Printable View for Presentation #31 (See also "Manual on a String").

Harvesting Steel Wire

Description of how metal wire can be recuperated from a worn out car tire. How to cut the rubber, how to use a sharp small knife to do a clean and fast job.
Also check the page Harvesting Steel Wire.

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Author: Demotech, design for self-reliance
Version: Juli 27, 2008 Feedback email info@demotech.org
Postal: Biesenwal 3, 6211 AD Maastricht, the Netherlands

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1

Obvious but obsolete method of cutting the rubber and canvas away from the steel wire ring

As the steel wire ring is only covered with a 2 mm thick layer of rubber with canvas, it seems the obvious method to remove this thin layer first. With a common sharp knife such as a cutlass, a start can be made by cutting away the rubber covering the side of the ring.
A better and faster method of harvesting steel wire is shown a bit later in this manual!

Keep the knife razor sharp!

While the rubber is cut with sawing like motions, the sharp edge of the knife is guided by the steel wire. This tends to dull the knife. Cutting rubber with a dull knife does not work. So teach yourself to sharpen your knife and check it regularly that it still sharp enough.
However beware of accidents! Make sure not to endanger others or yourself, plan your movement and your workspace carefully!
Have a First Aid Kit in close reach.
Search for instructions of how to sharpen knives at Google or look at the Instructable for sharpening knives

Cut rubber away from the steel wire ring

To cut the rubber as shown in the picture is still workable. More difficult is cutting the steel wire free at the inside of the tire. With some practice it is possible to clean the steel wire at three sides. Apart from practice it takes also longer time as hoped for!
When the steel ring is visible, also the place can be seen where the steel wire ends. This is the place to begin peeling the wire out.

Carefully lift the wire out of its rubber bedding

Do not use force, do not pull! If you do, the wire comes out well enough, but also bent in a tight irregular spiral. This makes the wire hard to handle, to scrape clean, and to store away.
The best way to get the wire out as little bent as possible is to force a knife between the wire that is accessible and the next layer of wire under the first.
This works well for the first round. The wire that is deeper embedded in the rubber is more difficult to get out.

How a roll of wire should look after harvest

As the picture shows it, that is about the best what you can expect when working really careful. It ask for cleaning away all the rubber and its canvas reinforcement. Any little bit of rubber that remains hinders the peeling out of the steel wire.
Demotech finds more good use for steel wire, also in larger quantities. So there is a clear need for an easier and quicker method. This method is described in the following pages.

Try to understand what is special about cutting rubber

A real sharp knife slides through rubber like through butter! But only under one special condition: the rubber that you want to cut should be drawn apart. This rubber should be under tension and never, never under compression. This is how it does not work, just try to cut as if rubber was wood or a potato. Then the rubber compresses around the edge of the knife. As rubber causes so much friction (yes, that's why it is used to keep cars on the road) the friction keeps the knife from cutting unless excessive force is used.
Therefore: lean in the inner ring of the tire and cut as it shown.

Cut rubber with a thin sharp knife

In the old days Demotech preferably used a strong thick knives such as a cutlass. This is shown in the first pictures. But we learned that sharpening a broken hack saw blade (for sawing metal) makes the ideal knife. A strip of inner tire is wound around the knife where you hold it.
Pull the rubber as is shown in this picture and cut out the side close to the steel fabric embedded in the tread of the tire.

The rubber disk, comes free with the wire!

Though you want to cut out the wire, you will find many uses for the flexible strip that you get as an extra bonus this way. Demotech makes hinges with it for doors and boxes, we use it as washers for the rope pump, but the strip is nog wide enough for cutting shoe soles out of it, unless for the smaller sizes.
Note that the cutting goes best with only a light pull at the disk. When you pull hard, it is hard to steer the knife and the edge gets ragged.

First disk done!

Of course there is a second site that should be cut out. When you have butchered the tire this way, it is time to ask yourself what to do with the tread of the tire. You can not cut the embedded thin steel 'textile' with a knife. But it works well to saw it with a very DULL metal hacksaw. Clamp the rubber between two bits of wood and saw close to the edge of the wood, where the rubber gets some support.
Each tread is 1,70 long. They can be put together lengthwise with an iron cramp. Thus they form a very strong flexible strip. Not difficult to find good use for this as well!

Time to cut off the rubber disk

Cut the disk as is shown. Cut along the steel wire. This takes some practice, but is easy to do with a helper who keeps the ring in the right position.
Again try to cut smoothly along the wire. This gives maximum width for the disk strip. And it safes work for later cleaning of the ring that contains the steel wire. This asks for good teaming up with your helper. Take safety precautions! Cut the rubber as shown. Do not endanger your helper by cutting in his or her direction.

Separate strip from ring

Let your helper firmly hold the ring, while you cut of the side wall strip. Store the two strips properly away for later use, as the 4 mm thick rubber strip is useful for many a purpose, such as for making a hinge.

Prepare a little better!

The steel wire springs up from the ring, but beware, do not force your knife in left over bits of rubber. This way the wire will not come out straight.

Thoroughly remove rubber left overs

The right way it to carefully remove the last bits of rubber, first on the outside, then (next picture) on the sides.
As you cut along the steel wire, you need to sharpen your knife more often.

Cut strips of rubber from the sides

The first layer of the four steel wires may already detach itself, but do not start pulling.
Continue the cutting away of the rubber at the sides. It comes of easily, specially when the helper pulls at the strip that comes off.

Peel the wire off the ring

Only now it is time to let your knife glide between the layer of wire that comes off (often 4 wires wide, that stick still together).
The helper winds the wire in a roll, but does not pull. Let the knife gently do the work.
When the steel wire it taken off, only the rubber inside cover is all that is left

Scrape off last bits of rubber from the wire

Little bits of rubber that sticks to the wire can now easily be removed. When you draw the wire towards you, clean the wire by scraping it at all sides with the knife. Look at the picture how the knife should be held.
While you wind the wire, the helper should let go while you scrape. The wire is about 9 meters long and there are four wires in each ring.

Harvest 35 meter steel wire

There you are, with a harvest of about 35 meters of steel wire. That is what comes off from one side. One car tire has two sides, so contains about 70 meters steel wire. The wire that comes off may be rusty when the heel of the rubber side wall was damaged and water has crept in between the steel loops.

Author: Demotech, design for self-reliance Version: Juli 27, 2008	Feedback email info@demotech.org Postal: Biesenwal 3, 6211 AD Maastricht, the Netherlands
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