Instructables

what is the function of a pulley in a elevator?

may i know can pulley be substituted with anything else as efficient?

Wisaam1 year ago
The function of a pulley is to mainly distribute the weight evenly which sort of makes the elevator lighter and the motor doesn't have to do much work to lift it. If you don't have pulleys than you can simply use wheels and hang ropes through them and it will also act as a pulley.

Else, you can also use gears to increase the torque of the motor. Just attach a small gear with the motor and attach a large gear with any wheel on which the rope or thread is wound. When the motor will spin with high speed than it will also rotate the large gear with increased torque but lowered speed. But I wouldn't recommend this method. It just isn't that much effective or applicable.
to pull it up and down
A roping system is used to attach the motor/gear reducer, the elevator car and the counter weight. There are many different kinds of arrangements that can be used. In one possible arrangement, such as shown in Figure 2, both ends of the elevator rope are anchored to the overhead beam. Both the elevator car and the counter weight are attached to free moving pulleys. The traction drive is attached to a stationary pulley.

The traction drive is the method of converting the input mechanical power (in this case the turning of a shaft) into useable mechanical power in the system (the vertical movement of the elevator). The friction between the ropes and the sheave grooves, which are cut on the pulley, initiates the traction force between the traction drive and the rope.

When the traction drive is rotated power is transferred from the traction drive to the elevator car and counter weight. Power is only needed to move the unbalanced load between the elevator and the counterweight.

An elevator's function is to convert the initial electrical power, which runs the motor, into mechanical power, which can be used by the system. The elevator is composed of a motor and, most commonly, a worm gear reducer system. A worm gear system is made up of a worm gear, typically called the worm, and a larger round gear, typically called the worm gear. These two gears which have rotational axes perpendicular to each other, not only decrease the rotational speed of the traction pulley (1), but also change the plane of rotation. By decreasing the rotation speed, with the use of a gear reducer, we are also increasing the output torque, therefore, having the ability to lift larger objects for a given pulley diameter. A worm gear is chosen over other types of gearing possibilities because of its compactness and its ability to withstand higher shock loads. It is also easily attached to the motor shaft, sometimes through use of a coupling. The gear reduction ratios typically vary between 12:1 and 30:1.

The motor component of the elevator machine can be either a DC motor or an AC motor. A DC motor had a good starting torque and ease of speed control. An AC motor is more regularly used because of its ruggedness and simplicity. A motor is chosen depending on design intent for the elevator. Power required to start the car in motion is equal to the power to overcome static, or stationary friction, and to accelerate the mass from rest to full speed. Considerations that must be included in the choice of an acceptable motor are good speed regulation and good starting torque. In addition, heating of various electrical components in continuous service should not be excessive

The most common elevator brake is made up of a compressive spring assembly, brake shoes with linings, and a solenoid assembly. When the solenoid is not energized, the spring forces the brake shoes to grip the brake drum and induce a braking torque. The magnet can exert a horizontal force for the break release. This can be done directly on one of the operating arms or through a linkage system. In either case, the result is the same. The break is pulled away from the shaft and the velocity of the elevator is resumed.

In order to improve the stopping ability, a material with a high coefficient of friction is used within the breaks, such as zinc bonded asbestos. A material with too high a coefficient of friction can result in a jerky motion of the car. This material must be chosen carefully.

Typically the efficiency of the geared machine is 60 percent for the motor and gear box assembly. This efficiency was estimated for a load of 2500lb, which matches a regularly sized residential elevator, being driven at 1.75 m/s.

The pulley distributes the weight more evenly so it makes the elevator lighter. The only other thing available that is easy is a wheel. There are more complicated things, but it would be harder. more strings from the pulley = object lighter
NE patsrock3 years ago
it goes up and down by a machine
tinker2343 years ago
the pulley is to hold the conter wheit and the box what happens is at each level basicly it drops the wheight and then stops at your level now the motor that pulls the wehight stops you could use a free fall mechensim but you have to be crazy besides it is too fast
Pretty much what he said...
yes inded hey you know the elavtor is cool
Yep, it certainly is!
wonder what hapend to anku218
Lol I know! He hasn't replied to any of these answers... Maybe he will show up sometime...
yeah hey maybe a private message
The most efficient and cost effective would be a hydraulic elevator. These work by using pressurized fluids in a cylinder to either lower or raise the elevator car. Thanks to pascal's law, you could use a relatively low power pump on a small surface area of hydraulic fluid which would then be transfered to the piston with a larger surface area. These lifts are commonly found in repair shops and by simply using a foot pedal to pump the fluid, people can easily lower and raise cars. Replace the foot with a pump and you have a simple, efficient elevator
I just re-read your post. I believe the gas station lift is run by compressed air, unless you are referring to portable lifts like a garage jack where you work the handle, but the big lift is far beyond foot action.
Hmm I was just going by memory I may be mistaken
could make a good workshop editon
I agree, but I'm pretty sure elevators in buildings that are lifted with hydraulic rams only go up about 5 floors. I think it's because the ram has to retract too far into the ground.
Yes that's true they do have a limited height, however if you either embed the piston farther into the ground you could have a farther range, but I dont think you'd need an elevator to go up more than 40' for personal reasons...but then again it is a very vague question he/she asked.
Please read my comments above. I work in the elevator trade as a journeyman mechanic. There are physical and environmental limitations as there is with any mechanical system.
Yes they are more efficient. Less moving parts, 50% duty cycle of the motor,and less time to install, and less service required to maintain the equipment, However they are limited by rise to several levels because however high it goes, it has to have somewhere for the piston in the jack to go weather it is in ground, hole-less, or roped-hydro. Also there are environmental concerns. Over time the jacks leak for a variety of reasons. They are now required to have PVC casings with inspection holes which is better than the old days when a leaking jack would pump gallons of hydro oil into the ground before a repair crew would be sent (big expense for the elevator co.) The company I used to work for sold a roped elevator product designed to fit in hydrolic tearouts called "hydro replacement. I know, more information that the original topic. I'm an elevator mechanic.
For taller buildings they are limited in hight as the above says, but also in speed. And as you go to a telescoping ram the barrel gets larger and the speed would decrease due to a larger volume of fluid required to travel a given distance. You do see hydraulic elevators very often in 2 story buildings, and they aren't rare in 3 or 4.
The tallest hydraulic I ever serviced was seven levels (floors). Four parking levels and 3 above ground level. This was a single piston and not telescoping. The maximum speed of hydros is 200 feet/minute or less. No matter what the arrangement the speed will be consistent because of Boyle's law of pressure and the pump capacity working with the controller and valve system. Regarding the 7 level installation it was a pig to service and maintain because it was "push up" (later levels added) and the original equipment was over stressed. Excessive vibration and heat would crack fittings and seals would wear out constantly. What the riding public sees of elevator equipment is only 10% of what it takes to make that little room go up and down, so some assumptions and speculations are inaccurate.
jrg3ni0us3 years ago
The pulley is run off of electricity to pull the elevator shaft up or down by rotating the circular metal gear the cable is attatched to
steve-lane3 years ago
Since the tension in each rope length is equal to the force exerted on the free end of the rope, the mechanical advantage is simply equal to the number of ropes pulling on the load. For example, in Diagram 3 below, there is one rope attached to the load, and 2 rope lengths extending from the pulley attached to the load, for a total of 3 ropes supporting it. If the force applied to the free end of the rope is 10 lb, each of these rope lengths will exert a force of 10 lb. on the load, for a total of 30 lb. So the mechanical advantage is 3.

