OK, I have no idea who to ask so I'll try here. Railroads carry a bunch of containers. Some are stacked 2 high with large ones, some small ones are stacked the same way. But a bunch have the small container on the bottom with a much larger one on top. Looks kind of unbalanced, kind of like my wife stacks things and they fall and make a mess. Anyone know why?

Dude, you've got way too much time on your hands!

One of my best friends worked for decades for Soo Lines. He explained it pretty well. Every thing is calculated down to the oz. They have transit centers that calculate all of that.

It's not just a vertical issue. The weight of each car has to be calculated. For instance, you don't want a spot of empty cars in the front with very heavy cars in the back.

H&K-Guy

But the weight would be the same if the large one was on the bottom. Then it wouldn't look like it would tip over.

No. As I tried to explain, the larger one can weigh less than the little one.

H&K-Guy

Have your wife read the following, and keep my name out of it!

Abstract

To improve safety measures of loading containers on double-stack rail cars, this paper develops a multi-objective optimization model that focuses on a number of practical requirements such as the center-of-gravity height of a loaded car and load balance considerations. A lexicographic goal programming approach is then used to address different priorities for potentially conflicting objectives and constraints. To minimize the center-of-gravity height, a linear-fractional programming technique is adopted in this study to transform the corresponding generalized mixed integer fractional problem into a sequence of mixed integer linear subproblems. . . .

http://www.civil.utah.edu/~zho...ainer_scheduling.pdf

I was told that the strength of intermodal containers is focused on the four corners. If a 40 foot container is placed on top of a 53 foot container, the weight of the 40 foot container would be placed in the middle of the weakest part of a 53 foot container. The reverse of that places the majority of the weight of a 53 foot container on the strong four corners of a 40 foot container....or so it was explained to me once...I think. I may not have been paying that much attention at the time...

TETRIS

You're welcome.

It's probably because the top one has to be unloaded before the bottom. Those thing are like Legos, "pineapples" secure them top to bottom and side to side, mucho secure.

It's not like they are just sitting there. They get pinned or bolted together don't they?


EDIT to add:
Found a vid

https://youtu.be/CLcBnhBV0MQ

quote:

Originally posted by ice1811:
I was told that the strength of intermodal containers is focused on the four corners. If a 40 foot container is placed on top of a 53 foot container, the weight of the 40 foot container would be placed in the middle of the weakest part of a 53 foot container. The reverse of that places the majority of the weight of a 53 foot container on the strong four corners of a 40 foot container....or so it was explained to me once...I think. I may not have been paying that much attention at the time...

Pretty much this. Also, most of the intermodal cars (cars that carry these containers) are set up for a 48' container maximum on the bottom. Putting a 48', 40', or two 20' down low allows for a 53' to be stacked on top and overhang the ends of the equipment. Lastly, most of the 40', 48', 53' containers have no provisions for securing the corners of the 20' containers if they were on top. The only locking points on these are typically on the corners only.

See examples below:

Remember way back when it was just one or two full blown semi trailers wheels and all on a flatbed?

quote:

Originally posted by Scuba Steve Sig:
Remember way back when it was just one or two full blown semi trailers wheels and all on a flatbed?

The TOFC (trailer on flat car) side of things has diminished over the years due to the popularity of contanerized freight. That said FedEx, UPS, and now Amazon have brought back more TOFC traffic as of recent.

quote:

Originally posted by Scuba Steve Sig:
Remember way back when it was just one or two full blown semi trailers wheels and all on a flatbed?

Then came the "roadrailers"...semi trailers with both sets of wheels, train and truck (God, I miss work)

Kind of the same topic, but how do they secure those things on ships? I've seen those things stacked what seems like 10 high on the decks of transport ships. I wonder how they keep them from falling off in even light seas. Seems like they'd tip very easily.

quote:

Originally posted by Twist18:
Kind of the same topic, but how do they secure those things on ships? I've seen those things stacked what seems like 10 high on the decks of transport ships. I wonder how they keep them from falling off in even light seas. Seems like they'd tip very easily.

They use a thing called a twistlock. Each of the corners of the containers have an oval opening on them and a large pin is inserted and twisted to lock them together. They can lock them not only top to bottom but also side to side so it's a very secure mechanical lock, hence why they can be stacked so high in rough weather.

Though they do go overboard sometimes, hence why there's a bunch of rubber ducks and lego that wash up on beaches worldwide.

quote:

Originally posted by Chach:

quote:

Originally posted by Twist18:
Kind of the same topic, but how do they secure those things on ships? I've seen those things stacked what seems like 10 high on the decks of transport ships. I wonder how they keep them from falling off in even light seas. Seems like they'd tip very easily.

They use a thing called a twistlock. Each of the corners of the containers have an oval opening on them and a large pin is inserted and twisted to lock them together. They can lock them not only top to bottom but also side to side so it's a very secure mechanical lock, hence why they can be stacked so high in rough weather.

Though they do go overboard sometimes, hence why there's a bunch of rubber ducks and lego that wash up on beaches worldwide.

Thanks, I always wondered about that. I know they do go overboard sometimes, and I thought I heard somewhere that they sometimes remain partially buoyant, just below the surface, and can pose a hazard to smaller boats/ships. Also, nice to see a fellow Rangers fan here in Nor Cal!

The top container is full of toilet paper, and the bottom is full of ammo.

If you ever see an empty chassis (those things that semi's pull the containers on), you can see the twist lock pins that secure the container.