Re: Vee engines

[Godfrey DiGiorgi <ramarren@domain.elided>]

>> >I have often wondered why automotive manufactures don't use a scissoring
>> >connecting rod setup on V engines to save weight, length and on moving
>> >parts.
>> 
>> I'm not sure I understand what you mean by a "scissoring connecting rod".
>
>On radial engines where you could have up to nine pistons acting on one
>crank shaft journal there is a master rod with other individual rods
>connected to a boss on the master rod.

Ah, you mean an articulated connecting rod ... 

Such setups were designed for different needs. On a radial engine, you 
want all the cylinders in the same plane as you typically have a camshaft 
in the shape of a ring operating pushrods, you want to be able to re-use 
the same cylinder and head castings for all of the 5, 7 or 9 pistons on 
each crankshaft throw. You also do this to keep the crankshaft short and 
stiff, and to keep the engine from becoming overly long and bulky. It 
would be unfeasible to design a radial engine with individual rods for 
each piston side by side on a crank throw ... it would really be a spiral 
engine, not a radial. 

Radial aircraft engines are typically not high rpm engines: the 
articulated connecting rods weigh more than the individual rods and 
longer crank throws which limits rpm, and they are more complex 
mechanically. They are designed for long running at relatively constant 
rpm and make power through supercharging and displacement, not through 
rpm.

Godfrey

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