Heavy-haul equipment has always fascinated me, ever since I was a little boy watching “steam shovels” dig basements in our then-expanding neighborhood in post-World War II Milwaukee.
 
The shovels (which were actually gasoline- and maybe diesel-powered) were carried to job sites on low-slung pull trailers. The trailers were pulled by dump trucks which, after parking the trailers on the street, also carried away some of the dirt from the new holes.
 
Today the equivalent is an equipment trailer with two or three axles and a heavy tongue that rests on the rear of a heavier dump truck. And over the years, the forward-scooping shovel became a large backhoe called an excavator. Everything’s bigger and heavier than in those long-ago days.
 
For a few months back in 1978 I edited a magazine called Transportation Engineer, and in every issue we ran an article or two about a big haul that used a multi-axle trailer, and I learned a little of the terminology. But I’d forgotten most of it by the time I saw the trailers displayed at the Mid-America Trucking Show in Louisville.
 
One, in the Talbert Trailers booth, was a lowboy called a “3-3-2,” and I called Greg Smith, the VP of sales & marketing, to ask what that meant.
 

“To clarify a bit of our conversation, the show trailer was in fact a 3+3+2 configuration, or the ’12-axle’ configuration that is on the sheet sent previously,” he said via email. (Right)
 
“However, due to space limitations, only the ‘3+3’ portion – the jeep and trailer – were actually in the show. The 2-axle booster with the mechanical axle extension had to be left out, as well as the extra beam deck. We thought about piling them on top of the trailer but didn’t think it would show as well.”

The 65-ton modular trailer was built for Catom Trucking, based in Geneva, Ill., Smith said.
 
A “jeep,” of course, is the forward booster with two or three axles and its own fifth wheel, on which rests the nose of the main lowboy trailer. Other trailers displayed outside had boosters stacked aboard, as Smith described, and they might’ve confused onlookers who don’t work with them.
 
The sheet of drawings shows progressively longer and heavier combinations, up to 13 axles (including a tractor). You may notice that there’s no 10-axle version. “They’re hardly ever used” because state weight laws don’t favor them, Smith explained, “so we don’t build many.”