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Stairs/Slide

Not so obviously simple to actually do
 
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I just did some searching for the old old well-known cartoon joke about a stairway turning into a slide, and while Google shows plenty of fictional references, I can't seem to find a case where anyone actually did it. I couldn't even find a mechanism described (well detailed) for it somewhere here at the Halfbakery. Time to correct that!

There could be a good reason for the apparent non-reality of this gadget. Maybe more than one. First is that when in "stairs" mode, the stairs have to be strong enough to support the load of people carrying stuff up or down. Well, if the tread of each stair-step (the horizontal part) is intended to pivot, that means the pivot points must be quite strong. Here I will initially assume that a heavy-duty water pipe of 2 inches (5cm) in diameter can be strong enough to act as the axle for the pivoting tread.

Another problem has to do with the riser, the vertical part of a stair-step. It has to pivot, too, and it logically should be located "under" the tread part:
______ (tread)
|
| (riser)
|
With the riser under the tread, the weight of a person on the step can be supported both by the axle under the tread, and by the riser, which of course is attached to its own heavy-duty pivot/axle. Maybe 1 1/2-inch pipes (4cm) will be sufficient, now.

However, the problem is that the two parts cannot pivot simultaneously. The riser must pivot first, at least a little, to get it out of the way, so that the tread can pivot. Also, if the pivot/axle under the tread is too big, then it will be in the way of the motion of the pivoting riser, and that would prevent the whole Idea from ever being workable.

Next, the riser and the tread must pivot in opposite directions! (below, the arrows try to show directions of motion for each edge of tread and riser)
|
V
______ ^
|-->
|
|<--
This alone significantly increases the complexity of the mechanism.

While a simple-SEEMING solution would be to put gears on the ends of every axle, so that as one axle turns clockwise, the next always turns counterclockwise (and vice-versa), this does not address the fact that the risers must pivot first, at least a little bit. Also, a "train of gears" that has as many elements as this one one comes with its own problems. (If there are 15 steps, then there are 30 gears in the train.) There is "slop", such that the the first gears might turn a significant distance before the last gears even start turning. And friction in the system is cumulative; you might not be able to turn them easily at all!

Before presenting my solution to those problems, there is still one more troublesome aspect to this Idea. This results from the fact that the sum of the vertical and horizontal distances of the riser and tread, in stairs-mode, is significantly greater than the diagonal distance, in slide-mode.
-/ (one tread, after pivot)
// (tread overlaps riser)
// (riser overlaps next tread)
// (tread overlaps next riser)
/ (one riser, after pivot)
If you want a smooth slide, then every tread and riser will have to be notched, to fit together precisely enough to accommodate the overlap.

Note: If you ever encounter a stairway with notched risers and treads, don't say you weren't warned!

Now, about that mechanism. I'm going to suggest that the first part of it be a rack-and-pinion system for the risers. Slop is minimized because as the stairway-long rack moves, all the pinions (gears they are) rotate simultaneously. This also facilitates using a Main Lever (that simply pushes the rack) to activate the slide-mode.

Next, there is a connection between the risers and the treads with some deliberate slack in it, to allow that intial motion of the risers before the treads start to move.
-| (ignore the hyphen)
_|<--
^
This ASCII sketch implies that the riser's motion will be blocked by the tread, but in reality the riser should be on top of the tread, so that its lower part can freely pivot toward the left as the horizontal arrow shows.

What isn't portrayed is a curving piece of metal attached to the back side of the riser, near its bottom, that curves around under the edge of the tread. It is far enough from touching the tread that this allows the initial rotation of the riser, before the curved metal starts forcing the tread to pivot, too. This curved piece of metal also has to be located far enough from the bottom of the riser to not be in the way of the overlap, and it must be spring-loaded, to be able to move out of the way as the edge of the tread as the overlap happens.
-|(ignore all hyphens)
-|(riser)
-|\
-|-|(curved piece of metal)
==-|(tread at far left, metal continues at its right)
--/
You may be able to "see" that as the riser and tread pivot to make a straight line (notch not portrayed), the metal starts to get in the way of the tread. Putting it on a spring lets it get out of the way, and also lets the metal act as a kind of clamp to hold the tread in place, next to the riser.

There needs to be more than one of those curved pieces of metal, along the width of each riser, of course. And use lots of grease here, to minimize friction as the tread fits into those curved metal pieces.

Finally, when you want to shift the Device from slide-mode back to stairs-mode, you simply move the Main Lever in the other direction. This directly rotates the risers, and, indirectly, the risers force the treads to pivot back to their normal horizontal orientation.

In the home, you would have two Main Levers, one at each end of the staircase. So when you are at the top of the stairs and want to slide down, you can, and when you are at the bottom of the stairs and want to walk up, you can.

