Richard Says photos.
Oily
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We build trailers to straighten out when loaded, we call it camber. I used to have a trailer that instead of having the camber bent into it, during manufacture, was fabricated into the chassis. It worked fine for (over)loading grain, but I was using it for fabricated structural steel. I needed higher dunnage front and rear, than in the middle.
I knew an unscrupulous salesman who sold a cocky an old swayback flat with three-way container pins. When comment was made on the apparent poor condition of the trailer, the salesman dismissed the concern wit, they’re built like that, so 40’ boxes don’t see-saw on them. 
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Yes we have that here as well, although a bit different. It’s called “pre-tension” and you can change the setting with plates.
On my trailer though, the more I extend it, the more it’ll look “bend”, without the use of plates. So it’s bit of a design thing whether plates are needed or not. Not sure if I made it more easy to comprehend now actually…
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I think the scraper steering rams are either disconnected or in free flow, enabling pivoting during transit.
The machine weighs 50~55 tonne, variant dependent, with the bulk of the weight over the front axle, which is carried by the bogie drive and bogie trailer, so 15~18 tonne per suspension group, the rear axle would be no more than 15 tonne, easily handled by the bogie jinker.
The Yanks, in some states at least, seem to love almost unlimited lifting axles, but a triaxle suspension group is highly unusual.
Of course this is pure conjecture on my behalf. I am not au fait with North American legislation or practices, but they tend to be closer to ours, than the Europeans are.
It all comes down to the state and the axles weights that they have, isn’t it? As most roads are made of cheese there, they only allow something like 8t per axle I believe.
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Which ties in quite neatly with my theory. We don’t work on axle loading, we use suspension grouping. There are various schemes that determine maximum group weights, but General Access conditions allow 20 tonne on a load sharing tri axle group.
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Federal rules say 80.000lb max vehicle wt. 20,000lb single 34,000lb tandem axle.
That is about…36,300kg …9,100 kg…15,400kg…
Michigan has max vehicle wt of 164,000lbs (74,400kgs)
Delaware 40,000lbs (18,100kgs)
Max axle wt I can see is 22,500lbs (10,200kgs)
https://worldpopulationreview.com/state-rankings/truck-axle-weight-limits-by-state
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Quite draconian and inefficient, eh? 
I can see why they’ve done it, but I don’t like the weight distribution in that last pic. So much weight behind the rearmost axle
As regards the Michigan regs, sometimes that causes axles almost along the whole length of the trailer. Does anyone know if they would be steerers, or what do they do to protect the road surface on corners and bends? I remember not that many years ago that heavy hauliers employed an accompanying truck to carry steel plates which were laid on the road and covered with grease at certain points because they hadn’t then got the hang of rear steering axles.
This was replaced after a few years with a 3 axle modular trailer can’t find pictures at moment
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I don’t think much has changed over the years mate, where the rest of the world has moved on (even the UK), they still prefer fixed axles in the US, partially because to keep the unladen weight down as much as possible.
The only trailer with steering axles I saw during my trip, a Faymonville that’s used by a firm that specialises in hauling windturbine parts.
Great to see this thread well and truly up and running on the new platform. A big thanks to all the contributors.
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Certainly a locally-made Dutch cab, but on which chassis? Perhaps Scania LBS 76? Interesting!
