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Author Topic: Sheesz, ANOTHER stoopid failure mode  (Read 738 times)

Offline Dennis Adamisin

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Sheesz, ANOTHER stoopid failure mode
« on: August 12, 2009, 07:38:47 PM »
Out flying the Mythbuster today, first time out since Brodak's.  At flight #5 (maybe 18 or so total for the bird) it shuts off midway through the second triangle - nice safe pullout, no issue except "WTH happened???"

Post flight revealed that the 3.5mm bullet connector on the safety wire had disconnected - and that the spring tabs were completely flattened - absolutely no retaining force.  I would have never imagined the connector could fail this way, certainly after only 20 or so cycles.


Has anyone else had problems with bullet connectors?
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Denny Adamisin
Fort Wayne, IN

As I've grown older, I've learned that pleasing everyone is impossible, but pissing everyone off is a piece of cake!

Offline Igor Burger

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Re: Sheesz, ANOTHER stoopid failure mode
« Reply #1 on: August 13, 2009, 12:32:25 AM »
DO not use power connectors where spring segment is also contact segment at the same time. It is just wrong idea and it fails often.

Deans are better, but they have only one contact segment and it can make problem in dust. I use multisegment MPJ connectors:

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Alan Hahn

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Re: Sheesz, ANOTHER stoopid failure mode
« Reply #2 on: August 13, 2009, 07:11:27 AM »
Interesting!

What do your bullet connectors on the motor-esc (assuming you use them) look like?

The new Scorpion connectors look like the MP-Jet ones Igor shows. I thought it was a PITA since now one motor/ESC  has different connectors than all the other ones I have. Maybe my concern was misplaced!

I bet it also matters who made the connectors, but to be honest, I think mine are from all over the place. And as I recall, somewhere I have a pretty loose connection, but I don't remember where!!! Need to take a look.
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Offline Dennis Adamisin

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Re: Sheesz, ANOTHER stoopid failure mode
« Reply #3 on: August 13, 2009, 06:47:59 PM »
I have not inspected the motor connectors lately, but I have gotten into the habit of a wrap of tape to "safety" them.  Because the are not routinely connected/disconnected I do not think there would be a problem with them. 

Igor:
I seem to recall that you alsu use bullet connetors on the battery to ESC connection?  Do you routinely disconnect to charge or do you use a ypass circuit to charge your A123's?


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Denny Adamisin
Fort Wayne, IN

As I've grown older, I've learned that pleasing everyone is impossible, but pissing everyone off is a piece of cake!

Kim Doherty

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Re: Sheesz, ANOTHER stoopid failure mode
« Reply #4 on: August 13, 2009, 09:04:57 PM »
Quote from: Dennis Adamisin on August 12, 2009, 07:38:47 PM
Out flying the Mythbuster today, first time out since Brodak's.  At flight #5 (maybe 18 or so total for the bird) it shuts off midway through the second triangle - nice safe pullout, no issue except "WTH happened???"

Post flight revealed that the 3.5mm bullet connector on the safety wire had disconnected - and that the spring tabs were completely flattened - absolutely no retaining force.  I would have never imagined the connector could fail this way, certainly after only 20 or so cycles.


Has anyone else had problems with bullet connectors?


Dennis,

If you solder a bullet connector without the use of a heat sink you will anneal the metal and ruin the spring. Drill the appropriate sized hole (the same dia as the female connector) in a small block of aluminum. Place the connector in the block and use lots of heat so that the connection is made quickly.


Kim.
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Offline Igor Burger

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Re: Sheesz, ANOTHER stoopid failure mode
« Reply #5 on: August 14, 2009, 01:14:06 AM »
yes, I disconnect them after flight, and it is also charging point. I have done ~400-500 flights on one battery and connectors are still the same. (every flight means 2 connections - one for flight and one for charging). But I think I will change them for next season.
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Offline Dennis Adamisin

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Re: Sheesz, ANOTHER stoopid failure mode
« Reply #6 on: August 14, 2009, 07:04:19 AM »
Kim:
Sounds like you found the smoking gun.  I hold them in a block of wood when I solder, and usually tke my time getting them very hot, pooling solder into them then inserting the wire.  I am geting a good solder joint but it NEVER occured to me that I was annealing - that has to be a be a contributor. 

Igor:
Thanks again.  Sounds like the MPJ connectors have served you well.  I will have to find a source for them on this side of the pond...
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Denny Adamisin
Fort Wayne, IN

As I've grown older, I've learned that pleasing everyone is impossible, but pissing everyone off is a piece of cake!

Alan Hahn

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Re: Sheesz, ANOTHER stoopid failure mode
« Reply #7 on: August 14, 2009, 07:24:28 AM »
Quote from: Dennis Adamisin on August 14, 2009, 07:04:19 AM
Kim:
<snip....>
Igor:
Thanks again.  Sounds like the MPJ connectors have served you well.  I will have to find a source for them on this side of the pond...

Hobby Lobby was where I bought mine.
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