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Thread starter
kyletheskater
Start date
Oct 28,Tags
In summary, The tension in the cable when the elevator is accelerating upwards at 1.2 m/s^2 is equal to the mass of the elevator multiplied by the sum of the acceleration due to gravity and the upward acceleration of the elevator. This is because the cable is providing an additional force to counteract the elevator's upward acceleration. Another way to calculate this tension is by subtracting the force of gravity from the net force acting on the elevator.
kyletheskater
JDHalfrack
Here are a couple hints (I hope they help):
- If the elevator was in free fall (accelerating downwards only due to gravity), the cable would not be exerting any force on the elevator.
- Also, if the elevator was just hanging there (not going up or down), the cable would have to exert how much force?
- If the first two hints helped, think about how much MORE or LESS force is required to get the elevator to accelerate up or down at the rates given
kyletheskater
So when the elevator is stationary the forces would be equal since it is not accelerating. When it's accelerating upwards the cable should have more tension right?
The way I'm trying to solve it I found the upwards force and the downwards force in a free-body diagram and then adding them. Am I on the right track or am I missing something? I found another equation T=m(g+a) do I need to add both accelerations before calculating the force in a direction to which more than one acceleration is affecting it?
JDHalfrack
Yeah, that's what I was trying to hint at. I didn't see you already posted this. Whoops!
Correct. In fact, whenever the elevator is not accelerating (whether it's stationary or not), the forces are equal because a= 0 (HINT for #3).Correct again! Now, the key is how much MORE tension? Again, remember F= ma. Since you're now getting the elevator to accelrate upwards with 1.2 m/s"more" acceleration, then how much MORE force does it take...EDIT:Yeah, that's what I was trying to hint at. I didn't see you already posted this. Whoops!
kyletheskater
FSW Product Page
Ok I'm starting to get this a little better now but there is one thing that still puzzles me. You said how much "more" acceleration, but the upwards acceleration is going up and gravity goes down so wouldn't the acceleration be (9.8 m/s2 - 1.2 m/s2)? When I do this I get a higher force when the elevator is accelerating DOWNWARDS which just doesn't make sense!
JDHalfrack
kyletheskater said:
Sorry for the confusion. To keep the elevator from accelerating upward or downward (basically to keep it at a constant velocity), the tension force MUST be equal to the force of gravity of the elevator. In essence, the cable is providing an upward acceleration of 9.8 m/sto balance out the downward acceleration of gravity. So, when the elevator has a net acceleration of 1.2 m/supward, that means it has to supply that much MORE force.So, the a= a- g.Going down, the cable only requires enough force to keep the elevator going at whatever acceleration is needed. For example, if the elevator is to be in free fall (9.8 m/s), the cable would provide NO force. If the cable were to accelerate downward at 9.7 m/s, the cable only needs to provide a 0.1 m/supward acceleration (and the force associated with it).So, in this sense, a= g - aDoes that make sense? Sometimes I find it easier to explain this on a board or in person instead of over the internet! Sorry!
kyletheskater
OOOH ok I got it now thanks sooo much! You actually justed saved me :)
JDHalfrack
kyletheskater said:
You're welcome. I'm glad I helped!
Symon
a) For when the elevator is accelerating upwards at 1.2m/s^2:
Tension = m(g+a)
= 2.7x10^3kg (9.8m/s^2 [upwards] + 1.2m/s^2 [upwards])
Is this correct? I'm trying to interpret this; g = 9.8m/s^2 [UP] because the Tension is acting opposite to gravities force on the elevator?
This would make sense because it would give me a greater tension when the elevator is accelerating upwards rather than downwards.
Another way that i did it prior to finding the tension equation was:
Fnet = Fgravity + Ftension rearranges to;
Ftension = Fnet - Fgravity
Would this equation work as well?
Tension on an elevator cable refers to the amount of force or stress that is being applied to the cable. It is typically measured in units of pounds (lbs) or Newtons (N).
Tension on an elevator cable is caused by the weight of the elevator car and its occupants. As the elevator car goes up, the cable stretches and the tension increases. Likewise, as the car goes down, the cable contracts and the tension decreases.
Tension on an elevator cable is important because it directly affects the safety and stability of the elevator. If the tension is too high, it can cause the cable to snap or the elevator car to malfunction. If the tension is too low, the elevator car may not be able to support its weight and could potentially free fall.
Tension on an elevator cable can be calculated using the equation T = mg, where T is the tension, m is the mass of the elevator car and occupants, and g is the acceleration due to gravity (9.8 m/s^2). Additionally, engineers will also consider other factors such as the length and diameter of the cable.
To ensure appropriate tension on elevator cables, regular maintenance and inspections are conducted by trained professionals. The weight of the elevator car and its occupants is also carefully calculated to ensure it does not exceed the weight limit of the cable. In addition, modern elevators are equipped with safety features such as emergency brakes to prevent free falls in case of cable failure.
This is the main part of Elevator which is designed for enclosed transport of passengers & goods
it is used to support the car (passing over the drive sheave to the counterweight) & pull the car. Usually number of lays depends on load & speed.
