My question is regarding a semi’s trailer design. First of all, it is a full semi trailer and not something that is shipped via railroad and bolted to a trailer frame. Second, I see them every day, so this design is not a rarity by any means.
Before you ask why in the world I simply didn’t post a picture of what is confusing me, let me say I searched mightily but simply couldn’t find one. So, I’ll do my best to describe it.
Okay, imagine your standard “box” design for a trailer. Now, remove the roof and remove the back doors so that the entire top and back are completely open. Now, permanently bolt a ladder to the middle of the back from the base to the frame running across the top. This “ladder”, if that is what it really is, not only blocks the free access to the back of the box because it is positioned smack dab in the middle, but it leads to the top of … NOTHING. There is no roof to stand on. The open top would be totally understandable if one were dumping rocks/soil, garbage into it with heavy equipment, but that can’t be the case because it has no back. The stuff would just run out onto the highway. So, what exactly is the purpose of this design?!
That’s pretty much it except that there are no extra bars going from the base to the top frame, just that ladder thingy bolted right in the middle. Also, they don’t have the front part of the trailer that almost touches the ground.
Timber, you say? In Chicagoland? The ones I’ve seen are always empty which, I guess, is why I have never known what they are for.
Are you talking about the triangle being on its point with the broad base up on top? Those are bottom dump trailers or perhaps like this? There is another variety for liquids, or finer grained solids that can flow like a liquid (sand, or fine silt or flour[well not flour but fine like that] or whatever) but I can’t seem to get google to bring up a picture of one those for me.
Edit; found one, its a dry bulk pneumatic trailer, I can’t seem to get a link to work for the one I found, but if you go to trailers of texas dot com, they have pics of them
Yeah kind of. It’s three triangle containers with the base at the top, and it’s completely closed in. It seems like it’s hauling a chemical to me. But why triangles instead of a cylinder?
Ah, “pneumatic” translates to forced air emptying the contents from the tanks. Lucky I saw this here now, otherwise I would have been back with another question!
They’re for viscous powdery solids like cement and flour. They tend to clump and hang up and refuse to empty. Ever been in the bottom of a silo that has a big wad of sawdust or whatever overhead, and it’s just suspended in the air, held in place by cohesion? If you ever find yourself in that spot, get out! The whole thing could WOOF down on you at once.
Anyway, they use air to empty these trailers. And they all have decals that say “do not bang on sides of trailer”.
Yes, people have actually been killed (suffocated) in that way. In fact, the 1985 Harrison Ford movie, “Witness”, had Ford offing one of the bad guys in just that manner.
The one I saw was so plugged, the workers were poking at it with long sticks, trying to start a small flow that would progress to a large flow, but without bringing the whole thing down at once. i was too young to know how dangerous what they were doing was. Other than setting off a small explosive, though, I don’t know what else you could do. Working it from the top is equally as bad.
coda: that silo later burned down. Took the whole building with it. At least no one got killed.
