8. Horizontal and Vertical Thrust Test Bed

While the salt water connected, VER 4.0, of my device worked well, it had repeatability problems of various kinds that are now addressed in Version 5.0. A later test proved my device does not work in vacuum (Blog 9). The thrust reported here is not the Mach Effect but probably due to some kind of air pressure interaction which I plan to investigate later. VER 5.0 is by far my best effort and is showing much improvement with repeatability. This will be the first of several installments regarding the VER 5.0 test stand and test results. Today the test stand will be briefly described, then a video will show vertical tests using piezoelectric chip (PzC) stack #7 previously tested in the salt water bath of VER 4.0.

Test Bed

The test bed was designed to allow 360 degree rotation of the stack in the vertical plane so that resulting thrust forces could be collected and compared in various orientations. It is made up of three parts: the balance arm, the support stand and the laser measurement device. The laser was previously described in Blogs 1 and 2 and will be used later. The stack is suspended with 4# nylon fishing line on the left end of the balance arm (Figure 1). The arm is made from 3/16″ Styrofoam poster board. The hub on the middle right is five layers of Styrofoam laminated with super glue and containing the support and contact needles. They are connected to the stack with 24 gauge silver wire for electrical contact. The counter weight on the right is Styrofoam and lead which can be removed for other testing modes. The complete balance arm is 55.9 cm long and weighing 15.3 g, is suspended on two powered guitar strings in the support stand.

The support stand is an A-frame construction of plywood and hardwood providing rigid support, alignment and connection for the guitar strings (Figure 2). The positive polarity string can be seen in the figure being tensioned with a rotating steel bolt. Both strings are tensioned to the same note in the upper range of the A string (~11 kg). They are mounted 55 cm above, aligned together and offset 3.75 cm from the plywood sides providing 5.0 cm separation. The offsets are hardwood, copper covered fret bars with electrical connection to the drive wires. The balance arm is shown hanging on the strings in the 90 degree orientation used for vertical thrust measurement. It was earlier tested in the zero degree orientation for horizontal thrust using the laser.

Vertical Measurement

A poster board with cm arc lengths is positioned behind the balance arm pointer so that movement can be recorded in video format. The first video shows stack #7 with the large mass pointing down. The led indicates when the drive power is energized with about 2 watts at 605 kHz (See Blog 7 for amplifier schematic). The thrust is up which is toward the small mass. (My design uses no added small mass; instead, it is assumed to be some unknown portion of the PzC itself.) One cm on the scale represents about 2 mg.

Another test was run with the large mass pointing up. The thrust is down as expected but it is only about half what was seen in the up video. This is an obvious bias problem. In my zeal to get this first vertical test completed, I carved the Styrofoam in a very nonsymmetrical fashion while stabilizing the balance arm. Regardless, these are really good results because it’s only necessary to average the two in order to remove the bias. The average thrust of both runs is estimated at about 15 uN. I also used a ~1.5 mg calibration weight ( 3.75 cm nylon line) to show the same approximate thrust effect as in the up and down orientations.

It was very surprising to find the large mass in stack #7 required only 17 mg which was just the square paper tube holding the PzC. This was discovered while attempting to determine the optimum weight for the large mass. (The naked PA2JEW chip used here weights 171 mg.) The paper tube can be bigger or a little smaller but when it’s a few mg the thrust disappears. Stack #4 reported in Blog 7 included a 170 mg brass large mass that worked well but at a lower frequency (444 kHz).

Conclusion

This is still an amateurish effort that could contain errors; however, I have made ever effort to eliminate false positives. For example, in order to go from the up to the down orientation I only need to rotate the balance arm 180 degrees. VER 5.0 test bed is an excellent way of testing PzC stacks in air but testing for the Mach Effect requires vacuum, which will be covered in the next post.

As before comment on any questions, error modes or suggestions that come to mind. Until next time, thanks for viewing. – Larry