Why Ferrules are a Good Idea on Stranded Wire

Discussion in 'Rocketry Electronics and Software' started by OverTheTop, Dec 11, 2019.

Help Support The Rocketry Forum by donating:

  1. Dec 11, 2019 #1

    OverTheTop

    OverTheTop

    OverTheTop

    Forum Supporter TRF Supporter

    Joined:
    Jul 10, 2007
    Messages:
    3,115
    Likes Received:
    678
    Gender:
    Male
    Location:
    Melbourne Australia
    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 likes this.
  2. Dec 11, 2019 #2

    Andrew_ASC

    Andrew_ASC

    Andrew_ASC

    UTC SEDS 2017 3rd/ SEDS 2018 1st

    Joined:
    Sep 22, 2017
    Messages:
    3,833
    Likes Received:
    492
    Gender:
    Male
    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
     
  3. Dec 11, 2019 #3

    OverTheTop

    OverTheTop

    OverTheTop

    Forum Supporter TRF Supporter

    Joined:
    Jul 10, 2007
    Messages:
    3,115
    Likes Received:
    678
    Gender:
    Male
    Location:
    Melbourne Australia
    Those SEW drives are really nice.

    The ferrules are mostly known as bootlace ferrules here.
     
    Andrew_ASC likes this.
  4. Dec 11, 2019 #4

    Andrew_ASC

    Andrew_ASC

    Andrew_ASC

    UTC SEDS 2017 3rd/ SEDS 2018 1st

    Joined:
    Sep 22, 2017
    Messages:
    3,833
    Likes Received:
    492
    Gender:
    Male
    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.
     
  5. Dec 11, 2019 #5

    Andrew_ASC

    Andrew_ASC

    Andrew_ASC

    UTC SEDS 2017 3rd/ SEDS 2018 1st

    Joined:
    Sep 22, 2017
    Messages:
    3,833
    Likes Received:
    492
    Gender:
    Male
    Back to rocketry. I think a ferrule could help anyone into the twist in tape method.
     
  6. Dec 11, 2019 #6

    Reinhard

    Reinhard

    Reinhard

    Well-Known Member

    Joined:
    Jan 18, 2009
    Messages:
    892
    Likes Received:
    50
    Location:
    Austria
    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
     
    Steve Shannon and Andrew_ASC like this.
  7. Dec 11, 2019 #7

    Andrew_ASC

    Andrew_ASC

    Andrew_ASC

    UTC SEDS 2017 3rd/ SEDS 2018 1st

    Joined:
    Sep 22, 2017
    Messages:
    3,833
    Likes Received:
    492
    Gender:
    Male
    Ah mybad
     
  8. Dec 11, 2019 #8

    jderimig

    jderimig

    jderimig

    Sponsor TRF Sponsor

    Joined:
    Jan 23, 2009
    Messages:
    2,943
    Likes Received:
    386
    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
     
    Steve Shannon likes this.
  9. Dec 11, 2019 #9

    blackjack2564

    blackjack2564

    blackjack2564

    Crazy Jim's Gone Banana's

    Joined:
    Jan 18, 2009
    Messages:
    8,875
    Likes Received:
    985
    Location:
    Savannah Ga
    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.
     
    Andrew_ASC likes this.
  10. Dec 11, 2019 #10

    Winston

    Winston

    Winston

    Lorenzo von Matterhorn

    Joined:
    Jan 31, 2009
    Messages:
    7,148
    Likes Received:
    449
    Gender:
    Male
    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.
     
    Steve Shannon likes this.
  11. Dec 11, 2019 #11

    Winston

    Winston

    Winston

    Lorenzo von Matterhorn

    Joined:
    Jan 31, 2009
    Messages:
    7,148
    Likes Received:
    449
    Gender:
    Male
    Here it is... again:

    Bradley Gawthrop: Wiring Boot Camp

     
  12. Dec 11, 2019 #12

    neil_w

    neil_w

    neil_w

    "The hex lug nut cut the mustard" TRF Supporter

    Joined:
    Jul 14, 2015
    Messages:
    7,073
    Likes Received:
    1,206
    Location:
    Northern NJ
    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.
     
    Last edited: Dec 11, 2019
    Steve Shannon likes this.
  13. Dec 11, 2019 #13

    jqavins

    jqavins

    jqavins

    Joseph Avins TRF Supporter

    Joined:
    Sep 29, 2011
    Messages:
    2,538
    Likes Received:
    528
    Gender:
    Male
    Location:
    Howard, NY
    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.
     
    John Kemker likes this.
  14. Dec 11, 2019 #14

    neil_w

    neil_w

    neil_w

    "The hex lug nut cut the mustard" TRF Supporter

    Joined:
    Jul 14, 2015
    Messages:
    7,073
    Likes Received:
    1,206
    Location:
    Northern NJ
    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.
     
