Investigating False and misleading claims plagueing consumers of Portable Air Compressors.
U.S. Water Rockets discovered today that the specifications printed on the packaging and in the instruction manuals for many major brands of 12 Volt Portable Air Compressors are false. We were attempting to set a World Record for altitude for true Water Rockets. These rockets are powered by a volume of water, known as a "Reaction Mass", expelled from the rocket engine by compressed air. The greater the pressure in the rocket, the faster it will fly and therefore go higher.
We recently began pressure testing various glues and sealants in an effort to design a rocket which can hold high pressure. To fill the test models with air, we procured an Air Compressor from the local superstore based on the claims printed on the box that the unit in question would reach pressures of 300PSI. The manual which accompanied the compressor also claimed that it would reach 300PSI but should be allowed to cool after running at this pressure. The pressure gauge on the unit itself was marked in increments from 0PSI to 300PSI as well. It appeared to be ideally suited for the tests
After completing a handful of baseline tests at pressures under 200PSI, the system proved to work. However, the next day a test was scheduled for 300PSI. At approximately 230PSI, the compressor hose detached from the pump and released all of the pressure. The pressfit hose clamp was replaced with a screw type clamp to repair the hose. The test was attempted the next day and the pump failed to pressurize more than 290PSI. The pressure gauge leveled off at 290PSI for a minute, and then the pump seized up and began to smoke.
The pump was replaced with another identical unit, which proved to be even less capable than the first. After reaching 250PSI, the second pump began to make a grinding noise. The test was aborted and the pump was inspected. The cause of the noise was discovered to be stripped teeth on the nylon gears in the pump.
A third pump from a different manufacturer was obtained because the packaging illustrated that the pump would pressurize to 300PSI, but after the pump was unpacked in the lab, it was discovered that the instructions stated that 200PSI was the maximum capacity of the pump.
U.S. Water Rockets obtained a high power air compressor to complete their testing and is contemplating a class action lawsuit against the makers of the faulty pumps.
The Water Rocket Forum