So I'm looking at this ladder and I'm wondering why they positioned the spreader at that exact height off the base and at that exact length.
I know that OSHA and ANSI each have lengthy manuals governing every dimension of a ladder. I figure there must be some kind of specification for those spreaders, something involving angles, geometry, maybe some trig if I'm lucky.
Maybe I'll ask the students where they'd find the spreader on a 15-foot tall ladder and at what length. Then I'll go find a 15-foot ladder and photograph it to verify their answer.
Or maybe we'll develop an algorithm together, converting our intuitive sense that this ladder isn't safe into a formula for the safe construction and placement of a spreader.
It Got Away
So I check the OSHA manual for stairways and ladders. Nothing on spreaders. Then I call Werner Ladder Co. to see if they have some kind of internal specification on the spreaders. Two days later, an engineer calls back to tell me that, nah, the spreaders are pretty much irrelevant to safe ladder usage. They only exist, this guy tells me, to guide the sides of the ladder to a specific location, at which point your body weight — not the spreader — keeps the ladder's position fixed.