What happens when we let an elevator weighing tons drop hundreds of feet? We do it all the time, just to make sure that they are safe for you. See how. www.kone.com/en...
It is a mechanical servo, the springs keep a safe decelleration so you don't break your neck. Obviously tested thousands of time in the lab and every five years in each installed elevator.
Because the maximum downward acceleration is a lot greater, in the event that the cables break. For a counterweight that is 25% heavier than the empty elevator cab, the maximum upward acceleration in the event that the motor fails would be 1.1 m/s^2. The maximum downward acceleration would occur when the cable breaks, and be 9.8 m/s^2. A fall after a broken cable is a lot more of a concern than a fall after a failed motor. The counterweight is specified to be as heavy as the elevator cab when carrying the average payload, so a failed motor could cause it to fall either way, but it will be a much more gentle fall than if the cable breaks.
Who else is here from the Cheddar vid comments? Watching this vid I see that Cheddar took footage from *this vid* yet still got their explanations wrong.
I am a retired elevator mechanic and have performed hundreds of five year full load overspeed safety tests. I have seen various failures happen during a few of those tests but only had two units that I can recall that the safeties did not set and they went fully loaded into the pits at very high speeds. One was due to a governor that would not trip and the other was due to wind up safeties that were rusted in place. Both of these units were "non contract" customers who were in a state that did not require building owners to subscribe to service contracts with elevator service companies who in turn kept the elevators in safe operating condition.
I was in a kone lift before christmas. The elevator jammed then fell the breaks screamed and we landed on something which bounced us around it happened 15 times in 45 minutes it's still being investigated but I'm trying to understand what actually happend to me. I've been left traumatised and have severe whiplash with a locked neck and a back injury the doors would not open and the emergency phone didn't work either
@@SergeAndOkkieForever the hydraulic stop at the bottom of the pit is what most likely stopped you and gave you whiplash. This is why I don't trust elevators
.that is basically 150+y old technology ..modern elevators should use safe mechatronic speed governors (e.g. Wittur EOS) to trigger not only on overspeed but also on over acceleration, that is much safer and obviously quicker....it may save lives if main brake fails with open doors while passenger exit or enter the car ....acting solely on over-speed in that case would be fatal in most cases....
“Setting the safeties” is the correct term. The elevator will then have a measurement which is the “slide”. The slide is the distance (markings) on the rails that tell you how many inches it took to properly slow down and eventually stop the car. There are requirements for how much slide you can have depending on the “rated speed” of that elevator. More commonly used now days along with other safety devices is the “Hollister-Whitney rope griper”. At anytime the safety circuit for an elevator equipped with a rope griped is broken the rope gripper will clamp all hoist ropes simultaneously. So for all the crazies out there that picture all cables breaking including governor rope there are other means associated with bringing a car to a complete safe stop. Yours truly, Elevator Mechanic Indianapolis
@@togatherwe2892 wrong!...at least very incomplete answer...watch the video!....the speed governor trigger the safety gears under (and/or over) the car frame....
Just one cable can support the elevator but there are usually 5-6 cables that are used (mainly for traction purposes). But suppose all 5 cables snapped--the elevator is still connected to the governor, a mechanical device, via a separate cable; and this will engage (mechanically) the safeties or brakes.
And if all cables snap simultaneously (including the governor cable) then the elevator falls down at high speed ! Only early safety gears (without o/s governor) could prevent this.
Rowan & MartinYTCZ Case in point. Just finished the cabbing up the car of a basement configuiration hoisting machine. Over the weekend the sprinkler system saturated the brake & of course the counterweights sucked the cab up into the hoisting beam ruining the cab & distorting the sheave's alignment as well. Yep cabs can fall up easier than down. Dover Elevator Mechanic's Helper 1981
your question does not make any sense....watch the video!....every elevator has a rated speed, lets call it VKN which maybe anything between 0.3m/s to 20+m/s....the speed governor would trigger at aprox. 1.2*VKN , engaging the safety gears.....so, if VKN=1m/s the threshold will be ~1.2m/s....if your elevator is a VKN=10m/s one that threshold is 12m./s.....this is all 150+y old technology ...modern elevators use or should use safe mechatronic speed governors to trigger not only on overspeed but also on over acceleration, that is much safer and obviously quicker....it may safe lives if main brake fails with open doors while passenger exit or enter the car ....acting solely on over-speed in that case would be fatal in most cases....
