Why does a bullet connector become unsoldered

[RC-Dude]

Why does a bullet connector become unsoldered?
Was flying with a 70mm EDF jet. Motor pulls 92 Amps on 6s. Motor starts sputtering while flying. Manage to land. Melted soldering lead 60/40 outside of one bullet. Remove the tubing and the bullet falls out. The other two bullets are still soldered rock solid.

Bad soldering connection and Amps too high for a poor connection?

 

[dure16]

Bad soldering connection and Amps too high for a poor connection?

Bingo

 

[Greengaunja]

Yeah I had this to happen a few times during my learning curve with electronic soldering. A bad solder creates alot of resistance, which heats it up. But I imagine even a good solder would melt if amps got too high for too long. One of the first I melted was a factory solder on the ec5 connector.

 

[WoodiE]

Bad soldering connection and Amps too high for a poor connection?

This is the way.

 

[rceverywhere]

Bullet too small for the amps will fail as well, one fails then the others are saved and look fine. Unless a bad soldering job or dirty/burnt out connector are not the cause

 

[Moirae]

haha man i went through this so many times when I first started soldering. Happened so much I started pulling on bullets every time I troubleshooted anything. Much better now!

 

[RC-Dude]

I suspect I must have touched the wire just before everything got solid.

 

[rceverywhere]

I suspect I must have touched the wire just before everything got solid.

That would do it! Try to set up a little jig to hold the wire and connector, or just become a statue for the precious seconds as the solder solidifies

 

[SrC]

If the solder joint is dull looking and not shiny, it is a "cold joint". They will come apart even with the slightest amount of heat and force.
A joint needs a decent amount of solder and must look very "shiny". Keep using 60/40 Leaded solder. best IMHO. Perhaps using a Flux paste will help better.
Always tug hard on the solder joints when you finish, to make sure. Yet even the best joint can melt apart, if your amp draw is beyond spec for the Connector in hand.
With an EDF Air RC setup, they run flat out at sustained full max amps for the most part during a flight. So your Soldering technique and using the correct connector for the job is paramount. 8mm bullets are probably best. Not sure if connector weight is one of your criterias, being an Air RC.
Soldering skills aside, the correct soldering iron temp, using a large "clean" blunt tip (pretinned) is needed.


Edited.