Why Ferrules are a Good Idea on Stranded Wire

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OverTheTop

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Found this article on why ferrules should be used on stranded wire. Worth a read :).

https://www.weidmuller.com/bausteine.net/f/7862/Weidmuller_Ferrules_White_Paper.pdf?fd=3

Executive Summary
Thanks to its superior flexibility, longer flex life, and resistance to vibration, insulated stranded wire is the ideal choice for most panels. From both a physical and electrical perspective, however, bare stranded wire is a poor choice for connections. Stripped of its insulation, stranded wire quickly loses the coherence that provides its strength and resiliency. Once it begins to unravel, it is subject to breakage and corrosion that can produce overheating, short circuits, and connection failure, as well as cause serious safety issues.
Ferrules can rectify this situation by giving stranded wire the qualities of solid wire where it is needed most, at the point of connection. Ferrules significantly simplify installation, improve safety, and diminish the risk of costly panel failure.


ferrules.png
 

Andrew_ASC

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They had these in those SEW (Swedish Eurodrive) 3 phase 480 volt motors anywhere from 2-5 hp at work on conveyors. I actually got to wire one up in training. It was fun. Never knew what a ferrule was but visually recognized It. We called them terminal end caps. Lol
 

Andrew_ASC

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Yeah what I thought was neat was the ferrules twist on over the exposed wire strands. Usually on a SEW there’s a bundle of wires you undo the ferrules then reference a chart and wire each one by one to like the corresponding wire and bringo it’s done then twist a new ferrule back over each wire strand that was twisted together. They also have baldor motor kits for any conveyor spec’s by customer for handling live ordnance. Moreso for the warranty isn’t on us if the motor were to cause an explosion.
 

Andrew_ASC

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Back to rocketry. I think a ferrule could help anyone into the twist in tape method.
 

Reinhard

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Back to rocketry. I think a ferrule could help anyone into the twist in tape method.
Sounds like you're referring to twist-on wire connectors which are different from ferrules.
Ferrules require a crimping tool, but they improve connection reliability. Imho they are especially useful if connections are regularly opened and closed (e.g. swapping altimeters between rockets).

Reinhard
 

jderimig

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Yes I use them all the time. I believe that there are din standards that forbid use of stranded wire in screw down terminals without using a ferrule.

Where I work it's a requirement for CE certification
 

blackjack2564

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Back to rocketry. I think a ferrule could help anyone into the twist in tape method.
Hi Andrew, nice to see things are going well for you.
Most of us doing twist and tape [folks I know] run match wire direct the terminal block. So every flight all wires get replaced, hence no need for extra step of using ferrule.
 

Winston

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Found this article on why ferrules should be used on stranded wire. Worth a read :).

https://www.weidmuller.com/bausteine.net/f/7862/Weidmuller_Ferrules_White_Paper.pdf?fd=3
Yes, a while back I posted a video about this that is no longer on this site for some reason. It was a presentation at some tech conference where it was pointed out that most techies in the US for some reason don't know, unlike their European counterparts, that ferrules are supposed to be used with screw terminals.
 

Winston

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Yes, a while back I posted a video about this that is no longer on this site for some reason. It was a presentation at some tech conference where it was pointed out that most techies in the US for some reason don't know, unlike their European counterparts, that ferrules are supposed to be used with screw terminals.
Here it is... again:

Bradley Gawthrop: Wiring Boot Camp

 

neil_w

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Are those ever used for stranded speaker wire? I find that my banana plugs need periodic retightening; a crimped-on ferrule would probably be much more reliable, although harder to modify.

Also interesting that they're referred to as bootlace ferrules, since the things on the end of shoelaces are called aglets.
 
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jqavins

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I've never used ferrules. I do prefer to avoid putting stranded wire into screw terminals, for the reasons stated. That's why I tin the wire ends. I don't have time during lunch to read the article (written, I see, by a company that sells the ferrules and crimp tools) so can someone tell me if it describes any benefits ferrules over tinning?

Also interesting that they're referred to as bootlace ferrules, since the things on the end of shoelaces are called aglets.
Darn you, you beat me to it.
 

neil_w

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I've never used ferrules. I do prefer to avoid putting stranded wire into screw terminals, for the reasons stated. That's why I tin the wire ends. I don't have time during lunch to read the article (written, I see, by a company that sells the ferrules and crimp tools) so can someone tell me if it describes any benefits ferrules over tinning?
In the case of speaker wire at least, often I'm working "in-place" (e.g.: wiring run through walls), and it would be inconvenient (although possible) to get a soldering iron in there. Crimping a ferrule on would be much easier.

In situations where it'd be easy to solder, I dunno. Haven't watched Winston's video yet.
 

jderimig

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I've never used ferrules. I do prefer to avoid putting stranded wire into screw terminals, for the reasons stated. That's why I tin the wire ends. I don't have time during lunch to read the article (written, I see, by a company that sells the ferrules and crimp tools) so can someone tell me if it describes any benefits ferrules over tinning?

Darn you, you beat me to it.
Tinning stranded wire for terminals is verbotten in industry. For a single use it's probably ok but it results in a very fragile fatique vulnerable failure of the connection. Hence why ferrules were invented....
 

