🚀 go-pugleaf

Chris (cbusch@ub.d.umn.edu) wrote:
:    Are there actaully rc jet engines?  I occasationally hear reference

  I've heard of two honest turbine jet engines.  One was made by a group
  of Porsche RCatics (Ref. "Lunatics"), and was a one-of-a-kinder.  It
  looked like it was made by Porsche engineers.  When asked how much it
  cost to make, they said "Oh, maybe around $20,000".  This is German for
  $50,000.

  There's a French firm said to be going into production of a turbofan
  engine for about $3500 -- they had one at the Topgun tourney last year
  and I've seen videos of it.  It looks and sounds like a turbofan.
  I've talked to three local jet jockeys in the Orlando area who tell me
  it doesn't seem to be quite ready for the world, but one of them has
  a severe "jet Jones", and I suspect he'll get one anyhow.  Starting is
  an experience -- they blow compressed air into it and hit "start".  
  Away she whines...

: to ducted fan engines, how do they work? If there are rc jet engines,
: are the jet engines pulse jet or normal turbine jets?

  There are ram jets available, but nobody in their right mind will fly
  them.  As near as I can tell, 49% of the energy emitted is heat, 50% 
  is sound and about 1% is thrust.  

  A ducted fan engine uses an extremely nervous reciprocating engine to drive
  a multibladed prop (or fan) inside a shroud.  There are also stationary
  blades which serve to "unscrew" the air, resulting in a more laminar airflow
  and increased thrust.  These engines usually spin >> 22,000 RPM, put out
  about 5 HP per cubic inch and have every conceivable problem a model engine
  can have -- vibration, noise, excess heat, carb instabilities, bearing 
  failures and they eat $10 glowplugs by the bushel basket.  If you're real
  lucky, the engine will seize when it fails and save the fan unit (only 
  costing about $300 for the engine instead of $500 for the engine and fan).
  Not for beginners.  Our club show team has three Byron's F-15s (two
  OS 90VFs each) and I get to see how much time it takes to keep these things
  in the air.  You have to be ready to make it your life.  Yet, about two
  times a year, we get people showing up at club meetings asking for help
  building a Byron or Violett jet they want to use as a "trainer".  Most of
  the jet guys have been in the hobby 5 to 10 years before tackling their
  first ducted fan model.

  Trainers should be like first girlfriends.  You will learn a lot more with
  one that's big, cheap and slow than you will with fast, good looking and
  expensive.

: Just curious.

  Don't give up, just remember the fun you had with the big, cheap and
  slow ones...

: --
: -=-=-=-=-=-=-=-=-= Chris Busch     cbusch@ub.d.umn.edu =-=-=-=-=-=-=-=-=-=-

-------------------------------
Bill Chidester   KE4WS
bill@a3177092.ssr.hp.com