Things Still Come Loose

  Turbine engines and electric ducted fan powerplants are dynamically balanced, smooth running machines.  When they are operating properly, you cannot feel any vibration affect on your model. Piston powered operation is quite different of course, and modelers who fly them are used to countering the associated low frequency vibrations.
  So, why do things still come loose on our jets?  Taxing, take-offs, landings, and trailer transporting, all contribute to imparting multiple frequency vibrations to every component that is mechanically fastened to the airframe and landing gear.  The frequency varies with the ground speed, runway texture, wheel diameter, tire durometer, strut shock absorbing capability, and number of operations. The amplitude of these forces is generally low, but the range of frequency is broad.

How To Prevent A Problem

  If you assembled your own model, you will be ahead of most problems. If your model was assembled by any other entity, be it a local builder, or an off-shore source, it would be good practice to check all threaded or clipped fasteners before the first flight. You might even find a missing set screw.  A drop of Pacer Z-42 (similar to blue Loctite) on threaded bolts into metal parts is an excellent practice.  This does not apply to metal fasteners into plastic however.

  To best ensure that a sheet metal screw, wood screw, or threaded bolt will not back out of hardwood, screw it in, then remove it and put a drop of ZAP Thin C.A. into the threaded hole, and then reinsert and tighten the screw. You can add a drop of Zap-A-Gap to the head of the screw as it seats against the part being secured.
  Self tap screws and threaded bolts that are tapped into thermoplastics materials such as BVM's injection molded Carbon Fiber Angle Brackets, usually don't need a lot of attention because of the elastic properties of the thermoplastic.
  Every machine needs periodic maintenance, especially high performance jet aircraft. Active BVM Representatives and customers who log hundreds of flights per year, suggest that jet pilots should perform these checks about every 20-25 flights. It's part of the hobby and kind of fun to fuss over your pride and joy, and it is insurance against a ground or airborne failure.

Trailer Transporting

  When you transport your jet, it is best to rest it "gear up" on a thick foam pad and of course, secure it with straps to the trailer shelf or floor.  This will save a lot of low frequency vibration wear and tear on the landing gear.

  We make it a practice to stop just a few miles after leaving BVM to check that the models are "staying put" after a few bumps and brake applications.

See also Foam Cradles



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