#### Rebel74

##### Well-Known Member

With an

**open**span of 20 feet plus I guess an 2 additional feet on each end for the supports, what size wood beam do I need to be able to support 3 120 pound heavy bags attached at evenly spaced intervals along the beam? So imagine two parallel walls, 20 foot of floor space between them, and a beam setting on top of the two walls spanning the open space between the walls. 3 heavy bags hanging from the beam with about 5 feet or so of space between them. I understand the pendulum load should be approx 2x the dead weight, so if each bag weighs 120 pounds, the pendulum weight should be about 240 pounds. So the total dead load would be about 360 plus the weight of the beam itself, and the "live load" (dynamic, pendulum load) would be about 720 assuming all three bags are swinging simultaneously. Adding a fudge factor of 1.5, this comes to about 1050 pounds live and 540 pounds dead (not including the weight of the beam). So how big a beam do I need? .

Obviously it needs to be mounted securely to the wall at each end, especially accounting for the "back and forth" forces and not just the "side to side" forces.

Any help would be appreciated. I have searched and searched and cannot find anything remotely approaching a knowledgeable answer on the glorious modern internet. 75% of the web results appear to be blog articles written by ESL speakers who are just regurgitating whatever they could scrape off the net from other ESL bloggers to create click bait no-real-answer webpages. The other 25% are people arguing about minor details without actually pointing anybody in the right direction or "span tables" that seem to assume the beam is going to be either a floor joist or roof rafter.