Head not spinning up

[jon.peart]

My recent incident took out more than I initially thought. On closer inspection I found the main shaft was bent.

I replaced tonight along with other necessary components including upgraded tail servo to DS520.

A quick hover test in the back garden at first proved all ok - hovered nicely so landed and went to take off again. This time the motor started to spin up but then stopped. The only way I can get to spin the head up is to rotate the main cog manually whilst throttling up. Spinning the auto rotation cog proves everything is spinning cleanly. I've checked the meshing with the motor and all looks ok.

Any ideas?

Thanks
Jon

[DT39]

one way bearing had it maybe.

[Cuppa]

One ways sh#g,d mate

[jon.peart]

Thanks for the responses but can you please explain why this is the case?? I don't fully understand the purpose of the bearing other than to say that this allows the auto rotation cog to turn in the correct direction when power is lost to the motor. This is moving freely as expected and will not turn in the opposite direction (I.e. As expected).

Like I say, I don't dispute the prognosis but I don't understand it.

[Cuppa]

Thanks for the responses but can you please explain why this is the case?? I don't fully understand the purpose of the bearing other than to say that this allows the auto rotation cog to turn in the correct direction when power is lost to the motor. This is moving freely as expected and will not turn in the opposite direction (I.e. As expected).

Like I say, I don't dispute the prognosis but I don't understand it.

one way bearing locks on shaft in rotation when driven by the motor
a sh#gd bering will not grip the shaft-or 'grab' taking off main gear
teeth al ist clarr yar

[tiddler]

Mesh between main gear and pinion too tight? or the motors faulty

[DT39]

Another thought is grub screws in the pinion come lose.

[jon.peart]

al ist clarr yar

Yes, I think so

Just removed, cleaned, regreased and refitted the main gear and all now working so must be one way bearing related but god knows why.

Just to clarify the issue I was getting - the motor would stop turning after a couple of rotations of the main gear (the head moved as expected and then everything stopped). Is there some sort of override on the esc to prevent the motor burning out? It was almost like there was too much resistance for the motor to continue so the esc shut it down. Meshing ok and turned manually ok?

One of life's little mysteries perhaps just glad it's working!!

[Cuppa]

Yes, I think so

Just removed, cleaned, regreased and refitted the main gear and all now working so must be one way bearing related but god knows why.

One of life's little mysteries perhaps just glad it's working!!

I do not belive it nessersarely (phew!)
a good idea to grease one way berings as it can cause them to 'skid/grab'
degrease and apply a few drpos of light oil, should be all the lube it
will need, when weathers cold the 'skid efect ' happens because the
grease becomes 'stiff' stpoing the one way operating properly.
cuppa tip 'lightly oil'd is best'

[jon.peart]

Ok, thanks cuppa. Off comes the main gear again!

[jamiem]

It sounds like ether one phase of the motor is dead (either motor or esc died, most likely esc), or one of the 3 motor wires are disconnected.

If you try and spool it up without kicking it over first, does the motor just Huddersfield back and forth a couple of times? Do you still get the startup beeps when connecting the battery?

[tourerjim]

I would won't to be more sure of the fault before attempting to fly.
Oneway bearing could be faulty after a crash as also esc & motor but it's difficult to say so perhaps get 2nd opinion.

[Balders]

I've had issues similar to this on a 450, turned out to be a burned out mosfet on the ESC.

[jon.peart]

... does the motor just Huddersfield back and forth a couple of times? Do you still get the startup beeps when connecting the battery?

I'm pretty sure the motor wasn't in Huddersfield at the time

I get all the normal startup noises from the esc and with the main gear out the motor spins perfectly on demand. It was almost like the motor was getting overloaded.

I've had issues similar to this on a 450, turned out to be a burned out mosfet on the ESC.

What's a mosfet?

Once the head was spinning (after I manually assisted) everything spun normally. I can't feel any play in the one way bearing either.

I'll drop the main gear out again, clean it up and oil as suggested by Cuppa and see if I get the same issue. will heed advise provided and make sure I give it plenty of ground tests before going for a flight.

Thanks
Jon

[Balders]

sorry, not sure if I've got the correct terminology, but one of the "chips" under the shrinkwrap on my ESC has charred. I'm guess that once it got past the point that this chip had any effect it was ok. This occurred after a crash (I'm guessing it overloaded) so sounds like similar circumstances to yours. I did post a photo of it waaay back, I'll see if it's still on here anywhere.