The force on the load is increased by the mechanical advantage; however the distance the load moves, compared to the length the free end of the rope moves, is decreased in the same proportion. Since a slender cable is more easily managed than a fat one (albeit shorter and stronger), pulley systems are often the preferred method of applying mechanical advantage to the pulling force of a winch (as can be found in a lift crane).

Pulley systems are the only simple machines in which the possible values of mechanical advantage are limited to whole numbers.

In practice, the more pulleys there are, the less efficient a system is. This is due to sliding friction in the system where cable meets pulley and in the rotational mechanism of each pulley
May I butt in? I see there are some misconceptions about elevator equipment. Regarding the number of ropes. They are designed so that one rope is sufficient to handle the weight of the car and counterweight. Yes, just a single steel cable can handle the weight. The main reason for multiple cables is simply to provide traction. This is designed into the sheive by cutting specifically angled grooves for the cables to ride in. Yes, they do wear down and decrease traction and need to be removed and "re-grooved".
waldosan3 years ago
the pulley's are used to lessen the load on the motor, it does this by swapping speed for torque, just like a transmission would do, the more pulley's the more weight it can hold, it'll just take longer getting to wherever it needs to go. kinda like at the elevator at my last job.

or more likely they are simply an axel like system so the motor can spin the counterweight.
^^ What he said
weasel9993 years ago
If its a fixed pulley it just changes the direction
a moving one cuts the needed strenth by 2 but u need twise as much work (golden rule of mechanics)
pulleys are one of the ''simple mechanizms''
s3 years ago
The function of the pulley in an elevator is to redirect the force due to gravity. So that when the average mass of passenger is in the elevator car the net force is zero. Now even a small motor can operate the elevator. This is more efficient because less energy is used because less work is done because the force required is almost entirely only compensation for frictional forces. For your second question, no. So far the best way to store the gravitational potential energy is the counter weight.
elevator edited.jpg
ipod1234 s3 years ago
what he said
Ditto
No-Shi-De3 years ago
just like what the rest said, its for the purpose of the counter weight, i believe the idea is to reduce the work required for the motor, cause imagine if the cable is reeled like in a fishing rod, even with no load, its very heavy... just an add on...
It is efficient and gives the cable a point to turn on.
Mechanical advantage, it's the most effective/cost reductive way to do it. I myself take the stairs; then again there's only 4 floors where I work.
TSC3 years ago
Here is a picture of what it looks like! I got the picture from this link!
otis-elevator-patent.jpg
acidbass3 years ago
There is a pulley because on one end there is the elevator car and on the other there is a counterweight which is used to move the elevator up and down (dumbwaiter system). In regards to your second question in this type of elevator no there is not a better way that is commonly available but there is development research that is looking into Maglev, Hydraulics, and pneumatics.
lemonie3 years ago

We don't really know what you're talking about here. Can you point us to a diagram / picture?

L
iceng3 years ago
Three types of elevators without pulley;
Maglev elevator,
Pneumatic vacuum elevator,
Hydraulic lift elevator.
Ben.land1013 years ago
Elevators work by a counterweight on the opposite end of the cable ran over a pulley. so when the car is about half-full, the motor uses almost no effort to lift the car.
kelseymh3 years ago
In an elevator, pulleys are arranged in groups called "block and tackle." That device is a force multiplier. Pulleys, being simple machines, are as efficient as you can find for the task they perform.
animan13 years ago
What would you consider equal efficient?
animan13 years ago
Pulleys easy up the strain on the moter. They are probaly cheaper then any other method (all you have to pay for is a pulley and extended cable). Plus they are *Maybe* quicker to install. I dont know much about elavators but I am just assuming these thoughts.