General Possible bent main shaft

bigone5500

Well-Known Member
What's the easiest way to check for a bent main shaft? There's a lot of vibration in my 270 that wasn't there before the crash. I was gonna try to fly it the other day and didn't want to chance it due to the amount of shaking. I weighed the blades and they came out at 19g each.
 

Derek

Well-Known Member
if you can take the main shaft out of the helicopter and place it on a glass surface (or very flat surface) and try to roll it. If the shaft rolls smoothly, the shaft is not bent. If the shaft kinda wobbles, or doesn't roll smoothly, it's bent. In my honest opinion, if you have a doubt about the shaft being bent, I'd just replace it and move on.
 

bigone5500

Well-Known Member
if you can take the main shaft out of the helicopter and place it on a glass surface (or very flat surface) and try to roll it. If the shaft rolls smoothly, the shaft is not bent. If the shaft kinda wobbles, or doesn't roll smoothly, it's bent. In my honest opinion, if you have a doubt about the shaft being bent, I'd just replace it and move on.

I was trying to avoid taking it out. But I may just have to. They're cheap enough I suppose that I could simply buy a couple.
 

Derek

Well-Known Member
Yeah, you should always have some spare main shafts and feathering shafts on hand. Good luck buddy!
 

Tony

Staff member
I agree with Derek, it's always good to have main shafts and feathering shafts on hand. They are the #1 most damaged part in a helicopter. And they will cause all sorts of issues.
 

Tony

Staff member
Wow that is an old video lol. But yes, that is a fantastic way of checking your feathering shaft without tearing the head apart.
 

Tony

Staff member
These plastic gears are known to have a wobble. And it is very rare to have a main shaft bent down low. Usually you can watch the bolt in the head button and see it wobble.
 

bigone5500

Well-Known Member
These plastic gears are known to have a wobble. And it is very rare to have a main shaft bent down low. Usually you can watch the bolt in the head button and see it wobble.

I did as shown in the video and didn't detect any wobble on the feathering. I will install the battery later and see if it does anything without blades. Then I will take the shaft out as a last method. Amain has two pack of shafts for $13. Will order just to have them anyway.
 

Tony

Staff member
I need to order new main shafts as well lol. My supply is running low at the moment. Keep us posted on how it is going.
 

bigone5500

Well-Known Member
I powered it up and looked straight down on the head. I watched the small threaded hole and did not notice any deviation from center. I will try sometime and get a video of the vibration with the blades installed.
 

Tony

Staff member
Since you did see that wobble on the gears, it may be worthwhile to go ahead and pull the shaft and roll it on glass. This will tell you for sure.
 

bigone5500

Well-Known Member
Since you did see that wobble on the gears, it may be worthwhile to go ahead and pull the shaft and roll it on glass. This will tell you for sure.
Will do. I probably won't be able to get to that till later tonight. My wife may get mad if I sit around working on helis on mother's day.

As a side note, the shaft has a larger diameter section just above the upper bearing that could hinder rolling on glass. I will have to roll it on the edge of the glass and watch the end of the shaft.
 

Tony

Staff member
lmao, mine is at work until 2300 and has to be back at 0700. She is not happy, but it frees me up for working on models hahahahaha
 

bigone5500

Well-Known Member
Here are a couple videos on the possible vibration issues. Maybe I'm wrong...


This one is of the servos. Do things look ok? I thought the elevator and aileron should return to center faster than they seem to.
 

Tony

Staff member
The swash returning slow to center is completely normal, and the tail holding pitch in HH mode is also completely normal. It looks like you have an elevator shake which means you need to lower your elevator gain with one of the pots on top of the gyro. I can't remember off hand which it is, but it should be in your manual.
 

bigone5500

Well-Known Member
The swash returning slow to center is completely normal, and the tail holding pitch in HH mode is also completely normal. It looks like you have an elevator shake which means you need to lower your elevator gain with one of the pots on top of the gyro. I can't remember off hand which it is, but it should be in your manual.

Can you explain elevator shake?
 

Tony

Staff member
It is the same as tail shake, or the tail gain being too high, except the tail goes up and down like you are going forward and backwards on the elevator.

Have you tried putting it into the air and see what happens?
 

bigone5500

Well-Known Member
It is the same as tail shake, or the tail gain being too high, except the tail goes up and down like you are going forward and backwards on the elevator.

Have you tried putting it into the air and see what happens?

Haven't tried that. Too nervous about it. I can try it later if the wind isn't too high.
 
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