A traction machine is used on all traction elevator equipment types. A standard traction machine consists of a motor, drive sheave, brake and machine bed plate. The traction machine motor turns the drive sheave shaft to turn the drive sheave. As the sheave turns the hoist ropes pass over the drive sheave and pull the car through the hoistway.
An Elevator controller is a system to control the elevators, either manual or automatic.
The controller usually tune down the voltage between 12V to 24V to the controlling system, only the motor needs 3-phase power supply. The low voltage power supply is for the controlling component and the fixtures to control the elevator
Everything that works under electricity must have a motor attached for the functioning & driven by VVVF drives.
In practice, elevators work in a slightly different way from simple hoists. The elevator car is balanced by a heavy counterweight that weighs roughly the same amount as the car when it's loaded 40%-50% (in other words, the weight of the car itself plus 40&#;50 percent of the total weight it can carry). When the elevator goes up, the counterweight goes down&#;and vice-versa, which helps us in four ways:
The space enclosed by fireproof walls and elevator doors for the travel of one or more elevators, dumbwaiters or material lifts. It includes the pit and terminates at the underside of the overhead machinery space floor or grating, or at the underside of the roof where the hoistway does not penetrate the roof.
Steel T-shaped or formed sections with guiding surfaces installed vertically in a hoistway to guide and direct the course of travel of an elevator car and elevator counterweights.
The buffer is an apparatus located at the bottom of elevator designed to protect people. Buffers can stop a descending car by accumulating or dissipating the kinetic energy of the car.
Most elevators have an entirely separate speed-regulating system called a governor, which is a flywheel with mechanical arms built inside it. Normally the arms are held inside the flywheel by springs, but if the lift moves too fast, they fly outward, pushing a lever mechanism that trips one or more braking systems. First, they might cut power to the lift motor. If that fails and the lift continues to accelerate, the arms will fly out even further and trip a second mechanism, applying the brakes. Some governors are entirely mechanical; others are electromagnetic; still others use a mixture of mechanical and electronic components.
Everyone who's ever travelled in an elevator has had the same thought: what if the cable holding this thing suddenly snaps? Rest assured, there's nothing to worry about. If the cable snaps, a variety of safety systems prevent an elevator car from crashing to the floor.
Each car ran between two vertical guide rails with sturdy metal teeth embedded all the way up them. At the top of each car, there was a spring-loaded mechanism with hooks attached. If the cable broke, the hooks sprung outward and jammed into the metal teeth in the guide rails, locking the car safely in position.
As normal doors, elevator doors are also meant for entry and exit. Elevator door is of two types: Manual doors and Automatic doors.
Thread starter
kyletheskater
Start date
Oct 28,Tags
In summary, The tension in the cable when the elevator is accelerating upwards at 1.2 m/s^2 is equal to the mass of the elevator multiplied by the sum of the acceleration due to gravity and the upward acceleration of the elevator. This is because the cable is providing an additional force to counteract the elevator's upward acceleration. Another way to calculate this tension is by subtracting the force of gravity from the net force acting on the elevator.
kyletheskater
JDHalfrack
Here are a couple hints (I hope they help):
- If the elevator was in free fall (accelerating downwards only due to gravity), the cable would not be exerting any force on the elevator.
- Also, if the elevator was just hanging there (not going up or down), the cable would have to exert how much force?
- If the first two hints helped, think about how much MORE or LESS force is required to get the elevator to accelerate up or down at the rates given
kyletheskater
So when the elevator is stationary the forces would be equal since it is not accelerating. When it's accelerating upwards the cable should have more tension right?
The way I'm trying to solve it I found the upwards force and the downwards force in a free-body diagram and then adding them. Am I on the right track or am I missing something? I found another equation T=m(g+a) do I need to add both accelerations before calculating the force in a direction to which more than one acceleration is affecting it?
JDHalfrack
Yeah, that's what I was trying to hint at. I didn't see you already posted this. Whoops!
Correct. In fact, whenever the elevator is not accelerating (whether it's stationary or not), the forces are equal because a= 0 (HINT for #3).Correct again! Now, the key is how much MORE tension? Again, remember F= ma. Since you're now getting the elevator to accelrate upwards with 1.2 m/s"more" acceleration, then how much MORE force does it take...EDIT:Yeah, that's what I was trying to hint at. I didn't see you already posted this. Whoops!
kyletheskater
Ok I'm starting to get this a little better now but there is one thing that still puzzles me. You said how much "more" acceleration, but the upwards acceleration is going up and gravity goes down so wouldn't the acceleration be (9.8 m/s2 - 1.2 m/s2)? When I do this I get a higher force when the elevator is accelerating DOWNWARDS which just doesn't make sense!
