Missileworks stranded wire recommendation - why?

I noticed that the RRC2+ instructions recommend stranded wire (20/22 awg) for all connections. I didn't have any so I recycled some e-match wire, which is single-strand copper. Everything looks good and the altimeter passed vacuum chamber testing. I know people wire e-matches directly to the board so this is not an entirely uncommon practice.

Does anyone know why they make the stranded reco? I'm not an electrician by trade but guess it is because stranded will spread and make a better contact in the pressure plates. Is that it or is there a more sophisticated reason?

Apologies if I butchered some of the wiring terms, hopefully I got the point across.

When copper wire flexes back and forth in the same spot (from forces during launch, deployment, landing, etc) it will eventually crack and break. If this happens with single strand wire, as soon as that one strand breaks, your connection is lost. It can happen inside insulation where it can't be seen. The first hint the wire has failed is your rocket coming in ballistic.

I use tinned ethernet cables (the twisted pairs). Advantages include cheap, colored, and pre-twisted. I always tin the ends to keep stray wires from floating off.

I replace all wires after each launch and I use extra electric match wires. I have never had an electronics failure.

cwbullet said:

I replace all wires after each launch and I use extra electric match wires. I have never had an electronics failure.

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I use stranded wires from the battery to the altimeters and switches, then direct wire my ematches to the altimeters (solid single wire). Its been reliable for about 50 or so flights so far.

Even most stranded wire will break after multiple flexes. I use high flex, fine stranded, silicone insulation wire. I have zero fear of failure. I've run this kind of wire for years in combat robots with zero problems. I have it in many colors and from 26ga to 16ga . The silicone insulation also handles high temps so soldering near the insulation won't melt it and short periods of over current won't damage it.

Wow Brian,,
I wish I had colors and sizes of silicon stranded wire...
Very cool ...
That's great stuff,, great quality..
Solid wire will break after you flex it a couple of times...

I use stranded speaker wire from Radio Shack..
Good quality,, but they closed up..
I'm sure you can find the same..

Teddy

Hobbyking sells stranded silicone insulated wire.

Oh yeah..
That's right Rich...
I forgot about them..
That'd be a good bet...
Stock up on that....

I hope you realize by the time I run out of the
Stranded speaker wire I have I'll never remember about
getting the stranded silicon wire from Hobby King....

Teddy

onebadhawk said:

Oh yeah..
That's right Rich...
I forgot about them..
That'd be a good bet...
Stock up on that....

I hope you realize by the time I run out of the
Stranded speaker wire I have I'll never remember about
getting the stranded silicon wire from Hobby King....

Teddy

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A 50' roll of speaker wire lasts about forever in rocketry uses.

rharshberger said:

A 50' roll of speaker wire lasts about forever in rocketry uses.

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Yep,, plenty long enough for me to forget where to replace it...lol...

Teddy

https://www.adafruit.com/categories/282

I used 18-22awg turnigy red and black from hobby king (~$0.80/m) for power connections that will supply more than one thing. But I use the colored 26awg from adafruit for everything thing else. I know they recommend heavier wire but when you consider the short lengths in an av bay, and that your e-match write is longer and thinner, I don't believe it's an issue. The ability to color code everything is definitely a plus.

Ravenex said:

https://www.adafruit.com/categories/282

I used 18-22awg turnigy red and black from hobby king (~$0.80/m) for power connections that will supply more than one thing. But I use the colored 26awg from adafruit for everything thing else. I know they recommend heavier wire but when you consider the short lengths in an av bay, and that your e-match write is longer and thinner, I don't believe it's an issue. The ability to color code everything is definitely a plus.

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+1 the color coding, it definitely simplifies organizing.

Looking solely at the user guides for each product, only the rrc3 notes the recommendation for stranded wire. The rrc2+ does not have any mention of such, especially since it states it is plug-and-play, if you will

The Eggtimer instructions warn to be careful of loose strands with the stranded wire -'once the insulation is stripped, the individual strands break easily and can be very hard to see, potentially getting where they shouldn't and causing a short. It's definitely a good idea to tin the ends. May not outweigh the other advantages for your setup, but worth being aware of.

Oberon said:

The Eggtimer instructions warn to be careful of loose strands with the stranded wire -'once the insulation is stripped, the individual strands break easily and can be very hard to see, potentially getting where they shouldn't and causing a short. It's definitely a good idea to tin the ends. May not outweigh the other advantages for your setup, but worth being aware of.

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+1. Best to tin the ends of stranded wire to prevent this.

Personally I use 22 gauge solid wire. I picked up a surplus spool of telephone wire off eBay when I first started the hobby--over 15 years and probably through less than 1/4 of it. I choose solid wire because I'd rather have a clean break. Years as an electrical engineer early in my career left me much attuned to debugging and I'd rather have something that gives me a clean break, than something that might degrade over time and become intermittent.

