Advice on 96 Civic pushrod problem

Whoa, that's way more complicated and a-typical than what I have in mind.
Also, I doubt truck engines are big enough to have a need to reduce the
cylinder wall side thrust and so have a connecting rod _and_ piston rod,
yada. (What's shown at the link above doesn't really deal with side thrust,
anyway. The piston rod doesn't move strictly linearly.)

I'm thinking of diesel engines designed like this nearly 8000 horsepower
(per cylinder) big bertha (see top drawing):

http://www.bath.ac.uk/~ccsshb/12cyl/

Granted this is obscenely big, but one can find smaller diesels (though
probably not car or truck size) with the same connecting rod, wrist pin,
piston rod, etc. set up. Many large steam engines had/have this set up, too.

Or see http://www.marinediesels.info/ for an animation of a diesel engine
with a connecting rod and piston rod. Though I see this site calls any
single rod from piston head to crankshaft (on diesel engines with a trunk
piston) a connecting rod, too. So maybe I have it wrong. I dunno. Lot of
interchanging going on. Lloyds casualty, the big ship insurer, says I have
it right, at least as far as ship engine vocabulary goes.
http://www.lloydscasualty.com/mt/seasearcher/glossary.jsp?init=C

Trivia...

 

I'm finding this on that page:
"connecting rod: a rod connecting lower end of piston rod with crank pin of
a reciprocating diesel engine"

and:
"crosshead: a rectangular block which connects and acts as a hinge between
the lower end of piston rod and the upper end of connecting rod in an
engine; at its athwartship faces, it carries guide shoes which transmit the
side thrust of the connecting rod to the guides on the columns"

They're making a clear distinction between one and the other in both
quotes.

In all my years I've never heard the "connecting rod" ever referred to by
any other name (other than contracted as "conrod".

 

Yes, NOT 'a rod connecting the piston head to the crank pin.' Such a single
rod does not exist for very large (ship size, say) engines.

I think we're having a miscommunication: Before googling yesterday, I felt
there was a clear distinction between the two.

Now I see "connecting rod" and "piston rod" used interchangeably a lot,
particularly at auto sites, with the term "connecting rod" appearing to
predominate as the (only) rod said to connect the piston head to the
crankshaft, on auto engines.

Which is consistent with many auto sites on the web.

Like I said, for my auto repairs, I plan to call it what Chilton's and the
parts site call it: "Connecting rod."

 

well, that's certainly a big one! interesting claims of thermodynamic
efficiency too - surprised me because i thought turbines held the honor
of being most efficient.

regarding comparison with automotive engines, you are indeed correct,
the piston rod is to mitigate side loads/wear on cylinder walls. but
note also that these engines are only revving at about 100rpm!!!
"excess" mass is not so much of a factor in such an application.

 

No, but inertia is! With a piston that heavy, side loading forces would be
immense.

Gad what a big engine. I've never seen anything that large in my life.
Those aren't main bearings, they're skateboard half-pipes.

 

side loading being immense, yes. as a result of inertia? no. it's a
function of the leverage of the piston against the crank, and that in
turn is a function of power.

 

Steam turbine CYCLE? Gas turbine CYCLE?

I figure you're confusing the fact that a Carnot cycle is the most thermal
efficient cycle possible. But practical considerations preclude achievement
of a pure Carnot cycle. Reheat, regeneration, and cogeneration plant
features throw another wrench into the discussion. In short, I don't know
what you're trying to say.

Thermal efficiencies for power plants with a "turbine" will range from
around 20% to 60%, just to give some idea of the numbers.

A thermal efficiency of over 50% for a certain diesel engine should NOT
surprise, though.

Yes, well that's not really accurate. It's the connecting
rod-crosshead-piston rod _design_ in total that results in strictly linear
motion of the rod attached to the piston (whatever one calls this rod), thus
minimizing side thrust on the cylinder walls.

I can't parse the above.

Yes. Horsepower plays a role, too. They're all linked, as I'm sure you can
figure: For the same RPM, higher horsepower (which develops more torque, of
course) leads to more thrust on the cylinder walls than lower horsepower.
But a higher horsepower also demands a larger piston head just to absorb the
combustion gases rate of expansion yada.

It's really a bit misleading: I don't want people to think the piston
rod-crosshead-connecting rod design is only needed for engines with
seemingly surreal amounts of horsepower. The typical diesel ship engine is
closer to maybe 20,000 hp, and many of these use the same piston
rod-crosshead-connecting rod design as the aforementioned, evidently
record-breaking, 100,000+ HP Big Bertha. But, yes, with even these, a person
can often walk inside the engine cylinders.

 

Looks like *all* the side force normally created by the crank throw is
eliminated. Pretty clever.

 

It's the connecting
rod-crosshead-piston rod _design_ in total that results in strictly
linear
motion of the rod attached to the piston (whatever one calls this rod),
thus
minimizing side thrust on the cylinder walls.

Looks like all the lateral force normally acting on the piston due to
the crank throw is taken up here where the two rods join. Pretty
clever.

 

No, it's just been displaced to a location that does not affect oil control
or compression.

 

Although I don't think it's done for either of those reasons, but to
reduce cylinder bore wear.

 

.... or reduce the strength (thicknesses, maybe materials) required of the
cylinder.

Your first response was spot on in the context of the thread. The side force
[on the cylinder walls] NORMALLY created is eliminated.