lml@lancaironline.net Mailing List Archive

<<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> << Lancair Builders' Mail List >> <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> >> Bob Froelich wrote: I have not seen any comments on the dynacam engine. It is proven in over 60 years of operation. The Dynacam was certified many years ago by satisfying the 150 hour FAA test of the time, but is (unfortunately) by no means "proven." Referring again to Taylor, "The Internal Combustion Engine in Theory and Practice," Vol. 2 page 579-580 (excerpted), section on "Barrel or Revolver Engines:" "These are piston engines with cylinders arranged parallel to the main shaft and acting on it by means of some kind of cam or "wobble-plate" mechanism. ... The objective of such designs is to secure a more compact arrangement than is possible with the conventional crank-and-rod arrangement. Many such engines have been built and tested, abut few have been found sufficiently rugged to withstand normal piston speeds and mean effective pressures for any but short periods. A marine Diesel engine of this type was put on the market in 1945 but was not a commercial success.... Such cylinder arrangements have serious disadvantages with regard to accessibility and mounting structure, which would make them undesirable for most services even if a reliable mechanism could be developed There is no likelihood of such engines becoming important competitors to the conventional types." Taylor is usually moderate and measured in his comments but his opinion seems clear on this configuration. I have inspected the DynaCam engines, and I believe the weak point is the roller that connects the pistons to the wavy cam that converts piston motion to rotary motion. The roller has a line contact on the cam, and so it only takes moderate pressure (or a little bit of knocking or detonation or excessive clearance) for the roller to dent the surface of the cam with unfortunate results. Oil sleeve bearings as used in our aircraft and in auto engines (and many other places) are very stiff, very tough, and very resistant to damage, in comparison. The engine configurations we have today (radials, in-line, V, flat opposed) are prevalent because many, many configurations have been tried and only these few have survived. Fred Moreno >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> LML website: http://www.olsusa.com/Users/Mkaye/maillist.html Builders' Bookstore: http://www.buildersbooks.com/lancair Please send your photos and drawings to marvkaye@olsusa.com. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>