DIY Network

RC Jets: Turbine Power From "Radio Control Hobbies" episode RCH-210

Chris Chianelli and jet expert Bob Violett check out some of the jet engines made by Bob's company.

In this segment, Chris Chianelli and guest Bob Violett discuss the turbine engines that power the RC jets designed at Bob's company, BVM®.

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Figure A

True Turbine Power

• In the early (but not-so-long-ago) days of RC jets, the aircraft didn't use turbine engines but were instead powered by a technology known as the ducted fan. One engine developed by BVM utilized a multi-bladed carbon-fiber fan driven by a single-cylinder piston engine (figure A). The extension from the back of the unit is a tuned exhaust that expels exhaust gasses, quiets the engine noise and adds about 1500 rpm to the engine's capability -- bringing the rpm total to about 24,000. It was designed in collaboration with racing-engine designer, Henry Nelson.
  

  Figure B

  Figure C

• Modern RC jets from BVM use turbine engines. One of the first successful turbine engines developed by the company is the AMT Olympus® (figures B and C), a relatively basic design that uses a centrifugal compressor similar to those used on actual automobile superchargers. The compressor is a diffuser section that takes the swirling flow of air and "straightens it out," slows it down and simultaneously lowers the pressure to help create the thrust of the engine. Inside the engine is a single shaft and two hybrid bearings connected to a compressor rotor on one end and a turbine rotor on the other. As with their full-sized counterparts, because the moving parts in the engine rotate only in one direction, the engine lasts a long time without wearing out.
  

  Figure D

  Figure E

• A smaller and more recent model is the Jetcat P-160® (figure D), a compact but very powerful engine. If features a small, electric motor on the front (figure E) equipped with a bendix-style starting device. The computer controls the starter that then engages the compressor so that it starts spooling up and initiates the fueling and igniting process. The small Jetcact is rated for top-end rpm's of about 125,000. It idles at about 35,000 rpm -- faster than the top speed of the piston engine described above.
  

  	Figure F
  	Figure G
  	Figure H
  	Figure I
  	Figure J

• As seen in the schematic diagram (figure F), compression occurs at the front end of the engine, followed by combustion in the center section. At this point, the fuel is injected and ignited by a simple glow-plug. A computer controls the entry of fuel into the engine. In the diffuser section, the pressure rises as the air is straightened and slowed.

• Next, Bob and Chris perform an engine test on one of the turbine engines mounted on a BVM jet body (figure G). The transmitter is set up inside the jet, and the fuel-valve is left open for manual shut-off as a safety measure.

• Once the start-lever is pushed into the start position, a sequence of green, yellow and red flashing indicator-lights (figure H) lets the pilot know that the start-up sequence is underway. Matching indicator lights on the hand-held controller give the same indication.

• As the throttle is moved upward on the transmitter, the motor begins to spool up and engine-ignition begins (figure I). As the kerosene fuel begins to reach the combustion chamber, the sound of the engine grows louder and higher in pitch. The sound is remarkably similar to that of a full-sized jet turbine.

• The remote-controller shows the rpm readout for the engine as it sits idling (figure J), in this demonstration reaching around 30,000 rpm before beginning to idle back down and stabilizing.

• Up to this point, a computer module has been controlling the flow of fuel to the engine. Once the indicator lights go solid-green, the pilot is in control of the engine.

In the segment that follows, Bob takes Chris on a tour of the facility where the parts are manufactured and put together for these jet aircraft.

GUESTS :
Bob Violett
President, BVM Jets
170 State Rd. 419
Winter Springs, FL 327008
Phone: 407-327-6333
Fax: 407-327-5020
Website: www.bvmjets.com