Interesting. I don’t remember ever seeing such a sign; but then, I haven’t been looking for them, and I haven’t been in many elevators lately.
The concern about jumping in an elevator isn’t about overloading the structural capacity of the system; the safety margins on modern elevators are such that there is no conceivable way someone could create enough additional momentum through jumping to exceed the structural margins of the car or lifting mechanism. The problem is in the additional dynamics that are added into the system that the elevator was not designed to accommodate because elevators are assumed to be lifting quasi-static loads, not unbalanced gyrating motors or a crew of men jackhammering the floor. These can cause the mechanisms that operate the elevator to jam or experience conditions that activates a fail-safe, locking the car in place.
Traction (cable-lifted) elevators have wire rope cables that pull the elevator and a counterweight. On older designs the sheaves were not shrouded and in rare circumstances too much slack on a cable could cause it to jump out of the sheave and get warped or tangled. I’ve never heard of this occurring because of someone jumping up and down in the car but it was a common occurrence during earthquakes. This could also happen in an overspeed event (motor runs too fast due to power fluctuations or mechanical problems). In either case, the elevator couldn’t actually fall but it may get cocked or hung up, and the governor for the motor would automatically lock it into place. Modern traction elevator designs use shrouded sheaves and tensioners that prevent this from happening and would probably prevent large oscillations. In any case, if a traction elevator were to catastrophically fail, braking systems will activate locking the car to members in the elevator shaft. There are so many things that would have to go wrong for a modern traction elevator to fail in a way that would severely injure or kill someone that it is virtually impossible without Dennis Hopper’s intervention.
Hydraulic (piston-lofted) elevators have a hydraulic piston that pushes up the elevator which is fed from a hydraulic reservoir by one or more pumps. Most hydraulic elevators are five stories or less, and are chosen primarily to minimize the footprint of the elevator since it doesn’t require equipment overhead; you see them in small office buildings, residential elevators, and anyplace where an elevator is retrofitted to comply with the Americans With Disabilities Act. These elevators are much more sensitive to movement within the car, and because of the nature of hydraulics will have a resonant response to agitation by occupants, so if children and emotionally underdeveloped adults are jumping in an elevator to make it bounce, it is very likely this type of elevator. Again, the structural and hydraulic design margins are such that this will not cause it to break catastrophically but if the control system detects large oscillations in the hydraulic pressure or the pump starts cavitating because of negative pressure on the demand side, the system may go into a failsafe mode where it shuts down the motor and either locks the car in place or allows pressure to slowly bleed off, lowering the car to ground level.
Jumping in elevators is like doing a ‘neutral drop’ in an automatic transmission car; you can get away with it for so long but someday it is going to shred itself, leaving you stranded in the middle of an intersection. It should go without saying that any sensible, intelligent person is not going to go around jumping in elevators any more than they should throw rocks through windows just for the pleasure of hearing glass shatter. It is a foolish, irresponsible, and thoughtless thing that people do much to the chagrin of elevator repairmen worldwide.
Stranger
I wonder if it is a function of being in California. I have never seen such a sign here and I’m in many elevators in many buildings at least once a well. Mostly Otis elevators with some Thysson-whatever sprinkled in.
Maybe the elevator repairmen of the world are trying to tell you something, @silenus. What have you been up to in elevators, eh?
Stranger
I don’t think it’s a CA thing. I am squarely in earthquake country and I don’t recall seeing anything like that.
Fair question…
Taking the elevator to the bottom floor during a flood where it stops and you drown is one way. Seems to happen somewhere once every couple of years.
I saw the coolest hydraulic lift elevator ever, out in NW Portland in a repair garage. They’d drive the cars onto the lift then lower it down to a basement where they’d work on it then put it back on the lift to get back up to street level. Thing is, the mechanism of the thing was over a hundred years old, it used water pumped from the Willamette River to give the pressure to operate the lift and the platform was completely unprotected–you could have, if you were insane, jumped down into the pit for the thing. You would not want to do that, though, because the seal wasn’t perfect and water would spray all around the pit as the lift went up and down. Looked scary AF but the people who worked there assured me the thing has been moving vehicles around without a problem for decades. I really wonder what they did if the pump or shaft mechanism needed parts though. Probably had to fab them onsite the way they do for the big machinery in the paper mills.
That sounds amazing. I love things like that, that don’t rely on electricity to work.
Yes, if you are inside the elevator car. IIRC about half of elevator deaths annually happen to workers repairing elevators and most deaths due to falling down an open shaft. A lot more less serious injuries are due to falling while entering and leaving an elevator.
I don’t think that is a failure of the elevator system, though. That is a failure of situational awareness of the occupant; when a building is flooding, you shouldn’t be using the elevator at all.
I like to imagine the same thing happened to her character on Star Trek: The Next Generation. They were always having problems with the turbolifts…
Stranger
Jumping can cause one of the safeties to trip. What will happen next Depends on the age of the elevator. An older elevator will have a mechanical safety that a mechanic will have to manual reset. They newer ones a mechanic will still have to come on sight and reset at the computer.
By the way if an elevator controls and break both fail an over traction cable elevator will fall up not down, unless it is heavily loaded.
Machine_Elf
I think Hydraulic elevators a cheaper that traction elevators. The machine room can be put any place where there is room. No need of an elevator machine room over or under the shaft.
