid. Half the fun though.

[PorscheBoy]

Think I must be watching a different vid as it shakes pretty bad when it gets off the ground. I agree a loose grip can cause vibes but not sure it will be causing those shakes. Go back to basics and take off the main and tail blades and spool it up. You may need to take off the tail and boom as well in order to find the problem. Could be any number of issues I'm afraid. Half the fun though.

You're right, watched the vid all the way through this time. Tail grips are certainly loose enough.

[milly0812]

Trex 450 Vibration issue

It looks like your belt is way too tight from the spool down, it stops almost instantly with no freewheel ?

Or the one way bearing is seized

[uiron]

review for vibrations. A most complete review is going from "ground up". On the bench, run it with just the motor (no main gear), then connect main gear but no tail or head, then add head, then tail witout blades, then tail with blades on... Every time spool up and see which step noticeably increases vibrations. With 450 size you can be perfectly safe when holding it in hand, though I'd recommend safe viewing angle when running with tail blades on.

If vibrations are reasonably low without main blades, you could look into your FBL setup. Maybe your cyclic gains are rather high and heli is nervous on the ground (any small vibrations are amplified by nervous cyclic correction when touching solid ground).

[Zander]

Cheers Guys you have given me a lot to think about i will let you know how i get on and what the issue was when i nail it down.