JDHalfrack
kyletheskater said:
Sorry for the confusion. To keep the elevator from accelerating upward or downward (basically to keep it at a constant velocity), the tension force MUST be equal to the force of gravity of the elevator. In essence, the cable is providing an upward acceleration of 9.8 m/sto balance out the downward acceleration of gravity. So, when the elevator has a net acceleration of 1.2 m/supward, that means it has to supply that much MORE force.So, the a= a- g.Going down, the cable only requires enough force to keep the elevator going at whatever acceleration is needed. For example, if the elevator is to be in free fall (9.8 m/s), the cable would provide NO force. If the cable were to accelerate downward at 9.7 m/s, the cable only needs to provide a 0.1 m/supward acceleration (and the force associated with it).So, in this sense, a= g - aDoes that make sense? Sometimes I find it easier to explain this on a board or in person instead of over the internet! Sorry!
kyletheskater
OOOH ok I got it now thanks sooo much! You actually justed saved me :)
JDHalfrack
kyletheskater said:
You're welcome. I'm glad I helped!
Symon
a) For when the elevator is accelerating upwards at 1.2m/s^2:
Tension = m(g+a)
= 2.7x10^3kg (9.8m/s^2 [upwards] + 1.2m/s^2 [upwards])
Is this correct? I'm trying to interpret this; g = 9.8m/s^2 [UP] because the Tension is acting opposite to gravities force on the elevator?
This would make sense because it would give me a greater tension when the elevator is accelerating upwards rather than downwards.
Another way that i did it prior to finding the tension equation was:
Fnet = Fgravity + Ftension rearranges to;
Ftension = Fnet - Fgravity
Would this equation work as well?
Tension on an elevator cable refers to the amount of force or stress that is being applied to the cable. It is typically measured in units of pounds (lbs) or Newtons (N).
Tension on an elevator cable is caused by the weight of the elevator car and its occupants. As the elevator car goes up, the cable stretches and the tension increases. Likewise, as the car goes down, the cable contracts and the tension decreases.
Tension on an elevator cable is important because it directly affects the safety and stability of the elevator. If the tension is too high, it can cause the cable to snap or the elevator car to malfunction. If the tension is too low, the elevator car may not be able to support its weight and could potentially free fall.
Tension on an elevator cable can be calculated using the equation T = mg, where T is the tension, m is the mass of the elevator car and occupants, and g is the acceleration due to gravity (9.8 m/s^2). Additionally, engineers will also consider other factors such as the length and diameter of the cable.
To ensure appropriate tension on elevator cables, regular maintenance and inspections are conducted by trained professionals. The weight of the elevator car and its occupants is also carefully calculated to ensure it does not exceed the weight limit of the cable. In addition, modern elevators are equipped with safety features such as emergency brakes to prevent free falls in case of cable failure.
This is the main part of Elevator which is designed for enclosed transport of passengers & goods
it is used to support the car (passing over the drive sheave to the counterweight) & pull the car. Usually number of lays depends on load & speed.
A traction machine is used on all traction elevator equipment types. A standard traction machine consists of a motor, drive sheave, brake and machine bed plate. The traction machine motor turns the drive sheave shaft to turn the drive sheave. As the sheave turns the hoist ropes pass over the drive sheave and pull the car through the hoistway.
An Elevator controller is a system to control the elevators, either manual or automatic.
The controller usually tune down the voltage between 12V to 24V to the controlling system, only the motor needs 3-phase power supply. The low voltage power supply is for the controlling component and the fixtures to control the elevator
Everything that works under electricity must have a motor attached for the functioning & driven by VVVF drives.
In practice, elevators work in a slightly different way from simple hoists. The elevator car is balanced by a heavy counterweight that weighs roughly the same amount as the car when it's loaded 40%-50% (in other words, the weight of the car itself plus 40&#;50 percent of the total weight it can carry). When the elevator goes up, the counterweight goes down&#;and vice-versa, which helps us in four ways:
The space enclosed by fireproof walls and elevator doors for the travel of one or more elevators, dumbwaiters or material lifts. It includes the pit and terminates at the underside of the overhead machinery space floor or grating, or at the underside of the roof where the hoistway does not penetrate the roof.
Steel T-shaped or formed sections with guiding surfaces installed vertically in a hoistway to guide and direct the course of travel of an elevator car and elevator counterweights.
The buffer is an apparatus located at the bottom of elevator designed to protect people. Buffers can stop a descending car by accumulating or dissipating the kinetic energy of the car.
Most elevators have an entirely separate speed-regulating system called a governor, which is a flywheel with mechanical arms built inside it. Normally the arms are held inside the flywheel by springs, but if the lift moves too fast, they fly outward, pushing a lever mechanism that trips one or more braking systems. First, they might cut power to the lift motor. If that fails and the lift continues to accelerate, the arms will fly out even further and trip a second mechanism, applying the brakes. Some governors are entirely mechanical; others are electromagnetic; still others use a mixture of mechanical and electronic components.
Everyone who's ever travelled in an elevator has had the same thought: what if the cable holding this thing suddenly snaps? Rest assured, there's nothing to worry about. If the cable snaps, a variety of safety systems prevent an elevator car from crashing to the floor.
Each car ran between two vertical guide rails with sturdy metal teeth embedded all the way up them. At the top of each car, there was a spring-loaded mechanism with hooks attached. If the cable broke, the hooks sprung outward and jammed into the metal teeth in the guide rails, locking the car safely in position.
As normal doors, elevator doors are also meant for entry and exit. Elevator door is of two types: Manual doors and Automatic doors.