Vernon, Nov 17 2006

An Easier Alternative http://www.bimmerbo...nal/SimpleStair.jpg
Simpler Way to do this [jhomrighaus, Nov 17 2006]

additional Details 1 http://www.bimmerbo...pleStairDetail1.jpg
[jhomrighaus, Nov 17 2006]

Additional Details 2 http://www.bimmerbo...pleStairDetail2.jpg
[jhomrighaus, Nov 17 2006]

Additional Details 3 http://www.bimmerbo...pleStairDetail3.jpg
[jhomrighaus, Nov 17 2006]

[link]






       They made one for A View to a Kill too. But that's Hollywood I suppose.
theleopard, Nov 17 2006
  

       Note that Hollywood, with its scene cuts and multiple sets, could have a stair-set and a slide-set. Then they simply move the actor from the middle of one set (the stairs) to the middle of the other (the slide), and restart the filming. You wouldn't see how the IMPLIED change from stairs to slide is actually done.
Vernon, Nov 17 2006
  

       [21 Quest], a riser isn't tall enough to cover that diagonal distance. Do the geometry, and see!
Vernon, Nov 17 2006
  

       Only when the space is omitted.
jtp, Nov 17 2006
  

       [21 Quest], tipping steps just a bit can't work, either. Consider the staircase as a WHOLE. All its risers together do not add up to equal the total diagonal. You'd have to tip the steps so far that their treads can provide the missing distance --and that leaves us with the overlapping problem I already described in the main text.   

       Next, a taller riser still does not make it tall enough to handle the diagonal. Consider the simple Pythagorean right-angle triangle, having sides of 3, 4, and 5. "5" is the hypotenuse, the diagonal, regardless if the tread was "3" and the riser was "4", or vice-versa. A taller triangle, say 5, 12, and 13, still leaves us with a riser that is shorter than the hypotenuse.   

       [rcarty], typical water pipes are also steel, I think. Perhaps a lesser grade of steel, but not cast iron. They are thick-walled to handle water pressure. I have serious doubts that thin-walled steel is strong enough. I suppose you could use solid steel, but somewhere I got the impression that tubes can be stronger than rods, and weigh less, too. The tube or rod has to run the width of the staircase, and we don't want them to become bent as people apply their weight.
Vernon, Nov 17 2006
  

       See Links for a simple easy to build design the results in a smooth, notch free slide when closed(small joint lines only) and is locked in when closed to elminate any excess motion, also distributes weight to stair above and below, thus requiring much smaller pivots. It is also very simple using a minimum number of parts. Entire system is accuated by a 10-12 inch linear motion(could be provided by hydralic ram)   

       See my profile for link to the free easy to use software used to make these images.
jhomrighaus, Nov 17 2006
  

       [21 Quest], OK, that could work, but you have to make sure the treads don't tip when somebody steps on them. And it looks like you have two distinct sets of motion to implement. Can it be done smoothly?   

       [jhomrighaus], That looks nice, but I'm not so sure about the very first part of the overall motion, when the treads unlock. See, while one tread ("A") is trying to move outward from the hook, you have the riser of the tread "B" above it, already resting on "A", trying to move downward even farther. That's a collision that impedes easy operation.
Vernon, Nov 17 2006
  

       I think you may missunderstand the motion that occurs, the treads only pivot they do not move in or out, the inital motion of the riser is in a backwards swinging direction out and slightly upwards from the tread its locked to. this inital motion will result in a slight rise in the nose of the treads which will elimnate any binding, also the Hook, has a small amount of play(think of it more as a bump than a hook) The lock comes more from the pressure of the locking bar than from the hook itself(ie if the lock bar is loose the hook would be ineffective) In reality I suspect the Hook may not even be required.
jhomrighaus, Nov 17 2006
  

       [jhomrighaus] - wow. very nice.
Zimmy, Nov 17 2006
  

       I think we are forgetting a fundemental application for this device as in almost all situations where it appears in Cinema the stairs rampify while the protagonists are in the act of using them and this generally occurs with out their knowledge and so any approach to this must have that in mind to ensure proper falling and sliding behavior on the part of the victims.
jhomrighaus, Nov 17 2006
  

       Why on earth would you think that? Pivot points are 3/8s to 1/2 inch(bicycles use 1/4 inch axles and they hold 2+ people just fine) The model is based on a 10 inch tread and a 7 inch rise The tread thickness is 1 inch. In a home that is typically handled with a 3/4 inch tread and a 1/2 inch Riser and if you figure that your stairway could readily support you carrying your wife up the stairs then most stairways can handle a 400lb load with ease. 1.5 inch bolts can easily support more than 1000lbs and there would be 2 per tread and the treads are interlocked in such a way that the load is shared over at least 2 tread pivots but normally over 3! The Pivots would be steel and supported by the side plates of the stair, and the hinge on the riser would be full length. The actuator bar would be fairly loosely mounted and would really just hang off the risers that rest on the treads which carry almost the entire load of the system.
jhomrighaus, Nov 17 2006
  

       Yes it would be locked by pushing towards the bottom of the stairway, my point was that the acuator bar was not a load bearing component of the system. It is using a realitively small amount of force to lock the treads and risers together kind of like a wedge.
jhomrighaus, Nov 18 2006
  

