What makes the BIG boats go ! Wartsila-Sulzer RTA96-C

[Jimbo1490]

In the absolute case it would always be possible to construct any such long stroke engine with a longer connecting rod and no crosshead. This is what i was alluding to in my first post when I mentioned logistical constraints. The connecting rod needed would be very very long indeed and make the engine unpractical and inefficient as the uber-sized connecting rod would result in very high reciprocating mass. Reciprocating mass is always a parasite on efficiency. This engine already looks to be 4 stories tall, so making it 8 stories is obviously out of the question

[apex1]

Took a while, but it seems we agree now....

[Jimbo1490]

Yes, of course. It's just that the wear issue is really just as big as the collision issue. The true crossheads (and even the quasi-crossheads, like with EMD and also Sulzer) appear even before collision becomes an issue, as it is in the really big boys. After all, It does no good to build an engine costing millions of Euros that only lasts for a couple of thousand hours before needing new cylinders, so crossheads are needed also to make these engines practical.

Jimbo

[apex1]

Nothing to complain!

[AlbaDiesels]

Originally Posted by FAST FRED

The crosshead is optimized for this function, which greatly extends the life of the cylinders.


The EMD (Detroit) train engines use a 2 piece piston with a ratcheting gear that turns the piston a tiny bit on each stroke, to equalize the wear.

As large as a train engine is tho, it would probably drop into one cylinder of a ship mover.

FF

The Wartsila ZA40 uses a similar rotating piston design. It has a spherical bearing with a ratchet mechanism that rotates the piston.

Have a look here http://www.marinediesels.info/4_stro...oke_piston.htm