NAMBA Propwash 04-2023 Web.pub

Spring Safety Corner By Lohring Miller NAMBA Safety Chairman There have been two rants on a model boat forum recently; one about the requirement for 2.4 radios in sanctioned events and another about lithium polymer battery dangers. First let’s discuss radio control system safety. The 2.4 GHz radios absolutely eliminate interference from other modeler’s radios. The pin system for the old frequencies depended on other modeler’s compliance. There was no control over anyone near to the race site, but not competing. Separating out higher frequencies from the 27 MHz standard then later separating the 75 MHz ground frequencies from 72 MHz aircraft frequencies in the past is an indication of the issue. The 2.4 GHz standard is just the latest step in this evolution. The DSM encoding along with fail safes on modern radios makes them a lot safer than the old radios. Though the electronics have improved, many of the mechanical issues haven’t changed. Since safe control depends on the entire system, let’s look at these issues. All radio systems still need power. This is provided by batteries. Again, batteries have come a long way. Today’s alkaline batteries are low cost and have a long shelf life. Some racers put new ones in their radios on every race day. Most of us use rechargeable batteries. The LiFe 6.6-volt receiver batteries are tiny and easily last all day. Servos like at least 6 volts for their best torque. That means 5 cell nickel cadmium or nickel metal hydride packs. Some of the newer servos are designed for 7.4-volt lithium ion batteries. Most boats only run one servo that draws significant current. Because of this there’s no need for an independent servo supply. Lithium metal hydride or nickel cadmium rechargeable 9.6-volt transmitter batteries are still good, especially for the older transmitters. Newer transmitters are designed for the 6.6-volt LiFe or 7.4-volt LiPo cells. All batteries need to be fully charged with a suitable charger before race day. The better radios display the transmitter voltage but receivers aren’t often monitored. This isn’t usually needed since one transmitter is often used for several boats. That way the transmitter battery gets a lot more use than the receiver batteries in the boats. The weakest link between the battery and the receiver is the switch. Electric boats with a battery elimination circuit in their speed control don’t have this problem. If there’s power to run the motor, there’s power for the receiver and servos. The common slide switch on a Dubro mount can suffer from leakage and corrosion. See the radio box switch picture below. A toggle switch with a waterproof cover is a better solution. The battery plug is also a problem area. Tape should be used to hold all plugs together. PROPWASH April 2023 9 Moisture remains as the most serious danger to modern elec- tronics. I believe that the 2.4 MHz radios are even more sensi- tive to water than the older systems. If it’s raining or even mist- ing, you need to keep the transmitter dry. A plastic bag over your hands and the transmitter works well for this. The receiver in the boat is the hardest to keep dry. Radio boxes have been the long-time solution. These days they have taped lids. Either 3M electrical tape or hockey tape is used. Electric racers use the hockey tape because they go through a lot and it’s much less expensive. The 3M tape works better under adverse conditions. Today. all the other components of the control system can be found to withstand moisture. The RC submarine pictured only has the receiver and ESC in the radio box. However, the latest Castle ESCs are now waterproof too. Oil or Corrosion X should be applied to exposed motors during and after the racing. Few radio boxes will remain completely dry if submerged. A second line of defense is wrapping the receiver in balloons. People have used everything from party balloons to unlubricated condoms. I double wrap my receivers. In addition, a sponge, paper towel, or even a tampon should be in the box to absorb any leakage. If there’s evidence of water in the box after a run, I recommend untaping the box, unwrapping the receiver, and letting everything dry out. Waterproof switches Castle ESC RC Sub