Flatbed semi-trailers - how come some flatter than others?

[AJMD429]

I see some actually flat, and others have such a pronounced arch to them that a long I-beam needs a 6x6 chunk of lumber under each end to keep the middle from hitting the flatbed.

Just wondering...why are any of them arched in the first place...?

[pwl44m]

A heavy load will straighten them out. A long beam doesn't put enough weight in the middle. Science Doc Science.
Perry

[fordwannabe]

usually the guys with the pronounced arch haul steel coils which may weigh 50.000 pounds each, and those trailers are aluminum decked. When you drop that coil on your aluminum trailer it had better have a arch or it will have a bow after.

[Don McDowell]

Wut dem guys sayd....

[Blaine]

Pre-Load......let's it hold more weight without putting permanent bend in the bed....Kind of like suspension springs.

[Don McDowell]

And the 6x6 lumber under the load is there so they can get what ever lifting/loading device under neath to load and unload.

[AJMD429]

Cool - that's kinda what I figured as far as why the 'arch' - kind of like a support-beam for a 'flat' roof. Some are already totally flat unloaded though, and I just wondered if those ones were that way because they were intended for different types of loads; I guess the advantage of a perfectly-flat bed would be the tradeoff in weight-bearing capacity would be offset by better stacking of light cubical loads or something?

[CJM]

I just spent 21 months in Ann Arbor for a contract job I had. Saw those aluminum arched trailers a lot on I-94 heading into and out of Detroit (I would guess hauling coils of sheet metal for the car factories). What really surprised me though was the trailers with all the axles on them. I'm from Colorado, and semi-trailers get taxed according to how many axles they have, so I rarely see more than two axles on a semi-trailer, but in Ann Arbor I saw a few extra long trailers that had as many as eight axles; three of which could be raised so they didn't touch the roadway when the trailer wasn't carrying a load. They were just one set of wheels after another, all the way along the length of the trailer.

[Bridger]

What is amazing is seeing pictures of the damage those little coils of steel do when they get loose. I saw a pic one time of a roll that got loose and rolled forward and bashed in the back of a truck. They just don't look that heavy is the funny thing.

[Griff]

I just spent 21 months in Ann Arbor for a contract job I had. Saw those aluminum arched trailers a lot on I-94 heading into and out of Detroit (I would guess hauling coils of sheet metal for the car factories). What really surprised me though was the trailers with all the axles on them. I'm from Colorado, and semi-trailers get taxed according to how many axles they have, so I rarely see more than two axles on a semi-trailer, but in Ann Arbor I saw a few extra long trailers that had as many as eight axles; three of which could be raised so they didn't touch the roadway when the trailer wasn't carrying a load. They were just one set of wheels after another, all the way along the length of the trailer.

Affectionately called, "centipedes". MI is one of the VERY few states that allows 'em. MI allows up to 106K (IIRC) gross weight on its roads. And they cause horrendous damage to the roads.

[AJMD429]

What is amazing is seeing pictures of the damage those little coils of steel do when they get loose. I saw a pic one time of a roll that got loose and rolled forward and bashed in the back of a truck. They just don't look that heavy is the funny thing.

I always wondered why they don't lay them flat instead of having them already in the 'rolling' position... Seems like a hard-stop and away-they-go...!