Tag Archives: pulley hoist

China supplier M20 304 Stainless Steel Single Sheave Pulley Lifting Pulley for Hoist Crane with Great quality

Product Description

Lifting single wheel pulley directional small pulley
&Double – wheel lifting pulley:


C30 Plastic Cable Trolley – Crane Festoon Parts:

Detailed Product Description

Mobile Electrification Cable Trolleys For Festoon System, C Track Festoon System for Crane, Galvanized Steel Conductor Rails With Brass Dowel, C Rail and Trolley, Stretched Wire Festoon System, Festoon Cable Trolley, Festoon Cable System.

Detailed Product Description

Festoon System can hold conductor cables and hoses (hydraulic and pneumatic applications) for delivering power & control to mobile equipment in a safe, efficient and maintenance free method. 

The C-track system is 1 of the most versatile festooning techniques available. It is an all-purpose system suited for either indoor or outdoor use under a broad range of operating conditions in a mild environment condition.

 

Application

C-rail systems applications: crane manufacturing, hoist units, transport systems, special engineering, stacking systems, conveyor system, etc. C-rails are available in zinc-coated and stainless steel version  Special versions are available for explosion-proof areas. 

 

Design features:

Compact arrangement, corrosion resistance and simple assembly are its essential features.  Easy for transportation and installation

To guarantee the normal operation of crane and avoid the personal casualty and mechanical damage, the safety device we
provide are not only the electric protective devices or alarm bell but also other
equipments as following:
1.Overload Limit Switch
2. Rubber Buffers
3.Electric Protective Devices
4.Emergency Stop System
5.Voltage Lower Protection Function
6. Current Overload Protection System
7. Rail Anchoring
8.Lifting Height Limit Device.

Safety Devices for overhead bridge crane and Other Install Spare Parts:
Photos of Crane Spare parts and Other Install Spare Parts:


Our After-sale Services– within 24 Hours:
(1)….Before–Sale Service :
01..Quality Control: Strictly Production Request base on signed contract ;
02..Delivery Time: Guarantee within contracted delivery time ;
03..Photos: Send photos to our customer after finish production and packing ;
04..Packing Details:Give complete packing size table to our customer;
05..Brand: Respect our customers’ advice to use our customers’ own brand & logo ;
06..Documents:Provide high efficiency service to post you all required customs clearance documents by DHL or TNT .  

(2)….After–Sale Service :  
01..Reply : Fast reply all your questions on line or by email or by telephone ;
02..Quality Problems:Our factory is responsible for any problems if it is resulted by our reasons (Such as give you free new parts to repair it  or give enough some compensation cost to you) ;
03..Safe Operating: Pls remind your customers to respect our Operating Manual to operate our machine rightly, to guarantee Safe when operate our machine.

Overview of Different Types of Pulleys

A pulley is a wheel mounted on a shaft or shaft. Its purpose is to facilitate the movement or change of direction of the cable or taut rope, and to transmit power between the cable and the shaft. Pulleys are typically used for lifting, winding or forklift applications. If you are building your own pulley system, the following design and installation considerations should be followed. This article will give you an overview of the different types of pulleys.
pulley

Pulley System Mechanics

There are many different ways to utilize the mechanism of the pulley system. The most basic pulley system consists of a fixed wheel and a support frame. Both components are connected by ropes or cables used to support the load. A pulley system is effective when the force required to lift the load is less than the weight of the object being lifted.
One way to use a pulley system is to suspend a block with a mass of 0.80 kg on a fixed pulley. Then another person can hang a bucket weighing up to 40kg. The weight of the bucket is transferred to the fixed pulley. The rope is attached to the pulley by a loop or sling. The rope will spin and pull on the barrel or block.
The pulley system is also an important tool for lifting heavy objects. Pulleys are often used in construction equipment to make lifting heavy objects easier. Gun tackles, yard tackles, and stationary tackle systems are common examples of these devices. They use the mechanical advantage of the design to guide the force that lifts the object. If you want to learn more about pulley systems, visit Vedantu. This website will provide you with a full description of the mechanism and its application.