OverTheTop

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Also the tin/solder has no elasticity and you will eventually lose pressure in the press. Ferrules are strong elastic metals which retain the clamping force in the block. They don't flow.
What he said. Also, tinning also creates a stress point where the solder stops, which becomes where that connection can fail.

I don't have time during lunch to read the article (written, I see, by a company that sells the ferrules and crimp tools)
It is worthy of being skeptical of some claims, but in this case the Marketing Department are promulgating good information :).
 

Voyager1

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What he said. Also, tinning also creates a stress point where the solder stops, which becomes where that connection can fail.


It is worthy of being skeptical of some claims, but in this case the Marketing Department are promulgating good information :).
Agree!
If you do use tinned connections, use some form of stress relief such as cable ties to secure the cables to the board, or a nearby mounting post. Hot melt glue around the joint is also useful.
 

cwbullet

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I have some first-hand experience of why it is a good idea to tin, place3 a ferrule, or use single strand wire. We just say the *boom* was up close and personal. To me, it is a matter of safety. One strand can result in an injury.
 

Wallace

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Tinned wire in a clamp connector is a certain fail at some point in time. If you absolutely refuse to use ferrules, at least DO NOT tin the wire before inserting it into any sort of clamp style connector. The solder will eventually flow and loosen the connection.
 

jderimig

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It is acceptable to tin the very tippity tip of a stranded cable to control loose strands. But if you must it's better to clamp on the strands not the tinning.
 
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vcp

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Tinned wire in a clamp connector is a certain fail at some point in time. If you absolutely refuse to use ferrules, at least DO NOT tin the wire before inserting it into any sort of clamp style connector. The solder will eventually flow and loosen the connection.
It is acceptable to tin the very tippity tip of a stranded cable to control loose strands. But if you must it's better to clamp on the strands not the tinning.
I estimate the FRR* on this advice to be about 15 months.

(*Forum Recursion Rate)
 

jderimig

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I estimate the FRR* on this advice to be about 15 months.

(*Forum Recursion Rate)
We should have separate forums on these FRR topics
To Tin wires or not to tin
Shear pins
Drag separation
etc
 

Wallace

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A sticky at the top of the electronics section? And,or eletrical/wiring sort of thing ?
 

Wallace

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I think potential liability tends to keep alot of this information withheld, which is truly sad. Is their such a thing as a "global" sort of waiver that might cover all?
 

Wallace

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Possibly a rating system? From #1 being a great idea, to #10 being, never do that?
 

Rocketjunkie

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I run the wires directly from the charge to the altimeter through a hole in the bulkhead. The ematch wires are solid 22 gage.Since they are replaced every flight, you don't need to worry about failure modes. I use a piece of left over wire from one of the ematches for the twist and tape arming switch. (High performance rockets use a screw switch accessed through a hole in the altimeter bay.)
 

cerving

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Personally, I don't like terminal blocks, so this isn't an issue. I solder stranded wires directly to the altimeter (Eggtimers, of course...), run them through the bulkplates (sealed with hot melt), tin them, then twist the ematch lead directly to them. No terminal blocks to come loose.
 

Winston

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TO FERRULE OR NOT TO FERRULE?
April 12, 2018

https://hackaday.com/2018/04/12/to-ferrule-or-not-to-ferrule/

Excerpt:

Making Stranded Wire Solid

If it sounds like ferrules are more a European thing than an American one, that’s with good reason. In order to get CE certification, electrical equipment must terminate stranded wire entering a screw or spring terminal with ferrules. There’s no such regulation in the US, and so it’s not common to see ferrules used in American equipment. But ferrules have specific advantages that are hard to deny, and their adoption appears to be spreading because they make good engineering sense.

To understand the principle, clip a small piece of insulated stranded wire of any gauge. Stranded wire is flexible, which is one of the reasons it’s used rather than solid wire in mobile applications and where vibration can occur. But it’s still somewhat stiff thanks in part to the insulation, which wraps the strands of the conductor, keeps them all in intimate contact, and maintains the twist, or lay, of the separate strands. Now strip off a bit of insulation from one end. You’ll notice that in most cases, the lay of the strands is at least partially disturbed — they untwist a little. Strip off more insulation and the strands get more and more separated. Take off all the insulation and the conductor will lose all structural integrity, falling into individual strands.
This is the essential problem that ferrules solve: they maintain the close association of strands in the conductor after the wire has been stripped and allow the connection to conduct its full rated current. Without ferrules, stripped stranded wires compressed in screw terminals tend to splay apart, reducing the number of individual strands that are in firm contact with the terminal. The resistance of such terminations is much higher than properly ferruled connections.

Squeezing Your Problems Away

There’s more to a ferruled connection than reduced resistance, though. Like other crimped connections, the strands inside a properly applied ferrule undergo tremendous pressure, in the process stretching axially and deforming radially. The stretching action tends to disrupt and displace surface oxidation on the strands, while the radial compression tends to remove the air spaces between the strands. These tend to make the crimped connection better at resisting oxidation than uncrimped wire, increasing the longevity of the connection.
 
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