Log bunks

Log bunks: Log bunks are the steel cross beams on a log truck or trailer that the logs rest on, each with an upright stake at both ends. Bunks and stakes cradle the logs and keep them from rolling sideways; chains or wrappers hold them down. Most log trailers have two or more bunks. Source

The federal log rule

Logs have their own securement section. Logs must be solidly packed, with the outer bottom logs resting against the bunks, bolsters or stakes. On frame vehicles and flatbeds with bunks, the tiedowns must add up to at least one-sixth of the stack's weight in working load limit, and longwood loaded lengthwise rides in two or more bunks with at least two tiedowns or wrappers. Source

Bunks, stakes and the headrack

The bunks carry the weight; the stakes stop logs rolling off the side; the headrack behind the cab protects the driver if the load shifts forward. Bent stakes, cracked bunks and worn stake pins are common defects, because loading with a grapple is rough on them. They belong on every pre-trip inspection.

In practice EXAMPLE

A logger loads a pole trailer with tree-length pine resting on the front and rear bunks. The stack weighs about 45,000 lb, so the tiedowns need at least 7,500 lb of working load limit in total; the driver throws three chains rated 5,400 lb each, then rechecks them on the paved road after the rough haul out of the woods. Logs are heavy for their size, so the bridge formula calculator is worth running on new trailer setups. More in the logging truck guide.

Loading logs on the bunks

Logs should sit solidly on the bunks, with the outer bottom logs against the stakes, and the load should be built so it doesn't overhang the stakes or rise higher than the trailer and route allow. Crooked logs and a loose stack shift under braking and in curves. Drivers watch the loader, step clear while it works, and check the load from all sides before throwing chains. After the rough woods road, they stop and tighten everything again.

Bunks and stakes take the worst of every load, so inspect welds, stake pins and wear every day.