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THE METAL-BENDERS” by JOHN B. HASTED

An important choice the experimenter must make is the size of the metal specimen and just how the strain gauge should be mounted in it.

When a strip of metal is gently stretched, the extension (strain) which causes the signal is directly proportional to the tension (stress). The thinner and narrower the strip, the larger is the extension for the same tension and the more sensitive is the equipment to force. When we require the greatest sensitivity, we may stick the gauge onto a metal strip only 0.75 mm thick and cover it with a thin piece of foil for electrostatic shielding. But the experiments concerned with the details of strong effects, such as those with Nicholas Williams or Jean-Pierre Girard, require much more robust specimens.

We must of course use the recommended strain gauge adhesives; there is a danger of paranormal forces tearing away the strain gauge from the metal. To attach the strain gauge with adhesive tape (a reported procedure) is quite inadequate. If the strain gauge itself is fractured by paranormal action, then the experiment terminates; but I have conducted sessions in which there was fracture of the specimen without destruction of the strain gauge and it was still possible to continue work.

When the strain pulses are sufficiently strong for the specimen to be deformed permanently, the chart-recorder trace may also show a permanent deflection. There might be a correlation between the magnitude of this deflection and the observed angle of the bend; an effort has been made to reproduce the data graphically in Figure 4.3 for sensors mounted in latchkeys in the Nicholas Williams experiments.

Figure 4.3 Comparison of permanent deflection chart-records with observed bend angles of latchkey during the Nicholas Williams sessions summarized in Table 5.1. The 45° straight line is merely a fitting to the data.

But the correlation is not an accurate proportionality, partly because the bend does not always take place exactly at the position of the strain gauge and partly because, ….., the signal may correspond only to a permanent extension and not to permanent bend.

NOTES

A latchkey will usually bend somewhere along the part that goes into the lock, while the strain gauge has been deliberately mounted in the handle and will continue to function even when the latchkey is fractured.

In the first session with Stephen North, using a long thin strip of aluminium, a very large visible bend or curl through 540° was produced more than an inch from the strain gauge, and no permanent deflection of the chart-record was manifest.

Sometimes the electrical connections to a strain gauge are bent or fractured paranormally during a session; in some early experiments it was my practice to embed them in solid epoxy-resin; but it is sometimes important to avoid alteration of the mechanical properties of the specimen.
When the strain gauge is embedded in the metal, the subject has no direct knowledge of its form, and it is very likely that any paranormal action will be on the metal itself. We have found evidence from subsequent experiments with several sensors mounted inside one specimen that it is usually the metal and not the strain gauge which experiences the ‘action’.

During the first ten hours’ experience with strain gauges exposed to metal-benders I learned much about their use from mistakes that were made. But after nearly two hundred hours of exposure l consider that I know sufficient to avoid mistaking drifts or artefacts for paranormal signals, and vice versa.

Among others, physicists Ron Miller, David Robertson and Elizabeth Rauscher have taken part in the exposures of strain gauges and have brought a fresh critical approach to the methods l use.