Yeah, big old honking diesel engine, loud as hell but it’s a mechanic’s shop, who cares? The thing is probably a Superfund site all its own at the end of the storm drain, but cool nonetheless.
I once worked on the 29th floor of the Century City North Tower in west LA. We frequently jumped on the express elevator, three and sometimes four full grown adults. Never had any problems, but it was a great deal of fun.
The signs about jumping would not be because of the earthquake safety device. Most that I have seen are an electrical wire running from the top of the shaft to the bottom of the shaft. ON the counter weight has an device that has a ring on it end mounted on the counter weight. The wire is in the center of the ring, and the ring travels up and down with the counter weight. The counter weight is held in between the counter weight rails. It will take a good earth quake to move the rails around or move the counter weight out of the rails. And if the counter weight is not being held in place between the rails it can hit the car. If the car is going up and the counter weight is above the car it can come crashing through the the room of the car. If the counter weight is below car and the car is going down the counter weight can rip the bottom of the car open.
The way the safety works depends on the position of the car and counter weight. If the counter weight is above the car and the safety trips the car should do an emergency stop. After about 5 seconds the car should start in the down direction at inspection speed (the lowest speed). When it reached the floor just below the car it should stop and the doors open and remain open. And stay at that floor with doors open until the earthquake safety is reset. If the counter weight is below the car the same thing shjould happen only the car should go up to the next floor.
After thinking about it I did have a set of hydraulic elevators that did have an earthquake sensor on them. The sensors were in the mechanical room not the cars. If the building shook hard enough the sensors would trip. If the car was mid floors it would stop and slowly blead down to the next floor below the door would open and there it would sit.
Not quite. There is a bit of added risk of falling over or injurying your ankle, knee, hip or back.
The landing could be at a bit higher or lower speed if the thing is accelerating while you are in the air…
Now because you may have jumped on a stationary surface many times, you may have the expertise required to coordinate the landing method, that is so finely tuned to the speed vs height of a normal jump, that somehow you trip yourself over because of the difference in speed of the floor of the accelerating elevator… Its not visual coordination , its not the same as “hand eye coordination…” , thats the expertise to adjust the hand due to visual feedback. Our feet ??? no feedback, its all pre-programmed. (Ok, it can be visual , but often its not. ) We walk and jump without looking right ? Thats why we can trip over on a 5mm lump on the floor ! Its an expert program in your brain… it knows the timings and forces when the motion is in 1 g ! and cooordinates quite a number of muscles… A failure to unlock the knee in time can cause the knee to be in locked state… when you don’t “benz the kneez”… you know how bad that is…
London had a hydraulic network back in the 19th century.
In 1871 after a successful pilot in Hull the company built a pumping station near Blackfriars Bridge with a network of hessian wrapped cast iron pipes providing power to cranes and factories in the docks. By the 1890s the network had expanded to five pumping stations and 180 miles of pipes. They powered theatre curtains, clocks and a turntable on the stage at the Royal Opera House. Hydraulic powered lifts meant that buildings could be taller, while hydraulic powered printing presses meant newspapers and books became more affordable.
I remember reading a book (probably fiction) where someone mentioned that the elevators in Russia used thinner cables - and they felt that they felt the car drop down a bit every time they stepped on. Very discomforting.
Is it save to jump up and down on an elevator? Well - there’s always the chance that you might get dizzy from the relative motion and fall over - striking your head on one of the walls. Or infuriate one of the other riders…
But for most instances, this cartoon seems appropriate:
I think it’s not wise to tempt fate, whether in an elevator or driving on highways. People die every day from just crossing the street, and not because they did something wrong, or “wrong” as the case may be. There are a lot of bad drivers out there. Life can get awfully dangerous awfully fast. I’m not “advocating” paranoia, nor suggesting that one should be anxious just when walking outdoors, strolling down the street, bur awareness, “being in the moment”, as psych people put it, has its merits. In other words, pay attention, be circumspect, look around you, and all the rest. The Boy Scouts put it nicely: Be Prepared. Damn good advice.
Is it safe to jump up and down in elevators?
True story
In one of my grad schools a group of us were heading down to the weekly symposium in the elevator. At this particular department symposia were well-attended. Unlike most other weekly symposium sessions I’ve been to, where people socialize beforehand with coffee or tea and little cookies or something, at this one they had donuts. And the grad students would rush for the donuts as if they had had nothing to eat since the previous symposium. It got so bad that they had to lock up the donuts, and not bring them out until after the symposium.
In any event, my point is that no one missed going to the symposium. You might miss out on getting a donut.
So quite a crowd got into the elevator, forced themselves inside enough so the doors would close, and pressed the button for the Lobby.
One of the students (my hefty-sized roommate), seeing the crowd, said
“I wonder what would happen if we jumped up and down.”
…and then did. Nobody joined him. But he was large enough by himself that you could feel the elevator jostle.
And then it stopped. Between floors.
We were there for an hour. We missed the donuts, of course.
So THAT’S what can happen if you jump up and down in an elevator. It’s perfectly safe, in that you’re not going to fall*. But you might get stuck between floors until somebody notices that the elevator’s stuck
*Otis’ inventio wasn’t a car that went up and down – they had those back in antiquity, and they were used in the Renaissance. It was the safety elevator., which had a mechanism to keep the car from plunging down the shaft if the cable broke.