quote:

Originally posted by Balzé Halzé: On a slow speed diesel like the Dali, it is a fixed blade propeller. The engine must be stopped and restarted numerous times during maneuvering …

OK, the gearhead in me wants to know how these engines, with cylinders a man can stand in and have to look up out of to see, are turned over.

It takes several seconds to start a slow speed diesel. They are started via direct air start meaning starting air is injected right into each cylinder to turn it over. One problem we often had was pilots who wasted orders and would start and then almost immediately go back to stop. There is only so much air in the air tanks. We used ~475# to start and every start reduces pressure. We had two air compressors and once you receive a bell, they are running. Sometimes hard to keep up with a pilot who isn't used to slow speed diesels.

These engines being directly connected to the shaft reverse by shifting the cam shaft. So when going from say dead slow to stop (or dead ahead), etc., that takes a little additional time.

quote:

Originally posted by StarTraveler:
That’s horrible for those involved and for their families. I hope they were able to rescue those involved but between the crash following the collapse, the risk of drowning and the shock of being in the frigid water if they don’t immediately, and the secondary collapses of the truss structure above (and its presence affecting potential rescue), I fear the death toll will be a high percentage of those involved.

As a structural engineer, situations like this are dreaded but ever-present risks.

A risk that can be greatly mitigated by spending the money to build effective barriers to protect the pilings. Yeah, they are expensive. However when you consider the cost of replacing this bridge it's pocket change.

^^^^Exactly right (referring to 6guns). The mates and pilots need to take into consideration during maneuvering that they have limited starts before they run out of sufficient air.

Off the top of my head, I believe the regulation is the ship must be able to make 9 consecutive starts. During the commissioning of my vessel, we literally had to start and stop the main engines 9 (?) consecutive times in front of the Coast Guard. Meaning we pumped up the air receivers to full, secured the air compressors, and then proceeded with the test. On heavy fuel, with the engine hot, the engine usually cranked up pretty fast. A slow speed diesel takes a bit more to get turned over as I'm sure you can imagine.

quote:

Originally posted by Scooter123:

quote:

Originally posted by StarTraveler:
That’s horrible for those involved and for their families. I hope they were able to rescue those involved but between the crash following the collapse, the risk of drowning and the shock of being in the frigid water if they don’t immediately, and the secondary collapses of the truss structure above (and its presence affecting potential rescue), I fear the death toll will be a high percentage of those involved.

As a structural engineer, situations like this are dreaded but ever-present risks.

A risk that can be greatly mitigated by spending the money to build effective barriers to protect the pilings. Yeah, they are expensive. However when you consider the cost of replacing this bridge it's pocket change.

There's a couple of dolphins on either side of the channel to funnel ships through and under the bridge however there's only so much that can be engineered to protect the pilings before you start encroaching into the shipping channel. Most people have never seen nor, do they understand the size of modern container vessels, a PANAMAX sized ship is going to destroy whatever gets in front of it, even a glancing blow is catastrophic.
Whatever replacement bridge design is selected, you can probably bet the span between pilings will be much further apart and you'll probably see more dolphins used to protect the pilings like in Tampa.

I think a more sensible (band)aid would be for tugs to do a longer escort. I see this happening in a lot of ports after this incident.

Figures...

https://townhall.com/tipsheet/...gn=nl&recip=26773771

Biden Explains Who Will Pick Up the Tab of Baltimore Bridge Collapse

Speaking from the White House Tuesday afternoon, President Joe Biden explained which government entity will foot the bill after a cargo ship slammed into the Francis Scott Key bridge in Baltimore, leading to its collapse and the killing of several people.

"The bridge is also critical to, for travel, not just for Baltimore but for the Northeast Corridor. Over 30,000 vehicles cross the Francis Scott Key Bridge on a daily basis. It’s virtually, well, it’s one of the most important elements for the economy in the Northeast and the quality of life," Biden said. "My Transportation Secretary is there now. As I told Governor Moore, I’ve directed my team to move heaven and earth to reopen the port and rebuild the bridge as soon as humanly possible. And we’re going to work hand in hand with the support of Maryland, to support Maryland, whatever they ask for. And we’re going to work with our partners in Congress to make sure the state gets the support it needs."

