SAFETY COMES FIRST!
We have four items for your consideration this month:
- Model aircraft vs. manned aircraft: Who has the right of way?
- CO-2 motor alert.
- Some of our fuel system components will not tolerate gasoline.
- RC fail-safe systems.
John Preston
BIRDMAN COLLIDES WITH TOY AIRPLANE
Such a headline could well have appeared in the newspapers across the country as a result of an incident we recently heard about. The "birdman" in the story was a hang-glider pilot who was hit in the head by an RC sailplane at a slope on the West Coast. Fortunately the hang-glider pilot was wearing a helmet and, other than bent frames to his glasses and a shock he will long remember, the sailplane did no lasting damage.
We discussed this incident with a friend who used to live on the West Coast. Our friend was not surprised since, on a visit to a well-known slope overlooking the Pacific Ocean, he had personally observed RC slope soarers and hang gliders launching within 100 yards of each other. We are reminded of the DOT/FAA brochure, "Model Aircraft Operating Standards," published in 1972. This brochure states, "Exercise vigilance for full-scale aircraft so as not to create a collision hazard." It also states, "Do not operate closer than three miles from the boundary of an airport unless permitted to do so." (Also, see the FAA "advertisement" on page 101 of the August issue of MA.)
We would be the first to admit that a hang-glider launch site can hardly be called an airport. However, in the eyes of the people who fly them, hang gliders are full-scale aircraft despite their freedom from FAA regulation. Simultaneous operation of RC sailplanes and hang gliders from essentially the same site appears to be a hazardous pursuit on the part of both groups of fliers. Perhaps if we lived on the West Coast instead of the flatlands of the East, we might view the situation differently. Any West Coast slope soarers care to comment? We would be particularly interested in hearing from any of the RC sailplane fliers who witnessed the collision.
We had planned to talk about control-line safety this month. However, a couple of letters mentioning possible hazards associated with products on the market caused us to rearrange the schedule. First, Free Flighters: a letter from Claude Short of Shalimar, Florida, brings a note of caution concerning operation of the Shark CO-2 motor in hot weather. We have heard from others concerning this problem. It appears that when a CO-2 capsule is being loaded into the Shark charger only one or two threads on the head of the charger are engaged when the capsule is punctured. It is possible for the head of the charger to be blown off by the sudden release of gas. Mr. Short attributes this phenomenon to possible softening of the plastic components under conditions of high heat coupled with an increase in gas pressure that is also a result of elevated temperature. According to an article on CO-2 motors that appeared in the November 1979 issue of the British magazine Aeromodeller, "Liquid CO-2 is stored at a pressure of 800 psi at 20°C (68°F) and may rise to more than twice this pressure on a hot summer's day." Remember that a British hot summer's day is just pleasantly warm compared to summer in many parts of the U.S.
We made several phone calls but were unable to determine if the Shark CO-2 motor is currently being distributed in the U.S. It is manufactured in England. We did find that the problem is not present in either the Brown or the Telco motors. If you own a Shark CO-2 motor and live in a part of the country where the summer brings very hot weather, perhaps the following tips from Mr. Short will prevent a mishap that could lead to injury.
- Keep the cartridge (CO-2 capsule) and charging gun in a cool place (for example, an ice chest) when not in use.
- Wear heavy gloves, preferably leather, mainly to protect against CO-2 "burns."
- Wear safety glasses or goggles.
- Point the charger head away from other people, objects, and yourself when screwing in the charger body.
Does the use of gasoline in plastic fuel tanks represent a potential hazard? The story we received was that some plastic tanks will dissolve if filled with gasoline. Again, we made several phone calls and carried out an experiment of our own. The result: gasoline does not dissolve either Sullivan or Kraft tanks. The rubber stopper on the Sullivan tank got a bit squishy, but it didn't leak. We spoke with Eric Startup at Sullivan Products and were told that they are changing the material of both the stopper and the clunk line to Buna-N rubber, which is superior to neoprene in resisting attack by gasoline.
We assume most people know that neither silicone nor surgical rubber tubing can be used to convey gasoline. Neoprene works OK for fuel lines outside the tank, but we are told that when used within the tank and immersed in gas it will degrade over time. Buna-N is the material used for rubber components on automobiles that come into contact with gasoline. Note that Buna-S, the material used for seals, diaphragms, etc., in the brake systems of automobiles (except Citroëns), is not resistant to gasoline. If you have ever put power steering fluid into the brake master cylinder reservoir of your car you will have sadly found out.
Before leaving the subject of fuel tanks, note that Sullivan Products now states their tanks should not be used with diesel fuel. At present we hesitate to recommend the use of a diesel fuel tank other than metal. Perhaps there are readers who can advise us on this? We have a personal interest because a large delta model being completed in our workshop is slated to be used to compare the performance of a .60 with a Davis diesel head against a variety of other glow-fuel motors. A metal tank and neoprene fuel lines are planned for that installation.
The final topic this month concerns more information on a safety device we mentioned in a previous column that will retard the throttle servo if the battery-pack voltage falls to a level such that the transmitter signal is lost. We noticed in Showgram the name of the device as "Battery Guard." It is manufactured in England by R. F. Enterprises, 106 N. Main Street, Arlington, Ohio 45814. They can be reached at 1-419-365-5360. Jim tells us that the current price is $49.95 and is "well worth it."
Another device, similar in purpose to the Battery Guard, is available in England. This is manufactured by a firm called Chromatronics and is known as a PPM/ACR unit that will work with any 3-wire positive-pulse servo and has individual pre-set controls for each of four servos with variable fault-detection thresholds. In addition to responding to low battery or loss of transmitter signal, the device will also trigger if outside interference is detected. When this occurs the four servos (or a lesser number) controlled by the PPM will assume their pre-set positions—could be neutral elevator, rudder, and throttle, etc. We acknowledge that this would not be much help in saving a pre-armed model in the process of performing a loop, snap, three aileron rolls, but it might be a worthwhile gadget for the sport flier living in an area of heavy interference. The price on this unit is $114.95 plus postage. The address, should you be interested, is:
Chromatronics Creative Electronic Design Coachworks House, Riverway Harlow, Essex CM20 2DP England
John Preston 7012 Elvira Court Falls Church, VA 22042
Transcribed from original scans by AI. Minor OCR errors may remain.
