Spehro Pefhany wrote:

On Wed, 10 Sep 2003 10:33:31 -0600, the renowned "James B. Millard"
wrote:



dann mann wrote:



Just how would they start that thing? Seems like it would have to be
heated for a few days then some explosive dropped into a couple opposing
cylinders to get a decent push off. And never shut it off again unless
you need to fix something that is moving too fast


On the large diesels (look like lawn mower machines next to this one) on the
cruiser I was on used high pressure air to start them. This was especially
nice for emergency generators since you don't have to worry about
batteries...



Do they have valves to relieve the compression to allow the thing to
rotate more easily?


Yes, I'm pretty sure they do. Many large Diesels release the compression
by locking the exhaust valves open with a little pawl on the rocker arm,
and then use a large air motor, like on air tools, to spin the crank up to a
speed where compression ignition of a cold engine will suffice. (Some
also use air preheating for starts at lower speeds.) The decompression
pawl is often engaged before the engine stops turning, to avoid shaking
the ship apart during shutdown.

Jon