Screw Terminal Reliability?

[Steve Shannon]

Here’s why I probably sound like a stopped clock when I harp about tinning leads used in terminal strips:
https://wiringharnessnews.com/article/2901/

 

[Sandy H.]

Here’s why I probably sound like a stopped clock when I harp about tinning leads used in terminal strips:
https://wiringharnessnews.com/article/2901/

Good short article. Worth a read for sure.

I love a good ferrule connection. Growing up with only the local autoparts store quality tools and parts, crimp connections were terrible and therefore always 'bad' and soldering etc., was required.

Now that I've seen (and done) industrial quality connections in various applications, I absolutely see that crimping, ferrules, soldering etc. all have the right application !when done correctly!.

Ferrules into screw terminals when done with proper ferrules, proper crimp tooling, proper installation and proper termination is a great industrial solution - my preferred 80+% of the time given the equipment I work around. Probably doesn't apply to nanometer chips or 5000mcm cables, but not a bad fit for industrial connections in the 24ga-8ga size range from my experience. Maybe even further up or down the wire size scale, not sure. . .

Sandy.

 

[Hobie1dog]

While working as a multi-craft facilities tech for many years, and 7 years of building pipe organs with thousands of connections, I've never tinned any of the wires.

 

[SteveThatcher]

great article by the guy at Phoenix. I agree that a tinned wire can deform and loosen with time. For installations that are considered permanent they are ideal. As I said before, the terminal blocks are engineered for that purpose. Our use in rocketry which can require the wires to be taken in and out a lot, is what I was talking about. I always double check terminal blocks connections before the rocket flies. If anything had loosened, I would have caught it. I will still tin wires in my bays to take care of wire strands, etc that could be a bigger problem.

 

[Steve Shannon]

great article by the guy at Phoenix. I agree that a tinned wire can deform and loosen with time. For installations that are considered permanent they are ideal. As I said before, the terminal blocks are engineered for that purpose. Our use in rocketry which can require the wires to be taken in and out a lot, is what I was talking about. I always double check terminal blocks connections before the rocket flies. If anything had loosened, I would have caught it. I will still tin wires in my bays to take care of wire strands, etc that could be a bigger problem.

I agree, Steve, and I certainly have tinned leads, but like you I check them and tighten them each flight. More than anything I just want people to know about the slight risk

 

[David Schwantz]

Not only all of the above, but I have had the wire get under the terminal in the block, could pull loose. Even though it had a connection, it was NOT secure. A gentle tug on the wire found it. Also, some of the screw blocks use an anvil that goes up to lock in place, instead of down. You must install the wire on top of it, if you'd install the wire below, it also would not be secure. Again, a gentle tug would find it.

 

[cerving]

If you're really worried about this, you can solder pigtails directly to the board. For Eggtimer stuff that's easy, for other manufacturer's stuff you'll have to unsolder the terminal blocks. For a no-terminal build, just run the pigtails out the bulkplates and twist-tape your igniters to the pigtails. Seal the holes with sticky putty or hot melt glue.

 

[jderimig]

Screw terminals should be used with ferrules. No excuse not to. The problem with bare stranded copper wire and tinned wire (worse) is the clamping force on the wire relaxes because the wire yields. A crimped ferrule stays elastic under the screw clamp.

https://www.amazon.com/Ferrule-Crim...prefix=ferrule+kit,aps,109&sr=8-1-spons&psc=1

 

[SolarYellow]

Any strong opinions on square vs. hex crimpers for the ferrules in these applications?

 

[jderimig]

Any strong opinions on square vs. hex crimpers for the ferrules in these applications?

I didnt even notice there were those options. I use the 4-jaw crimper and its great for me.

 

[user 30299]

I didnt even notice there were those options. I use the 4-jaw crimper and its great for me.

Any suggestions on the three or four ferrule sizes to keep on hand for the basic wiring of avionics bays?

And I do realize this is dependent on the wire gauge, terminal block, etc. But in your experience what
sizes cover most applications for your builds. (trying to avoid turning this into a glue thread, lol)

 

[SolarYellow]

There's a chart here with sizes and color codes (in the three different systems):
https://www.efixx.co.uk/Know How/ferrules
This one recommends ferrule size vs. wire gauge:
https://www.interpower.com/ic/desig...guides-and-charts/ferrule-selection-guide.pdf

 

[jderimig]

Any suggestions on the three or four ferrule sizes to keep on hand for the basic wiring of avionics bays?

And I do realize this is dependent on the wire gauge, terminal block, etc. But in your experience what
sizes cover most applications for your builds. (trying to avoid turning this into a glue thread, lol)

The White ones. But seriously I get the kit and only a few will fit any individual terminal block. After that the one thats close to the wire diameter used.

 

[SolarYellow]

There are also uninsulated. They don't have the strain relief properties of the insulated ones, but are lighter and might help with the packaging for those squeezing electronics into too small rockets, while doing all the other positive things ferrules do. Accomplishes everything tinning does with none of the drawbacks.

 

[user 30299]

There's a chart here with sizes and color codes (in the three different systems):
https://www.efixx.co.uk/Know How/ferrules
This one recommends ferrule size vs. wire gauge:
https://www.interpower.com/ic/desig...guides-and-charts/ferrule-selection-guide.pdf

The chart on that link stops at 20 gauge. The white ferrules are good for 22 gauge. Good to go.

 

[Steve Shannon]

The chart on that link stops at 20 gauge. The white ferrules are good for 22 gauge. Good to go.

