Saturday, January 7, 2017

First Wire Wrapped and Soldered Bracing Cable Terminal

 All of the external bracing cables on the wings and tail of my WACO were made from 1x19 galvanized wire rope (cable).  At some point in 1927 they changed to the more expensive, solid, streamlined wires as used on the WACO TEN and later WACO planes.  The ends of the non-flexible cables were formed using the Wire Wrapped and Soldered Cable Splice.

 Today we use either a fitting swaged to the end of the cable or a Nicopress sleeve to form the splice.  I plan to use the original wrapped and soldered method for all the bracing cables.  Flexible control cable used a woven method like is used for the ends of ropes.  I'll get to those later.

On our Fly Baby we made all the 1x19 bracing cables ends using Nicopress sleeves.  The problem is it leaves one end sticking out to snag skin, clothes, or anything else that gets close. The Nicopress sleeve makes a splice which has the full strength of the ecable.  The wire wrapped terminal only has 90% of the strength of the cable so I couldn't use it on the Fly Baby without a lot of engineering work.

To give the Fly Baby that old time look I decided to make the loose end of the cable (sticking out of the sleeve) a little longer and wrap it with wire to look like a wrapped splice.  This would also let me practice doing the winding and soldering in a way that would not risk cable failure while learning how to make the cables for the WACO.  I also used a zinc plated sleeve so it would be less obvious what I had done.

I found some 22 gauge galvanized wire at the last real hardware store in Charlottesville.  They had packs of 100 feet so I bought the three they had.  It takes about 5 feet per splice.  I had previously bought 20 gauge wire.  The WACO Drawing Room Manual (D.R.M) page II-4 Shows 0.035" (20 gauge) wire for 1/8" cable as does WACO drawing 3800, per the Army-Navy Standard.  The D.R.M references WACO Spec. No. 25513 which I do not have.  I'll need to find a copy of it.  The cables on my WACO clearly use 0.025" (22 gauge) wire as shown in CAM 18 which is what I will use unless I can find proof the heavier wire makes a stronger joint.

For the Fly Baby I installed the Nicopress sleeve, trimmed the loose end of the cable at the point where it would have been for a wrapped splice, and then wrapped it with the 22 gauge serving wire.
 I have a soldering pot I made but I did the soldering with just my big iron and it came out great.  I was able to use the soldering iron to get right up to the Nicopress sleeve without making a mess on the sleeve.

 Since my earlier post, I've learned there is an easy cheap source of rosin.  Dancers use it to dust their shoes.  They sell it in quantities up to 50 pound buckets.  I ordered a pound of it, about $20, to make a new batch of flux.  I believe the old batch got overheated and does not work as well.  In the future I will only re-heat with a double boiler well below boiling to avoid damaging the flux.  This batch works so much better.
 This rosin is a mix of chunks and powder.  The dancers use it as a powder to coat the bottom of their shoes.  For our purposes it doesn't matter since we're melting it.  I like seeing it as chunks so I'm more confident I'm really using rosin.

 I cut some of the candle shaped tallow into chunks to help melt it.  I'm making a mix with 40% tallow (stearic acid) so I've measured out 4 ounces of tallow.

This time I was very careful to heat it slowly to avoid any chance of damaging it with heat.  I set the hot plate at it's lowest setting and let it heat very slowly.  Again, in the future only re-heat with a double boiler.

The tallow was fully melted at about 170 degrees F.

 Once it was melted I added 6 ounces (60%) of rosin, stirred it in, and let it slowly melt.

It was a gooey mess as it slowly heated and melted.  This took about an hour.

As it got to 200 degrees the rosin was fully melted.

The old batch had turned a very brown color.  This batch looks like you would expect with the yellow resin and white tallow mixed.  I made application sticks as with the old batch and did some soldering.  This batch is like magic.  I'm discarding the old batch.  The new flows faster and only takes one application of flux.

I made my first wire wrapped terminal to tryout the process.  I'll write up a detailed explanation of the process once I've had some more practice.  I soldered the Fly Baby terminals with the soldering iron to keep solder off the Nicopress sleeve.  I dipped this whole terminal in the solder pot.  The one thing I noticed doing that was that it is hard to get the gap under the wire wrap to stay full of hot solder.  It all wants to run out because everything is so hot.  With the soldering iron you can control the heat a little better.  We'll see what works best with some practice.  CAM 18 requires the gap under the wrap wire be filled with solder.  CAM 18 also prefers you to use a solder pot.  One of the old text books I have prefers you use a soldering iron, go figure.

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