Starting Gasoline Engines—Safely!

Jun 07, 2011 No Comments by

To properly operate and maintain models, you need support equipment that is up to the task. Two of the most important concerns we have with giant-scale models are safely starting the engine and handling the fuel (gasoline). When we switch from glow engines to gasoline burners, we need to change some of our equipment; we need to start thinking big!

MIGHTY MEGATRON

Hand-starting gas engines is a common practice, but it is much safer to use an electric starter. The old 12V starters that easily crank a standard glow-powered 2-stroke just won’t work when you attempt to start a big gas burner. One solution is the doublehandled, 12/24V Megatron starter from Sullivan Products. The Megatron uses the same powerful Model 4 motor that powers Sullivan’s popular model-boat starter, and it is equipped with dual handles; it is specifically intended for starting large RC airplane engines. The Megatron can start most gasoline engines with up to 8ci in displacements. The power switch is incorporated in one of the rubber-padded handles, and the steel end plates prevent the motor from slipping under load. The Megatron comes equipped with a huge 3-inch aluminum cone and a sure-grip silicone rubber insert. The starter can operate on 12 or 24 volts and at a maximum of 100 amps. At 12 volts, its torque is 600 oz.-in.; at 24 volts, it’s a whopping 1,200 oz.-in. It has a no-load rpm of 2,800 at 12 volts and 5,600rpm at 24 volts. Two silicone rubber adapters are also available for the Megatron. The small adapter (item no. S636) is for 2V4- to 41/2-inch-diameter spinners, and the large one (no. S637) fits spinners from 3 1/2 to 6 inches in diameter. Give them a try!

ONBOARD STARTING

Another way to increase the safety factor is to install an onboard starter. The simplest is a spring starter that is attached to the aft end of the engine’s crankshaft. It consists of a heavy-gauge spring, attachment bolts and a coupler containing a one-way roller bearing. After you have installed it, start your engine by simply rotating your prop about 1/3 of the way backward (clockwise) and then release it. The spring flips the prop counterclockwise in the same way as a Cox 1/2 engine is started. Though very simple, these spring-starter systems work very well and almost never wear out. When it comes to all the “firewall forward” parts, it’s important to use the correct equipment for the job and to always be careful—especially with gasoline-powered engines.

SWITCH ON!

An easy-to-install, but often-neglected, safety device is the engine kill switch. A safety requirement at any IMAA-sanctioned event, an engine kill switch grounds the ignition system (magneto) to the engine case and makes it impossible to accidentally start the engine. With electronic-ignition-equipped engines, the same thing can be achieved by adding a switch to the system’s battery lead. Several pre-made switch harnesses are available, but you can easily make your own out of parts from an electronics store. All you need are two lengths of wire and an on/off toggle switch.

One wire goes to the engine case (it’s usually attached under a bolt head with a wire lug), and the other one is connected to the magneto. Most magnetos have either a wire lead or a solder tab to which you connect the grounding wire. Keep the wires as short as possible.

To make removal of the engine cowl easier, attach the switch to the firewall with a plywood or aluminum bracket, and let the switch toggle pass through a slot that has been cut into the cowl. Get into the habit of using the switch to shut off the engine, and make sure that it remains in the off position when the model is not in use.

PUMPING GAS

A typical gasoline fuel tank used in giant-scale models holds anywhere from 16 to 32 ounces of gasoline. It takes a long time to hand-pump this much fuel into our models, and a standard electric fuel pump is not an option. Gasoline is much more volatile than glow fuel, and electric pumps can cause sparks—not a good thing around gas fumes. What’s the answer? How about a fuel pump specially designed for gasoline that contains no electric motor, diaphragm, bearings, or any other part that could create a spark? That’s just what Sonic-Tronics has developed with its new

NIFTY GASOLINE PUMP

This totally sealed, solid-state unit is self priming and operates in only one direction, which is clearly labeled on its case. To empty your fuel tank, you must reverse the fuel lines. Reversing the battery leads with a switch will not operate the pumping mechanism; it won’t hurt the unit, but it won’t work. The pump produces a constant 6psi of flow pressure, and Sonic-Tronics recommends that you use a larger (1/8 to 5/32-inch i.d.) fuel lines and fittings in your model. The Nifty Gasoline Pump operates on 12 volts and requires about 1 amp of power. The unit comes completely tested and ready to use, but you have to supply your own power connectors. To identify the wiring polarity of the pump, the negative lead is marked with a black band. Used with gasoline-compatible fuel lines and an approved gasoline-storage container, the Nifty Gasoline Pump makes your pit area safer!

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About the author

Senior Technical Editor About Me: I have a lifelong passion for all things scale, and I love to design, build and fly scale RC airplanes. With 20 plus years as part of the Air Age family of magazines, I love producing Model Airplane News and Electric Flight.
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