OS105 bad vibes after crash

[T-mac]

Hi Folks,

A few weeks i crashed my NX7 doing side tick tocks too close to the ground. Damage wasn't too bad actually, the most work was replacing the burnt out clutch liner since i didn't hit throttle cut quick enough. The engine was tuned pretty well before i crash with not too bad vibrations. Now when i spool it up and lift the heli into the air its dancing all over the place mostly from the feedback into FBL controller (BD 3sx)

As soon as i hit throttle hold the bird goes silky smooth so i know the blades and head are well balanced. I took the engine apart and inspected the internals after i crashed, bearings were all good. Should i be ordering a new crankshaft at this point?

[Drivelayer]

I've had some pretty bad crashes. before I suspected the crank, it is somewhat protected, I would look at main shaft bearings / bearing blocks, tail rotor shaft, torque tube and finally starting/ pinion gear bearing block for vibes.

if the engine ran post crash and the clutch slipped I would also inspect the clutch and clutch bell for distortion. had a buddy who crashed and the clutch kept slipping, the bell go so hot it shattered before we could get to it.

good luck

[T-mac]

I replaced the main shaft, main bearings, feathering shaft, tail, shaft, torque tube. I'm pretty sure the tail rotor shaft is fine, the tail blades weren't damaged in the crash. The clutch slipped and burnt the clutch liner off before I could hit throttle cut.

I guess it's possible it could be the clutch bell or clutch being warped but they seem fine when I glue the clutch liner in. The clutch bell spins freely and the liner gap is tight.

[Glenn Goodlett]

Sounds like either the clutch or crank. You can check the crank with a dial indicator.

[T-mac]

I've got a dial gauge and stand on the way. I never checked the runout of the fan hub or clutch when I built it. Once i make sure the crank is straight i'm going to check the runout of the fan hub, clutch as well as balance the fan hub. That should hopefully solve my problems!

[Rob43]

Fan hub, and clutch bell are good points to check with your dial indicator. i bet it will tell the story.

[T-mac]

Well i dial indicated my clutch and the runout was 0.005" the clutch bell had a runout of 0.006" and the engine crankshaft runout was 0.0005" so its definitely not the crank. After more inspection I took out the crank and the rear bearing is rusty and doesn't feel all that smooth. I put the fan hub with fan on the balance and it could use some balancing as well.

Once i get all my runout down as low as possible, balance the fan and replace the bearings she should be butter smooth again.

[mqowen]

Originally Posted by T-mac

Well i dial indicated my clutch and the runout was 0.005" the clutch bell had a runout of 0.006" and the engine crankshaft runout was 0.0005" so its definitely not the crank. After more inspection I took out the crank and the rear bearing is rusty and doesn't feel all that smooth. I put the fan hub with fan on the balance and it could use some balancing as well.

Once i get all my runout down as low as possible, balance the fan and replace the bearings she should be butter smooth again.

Did you get this worked out?