Types of pulleys

Many different types of pulleys are used to lift heavy objects. They change the direction of the force and are an integral part of the cable system. Therefore, pulleys can move large and heavy objects more easily. However, before buying a pulley, you should have an idea of ​​the benefits it brings. Below are some of the most common uses for pulleys.
Conical Pulley: Consists of several small conical pulleys connected to each other. The larger base of 1 pulley is used to guide the force. Round pulleys are used in the same way as step pulleys. They are widely used in industry and can be purchased at any hardware store. Pulleys are a huge investment, and the benefits they provide far outweigh the cost.
Movable Pulls: These are similar to their names, but work by allowing objects to move with the pull. Their movable parts are attached to the object to be lifted. They are also ideal for lifting heavy loads and can be found in utility elevators and construction cranes. They are also used in many other industries. They can also be made of wood, plastic or metal. The type of pulley you use depends on its intended use.

Mechanical Advantages of Pulley Systems

A pulley system is a simple machine that reduces the effort required to lift heavy loads. This mechanical advantage is proportional to the number of loops. For example, if you have a single rope loop, you must apply equal force to lift the weight. When you add another rope loop, you can lift heavier weights just by applying the same force. Therefore, a pulley system is an excellent way to use gravity to your advantage.
Mechanical advantage is a measure of the effectiveness of a pulley system. This ratio of force to work is called the mechanical advantage. In other words, if the rope system has a large mechanical advantage, it means that it requires less force to lift heavier loads. This advantage is usually measured in kilograms and is the same for all pulley systems. In general, the greater the mechanical advantage, the less effort is required to lift the load.
The mechanical advantage of a pulley system is that a single movable pulley requires half the force to lift an object than a single fixed pulley. Assuming frictionless bearings, the MA of a single pulley system is 2, similar to the MA of a single lever. A single pulley travels twice as much as it takes to move heavy objects manually.
pulley

Considerations when designing and installing a pulley system

The capacity of the pulley depends on the type and diameter of the cable. Besides its diameter, its sheath should also support it well. The basic function of the pulley is also important. However, most people tend to ignore the pulley selection process, resulting in ineffective load-pull capabilities. To avoid such problems, different parameters must be carefully considered during design and installation.
During the design and installation of the pulley system, the ratio of the cable diameter to the largest pulley diameter must be considered. Those who work in the industrial sector will have an idea of ​​this ratio. The greater the D:d ratio, the greater the capacity of the cable to withstand the load. The best way to ensure secure design is to take the right information and use it to design a system that is both robust and secure.
When designing a pulley system, it is important to remember that the pulley needs to have enough power to operate safely. In addition to horsepower, the belt should have sufficient elongation to absorb shock loads. If the elongation of the belt is very small, it is very likely that the teeth will be sheared or broken, causing serious damage to the system. Extensive belt sag should be compensated for by offsetting the driven pulley. Finally, the frame supporting the pulley should be rigid. Otherwise, the non-rigid frame will cause center distance and tooth skipping changes.

Add more pulleys to the system

Adding more pulleys to the spool might have some effect. The friction between the rope and the pulley increases with the number of pulleys, which in practice limits the number of spools. The best solution is to combine the pulleys into 1 housing. If the load is small enough, adding a few pulleys probably won’t make a difference.
Using multiple pulleys allows a single load to be lifted with half the force required. The longer the rope, the greater the mechanical advantage. In fact, a spool can withstand a load of 100 N. Additionally, adding more pulleys quadrupled the mechanical advantage. In this case, a single 100 N load would require a force of 25 Newtons.
When the rope is used, it stretches as the weight of the object increases. This will make the rope longer, increasing its length and increasing the distance over which the load can be lifted. Eventually, the rope will break and the lifted object will fall. Then you will have to buy a new rope. It may seem like an expensive proposition, but it pays off in the long run.

cast iron pulley

Cast iron pulleys are the most popular choice among industrial users. They are made of solid cast iron and usually cost very little. Their rims are held in place by a mesh that extends from a central boss. They also have spokes and arms that hold them in place. These pulleys are ideal for a variety of applications including fan belts, compressors and conveyors.
V-groove drive pulleys are ideal for general purpose pulleys. It has an inner diameter of 1 inch and is commonly used in feeders and ventilation curtain systems. Its steel straps prevent rust and ensure it meets or exceeds industry standards. 3-1/2″ cast iron pulleys are also available. In addition to the V-groove drive pulley, there are similar pulleys for power transmission. The V-groove drive pulley is powder coated for added durability.
The cross section of the arm is elliptical, with the long axis twice as long as the short axis. The radius of the arm is equal to the diameter of the pulley. The thickness of the arm is a key factor to consider when purchasing a pulley. If you’re not sure which material you need, you can always consider wooden or steel pulleys. They are lighter and have a higher coefficient of friction than metal pulleys.
pulley

