Wave

The 14-day test

June 22, 2020

by David Conklin

On May 14th , three members of the Rose City Park Neighborhood Emergency Team sat (masked and socially distanced) with me on my front porch and examined a DayZero water box. I told them about the 10,000-crank test that we were preparing to run with 5 similar units (https://uv-h2o-box.com/the-technical-details/the-10000-crank-test). We talked about the possibility of including the water box in the caches of emergency supplies that are located around Portland. One NET member speculated that, while the electrical power would be out after a big earthquake, there would be no shortage of volunteers to turn the crank on a water box. Then he said, if the water box could be relied on to treat 100 gallons of water a day for 14 days in a row, it would make a good addition to the emergency caches.

Naturally, we at DayZero decided to see whether our water box would pass the NET test in addition to the 10,000-crank challenge from https://theprepared.com/. We successfully completed the 10,000-crank test on 5 units on May 27th . The very next day, we began a 100-gallons-a-day-for-14-days test.

Almost immediately, our test stand broke down. The motor in the test stand began to draw more than its rated current, causing the power supply to decrease the DC voltage to the motor, causing the motor to slow down. We realized that the connection was loose between the drive motor shaft and the wooden disk used to push the water box crank handle. It was loose because we had worn it out in the 10,000-crank test. The amount of current drawn by the motor had been increasing from one unit to the next over the course of the 5-unit 10,000-crank test, and on the fifth unit, it had been 2.7 A, just shy of of the 2.85 A rated maximum for the motor.

We rebuilt the test stand, using a 12” aluminum bar to connect the motor shaft to the wooden disk, in place of the worn-out 6” aluminum bar. We began the 14-day test again on June 1st , using one of the units that had already completed the 10,000-crank test. The 14-day test was completed successfully on June 14th . Including the usage during the 10,000 crank test, the unit had logged 130,000 cranks, simulating the treatment of 1,588 gallons of water. The actual number of turns of the crank was higher still, because the sensor that counted turns had gradually gotten out of position during the first week. I noticed that it was missing some of the rotations and adjusted it on June 8th . I estimate that the actual number of turns is about 140,000.

At the end of the test, there was noticeable wear on the generator bushing and some blackening of the ends of the UV light tube. Nevertheless, the unit was still working mechanically and was still delivering a UV-C light intensity comparable to a new unit.