Modelers thrive on innovation. This month I’m going to look at a couple of innovations from everyday modelers who I am honored to call friends. Both innovations are low cost, commercially available products and would make great holiday gifts.
Redundant Battery System
I met John Bentley when he attended my club’s Treasure Valley Pattern Contest in Boise, Idaho, several years ago. He has attended the contest every year since and CDs the Desert Pattern Challenge contest in Apache Junction, Arizona.
While calling for his friend, John repeatedly instructed “right rudder.” Shortly afterward came the infamous words “I ain’t got it!” The airplane eventually crashed into a tree. After determining the LiFe receiver battery had failed, John assured his friend, Steve Hosner, that this would never happen again, and proceeded to design the Redundant Battery System (RBS). John and Steve now offer the RBS to other modelers for $25.
Unlike many other redundant systems, RBS connects two batteries to the receiver in parallel. During normal operation, both batteries simultaneously power the receiver through independent circuits. Each circuit has a small LED that illuminates when energized.
In the event of a switch or battery failure, instead of switching to a secondary circuit, RBS isolates the failed circuit from the receiver.
My evaluation RBS unit was mounted in my BJ Craft Prolog “Pinky” with a small square of Velcro. Each supply side circuit consists of a heavy-duty switch connected to a 700 mAh Lithium iron phosphate (LiFePO4) battery. A lack of open ports on the Futaba six-channel receiver dictated a Y connection be used on the receiver side. Other than weight, using a Y connection is a nonissue because isolation occurs upstream of the receiver.
After turning the transmitter on, one side of the RBS is switched on and the controls are cross-checked. Next, the other RBS side is turned on and the first side turned off. Controls are cross-checked again before turning the first side on again. Ready for flight!
This is the third battery system I’ve used in Pinky. I replaced the original 80-gram 2S LiPo/regulator setup last year with a simple battery/switch 109-gram A123 setup.
The complete installed RBS system weighs 126 grams—17 grams more than the A123 system, and 46 grams more than the LiPo/regulator system.
The weight penalty for redundancy is slightly more than 11/2 ounces. It works on the bench with simulated failures; however, I have never needed (and I hope nobody ever needs) redundancy with their airplane in the air.
Throughout the years I have gone from carrying a generator and charging at the field to charging at home and carrying only batteries to the field. I typically take four to six packs to the field, depending on how long I plan to fly. I can buy many batteries for the cost of a good generator. In a pinch the car battery—with the car running—can be used for charging.
For the past couple of years, I have transported batteries to the field in LiPo-safe charging bags. I keep them within arm’s reach, periodically touching them and checking for heat. If something goes wrong, having them close provides half a chance to quickly get them out of the car.
I have known Pat Johnston for more years then I can remember. Pat designs and flies CL Stunt airplanes. Several of his designs have been published in MA.
Pat recently began flying electric airplanes and needed a battery tote. He whipped up a simple design using AutoCAD and cut a couple of kits from lauan plywood with his laser cutter.
Pat’s models are powered by 4S packs, but it did not take much persuasion for him to modify his design to accommodate the 10S packs typically used in modern Pattern airplanes. The shortened and widened redesign is unofficially named “10S six-pack.” He charges $20 for either design. He cut me a kit for his material and laser cost.
After I applied Titebond glue to the interlocking joints, the seams were taped and the complete assembly was weighted down to ensure its shape. Interior partitions were added after the glue dried. I sanded the entire box before finishing.
After sanding between coats, three coats of satin polyurethane varnish were applied, making for a utilitarian finish.
Congratulations to our US F3A World Championship team: Andrew Jesky, Jason Shulman, Brett Wickizer, and Junior competitor, Joseph Szczur. The RC Aerobatics team will compete in Switzerland next year.
Sportsman of the Month:
Sportsman of the month, Pat Loss, competed in the Treasure Valley Pattern contest in June 2014. This was Pat’s first contest. He finished third and had a great time.
National Society of Radio Control Aerobatics (NSRCA)