timing pulley

Plastic timing pulleys have many advantages over steel timing pulleys. On the 1 hand, they are lightweight and corrosion resistant, making them ideal for applications that do not require high torque and tensile strength. Another benefit is their resistance to high temperatures. Plastic timing pulleys are ideal for applications involving flammable gases, solvents or particles. They can last for many years. For more information on the different types of plastic timing pulleys.
Vertical shaft drives require flanged timing pulleys. For large span drives, at least 1 of these pulleys must be flanged. The flange provides a secure connection to the shaft and prevents ratcheting of the timing belt. Finally, HTD timing belt teeth prevent timing belt ratcheting. These teeth need a large enough space to be seated. However, they can also cause a backlash. These pulleys are not suitable for applications where positional accuracy is critical.
Timing belt systems are designed to avoid such problems. The drive shaft and the driven shaft are aligned with each other. The pulleys are located on different planes and are connected by pitch lines. The pitch line of the timing pulley coincides with the pitch line of the belt. These pulleys are also easier to implement and maintain. It is better to use a synchronous system because the resulting gear system emits less noise than other systems.

China supplier M20 304 Stainless Steel Single Sheave Pulley Lifting Pulley for Hoist Crane with Great qualityChina supplier M20 304 Stainless Steel Single Sheave Pulley Lifting Pulley for Hoist Crane with Great quality

China Custom CZPT Pulley for Building Hoist Spare Parts with high quality

Product Description

Commodity Xihu (West Lake) Dis. Pulley
Part used Building hoist
Packing size 130*130*130mm

ZHangZhoug CZPT Engineering Co Ltd. is a manufacturer and high-tech enterprise integrating R&D, design, manufacturing and marketing.As the company’s core industry,engineering construction machinery currently mainly covers 3 series:concrete machinery,crushing machinery and construction machinery
    CZPT insists on a high starting point and high quality, and uses 5% of its sales revenue every year on technologe research and development, trying to making high-end products. In terms of management, CZPT adopts the 6S management system,so quality control is strictly implemented in all aspects of parts procurement, production, packaging and shipment,which makes our products reach the international advanced level.
    CZPT actively responds to the national “Made in China 2571” strategy and the call of energy conservation and environmental protection.With the help of the national “One Belt and One Road” strategy, it continues to introduce professional talents and advanced technology. Through unremitting efforts, our services reach every corner of the country. Users anywhere in the country can get thoughtful and meticulous service.
 

Types of Pulley Systems

If you’ve ever tried to lift a pail of water, you’ve probably seen the pulley system in action. Pulleys are extremely useful tools for everything from household appliances to heavy industrial machinery. Different kinds of pulley systems are classified according to their amount of motion. Some types have fixed axes, while others have movable axes. Some common uses of pulleys are listed below.

two-wheel pulley

Pulleys are complex structures with thin-walled and thick-walled sections. Therefore, they require specific forging designs. The tool concept for the production of pulleys is shown in Figure 11.6. Using the generated tool, the pulley can be forged into different shapes. Process parameters must be optimized based on material, surface quality and metallographic analysis.
Pulleys are wheels mounted on shafts. Its main function is to assist the movement of heavy objects. A single-wheel pulley can change the direction of the force, enabling a person to pull heavy objects. A dual-wheel pulley distributes the weight evenly across both wheels, allowing it to lift the same weight with half the effort.
The mechanical advantage of a two-wheel pulley is that it reduces the force required by about half. A 100 kg object can be lifted with a force of 500 Newtons. The mechanical advantage of a pulley with 2 wheels is twice that of a single-wheel pulley. However, care should always be taken when using two-wheel pulleys.
Two-wheel pulleys can be fixed or movable. A single wheel pulley can only change direction when the load is placed on 1 side of the wheel. Two-wheel pulleys change direction when lifting a load, requiring half the force. Live wheels are better for heavier loads. The movable pulley can be adjusted with the load, and the load distribution is more uniform. Active pulleys can be used with single-rope or two-wheel pulleys.
A pulley system with 2 wheels is called a compound pulley. This type of pulley system has a complex design that reduces the force required to move the load. Two-wheel pulleys are common in industrial and construction environments. These pulleys require a lot of space to install and operate. Additionally, they require regular maintenance to avoid wear and tear.
pulley

