main shaft wobble problem

[gdub73]

hi, i ve recently crashed ,trex 450 se v1, i relaced all the the bent parts feathering and main shafts, but the heli has a slight wobble, ive removed everything off the main shaft so its just the shaft and it still has a wobble, any ideas where abouts the imbalance is coming from

[Wolfpackin]

Check the main shaft bearings for a notchy or gritty feeling when turned by hand with a slight side load.

[Finskeeper]

Did you remove the main gear assembly from the shaft? If not, the main gear being out of round is suspect.

[Tag1260]

Bent NEW main shaft? I suppose it could happen.

[flerpie]

Pre-Bent new shaft or motor pinion too tight against driven gear.

[zen]

gdub73— It is not uncommon to bend the head block in a really good, high-energy crash.

As an old 450 SE v1 guy I suggest that you remove the rotor head and spin the main shaft by itself with the motor. If it is perfectly straight its outline will not blur and a tool touched to its side as it spins will not vibrate. If the main shaft is straight and true, install the rotor head block only and spin it. If the little hole that the head button goes into does not blur the main shaft and head block are okay and you can carefully rebuild the rotor head and check:

1. Flybar is exactly centered. (Take some time on this; it really counts.)
2. Paddles weigh exactly the same, to within 1/10 gram.
3. Main blades weigh exactly the same.

Good luck,

Glen

[gdub73]

hi, i do have to add that i have everything off the top of the shaft, so every thing from swash plate is off the main shaft and it still has a slight wobble, when i crashed i broke the belt, could the cog that the belt goes around be bent, does that sometimes bend?

[Wolfpackin]

More likely it would strip or slip on the shaft, those things would cause tail issues not a wobbling main shaft.

Check the main bearings and try another "new" main shaft as others have suggested.
It's not unheard of to get a bent one either from the factory or one that's been bent during shipping.

Also make sure the lower jesus bolt is not too tight. That can cause the main gear to wobble which in turn could cause the main to do the same.

Check the meshes between the main gear/pinion and main gear/tail drive shaft gear to see that it doesn't change drastically throught the circumference indicating a warp or bend somewhere.

[gdub73]

its not the main shaft as ive tryed 3 already with the same result, whats the jesus bolt, is that the bolt that goes through the bottom cog and the main shaft

[nismo200sx16]

when you say wobble do you mean you see vibration when spooling it up? if so check out the tail. if your tail shaft is slightly bent it will shake the entire heli. also tail shaft bearings.

[gdub73]

when i say wooble i mean its not turning true, when u spool up and look down the shaft u can see the shaft is balanced also if u put a tool or ur finger on the shaft u can see and feel vibration,but it is bouncing all over the place when i spool up, i dont think its tail cause i have the belt off, i thought it might be that until removed the belt to elemitate the problem, im taking a dail gauge home with me to confirm the main shaft isnt running true

[wanderer56]

Originally Posted by gdub73

its not the main shaft as ive tryed 3 already with the same result, whats the jesus bolt, is that the bolt that goes through the bottom cog and the main shaft

Yes, the screw/bolt that secures the lower gear(tail drive) to the main shaft. It does not need to be super tight, just snugged up. It should have a nylon lock nut on it as well. If you did not get the OWB sleeve "seated" in the lower gear good, that could cause a wobble also. Or overtightened the sleeve and deformed it.

Or a bent motor shaft is something to check also.