Engines of the Golden Era – Drone Diesel (the second model)

Drone diesel engine is a miniature power plant, a power plant that operates without a spark plug, coil condenser, batteries or wires—it is “ignitionless”! The Drone diesel has been developed over a long period of time and is a complete compact power plant that is easily installed in any model car, boat or airplane. It has characteristics that are most desirable in a miniature power plant—light weight, easy installation, easy starting, tremendous power and simple foolproof operation, plus economy of operation. It is a power plant that will give its owner many, many hours of enjoyment. The engine has been built with infinite care and precision with the best materials known and has been thoroughly factory tested. The engine differs from conventional spark-ignition engines in many respects. The fact that the Drone derives its ignition through compression of the fuel is so revolutionary that it astonishes all those who see it operate for the first time. The engine is a complete power plant in itself as it comes out of the carton all ready to run.


The engine has been designed to operate on Drone Diesel Fuel or a fuel mixture of 3 parts ether mixed with 1 part S.A.E 20 motor oil. A deviation from this ratio, to any great degree, will affect the operation of the engine. This fuel mixture is as important to the engine operation as the spark timing is to the conventional engine. The ether recommended for the mixture is sulphuric ether. Other types of ether, such as Motor Priming ether, or Anesthesia ether, can also be used with a varying effect on the power output.


The Drone is an exceptionally powerful miniature engine. Because the engine doesn’t belch fire or make a loud exhaust noise with a wasted power it may not impress some modelers. It is characteristic of this type engine to run steadily and quietly in a smooth drone—hence the name “Drone Diesel”! More power and efficiency is derived on each stroke with the Drone than with conventional engines, therefore a higher pitch or larger diameter propeller can be used to greater advantage. The power output of the Drone is greater than conventional engines at its near maximum R.P.M. The H.P. curve on the Drone is more constant when compared with the peak and comparative sudden drop in the power curve of spark ignition engines. Transmitting this power through the higher pitch or larger diameter propeller is the way to best use the Drone Diesel Engine.


The engine is by far the easiest starting engine ever. Normally a few flips are all that is necessary. The recommended procedure for starting is the same as for conventional engines. Open the needle valve approximately 3 or 4 turns, choke the engine by covering the intake tube with your finger. Flip the propeller in a counter-clockwise direction with a snapping movement. The Drone should start running after a few flips.


The needle valve adjustment on the Drone Diesel is opposite to that of conventional engines. On the Drone, turning the needle valve down or leaning the mixture causes the engine to slow down and start knocking (pre-ignition). Opening the needle valve will make the engine “rev up”. If the valve is open too far the engine will stop abruptly. Maximum power is derived with the needle valve setting at approximately 1/4 to 1/2 turn before it cuts out abruptly. There is normally very little warning before the engine will cut off so the operator should familiarize himself with this characteristic before installing it in a model.


This attachment, when installed on the engine, enables the owner to have a single power plant that is ideal for all sorts of uses. For U-Control, a third line or relay control connected to the attachment will allow an absolute foolproof remote control system with no installation difficulties or additional equipment necessary. For Free-Flight use, complete engine speed control is yours at your fingertips. The Drone is the only Diesel Engine that has this exclusive feature. You can test your model and use any amount of power desired. Connecting your flight timer to the shut-off spring enables you to predetermine your engine run. Shut-off is instantaneous and foolproof. Ask your dealer or write for additional information on this attachment.


Mount the engine on a block of wood. Screw or bolt the test block to your workbench. Use a “Drone Prop” for best results. Use heavy wood (approximately 1/2″ thick) with 4-40 bolts, and secure. Test block for firmness before attempting to start.


Since there is no spark plug to foul, or no timer points to get pitted, the operation of the Drone can be in any conceivable position. The engine operates as well inverted as it does upright or sideways. When inverted the engine should not be flooded, since this may not allow the operator to turn the prop over. Forcing the piston past the top of the stroke could possibly bend the connecting rod or blow the cylinder head gasket— remember the Drone Diesel operates with a compression ratio of 18 to 1.


We recommend using a metal wedge-type tank for smooth running. The level of the fuel draw line on the tank should be in the same horizontal plane with the carburetor jet. Fill the tank either through the neoprene fuel line or through either air vent. Use only Drone Diesel Fuel or a mixture of 3 parts Sulphuric or Anesthetic Ether and 1 part S.A.E. 20 motor oil.


From a closed position open the needle valve 4 turns. Place finger over intake tube as pictured. Crank the prop over briskly in a counterclockwise direction several turns. Remove finger from the intake and crank the prop. After a few flips, the engine should start. If the engine does not start after several cranks, repeat the operation.


Turn needle valve right or left until engine runs smoothly. Too lean a mixture will cause the engine to knock and smoke — Turn needle to left. Abrupt stopping of engine indicates too rich a mixture — Turn needle right. Run engine for 2 hours to break-in and familiarize yourself with the operation of your engine.