Tinning the ends of stranded wire to be used in terminal blocks is controversial even in professional aerospace. If I recall correctly, NASA insists that such tinning never be done because of embrittlement and stress concentration of the wire at the tinning, and ESA insists that it be done because of loose strands. If you were only going to make the connection once and leave it, I agree with NASA, but if you often mate/demate your connections, the loose strands are a real danger. Either way, be careful.

Really good discussion, thanks for all the comments. It sounds like there are pros and cons to both. I didn't think to tin the stranded wire because it eliminates the splayed contact benefit, but the loose strand issue has me rethinking that approach. I need to explore this stranded silicone insulated wire - is that inherently more flexible or less prone to breaking? I am still leaning toward the solid copper but need to be diligent with checking to ensure that the wire hasn't broken. Seems like altimeter startup protocols would identify any wire break points - unless the break occurs due to g-force mid-flight. That would be sad.

Also- Chuck, you replace wires after every launch? You must love soldering I did sleeve my connection points, including on the switch. Do you sleeve? Seems it would complicate the rewiring process quite a bit.

The silicone insulated write typically used lots of very fine stranded which makes it high flex. Also the silicone is soft and flexible so it doesn't try to stay in a bent shape. This kind of wire is often called "wet noodle" wire since its about as flexible as cooked spaghetti. As for tinning the wire, I've done it on combat robots because it make it easier to fit heavier gauge wires into screw terminals without creating stray strands, The non-tinned wire next to the tinned section it flexible enough that I have never had a failure even with extremely sharp bends and repeated movement and disassembly/reassembly. For rocketry I don't bother since the wire is so much lighter than the terminals can accept I just twist the strands and carefully install them. They only fray if they catch the edge of the screw terminal, so a little care makes this a non issue.

mikec said:

Tinning the ends of stranded wire to be used in terminal blocks is controversial even in professional aerospace. If I recall correctly, NASA insists that such tinning never be done because of embrittlement and stress concentration of the wire at the tinning, and ESA insists that it be done because of loose strands. If you were only going to make the connection once and leave it, I agree with NASA, but if you often mate/demate your connections, the loose strands are a real danger. Either way, be careful.

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Yes, understood. And there is a difference in approach based on high voltage vs low voltage. My practice was learned before the breakup of the old Ma Bell, which didn't use stranded too often (per my reasoning earlier), but practiced a century+ of tinning and probably most of those connections are still doing just fine.

In my commercial world, we seldom use single strand for electrical/electronic connections, and never use tinned multi strand (tinned ends will crush, and being soft, will permanently deform and loosen over time given any vibrational stress). Instead, to terminate we use crimp ferrules :

We recommend that you tin the wires then secure the ends next to the blocks/board with zip ties. If it can't move, it can't come loose... assuming you check the screw terminals before you fly, of course.

Ravenex said:

Even most stranded wire will break after multiple flexes. I use high flex, fine stranded, silicone insulation wire. I have zero fear of failure. I've run this kind of wire for years in combat robots with zero problems. I have it in many colors and from 26ga to 16ga . The silicone insulation also handles high temps so soldering near the insulation won't melt it and short periods of over current won't damage it.

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Who/where is your source?

Shade said:

Who/where is your source?

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https://www.hobbyking.com/hobbyking/store/RC_PRODUCT_SEARCH.asp?strSearch=silicone+wire

Banzai88 said:

In my commercial world, we seldom use single strand for electrical/electronic connections, and never use tinned multi strand (tinned ends will crush, and being soft, will permanently deform and loosen over time given any vibrational stress). Instead, to terminate we use crimp ferrules :

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^+1 This.

had an intermittent contact on a rocket that had flown a few times- Criss leaned over and shook the multistrand power leads- source of issue. I will take his advice and be tinning the ends. Love those crimp connectors with reliefs in above comment!

rharshberger said:

https://www.hobbyking.com/hobbyking/store/RC_PRODUCT_SEARCH.asp?strSearch=silicone+wire

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T'anks!

https://www.digikey.com/product-sea...-conductor-cables-hook-up-wire/1638740?k=wire

go have fun.

TEW or TRW 18-16AWG should be enough

https://www.digikey.com/product-search/en/cables-wires/multiple-conductor-cables/1638739?k=wire

for neat & tidy wiring arrangements..

I use about 12 different colours of 20AWG PVC stranded tinned copper wire with a temperature range on the insulation of -40° to +80°C. After many years of hopelessly trying to strip small gauge wire I finally purchased a higher grade wire stripper which is very good at removing just the insulation and not damaging the wire. I crimp then very lightly solder solder the terminals and use 2:1 colour matched flexible polyolefin heat-shrink tubing. All wires are secured to the boards with a slight bit slack at both ends and wrapped in an abrasive/heat resistant cable wrap in certain spots.

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What type of wire stripper? What type of terminal is that?