TIL a lighter load can actually make the boom bounce worse on tight lifts

Everybody told me to always keep it light for precision picks, but last week on a job near downtown, I had a 4 ton beam swinging way more than when I haul closer to the limit. The extra weight damped the cable sway better, so I learned to match the load to the wind conditions not just the crane capacity. Anybody else notice this or was my setup just off?

2 comments

2 Comments

anna_craig26d agoMost Upvoted

I read a good article from a crane training outfit that said the same thing, @aaronrobinson. They talked about how lighter loads have less inertia, so the cable can twist and bounce easier. That 2 ton HVAC unit hula sounds about right. The extra mass in a heavier pick actually absorbs the movement, like a shock absorber. I had a 6 ton steel beam do the same dance last spring, then I bumped the load up and it settled right down. It goes against what everyone says, but the physics is pretty simple once you see it happen.

aaronrobinson26d ago

Keep it light for precision picks" is exactly what got me into trouble last week. I was babying a 2 ton HVAC unit on a calm day and that thing was doing the hula like it was at a luau. Meanwhile I've had loads right up to the chart that sit there like a rock in a windstorm. You'd think lighter means less mass to get pushed around but it's the opposite. It's like trying to steer a shopping cart with one bag in it vs a fully loaded one. The physics just don't work the way you'd guess from common sense. Next time someone tells me to go light I'm asking them if they've ever actually run a crane in a breeze.