  15. Dec 11, 2019 #15

    jderimig

    jderimig

    jderimig

    Sponsor TRF Sponsor

    Joined:
    Jan 23, 2009
    Messages:
    2,943
    Likes Received:
    386
    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....
     
  16. Dec 11, 2019 #16

    jderimig

    jderimig

    jderimig

    Sponsor TRF Sponsor

    Joined:
    Jan 23, 2009
    Messages:
    2,943
    Likes Received:
    386
    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.
     
  17. Dec 11, 2019 #17

    OverTheTop

    OverTheTop

    OverTheTop

    Forum Supporter TRF Supporter

    Joined:
    Jul 10, 2007
    Messages:
    3,115
    Likes Received:
    678
    Gender:
    Male
    Location:
    Melbourne Australia
    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 :).
     
    g.pitts and Steve Shannon like this.
  18. Dec 12, 2019 #18

    Voyager1

    Voyager1

    Voyager1

    Forum Supporter TRF Supporter

    Joined:
    Oct 23, 2015
    Messages:
    327
    Likes Received:
    82
    Location:
    Oz
    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.
     
    OverTheTop likes this.
  19. Dec 12, 2019 #19

    cwbullet

    cwbullet

    cwbullet

    Obsessed with Rocketry Staff Member Administrator TRF Lifetime Supporter Global Mod

    Joined:
    Jan 24, 2009
    Messages:
    22,603
    Likes Received:
    1,437
    Gender:
    Male
    Location:
    Glennville, GA
    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.
     
  20. Dec 12, 2019 #20

    Wallace

    Wallace

    Wallace

    Sponsor TRF Sponsor TRF Supporter

    Joined:
    Feb 16, 2017
    Messages:
    2,414
    Likes Received:
    414
    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.
     
    g.pitts, OverTheTop and jderimig like this.
  21. Dec 12, 2019 #21

    jderimig

    jderimig

    jderimig

    Sponsor TRF Sponsor

    Joined:
    Jan 23, 2009
    Messages:
    2,943
    Likes Received:
    386
    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.
     
    Last edited: Dec 12, 2019
    Wallace likes this.
  22. Dec 12, 2019 #22

    vcp

    vcp

    vcp

    Well-Known Member

    Joined:
    Jan 28, 2009
    Messages:
    982
    Likes Received:
    111
    Location:
    Meridian, ID
    I estimate the FRR* on this advice to be about 15 months.

    (*Forum Recursion Rate)
     
    g.pitts, Nytrunner and mbeels like this.
  23. Dec 12, 2019 #23

    Wallace

    Wallace

    Wallace

    Sponsor TRF Sponsor TRF Supporter

    Joined:
    Feb 16, 2017
    Messages:
    2,414
    Likes Received:
    414
    Good one!
     
  24. Dec 12, 2019 #24

    jderimig

    jderimig

    jderimig

    Sponsor TRF Sponsor

    Joined:
    Jan 23, 2009
    Messages:
    2,943
    Likes Received:
    386
    We should have separate forums on these FRR topics
    To Tin wires or not to tin
    Shear pins
    Drag separation
    etc
     
  25. Dec 12, 2019 #25

    Wallace

    Wallace

    Wallace

    Sponsor TRF Sponsor TRF Supporter

    Joined:
    Feb 16, 2017
    Messages:
    2,414
    Likes Received:
    414
    A sticky at the top of the electronics section? And,or eletrical/wiring sort of thing ?
     
  26. Dec 12, 2019 #26

    Wallace

    Wallace

    Wallace

    Sponsor TRF Sponsor TRF Supporter

    Joined:
    Feb 16, 2017
    Messages:
    2,414
    Likes Received:
    414
    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?
     
  27. Dec 12, 2019 #27

    Wallace

    Wallace

    Wallace

    Sponsor TRF Sponsor TRF Supporter

    Joined:
    Feb 16, 2017
    Messages:
    2,414
    Likes Received:
    414
    Possibly a rating system? From #1 being a great idea, to #10 being, never do that?
     
  28. Dec 12, 2019 #28

    Rocketjunkie

    Rocketjunkie

    Rocketjunkie

    Addicted to APCP

    Joined:
    Jan 19, 2009
    Messages:
    3,785
    Likes Received:
    138
    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.)
     
    Wallace likes this.
  29. Dec 12, 2019 #29

    cerving

    cerving

    cerving

    Owner, Eggtimer Rocketry TRF Sponsor TRF Supporter

    Joined:
    Feb 3, 2012
    Messages:
    3,277
    Likes Received:
    462
    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.
     
    Jmhepworth likes this.
  30. Dec 12, 2019 #30

    Winston

    Winston

    Winston

    Lorenzo von Matterhorn

    Joined:
    Jan 31, 2009
    Messages:
    7,148
    Likes Received:
    449
    Gender:
    Male
    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.
     

Share This Page