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  #1  
Old 01-27-2006, 02:09 PM
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dpaton dpaton is offline
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Quote:
Originally Posted by MarbleTurtle
Don't even get me started on the CRIMP but don't SOLDER diatribe in his book! Since when is Boeing or Lockheed standard operating procedure empiracal evidence that something should be done one way or another!
Sorry MT, but I've got to. It's the engineer in me...

There is some merit to this. A proper crimp (mil-spec) is not only mechanically secure, but is gas-tight, and effectively forms a cold weld at the interface between the wire and the contact. Proponents say it:
* reduces resistance (possible, I haven't verified it)
* is better mechanically (because solder doesn't wick into the wire, stiffening it and providing a stress point where the wicking stops)
* that removing extra metallic things from the connection (Sn, Pb, etc) provides for a longer lifespan.

I do know that for high vibration and heavy use multipin assemblies (>64 pins in a circular connector on the end of a cable) crimps are preferred, and that the MTBF supports that choice relative to soldering. That's personal experience talking.

In normal applications, for low voltage and high current, I totally support crimps over soldering. On things like battery terminals (starter lugs, charging jacks, linear actuator connections, etc), a failing joint or an overcurrent situation will melt the solder, causing an uncrimped connection to come loose and arc, and send solder flying everywhere. I've had that happen too. For things like the DB25 that comes out of the back of an HSI or the DB9s that BMA uses on their autopilots, I don't have a problem soldering connections, provided they're properly strain-relieved and carry low current. Everything I do, professional or personally, over 5A, gets a crimp if I can manage it.

Personally, I'll be splitting the difference between Greg and Bob's papers. CBs, backups, fault tolerant design, and sound engineering practices. I'm a lot more worried about the wings falling off than I am about a systems failure.

-dave
(EE, high power systems, microvolt sensors, and everything in between)
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Last edited by dpaton : 01-27-2006 at 02:23 PM.
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  #2  
Old 01-27-2006, 02:26 PM
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Uh oh...new thread time

-dave
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  #3  
Old 01-27-2006, 02:30 PM
ddillon ddillon is offline
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Quote:
Originally Posted by dpaton
A proper crimp (mil-spec) is not only mechanically secure, but is gas-tight, and effectively forms a cold weld at the interface between the wire and the contact.
What type of crimp and with what crimping tool constitutes a mil-spec crimp?
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  #4  
Old 01-27-2006, 02:32 PM
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the dam ones that we paid 200 for 1 and 150 for the other and now just had to buy new inserts for one of them as the garmin pins are diferent.

the tool has to match the pin andwire connection it is being used on
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  #5  
Old 01-27-2006, 02:55 PM
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I went through a NASA High reliability soldering school back in the Apollo days. A proper crimp is superior to a solder connection. It is lighter, and places less stress on the wire-to-crimp junction. Proper soldering and crimping techniques can reduce the weight of a Saturn V5 by as much as 2,000 lbs. Just in case somebody is homebuilding a Saturn V5 Rocket.

The key being, "Proper Crimp tool and crimp pins" , not the "Kraygen Auto" varity.

With that said, I solder my pins, mainly because I'm to cheep to buy the expensive tool and the mating pins.

Waiter
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  #6  
Old 01-27-2006, 05:37 PM
Nathan Gifford Nathan Gifford is offline
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I agree with Waiter. Crimp$ are $uperior with the proper tool$. The tool I have for crimp amp pins/sockets costs $450. It works great; certainly better than solder.

Unless you are using certified tools and components, a dab of solder on crimp pin or lug is a pretty good idea.
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  #7  
Old 01-27-2006, 06:39 PM
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Maybe if you ham fisted lyco drivers knew how to soder properly, your crystalized lump of metal wouldn't vibrate apart on every chitty chitty bang bang. And get a Rotary for goodness sakes!

(Chasing sacred cows with a weed-whacker!)
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  #8  
Old 01-27-2006, 11:01 PM
eracer113 eracer113 is offline
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Crimps are far better, I know from experience, and I know how to solder. I had my electric nose gear soldered for about a year and on landing one fine day, I did not check the window for the nose gear and did a nose gear up landing, scuffed the puck off and a little glass on the nose. Very embaressed, went back to my hanger, found a broken wire on the down side switch,repaired it and the minor damage. About 6 months later I noticed the nose gear not retracting, manually retracted the gear, found another broken wire. Since then,(5yrs) after I crimped the wires. (with a good crimper)I have not had a problem. You must use quality AC terminal ends and tools.

My experience
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E Racer113
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  #9  
Old 01-27-2006, 11:38 PM
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This one produces an 8-indent Mil spec crimp.

Daniels Manufacturing Corporation makes a number of great (and expensive) crimp tools.

If you are going to crimp. Use a good tool, otherwise it's not worth it; Just solder it. But strain relief in either case.
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  #10  
Old 01-28-2006, 04:34 AM
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That's the crunch hey?
Maybe I would lash out and spend close to $800 AUD on an MIL spec crimping tool with matching jaws and connectors I'm going to likely use once. Well twice, maybe three times in my case.
The other thing I could do is solder and strain relieve all my connections. I've yet to have a solder joint fail me but then I've not built an aircraft before, however a motorcycle (I've built plenty of these) is a vibration and shock intensive environment.
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  #11  
Old 01-28-2006, 08:50 AM
Nathan Gifford Nathan Gifford is offline
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Quote:
Originally Posted by mplafleur
This one produces an 8-indent Mil spec crimp.

Daniels Manufacturing Corporation makes a number of great (and expensive) crimp tools.

If you are going to crimp. Use a good tool, otherwise it's not worth it; Just solder it. But strain relief in either case.
Yes, I have the bottom one at work and it never goes in the tool bag (I have one stolen over the years). Over $500 with the accessories.
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  #12  
Old 01-28-2006, 10:55 AM
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I haven't had a chance to work with the high end crimpers. The low end stuff always nicks the wires.

I'm actually not against crimping. From what I can tell, the manufacturers are against it because a good soder joint is difficult to repeat continuously where as a crimp can be repeated exactly the same every time. Once a crimping tool is found that meets the minimum specifications, there's no need to change or use something else.

How is everyone going about sealing the wire connections against corrosion?
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  #13  
Old 01-28-2006, 11:07 AM
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Wire nicking - for that i bought thermal wire strippers by teledyne offa ebay

the best way to buy these tools - groups of builders in a region. Waiter and i bought the wire marker together.

mplafleur has some crimpers and thane, clifford and i now have others
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  #14  
Old 01-28-2006, 11:51 AM
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Something like these?

http://cgi.ebay.com/DMC-M22520-2-01-...cm dZViewItem

http://cgi.ebay.com/Daniels-DMC-AFM8...QQcmdZViewItem

http://cgi.ebay.com/Daniels-Crimp-To...QQcmdZViewItem
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  #15  
Old 01-28-2006, 12:44 PM
Lynn Erickson Lynn Erickson is offline
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On large cable as battery cable I use the crimp and then I solder and then shrink wrap. This may or may not be the excepted aircraft way but it works. I use to use the crimp only on our #0 welding cables and after draging them around and through the mud the the connection would get corroded and we would have a hot connection and then it would really get corroded. I started soldering the connection and the corrosion stopped. most of the connections have lasted ten years or more of every day use. don't use solder only because if the connection is over loaded the solder won't just melt is will explode and come apart. I guess Nuckolls has not been there and done that yet on his cable flag terminal that he say's to just solder.
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