composite pulley

Compound pulleys are used to increase lift. One fixed pulley is attached to the overhead while the other fixed pulley is attached to the load. This setup minimizes the force required to lift weights, allowing you to lift heavier weights. There are several different types of compound pulleys, each with their own strengths and weaknesses. Below are some examples of their application. Some of the most common are listed below.
Composite pulleys are usually made from 2 different types of wheels. The first 1 is fixed and secure. The second type, movable, is attached to something that moves. The third type, compound pulley, is a combination of a movable pulley and a fixed pulley. Below are 3 types of comparisons. The table below compares them and explains their advantages and disadvantages. Composite pulleys are the most versatile of the three.
The number of sheave segments that make up the composite sheave system increases the mechanical advantage of the system. Each segment adds 1 percent of the total weight, and the ideal mechanical advantage is 2 or more. So a compound pulley with 4 segments will lift three-quarters of the weight. This is because the force applied to the load is multiplied by four. The result is a better boost.
While composite pulleys have many uses, they are most commonly used on larger sailboats. These pulleys work by changing the direction of the control wire or by changing the mechanical force of the rope. They also make it easier to lift heavier objects. Composite pulleys are more expensive than simple pulleys, so consider your needs before buying. The advantages of composite pulleys outweigh the disadvantages.
A basic compound pulley is a device consisting of 2 wheels with fixed points. Ropes are looped around the wheels and are used to lift heavy objects. When you pull on the rope, the rope pulls the 2 wheels closer together. Serious injury could result if this equipment is installed incorrectly. Never exceed the lifting capacity of pulleys and other safety devices that may be attached. When using pulleys, be sure to follow the instructions on the mounting hardware to avoid accidents.
pulley

Fixed pulley

Moving pulleys and fixed pulleys are different types of mechanical devices. The movable pulley moves with the object it is used to lift. Because it attaches to the object it is used to lift, it is great for lifting heavy objects. These devices are used in construction cranes and multipurpose elevators. There are many different types of pulleys, and their uses vary widely. Below is a brief overview of these devices.
The simplest pulley set consists of a wheel that is mounted on the ceiling. A rope is attached at 1 end and a person pulls at the other end. The rope is strong enough to keep a person standing while lifting weights. It takes about 200 Newtons of force to lift a 20 kg weight. In contrast, a movable pulley requires a force of 1000N, which makes it easier to lift heavy objects.
Fixed pulleys are another common lifting device. They work by using ropes and slotted wheels attached to the object to be lifted. These devices are convenient to use because they are easy to set up. Moving the scroll wheel doesn’t change direction, so it’s easier to move objects without putting too much pressure on the back. Unlike a moving rope, a moving object will feel much lighter than its actual weight.
Fixed pulleys are widely used in construction and agriculture. Fixed pulleys can help lift supplies and equipment from scaffolding. These items are often heavy and difficult to lift directly. Fixed pulleys at the top of the scaffolding will allow people at the bottom to lift objects more easily. As a result, those at the bottom are less stressed and more productive. Fixed pulleys will save time and money compared to moving ropes.
Composite pulleys combine fixed and movable pulleys to increase the power of movement. A compound pulley system uses both types of pulleys and enables a person to change direction by reversing the direction of a force. The compound pulley system will save time and effort as the user only has to put in half the effort. Unlike moving ropes, composite pulleys are easy to adjust and are the most versatile system on the market.
pulley

Blocks and tackles

A pulley block system is a rope hoist that uses a set of pulleys mounted on a frame. The blocks are arranged in a row, and the threaded rope is called a pulley. Pulley systems help amplify the tension of the rope and are common in sailboats, cranes and drilling rigs. However, these systems are not without drawbacks.
The pulley pulley system can be equipped with as many pulleys as required. This method allows a person to lift heavy objects. The pulley block system can contain the required number of pulleys to achieve the desired height. The main disadvantage of pulley systems is that they create a lot of friction on the pulley shaft.
Pulley systems use 2 types of pulleys. A movable pulley is attached to the load, allowing it to move with the load. On the other hand, fixed pulleys are fixed on fixed points. Therefore, a pulley block system may consist of multiple pulleys mounted on a shaft. For example, the 2 pulleys attached to the shaft each have their own mechanical advantages.
Several types of tackle systems have been developed in recent centuries. The most basic is the gun mount, which uses 2 pulleys to lift the load. The mechanical advantage of such a system is 2 to 3 times the distance required by the rope to move the load. Depending on how they’re assembled, the system can lift 400 pounds with 80 or 100 pounds of force.
Another type of pulley is a combination of multiple wheels. The wheels on pulleys are supported by a housing or frame. The chain is attached to the pulley, and the rope is pulled to lift it. A combined pulley system will have multiple wheels. As the load increases, the force on the pulley also increases. This approach is generally more expensive than intercept and intercept systems.

