It might seem odd I don't remember that, but it's almost 3 am and I just got back from overseeing a club show. What's rrrreally weird is that I'm not going to bother going back to check. If I contradict myself, so be it. Consistancy is the hobgoblin of small minds.
It really isn't the
wheels themselves that are an issue. On a
level surface, with a significant downward force, wheels don't really impact the stability of the
unit in the sense we're talking about. In the same way, I think
caster locks are slightly superfluous from a theoretical standpoint. Practically though, they can't hurt. If I seemed to imply that one was safer than the other, I apologize. Also, the bracing of a
scaffold doesn't really matter in the scenario we're talking about. We aren't talking about structural stability, but...someone fill this in for me, please...I guess...topple stability? Geeze, it is late. If one is safer than the other, I'd imagine it's a ladder because it's top weight is centered, whereas a
scaffold, with a relatively similar footprint to an a-frame on wheels, has that top load distributed. That conclusion doesn't have my stamp of approval yet, though. Maybe others would like to weigh in on this specific issue. I say ladder.
So it's a matter of height vs. footprint and weight distribution.
It all comes back to what we were talking about before and the matter of
pushing any of these units with significant top loading (i.e. a person). Your dynamics are toootally thrown off when you apply a force at the bottom. It just isn't the same
unit, from a physics standpoint. I just can't believe there are people out there who totally ignore this, and I'm talking the pro world. It's a matter of going through the motions and actually knowing, down to the physics
level what you're doing. It's like throwing a
gel up to get a color, but having no understanding of
what is happening to the light when you do that. That sort of lack of understanding has a way of catching up to a person. It has to me many a time.
From single man, hydraulic bucket lift to a-frame ladder to rolling
scaffold, you have to be aware that none are going to be very safe to push around. I personally don't go around doing the math on this to ensure its
safety, though. Often it's a visual or gut ability to
gauge it. And my gut almost always says don't. A genie lift with or without outriggers has a fairly small footprint, especially in proportion to a well extended lift and I never push that. A-Frame ladder and
scaffold are safer. With both it cannot hurt to
throw some sandbags at the
base, just to increase your
safety margin. Remember, in rigging, we use a 5-7x loading factor. There's no reason not to apply this methodology to the actual working environment. Plus, think of the practicality.
Also,
scaffold is all different as are ladders, so to take a dogmatic approach is foolish. If you want to do a force diagram and acceleration calculations, all the better, but the smarter way is to simply not try and decrease
load-in time by being unsafe.