For even smaller wires, FerrulesDirect has some:
https://www.ferrulesdirect.com/products/aw02508

 

[jderimig]

For even smaller wires, FerrulesDirect has some:
https://www.ferrulesdirect.com/products/aw02508

You know we are living in a guilded age when there is such a thing as "Ferrules Direct"

 

[Steve Shannon]

You know we are living in a guilded age when there is such a thing as "Ferrules Direct"

Exactly my thought. It’s like a David Letterman thing.

 

[jderimig]

Exactly my thought. It’s like a David Letterman thing.

 

[Hobie1dog]

So now, ferrules are the only way to go?

 

[Steve Shannon]

So now, ferrules are the only way to go?

No, but if you tin your leads and insert them into terminal strips like Phoenix makes you should check them periodically to make sure they’re still tight.

 

[FredA]

Ferrules are the BKM for terminating wires into compressive terminal blocks.

 

[Sandy H.]

Any strong opinions on square vs. hex crimpers for the ferrules in these applications?

When we decided to go to using ferrules at work, we asked the ferrule supplier (pretty sure it was Phoenix) what they recommended and it was the 6-jaw hex style. Once I found out how nice it is to work with ferrules, that's the type I bought and I do like it. I can't say for sure if it is better than others or not. I'm guessing it might be better in some terminal blocks than others, depending on the terminal block design, but that is just speculation on my part.

In addition to the regular ferrules, they make multi-wire ferrules so you could insert 2 wires into the ferrule before crimping and then install in the terminal. While you could likely do this with 2 wires by just going to the next ferrule size, I like the way they give more room for the insulation.

The reality of the matter is that I like my electrical toys. That's why I have a Panduit zip tie gun and put ferrules on stuff. Definitely not required, but if you're going to do something, do it the best way you can and use the proper tools and supplies. My opinion only.

Sandy.

 

[SolarYellow]

The reality of the matter is that I like my electrical toys. That's why I have a Panduit zip tie gun and put ferrules on stuff. Definitely not required, but if you're going to do something, do it the best way you can and use the proper tools and supplies. My opinion only.

Sandy.

I'm a mechanical, not a sparky. That my be why I invest in the tools to make the mechanical aspects of my wiring groovy.

 

[Sandy H.]

I'm a mechanical, not a sparky. That my be why I invest in the tools to make the mechanical aspects of my wiring groovy.

Me too. I have always been a mechanical guy, but after I found out that electrical stuff wasn't impossible, I became a little bit of both. At work, I became the controls engineering manager for a while, as nobody could BS me, as I knew enough about all 3 disciplines (mechanical, electrical and software) and how they interacted to figure out if somebody was blowing smoke. Software would blame sensors or mechanical, electrical would blame software or mechanical, mechanical would blame both software and electrical at the same time. I had no problem figuring out what the real issue was and then telling the right group to fix it. Did some pretty cool stuff. Once everybody realized I was going to figure out who to make responsible to fix things, everybody started working together better instead of trying to make up stuff to deflect responsibility. They would often see something wasn't working right and try to make sure they weren't really the cause instead of immediately blaming a different group. Often times, all three groups would then find areas that were deficient (i.e. mechanical would see a tolerance that was too loose, electrical would see sensor drift and software would realize that a calculation was a little off). Once everybody fixed things in their own discipline, the whole product got soooo much better than any single fix would have made.

Regretfully, it was a short term (4-year) job, as my whole point of doing the job was to help complete the last few 'old design' systems as the company transitioned to an entirely new system. I wasn't interested at all in the new system and once the last machine with that old system shipped I moved to R&D.

Sandy.

 

[jderimig]

I'm a mechanical, not a sparky. That my be why I invest in the tools to make the mechanical aspects of my wiring groovy.

Electrical connections is mechanics.

 

[Sandy H.]

Electrical connections is mechanics.

Our electrical department would agree, as would the hydraulics department for both wet and dry connections. The mechanical department would disagree and the assembly department would say for sure that the mechanical guys sure as he$$ should not be specifying electrical or hydraulic connectors/fittings. After specifying both hydraulic fittings and electrical connectors, I understand why electrical engineers seem to have twitches more often than not. Working through the BS of "any option is an option, except it isn't available" is much worse in electrical for smaller purchasing companies vs. the hydraulic guys for small companies. The hydraulic guys seems to say "heck no, you can't get that, so use these two" while electrical guys seems to say "sure, no problem, put that on your BOM and we'll kill your lead-time once you place a PO". My experience only. Possibly also the current automobile, industrial/commercial, aerospace , housing and construction (and likely a few I didn't think of) industry experience as well, but I don't claim to represent those industries (nor the industry I do represent in my limited capacity. . .I represent nobody, not even myself. I think that's enough disclaimers. . . )

Sandy.

 

[gdjsky01]

There is nothing wrong with them. Who gives a you know what if NASA does not use them. Used properly they work fine and ALWAYS have for me. YMMV. Especially if you are prone to not checking things. My biggest beef with some electronics is they don't come with terminal blocks making a tangled mess of pasta all around the board. Blocks make for clean, and portable, installations. If I wanted to be certain and portable, cannon plugs like used in jet fighters would be my choice. Except I don't build overpriced pieces of junk like the F35 or F22, so I stick with terminal blocks.
And yes! YMMV Greatly!
Do what you will!

 

[FredA]

Electrical connections is mechanics.

In properly designed electronics, the failure are more mechanical.

 

[jbr]

so my connections that have been working for 20 years are now subject to failing? I use ferrules on mains voltage, using on 12v for me is a waste of time and money, what works for me may not work for you YMMV