China Custom CZPT Pulley for Building Hoist Spare Parts with high qualityChina Custom CZPT Pulley for Building Hoist Spare Parts with high quality

China Hot selling Groove Sliding Gate Roller Wheel and Pulley Wheel for Sc200/200 Building Hoist Spare Parts with Free Design Custom

Product Description

Product Description

Product Application

We are special supplier of building hoist in China, our building hoist have been Widely exported to all over the world and won good reputation, whose payload capacity is as much as 5000kg, lifting speed can reach up to 96m/min, and the erection height reaches up to 550m., our products have been widely used for transportation for both men and cargo in field of general buildings, but also industry, electric power, mining well, oil, chemical industry etc.
SC200TD, SC200/200TD building hoist:
1). Each cage load capacity: 2000kg
2). Lifting speed: 36m/min or 48m/min or 96m/min
3). Mast section: Paint or hot dipping zinc
4). Cage: Single cage or twin cage
5). Recommended cage inner dimension(LxWxH)(m): 2.5×1.3 x2.5; 3.0×1.3×2.5; 3.2×1.5×2.5; 3.6×1.5×2.5; 3.8×1.5×2.5; 4.0×1.5×2.5; 4.2×1.5×2.5, cage dimension is according to requirement of customer and special project.
6). Motor and reducing device: Made in China, can be SEW Germany according to requirements.
7). Counterweight: With counterweight or without counterweight
8). The colors of cage: Yellow, or red, or blue
9). Other each cage load capacity for your to choose: 1000kg, 2000kg, 2700kg, or 3200k

SPECIFICATIONS FOR OUR BUILDING HOIST

 

Model

Capacity(kg)

Lifting Speed(m/min)

Motor  Power(KW)

 

Single cage

SC100

1000

36, 63 or 96

2*11

SC200

2000

36, 63 or 96

3*11

SC270

2700

36, 63 or 96

3*15

 

double cage

SC100/100

2*1000

36, 63 or 96

2*2*11

SC200/200

2*2000

36, 63 or 96

2*3*11

SC270/270

2*2700

36, 63 or 96

2*3*15
 

Notice:

  1. Delivery time : (3-5 days)   
  2. Packinf: Carton or wooden case packing
  3. Warranty:3-12 months
  4. 24 hours online service

Company information:

TRUEMAX specialized in the production of construction machinery spare parts, such as: concrete batching plant, concrete truck mixer, concrete placing boom, concrete pump, concrete line pump, concrete truck-mounted pump, building hoist.

 

What is a pulley?

Pulleys are shafts or wheels on a shaft that support the movement and change of direction of a taut cable. The pulley also transfers power from the shaft to the cable. A simple pulley is used to raise the school flag. Read on to learn about the basic types of pulleys. We also covered the use of pulleys in everyday life. Read on to learn more about this important mechanical part.
pulley

composite pulley

A composite pulley is a mechanical system where 2 or more pulleys and ropes are connected together. It reduces the force required to lift the load because the force is divided by the distance of each pulley. Distance is equal to the mass of the object. Composite pulleys are a common mechanical system on sailboats. Composite pulleys can be used to lift heavy equipment such as sails.
The compound pulley unit consists of 2 pulleys, 1 fixed and the other movable. The fixed pulley is fixed overhead, while the movable pulley is connected to the load by a chain. The lift applies force to the other end of the rope. Anchor points are attached to fixed joists, ceiling joists or sturdy branches. The chain should be long enough to support the load during lifting.
Composite pulleys can be made from a variety of materials. Some are fixed and remain fixed. Others are detachable. The composite pulley combines the advantages of both types, making it a versatile tool. In the table below, these 3 types of pulleys are compared. It’s easy to see which 1 is best for your needs. The right choice depends on your specific needs and budget.
The compound pulley system consists of 2 fixed pulleys and 1 movable pulley. The compound pulley system multiplies the force by a factor of 2. The compound pulley system is particularly suitable for heavy loads and is ideal for construction sites. Workers apply less than half the load force on the composite pulley, significantly reducing the force required. This is a major benefit for many people.

