Convert the Great Planes Little Toni to E-power

This quiet racer has great performance

With Its streamlined design, wide performance envelope, one-piece fiberglass fuselage and racer wing, the Great Planes .61 Little Toni ARF just begs to be converted to clean, vibration-free electric power. This power swap doesn't involve any re-engineering or deviation from the standard ARF assembly other than adding some cooling holes.

I decided to use the Kontronik brushless 600 power system in the Little Toni. Kontronik systems are "plug and play" and come with matched components to eliminate the guesswork of choosing the right parts to power your model. These highefficiency brushless motors and matching electronic speed controls (ESCs) also come with premounted gearboxes that allow you to use larger props.

The 600 set comes with a Jazz 55-10-32 ESC and a 4.2:1 gearbox. This ESC has a maximum sustained current rating of 55 amps and is intended for use with 10 to 32 Ni-Cd or NiMH cells or 3 to 9 Li-poly cells in series. When you use the highest cell count, this 600-size brushless motor can even outperform a .61 glow engine!

Instead of using a typical receiver battery to power both the receiver and servos, I used a Kool Flight Ultimate Battery Eliminator Circuit (UBEC). This new 6V output unit speeds up your servo responses and makes them stronger-a great advantage for high-speed pylon racing! The UBEC is about 1/3 the weight of a 5-cell receiver pack and draws power from the main flight pack. If your receiver doesn't have enough channel connectors to accommodate the circuit output cable, you can connect it in parallel with any channel using a Y-adapter cable. The UBEC can supply enough power for a receiver and up to 9 servos.

MOTOR INSTALLATION

Converting the Little Toni to electric power was easy; I simply mounted the Kontronik motor onto the engine mount using two 2 ¾-inch steel hose clamps from a home-improvement store. To ensure a slip-free mount, I wedged a piece of emery board between the motor wall and the engine-mount post. To force the motor to follow the built-in right thrust angle of the firewall, I inserted two short plywood pieces on the right-hand side. It was easy to get a perfect motor-shaft alignment because the fiberglass cowl fits over the nose in a fixed, keyed position. This allowed me to test the position of the motor many times by press-fitting on the cowl and then the prop-adapter assembly with the aluminum spinner backplate before completely tightening the hose clamps. After I had tightened the two hose clamps, I was able to pick up the entire fuselage by holding only the clamped motor.

The motor is cooled in flight by the stock cowl openings and the air scoop that's built into the Little Toni design. I drilled evenly spaced holes into the firewall so that air can flow into the cowl and through the firewall holes to cool the battery and ESC. I also made an air exit in the bottom side of the fuselage just aft of the wing saddle. I used two, 1-inch plastic Master Flow Circular Louvers from Home Depot.

I positioned the motor to allow the MP Jet 6mm prop adapter about ¼-inch clearance for the aluminum spinner. The prop adapter has an 8mm output shaft that will mate with the spinner adapter. The thread spacing was not exactly the same but was close enough to work well. The stock aluminum spinner looked great when mounted! Unfortunately, after a few flights, I had to replace the stock spinner with a 3-inch red C.B. Associates spinner; using the prop adapter for the electric motor caused too much vibration.

BATTERY OPTIONS

My initial setup for the Kontronik 600 motor used 20 Sanyo CP2400 Ni-Cd cells. When using an APC 14x7 e-prop, I drew about 41 amps and later switched to a 14x10 prop that drew 51 amps. This setup flew incredibly well!

I could replace the 44-ounce, 20-cell CP2400 Ni-Cd pack with 8 ElectriFly 1500mAh Li-poly 3-cell packs (6s4p, or four parallel sets of two, 3-cell packs in series) to provide a comfortable current delivery of 50 amps. Since each pack can deliver a continuous current of 12 amps, four packs in parallel could deliver 48 amps continuous current with a peak delivery of more than 60 amps! This super pack would have 6000mAh capacity, which would have 2.5 times the flight duration of the 20-cell Ni-Cd pack. Further, the super-lithium pack would weigh only about 32 ounces-that's a 12-ounce drop in flying weight! This incredible gain in electric flight performance is a cost tradeoff.

FINAL ASSEMBLY

I mounted the two 10-cell Ni-Cd packs in the front half of the fuselage so that the ends of the packs touched the back of the firewall. I connected the two packs in series using a portion of an FMA Series Connector Module. I taped the packs together and rested them in the frame of the plywood former just behind the firewall. Small pieces of wedge-shaped, high-impact foam hold the pack in place. I also cut a piece of foam to fit in the fuselage with an opening in the middle for the rear of the two packs to stick through. This held them firmly in place for added security during maneuvers in flight.