Boingers

[Raymond C Drouillard]

On Tue, 5 May 1998 23:05:34 -0600 "Zack" <zubenubi at inetport.com> writes:
>> There are other ways of reducing the loss due to
>> forcing a few ounces of metal bounce back and forth.  You could hold
>> the crank still and rotate the cylinders.  I believe the British
>> made an engine that did that.
>
>Ray,
>
>If you hold the crank still, you -still- have that metal 
>bouncing back and forth.  You cannot, even in theory, create a piston 
>engine with perfect dynamic balance.  You can in theory achieve 
>perfect dynamic balance in a rotary engine, and some designs have in 
>fact achieved this (the Moller Rotary for one), though most have not 
>(the dynamic balance of Mazda's rotaries is not perfect).
>.	As for the rotary piston engine (which cannot be dynamically 
>balanced) lots of people made rotary piston engines, not just the 
>British (the rotary kind on the old WWI planes, where the entire 
>engine rotated around the stationary crankshaft).  They were a very 
>unfavorable design for lots of reasons, and didn't last very long.

It is theoretically possible to create a piston engine without
recriprocating parts.  The cylinders (I would use a radial design) rotate
around a central axis  The pistons and connecting rods each rotate around
an axis that is offset from the central axis by a distance of one half
the stroke of the engine.  Each of the two assemblies would rotate in a
balanced fashion.

I'm not quite certain what you mean by "perfect dynamic balance", but the
point is that the piston isn't being forced to acellerate and decellerate
some 2000 - 14000 times a minute.  They are simply rotating around a
fixed point.  They'll tilt back and forth a bit relative to the
connecting rod, and the rotational velocity of the connecting rod and
piston will go up and down slightly, but this is nothing compared to the
constant wobbling back and forth that occurs in a standard piston engine.

If you wanted to make such an engine (valving might be a challenge), you
could go with heavy pistons if you want.  After all, they aren't forced
to bounce up and down all the time.

Ray Drouillard

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