"It’s my intention that federal government will pay for the entire cost of reconstructing that bridge, and I expect the Congress to support my effort," he continued. "This is going to take some time. And the people of Baltimore can count on us, though, to stick with them at every step of the way until the port is reopened and the bridge is rebuilt."

cont...

Politicians have their own language

quote:

Originally posted by 6guns:
"It’s my intention that federal government will pay for the entire cost of reconstructing that bridge..."

You mean the shipping co and its' insurer aren't responsible for at least part of it?

There are people suggesting the event was instigated by cyber attack. Biden running out to make one his stupid speeches about it removes all doubt. The Swamp isn't all that difficult to figure out.

quote:

Originally posted by 6guns:

These engines being directly connected to the shaft reverse by shifting the cam shaft …

So these are four-stroke engines? Are there two camshafts, one for forward and one for reverse rotation? Separate, or housed within one another?

quote:

Originally posted by egregore:

quote:

Originally posted by 6guns:

These engines being directly connected to the shaft reverse by shifting the cam shaft …

So these are four-stroke engines? Are there two camshafts, one for forward and one for reverse rotation? Separate, or housed within one another?

Two-stroke engine. The cam is shifted (moved fore and aft) so that the start is 180 degrees out, starting the engine in the other direction.

Here is my SWAG
Scientific Wild Ass Guess.
As they approach, they lose power.
Capt drops the starboard anchor to try and stop the boat.

Anchor drags towards the pylon and once it grabs the brige pylon it spins the ship and the anchor chain wraps drawing the ship back to it for a simultaneous ram and squeeze.

I have never in my life seen a boat that big turn that sharp. This is the basis of my SWAG.

^^^^
There's the distinct possibility that the ship pushed up against and pivoted along the dolphin that sits astride the channel forcing the hard direction change.

My image-pasting skills aren't so good, if someone wants to paste an overhead shot, that gives a good perspective

https://www.twz.com/sea/uscg-l...more-bridge-collapse


Also, What's Going on with Shipping as a new video going over teh ship's track

Terrible.

quote:

Originally posted by Timdogg6:
Here is my SWAG
Scientific Wild Ass Guess.
As they approach, they lose power.
Capt drops the starboard anchor to try and stop the boat.

Anchor drags towards the pylon and once it grabs the brige pylon it spins the ship and the anchor chain wraps drawing the ship back to it for a simultaneous ram and squeeze.

I have never in my life seen a boat that big turn that sharp. This is the basis of my SWAG.

The guy in the video on page 2, posted by bald1, describes how he thinks they were backing down to prevent the collision. In doing so, that action caused the ship to turn. If this is true, sounds like they'd have stayed going (more?) straight if continuing ahead. Also the intense black exhaust would explain an intense effort to go astern, overloading the engine. He also states it was the port anchor that was dropped.

quote:

Whatever replacement bridge design is selected, you can probably bet the span between pilings will be much further apart and you'll probably see more dolphins used to protect the pilings like in Tampa.

^ I saw what you did there. My father was on the Blackthorn & saw the writing on the wall. He transferred off to another assignment. His captain was still captain when the Tampa collision happened.

Forgive me for being pedantic, but technically this was an allision, not a collision.

quote:

Originally posted by Timdogg6:
Here is my SWAG
Scientific Wild Ass Guess.
As they approach, they lose power.
Capt drops the starboard anchor to try and stop the boat.

Anchor drags towards the pylon and once it grabs the brige pylon it spins the ship and the anchor chain wraps drawing the ship back to it for a simultaneous ram and squeeze.

I have never in my life seen a boat that big turn that sharp. This is the basis of my SWAG.

^^^^^
So you are saying that this is actually possible (53 seconds in)?

quote:

Originally posted by Balzé Halzé:
Forgive me for being pedantic, but technically this was an allision, not a collision.

Wow. I've never seen that word before in my life, and I read a lot.

Took a guess and sure enough:

allide v. 1. To impact a stationary object.