Special to RC Modeler Magazine
September 22, 1995
It may have the appearance of grown men playing with a remotely-controlled toy tank, by the reality is that the Tire Assault Vehicle (TAV) - created from a one-sixteenth model of a German World War II tank - was an important safety feature for the CV-990 Landing System Research Aircraft (LSRA) and ground crew members at the NASA Dryden Flight Research Center, Edwards AFB, Calif.
The TAV was built from a Tamiya King Tiger tank kit and modified into a radio-controlled, video-equipped machine to drill holes in aircraft test tires that were in imminent danger of exploding because of one or more conditions - high air pressure, high tire temperatures, and cord wear.
An exploding test tire releases energy equivalent to two and one-half sticks of dynamite and can cause severe injuries to anyone within 50 feet of the explosion, and ear injury - possible permanent hearing loss - to anyone within 100 feet. The danger condition is determined by the temperature, pressure and cord wear of a test tire.
The TAV was developed by David Carrott, a PRC employee under contract to NASA, for use by the CV-990 project which tested space shuttle tires on the main Edwards AFB runway and also on the base's dry lakebed. The need for a tool like the TAV arose when the project began tesing space shuttle tires beyond normal limits to determine conditions that would cause them to fail. Simpler methods of puncturing the tires under high pressure after each test were tried, but were ineffective and even dangerous.
Air Force personnel at Edwards routinely use a robot for bomb disposal and it was available to assist NASA in tire test, but not always at the time that is was needed. The bomb robot, which weighs 450 lbs and cost $100,000, is also 4 feet long, 4 feet tall and 3 feet wide - too big to always be moved under the CV-990, a former commercial transport. NASA needed an alternative, so Carrott followed the agency-wide concept of doing things "faster, better, and cheaper," and developed the TAV at a cost of less the $3000.
The unit weighs just 20 pounds, and it's only 18 inches long, 12 inches high and 8 inches wide - small enough to be easily maneuvered under the CV-990. Because of its instant availability and fast set-up time, it answered the need for a robotic unit to eliminate unsafe conditions resulting from hazardous tire tests.
Approximately 25 percent of the original model parts were used by Carrott to build the TAV, which features a 3/8-inch drill mounted on its top side. It is powered by a single 12-volt, rechargeable gel cell (7AH) battery driving three Black and Decker drill motors. Two motors are geared through a transmission to independently drive the left and right tank tracks. The third unit is the variable-speed drill motor itself.
Motor control is with solid-state custom VANTEC remote control speed controllers, one for the drill and one each for the two tracks. The transmitter/receiver is a JR Model X-388S airplane r/c system modified for government frequency and independent spring center track control.
The r/c system includes direct servo control (DSC) permitting operation of all controls and servos without generating a radio signal.
Video reception is handled by a down-converter to RF composite signal feed to a portable black and whte television.
The TAV was available to support 32 tire test operations between February and August of this year, and was used to drill into nine test tires to relieve pressure - four of them considered to be extremely dangerous and on the verge of exploding.
Although the TAV was developed to support the shuttle tire test program at NASA Dryden, it can be used in any environment where personnel safety is at risk due to the possible explosion of an aircraft tire.
With its video transmitting capability, the TAV could also be used as a visual scouting vehicle in other situations that present an environmental or health hazard.
--nasa--Note to Editors: