450 Belt Drive Vibration

[Ronald Kessler]

I put the 450 assault together and program the Turnigy gyro with your guyses help and everything checked out I got the right color lights I'm going to go do a maiden flight today but on spool up when it gets around halfway there's a terrible vibration starts bouncing around and it does it sometimes without the blades and if you hold it it doesn't do it I wish I could take a video but I don't know how to do it the show you guys if you have any suggestions let me know it's a belt drive which I have no experience with

 

[Smoggie]

You could work through eliminating one thing at a time:

1. Does it vibrate with the main blades removed yes or no? (this eliminates main blades and/or feathering shaft issues)
2. Does if vibrate with the tail blades removed yes or no? (eliminates tail blades/tail hub)
3. Does it vibrate with the belt remove yes or no? (eliminates anything to do with tail or belt drive)
4. Does it vibrate with pinion removed yes or no? (if yes it's the motor, if no it's the main shaft/main gear)

To post a video just upload it to Youtube then put the Youtube URL link into this thread

 

[Tony]

This could be just a resonance vibration that is in all helicopters. If it stops when you are ready to go into the air, you should be fine. Just tossing ideas without seeing it.

 

[Ronald Kessler]

That is a treasure chest full of information thanks guys I'm going to go and gently try to get it in the air see what it does I'll keep you posted

 

[Ronald Kessler]

Well I did the test flight and it vibrated a little so I tried to pop it up in the air the tail went down the nose came up when it started heading right for me so I tiltted it over and laid it down and put throttle hold on. It damaged the tips of my carbon fiber blades broke one Servo arm off and the second I think is okay. I just want to thank Smoogie for the checklist now that I wrecked it I did what you said and it does have a bent main shaft I rolled it on a table but couldn't see it but at high speed it definitely has a big vibration

 

[murankar]

Was your belt tensioned correctly? Sometimes that can play a role in vibrations. Also check your thrust bearings. Especially if you have thrust bearings in the tail blade grips. If that was assembled incorrectly you can get vibes from that.

 

[Ronald Kessler]

I sent for a new main shaft it should be here in a couple days and my feeling is that that was probably the problem I rolled it on the table and I couldn't see the bend but I spoiled it up without the head and it's like spinning oblong like an eighth of an inch at least off center. Pretty negligent on my part. Thanks for those other suggestions I will be addressing those as well

 

[murankar]

The best way to check shafts is to chuck them in a drill and spin the crap out of them. I found that to be the easiest and safest way to check them. Rolling them ion glads works but your eyes could play tricks on you.