Frame Flex=Broken Main Shaft?

[Troy003]

I do not own a 300x but have been looking at adding one to my fleet. One of my concerns is hearing about the main shaft breaking during flight. I have also heard that the frame might flex during hard collect/direction change causing stress on the spinning shaft. Defective main shaft/frame or combination both??? Please share you experiences with these issues. Is the 300x worth it? Thanks.

[Drivinfast247]

Wrong section buddy.

[ChrisH]

Moved to 300X forum.

[branmuffin]

Very small number of defective main shafts. There is some frame flex in some models but havent noticed it myself. I fly mild 3d and pretty often mash the sticks and have not noticed any ill effects yet after 50+ flights. No rubbing or breakage.

[stevebaker]

The frame flex is a poor design.
If you don't mind stiffening it up then it's still a nice heli worth having. It really needs stiffening as it causes / amplifies vibes, rubs the servo link and stresses the main shaft

[ahahn]

Originally Posted by stevebaker

The frame flex is a poor design.
If you don't mind stiffening it up then it's still a nice heli worth having. It really needs stiffening as it causes / amplifies vibes, rubs the servo link and stresses the main shaft

I think this is an oversimplification of the problem.

It is the vibration that one needs to fix.

I've been flying mine, nothing extreme, but flips, circuits,....smooth as silk. I admit I am lucky everything is so smooth.

No rubbing or such.

[GSPI]

These issues are a result of airframe stiffness or lack of stiffness that would cause this shaft failure. I have been delving into this problem and I can relate this to airframe stiffness problems which seems to be related to possibly inconsistent manufacturing practices. I have a very long thread here on my assessment:

http://www.helifreak.com/showthread.php?t=438478

There are many here noticing the issue but others not so it relates back to the consistency of the airframe molding and possibly the design.

[kvandenbroucke]

Originally Posted by GSPI

These issues are a result of airframe stiffness or lack of stiffness that would cause this shaft failure. I have been delving into this problem and I can relate this to airframe stiffness problems which seems to be related to possibly inconsistent manufacturing practices. I have a very long thread here on my assessment:

http://www.helifreak.com/showthread.php?t=438478

There are many here noticing the issue but others not so it relates back to the consistency of the airframe molding and possibly the design.

I can add to this statement, my 300X has no vibes at all and i can spoil it up on the floor in the house without vibes, even light on the skids there were no vibes.
Still in flight during the 3rd battery the main shaft snapped.
The tower of the mainframe moves around when you give ail/cycl/pitch,
this makes the shaft bend at the bolt above the main gear, just a little but enough to cause metal fatigue. The hole for the bolt is 2mm, the shaft only 4mm. So you have only 1mm metal to handle all the force. This might be enough for stiff tower but not for my flexible tower though.
You can calculate the hardness of a shaft based on torsion forces, but when the shaft also bends this is a whole other scenario and you calculations is wrong.

Conclusion: we need a stiffer frame from another material like the 450X has.

[CousinLarry]

Yep - that's it. I replaced the frame in mine because that tower broke off in a crash. The new frame I got is about one step above rubber on the hardness scale

I could twist it and bend it any which way. Feels almost like soft nylon or something. If it was just rigid hard plastic it would be so much better. Pretty crappy if you ask me.

And the second I un-boxed mine, my first thought was "Damn that mainshaft looks thin."

Hope a solution is found soon or I'm not sure how long I'll keep the 300X.

[mixfisto]

Originally Posted by CousinLarry

Yep - that's it. I replaced the frame in mine because that tower broke off in a crash. The new frame I got is about one step above rubber on the hardness scale

I could twist it and bend it any which way. Feels almost like soft nylon or something. If it was just rigid hard plastic it would be so much better. Pretty crappy if you ask me.

And the second I un-boxed mine, my first thought was "Damn that mainshaft looks thin."

Hope a solution is found soon or I'm not sure how long I'll keep the 300X.

Its a shame they made this heli with such a weak frame... I personally love this heli and will just wait until someone starts making a stiffer frame or a solid stiffining fix.

[ahahn]

Originally Posted by mixfisto

Its a shame they made this heli with such a weak frame... I personally love this heli and will just wait until someone starts making a stiffer frame or a solid stiffining fix.

Well you will miss a lot of flying!

[mixfisto]

Originally Posted by ahahn

Well you will miss a lot of flying!

Oh contrare, mufrare... I will be flying A LOT!!

Just saying that I'll be among the first in line to upgrade the frame

[Eric_heli]

my 300x frame doesnt flex nor does the servo arm . link touch the motor. however while i was on my 4th battery and 4th flight my main shaft snapped. all i was doing was fliping her around and snap.