Help with potential energy quandry
Help with potential energy quandry
(OP)
Hi everyone, I have a problem to solve, imagine your standing on a platform 7 ft in the air and the only way to get to the ground is a stair stringer that raises and lowers in front of you rotating on an axis on the end of the platform on which you are standing. In the raised position the stair stringer is perpindicular to the platform and lowered it extends to the ground. Now here is the problem; the stairs used to be raised and lowered with a hydraulic pump system, now I am faced with the task of moving it with a non powered system ie. Torsion springs or some other means of stored energy. What I need to know is if there Is a method that I could use to lower the ladder and store enough energy to facilitate its return with little or effort. Any help or guidence would be greatly appreciated. Thanks





RE: Help with potential energy quandry
RE: Help with potential energy quandry
Can you provde a sketch of the situation and some physical sizes/ masses of the stringer etc
RE: Help with potential energy quandry
RE: Help with potential energy quandry
RE: Help with potential energy quandry
http://picture.vzw.com:80/mi/773703875_2749482369_...
RE: Help with potential energy quandry
RE: Help with potential energy quandry
Ted
RE: Help with potential energy quandry
RE: Help with potential energy quandry
RE: Help with potential energy quandry
RE: Help with potential energy quandry
RE: Help with potential energy quandry
RE: Help with potential energy quandry
I'm thinking a torsion bar on or near the hinge line to balance most of the weight of the deployable stair, with a gas cylinder or two to fine tune the force required to lift it manually, and a sturdy latch to hold it in the stowed position.
I'm guessing the torsion bar will need to extend behind the plane of the paper for a fair distance, i.e. along the frame horn for a couple of feet.
Mike Halloran
Pembroke Pines, FL, USA
RE: Help with potential energy quandry
RE: Help with potential energy quandry
RE: Help with potential energy quandry
Regardless, you are ahead of the game if you have a suitable stair already designed. Given its weight, CG, and geometry, it's a relatively pleasant engineering exercise to work out the forces and torques required to move it over its range of rotation, either graphically or with Excel or whatever numerical hammer you have.
Actually, since you probably already have a physical stair available to mess around with, it might be quicker to mock up the truck's landing platform, and alternate design sessions with physical hacking sessions, measuring what happens and raiding the local junkyards for parts. Work fast, but be careful.
Mike Halloran
Pembroke Pines, FL, USA
RE: Help with potential energy quandry
RE: Help with potential energy quandry
I vote for the counterweight idea.
The problem with the torsion spring or bar is that you reduce your input energy by only 1/2 . Ideally the counterweight is theoretically much superior; you fight friction only.
Perhaps a little more thought should go into this before you discard it.
RE: Help with potential energy quandry
Springs work well for linear systems. A garage door is a great example of this, where the weight diminishes linearly as the door opens.
Counterweights work best for rotating systems, as they match the non-linear (sinusoidal) function of force as the system goes through its range of motion.
RE: Help with potential energy quandry
1) you show a single staircase deploying. maybe it's just a sketch, but i'd suggest using a double folding staircase ... ie one stage deploys, anf then 2nd (folded onto the first) deploys, this'd reduce the stowed height; but maybe you've already thought of this (deploying only 1/2 the staircase ?)
2) instead of unpowered, maybe a simple mechanical system with a lot of advantage ?
3) how are you going to inter-connect this with the truck ? presuably you don't want the truck moving with the stairs down ? presumably a sticker to this affect would be treated with the utmost distain by your operators ? so you need an interlock, presumably with the transmission, yes?
4) it looks as though it would be convenient to hide the counter-weight under the fixed staircase.
RE: Help with potential energy quandry
But suppose you made a cable rail _stair_? I.e., use two or four cables, mounted at a slant, with steps level, or level as could be. ... or one pair of vertical cables per step, cables of stepped lengths in an array.
Or, this might involve payments to the patent holder, a Lapeyre Stair using a single fat slanted cable as its backbone?
Mike Halloran
Pembroke Pines, FL, USA
RE: Help with potential energy quandry
Link
Doug
RE: Help with potential energy quandry
The key is keeping the CM fixed vertically, which is less demanding than keeping t fixed ( as in a counterweight setup.
RE: Help with potential energy quandry
Now you have the PE fixed and all you need is a handcrank to rotate one of the stair pieces, just overcoming friction.