The FVR/NIRA brain trust was just refurbishing launch equipment over the winter, so we can be ready for spring. Of course this includes clip lead maintenance.

Our clip leads are pretty typical: 3-6' of zip cord with a dual banana jack on one end, and micro-clips on the other end. We're replacing a lot of the clips.

What we noticed is that cutting off the clips and an inch of wire leaves newly stripped ends that are already corroded. Cutting off several more inches and we found the same crap. Since all of the wire was clear speaker lead, we could actually see that there was corrosion INSIDE the leads going back at least a foot. Even more bizarre, they all stopped at a knot in the wire. If we cut past the knot, the conductors were usable.

Has any one else ever noticed this? Is it a "feature" of speaker cord, or does lamp cord do the same thing?

Has any one else noticed that a knot in the wire stops whatever process causes the corrosion?

Any recommendations to prevent the corrosion? Cutting off that much wire leaves lots of leads too short to be usable any more.

In an email, Jim Fackert recommended using silicon wire for clip leads. Has any one used this, and how does it work? Where do you get it, and what does it cost?

Finally, can any one recommend a procedure for soldering to the NARTS stainless steel clips. I made one clip lead for my personal launch system, and after 2 years of use the clips are fine, but since they are only crimped to the wire, the wire is starting to fray. I need to be able to use the crimp tabs to grab the plastic jacket for strain relief, meaning the clips really have to be soldered to the wire.

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We use about a foot of zip cord from the attach point on the torture rack. It has the same corrosion from being shorted out and covalence change.

The knot is something I noticed and never made a point of fixating on it. That might work. The rule is to have a straight line to the source with no loop or knot. To me, it feels like if you have to change a foot of zip cord once every year or two of near constant use falls within "reasonable maintenance expense" and labor.

Jerry

I wondered about soldering to the stainless clips from NARTS as well.....so I wimped out and got some copper Mueller ones from DigiKey to replace some failed clips I had.

Perhaps you could crimp them well but then sleeve the joint with 3/16 heat shrink tubing (not unlike the way the joints are covered on current production Estes controllers)?

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Black corrosion under the wire insulation is common. I put general purpose automotive grease on my rack launcher's microclips after cleaning them off, tip to tail. I wipe the grease off when I set it up for the next use. It won't prevent the wire corrosion, but it seems to have minimized the process and does a world of good on the microclips. I use clear speaker wire also and I've never had more than a couple inches of the black corrosion. I don't bother replacing the wire until it becomes brittle. Even with an inch or two of corrosion, it carries enough current to handle clusters. I use common flux and solder to attach my clips.

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Soldering Stainless requires a special flux. i bought a bottle at a local welding store. Duzall is the brand name. It has all the chemical goodies found in regular flux, but they are dissolved in an acid (actually, it appears to be a diluted HCl solution).

I had first tried using some pool acid (muriatic or HCl) using a toothpick to transfer just a bit and it worked instantly, but the commercially available acid flux is the best.

I'm not sure about the corrosion, since I don't do the repairs on the club equipment. I will refer this thread over to the person who does some of the repairs and maybe he can comment on the wires we use and how the corrosion does or does not creep up the wires.

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-Fred Shecter NAR 20117 (L2)
Southern California Rocket Association, NAR Section 430

Interesting...that behavior at the knot indicates the corrosive substances do not work back along the wire by capillary action alone, but also by gravity assist. It does not go uphill, hence stops at the knot.

Perhaps a partial solution is to store the leads hanging with the clips down?


Bill

This sounds very similar to "black wire corrosion" that plagues battery packs. I had to replace the wires in a Futaba 7UAF a few years ago because of corrosion that had eaten all the way back to the circuit board.

Do a Google search for "black wire corrosion" and you'll get quite a few hits. I see everything from RC systems to EVT (Emergency Vehicle Techs) to digital cameras to BMW auto headlights...

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I have used silicone-insulated wire in the past for clip leads. It's nice stuff - very soft and flexible. Biggest drawback is higher cost. Look for it in the R/C section of your local hobby store. Many will stock silicone wire from MPI:
http://www.maxxprod.com/mpi/mpi-5.html
Note that this is all single conductor.

The NARTS stainless clips are actually made by a company called Lakewood Products located about 12 miles from my house.
http://www.lakewoodproductsinc.com/test.htm

Last year, I bought 100 clips directly from Lakewood. When I went to solder some to the leads, I could not get the solder to stick. I was roughing up the surface, using my normal electrical flux and lead/tin electrical solder with my regular soldering iron set to 650 deg F.
I called up Lakewood and talked to them. They said that, when they solder wire to these clips, they also use a regular soldering iron with lead/tin electrical solder but use an acidic flux on the clip.
I ran down to my local hardware store, explained what I needed, and they found me a bottle of "stay-clean" flux in their store room. Using that stuff, solder stuck beautifully to the clips. Because it is acidic, remember to thoroughly flush the clips with water after soldering. Also rinse all tools that come in contact with it - otherwise they'll rust up on you. If you're really paranoid, I'd think that using solution of baking soda in warm water would make sure that the acid is neutralized.

Alan

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Acid will not make any metal rust (or oxidize). Acid reduces or removes the oxide. That is why it works on stainless steel - it removes the protective outer oxide layer that prevents the solder from sticking. once the oxide is removed, the solder will grab hold of the metal. Then you want to wash off the acid and allow it to dry.

Do not soak in anything (like baking soda) that is basic, as that will eat through the metal itself. Ever drop some aluminum foil in Lye? Or watch how the lye in Drano dissolves the metal bits they include in it to produce heat and bubbling (Hygrogen gas) action to melt through hair and grease? That's why you have to be careful using lye on metal pipes.

Soldering normal copper can be done with normal rosin core flux. you always clean the surfaces to make them shiny, but the instant they are exposed to the atmosphere, a tiny amount of oxidation starts. Normal solder has a flux that will combat this small amount of oxidation. It will NOT work on stainless steel. For that, you need the liquid acid flux. The stuff sold at the hardware store as "acid core flux" solder will not work as the acid is not strong enough.

Use the Duzall brand or equivalent flux.

I beleive our clip maintainer soaks the copper clips and leads in a mild dishwashing detergent solution in a bucket and then allows them to dry after each launch. Otherwise, the acids left behind by the rocket exhaust will embrittle the solid copper clips and they will begin to crumble.

We have not used a lot of our NARTS stainless clips yet, but they are going to be used very soon to replace a bunch of our copper clips that have bad springs or are worn away (some folks sand them clean between flights with coarse sandpaper which is insane .....). The stainless clips will be easier to clean between flights and after launches.

Also, as is his nature, Larry Chaney has been going insane with a few of the NARTS clips I gave him and he is playing around with non-solder connections including a mechanical (screw and nut) connection using a small copper or brass tab with the wire leads soldered to the tab and the tab screwed to the stainless clip through the hole. No crimping is done with this method. I find that to be overly complicated and time consuming and I think that there will be a crud/gunk layer problem interfering with the electrical connection at the mechanical attach point.

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-Fred Shecter NAR 20117 (L2)
Southern California Rocket Association, NAR Section 430

After my last clip soldering session, I neglected to rinse the flux off of my wire strippers. When I grabbed them out of the toolbox two weeks later, they were rusted everywhere that the flux had touched them. Perhaps the acid removed the protective coating...

To get the motor gunk off of the stainless NARTS clips, I soak them for a few minutes in white vinegar. The gunk then wipes right off with a rag; I rinse them in clean water and allow them to air dry.

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