Fixed pulley

Fixed pulleys are fixed gears of fixed length that are mounted on solid objects. There are many different types of pulley systems. Some cooperate with each other, but not “fixed”.
Fixed pulleys can be used for a variety of purposes. One application is to lift small objects. They have a one-to-1 mechanical advantage. Often, a single pulley can lift small loads. The force required to lift a single fixed pulley remains the same. They are usually used to lift lighter objects. They can even be attached to buckets used to draw water from wells.
While single fixed pulleys have desirable mechanical advantages, they are not suitable for force multipliers. Because their mechanical advantage diminishes over time, they are not effective force multipliers. They are used to redirect work so that it can be applied in the most convenient direction. This mechanical advantage is the main advantage of fixed pulleys and the most common way of moving objects. They have several benefits, including the ability to increase the speed of moving objects.
Another application for fixed pulleys is lifting supplies. A scaffold can weigh more than 1 and can be directly hoisted. In order to facilitate the transportation of materials, fixed pulleys are usually installed on the top of the scaffolding on construction sites. Then thread the rope through the edge of the groove that holds the pulley. The fixed pulley exerts the same force on the pull side as on the push side. The same is true for moving objects with fixed pulleys.
pulley

moving pulley

A movable pulley is a device whose part is fixed to another object, usually a rod or beam. The movable part moves with the load, making the load feel lighter. This is a useful tool for those who need to carry heavy items such as large bags. The advantages of moving pulleys are many. Here are some of them. Read on to learn more about them.
One of the most common uses of movable pulley systems is climbing high objects. Climbers act as pulley loads and pull ropes to lift objects. Eventually, when the traction stops, the climber descends. However, it is still a useful tool in other situations. The movable pulley system can help you climb the tallest objects or lift them to level surfaces.
Another example of movable pulleys is in industry. Depending on the load, movable pulleys make handling and moving loads easier. You can use them in a variety of applications in manufacturing and industry, including cleaning. For example, the American flag is raised and lowered every day. Removable pulleys are a handy tool when buildings need cleaning.
If you’re not sure whether a task requires a pulley, a zipline might be a good option. Connect the 2 ends of the rope and the pulley will move along the rope, then attach the rope to the metal cable. The load is the person holding the pulley, and the force comes from the attachment on the other end of the rope. There are 2 types of live pulleys: simple pulleys with just 1 wheel and live pulleys with many ropes attached.

School flag raised with simple pulleys

How is the school flag raised? It is pulled up by a rope attached to a pulley at the top of the pole. When the rope is pulled, the pulley turns, raising the flag. A pulley is a simple mechanism that helps people move heavier objects with ease. The rope must be securely attached to the pulley to keep the flag stable.
A simple pulley is a spinning wheel with grooves on 1 side and ropes on the other. The rope can be any length and the wheels can be any size. The rope has to go through the groove and the load is attached to the other end of the rope. Simple pulleys are pulleys with fixed shafts. An example is the wheel on a school flagpole.
A simple pulley system consists of a primary pole, a secondary pole and an outer member. The primary flagpole is connected to the track by a detour, while the secondary flagpole is connected to the track by a pipe. There is a groove on 1 side of the track, which passes through the inner cavity of the flagpole. An open track at the upper end of the track connects the 2 parts of the pulley.
A simple pulley can be used for many purposes. This is a useful machine that can be used to raise the flag. Among other things, it can be used in clothing lines, bird feeders, and even roofers. And, of course, you can use the pulley to raise the flag. Its versatility makes it an essential part of school decor.
pulley

cast iron pulley

If you are looking for pulleys for your machine, you may come across cast iron pulleys. They are usually cheap and available in a variety of sizes. The rim is held in place by a mesh attached to a central boss. The arms and spokes can be straight or curved, but most are oval. There are many uses for this type of pulley.
You might wonder why the arms of cast iron pulleys are so curved. Bent arms tend to yield rather than break. Cast iron pulleys are usually round with a slight bump on the rim, which helps keep the belt centered on the rim as it moves. On a 300mm diameter pulley, the bumps may be as small as 9mm.

China Hot selling Groove Sliding Gate Roller Wheel and Pulley Wheel for Sc200/200 Building Hoist Spare Parts with Free Design CustomChina Hot selling Groove Sliding Gate Roller Wheel and Pulley Wheel for Sc200/200 Building Hoist Spare Parts with Free Design Custom