       The acuator bar is limited in it movement to motions parallel to the slope of the stair but there is some play in its guide alowing for slight vetical motion perpedicular to the slope of the stair to allow for the pivots to move of thier rest point. There is just a small lip that the back of the tread rests on. It holds very little weight mostly it prevents the rotation of the tread. The actuator bar locks things together when pressure is placed against it in the direction towards the bottom of the stairs parallel to the slope of the stairs. Since the lip is flat on top the actuator only needs enough pressure to keep it from moving , the forces are then only in the vertical axis(straight up for the tread you are standing on and straight down for the ones above and below) When the actuatorbar moves towards the top of the stair parallel to the slope it will first pull back on the riser alowing the tread to disengage from the lip, this motion could be as little as 1/8 to 1/4 of an inch. At that point the risers will slide back along the tread causing the nose of the tread to first rise minutely then it will begin to fall into position. Once closed the treads are self supporting and no force is required to hold them in position. If a small force is maintained in an upward towards top of stair direction the treads will be prevented from moving or accidentily opening if force was placed at the top edge.   

       This is the same basic principal as a quick relaease mechanism, in particular those used on large concrete lifting buckets that have a small lever activated tab that holds the bottom doors shutalowing it to hold tons of concrete. Whack it with a shovel and it dumps the whole load.
jhomrighaus, Nov 18 2006
  

       I love that I've been here long enough that when I have to scroll down more than twice I think "Ah, this must be a [Vernon] idea."
PollyNo9, Nov 18 2006
  

       If you can make it so a random step causes the collapse when weight is put on it, then it gets my bun.
Ling, Nov 18 2006
  

       [Ling], that would be easy enough; just put a step-on-it button somewhere among the treads, and have that button activate a large solenoid attached to the "rack" part of the mechanism.
Vernon, Nov 18 2006
  

       You people are nuts.
zeno, Nov 18 2006
  

       //I love that I've been here long enough that when I have to scroll down more than twice I think "Ah, this must be a [Vernon] idea."//   

       Quite so. You can set up your opening page to show the posting-person's name, if you'd like a bit more warning.   

       Vernon, I didn't read the whole thing, but I wonder if you took into account that the stair treads will be somewhat grippy, for at least the appearance of safety, and won't make an ideal sliding surface. Hmm, maybe carpet would work.   

       Mainly, though, I wonder why you don't just copy those rotating billboards for this. Make each step a triangular bar, which would look stylish, and rotate about thirty degrees to get from steps to slide. Add some carpet to disguise it if you want.
baconbrain, Nov 18 2006
  

       [baconbrain], yes, that could work. You will need to be careful to ensure the triangular pieces CANNOT rotate until you want them to, or else the very first step a person takes, it will become a slide. My proposal here doesn't have that problem, since the risers prevent the treads from rotating.
Vernon, Nov 19 2006
  

       Stop thinking about the stairs in such a square mannor. It would make more sense to have triangles with the hypotenuse faceing out. the top back of each stair could be on a pin style hinge. With the pull of a lever the hypotenuse would now face downward and the leg of the triangles would match up producing a slide.
Chefboyrbored, Nov 21 2006
  

       The steps on an escallator would seem a suitable design point. They're even designed to fold flat (as they do at the top and bottom).
supercat, Nov 21 2006
  

       why do the steps have to be made as right angled triangles? an isosceles would work easier. with the two equal sides being the horizontal step part and part that is parallel to the gradient upwards. the shorter side would be the prop to hold up the step and could be made to fold away underneath the it, perhaps along runners where it connects to the bottom side of the triange?
Helixthecat, Nov 21 2006
  

       [supercat] // The steps on an escallator would seem a suitable design point. //   

       Hey yeah. No need for a slide. When the offending person attempts to use the stairs (up or down) just crank up the escalator to full speed. No matter how fast they run up (or down as the case may be) they never get anywhere.
MoreCowbell, Nov 21 2006
  

       I imagine that this could be probable being that there are super sized louvered vents in factories and industrial plants. When the vent is closed its a flat surface but when its opened you have individual slats. Now imagine that vent being slanted at a 45 degree angle.
Jscotty, Nov 22 2006
  

       Fishbones or not, I am attempting to build this set of stairs. Granted, I am only needing two steps and three risers, but the fact that a verticle set of "disappearing" steps has piqued my interest. For my use the weight of the person is nominal, being only one child at a time, and will include a mechanism that sings the bottom end outward to create a stable platform. I also agree with jhomrighaus, in their Nov 17 2006 post that the pivot diameter can be vastly improved. I will be using 1/4 to 3/8 blind welded bolts. I am also planning to add a channel to the actuating 'slide lever' and thus use 14 ga cold rolled flat stock. Will post soon about my success (failure) with this design. Thanks for the forum,
kennbobvilla, Jun 15 2007
  
      
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