While on a road trip on Monday, my friend and I noticed two features on some semi trailers, which neither of us were certain what they were for. I figured that the knowledgeable people here might know more.
First, we saw several intermodal trailers (i.e., an intermodal container mated to a “skeletal” trailer), where there were two zip-ties, each attached to a rear corner of the trailer, very close to the mating point between the container and the trailer. We certainly hoped that the zip-ties weren’t what was keeping the container on the trailer, but they were clearly there for some purpose.
Secondly, we saw several trailers which had some sort of devices attached to the trailer wheels. They looked almost like big yellow streamers, about 2" wide, and maybe 2 feet long, with one end anchored to one of the wheel’s lug nuts, and the other end extending across the wheel, and to over the tire. I don’t think that they were fabric, as they seemed to hold their shape as the wheels turned (suggesting that they were metal or something like that).
Any knowledge that any of you can shed on the purpose of either item will be greatly appreciated!
Don’t know about the zip ties but the “streamers” or “wheel rotation indicators” let the driver tell if a wheel has frozen. Wheels can freeze up for any of a few reasons, and it can be hard to tell what and where the problem is. The indicators are visible in the mirrors and let the driver confirm if a wheel is not turning.
The front of the two wheels with the rotation indicators? I think that there are two wheels (and two tires) there, and the gap between the two may be what you’re seeing.
“Warning: High Cube” on the back of some semi-trailers. #1, a trailer isn’t a cube, it’s a rectangular prism (cubes of course are subsets of same). #2, yeah, a trailer can be high, but everybody knows that as a default, so what’s the point? It’s not like the ones which are higher than the others get the warning pasted on the back (they look the same as the others to me in any event). #3, who are they warning? The truck driver himself? Fellow drivers? The guys who remove and unload the trailer?
The white spot looks like simple scuffing where they ran over something white, like spilled white powder or a hunk of drywall. Or even from ops in a gravel lot.
That’s a triple tandem axle set, and some sideways scuffing happens to every tire on every turn. Triple tandem setups are also IME more common on dump trucks or cement trucks than on over-the-road box vans or tankers. So the tires picking up color from the dirt, gravel, etc., they roll over at construction sites and whatever is the other end of their trip is commonplace.
I’m not seeing the thing you’re calling a bulge. There is a darker area just clockwise from the white area, which I take to just be different amounts of dirt / dust stuck to the tire.
Standard trailer height since the dawn of time (or at least the 60s) is 13’6". All interstate highway bridges, and most other bridges, are designed to clear a 13’6" trailer. The ones that aren’t are old, and have signs and barriers and still peel the tops off trucks on a regular basis.
But by that fact, most interstate bridges are designed with extra clearance, like 14’8" for example. Hi-cube trailers take advantage of that.
This also applies to railroad cars.
In ye olden days, railroad cars were limited in height so they wouldn’t get stuck in tunnels. As railroads improved higher car heights were allowed. Box cars with hi-cube heights, as they were called (cubic feet, not geometry), have the “extra height” portion of each end painted white. Next time you see a train, look for it.
PS this is what holds containers to the train, trailer, ship, and each other. This simple lock makes containerized shipping possible. You put one at each corner, rotate the lever, and voila! Containers are locked, and locked so well, they can tip over and not come apart. They make these things by the millions, I expect. At least four required for ever container in existence.
There is a gray stripe around the center of the tire. There is a prominent white patch outside the gray. That patch terminates abruptly with what appears to be a diagonal line. That looks like a bulge to me. It could just be an illusion caused by the tread curves and color patch.
The white could be scuffing. I see parallel striations, especially at the outer edge. Maybe ran over a curb or something.
