10 Things You Need to Know About Couplings

10 Things You Need to Know About Couplings 

How much do you honestly know about couplings? As a leading provider of couplings used for connecting shafts, we have many different styles, sizes and types for you to choose here at Greenbank Machinery and Plant. Take a look through our collection of premium quality shaft couplings and we are confident you will find something suitable for your application, especially if you require a flexible or rigid coupling to use with a tachogenerator.

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Providing both types of couplings enables us to serve a wider client base. As well as having rigid couplings that are perfect for transmitting power, we also have more flexible types of shaft couplings. These are ideal when there’s a degree of misalignment or some kind of end movement.

Finding the right type, size and style of coupling will help to protect pumps and motors, preventing unnecessary wear and tear. Unfortunately, shafts are seldom aligned perfectly and machines have a habit of vibrating, which means that shafts will move, so you need to have confidence in the coupling that you choose.

Making the right coupling choice can be tricky but we can advise you here at Greenbank Machinery and Plant Ltd as you make those major decisions. Speak to us about the different types of couplings we stock and find out more about our spare parts and universal couplings here, through these informative coupling facts.          

Couplings connect two shafts together

Quite simply, the main aim of couplings is to connect two shafts together so torque can transmit from one shaft to the other.  When one shaft spins, the coupling connects the two, enabling the second shaft to spin also. Couplings help to transmit power. This is their primary function and their basic principle of operation.

They can be used to absorb shock and vibration

In some instances couplings are used to absorb shock and take up vibration. This is especially true of flexible couplings which dampen a range of movements. By choosing flexible couplings this helps to accommodate misalignments and manage them better, thanks to an integrated flexing element.  

Choosing the right coupling depends on how the shaft is likely to move

Shaft misalignment is one of the biggest factors to consider when choosing couplings for machinery. This can affect the performance of the coupling depending on how the shaft moves or aligns. In general, when a pump, generator or other piece of equipment is connected by a coupling, any misalignment between the two items increases stress on the shafts. Shaft misalignment can take many forms including:

• End Float – Both shafts have axial movement moving in and out
• Parallel misalignment – Two shafts both of which have different rotation axis
• Angular misalignment – This happens when the shafts are neither, parallel or coaxial
• Torsional flexibility – Caused by shock or vibration creating torsional movement in shafts    

Universal and lateral couplings are capable of tolerating large misalignments and widely used for pulse generator drives. Multi beam couplings accommodate axial, angular and parallel misalignments with no backlash whatsoever.   

Couplings are often used at high speeds

Certain types of couplings are used specifically for high torque and high speed applications. Grid, gear and disc couplings are typical examples, used for high horsepower environments. This type of coupling can often be stiffer with more torsional rigidity. A Flex G Jaw Coupling for example, allows for high torque outputs with little or no backlash.   

Getting the size right is important

Getting the right coupling for the right application is important to reduce stress on pumps and motors and decrease the chances of flexibility or misalignment issues. One way to do this is to calculate the coupling sizing torque so you know what size coupling to choose. To find the nominal torque you can use these equations:

Nominal Torque = Horse Power x / RPM = Application Torque (in-lbs)

Once you have this figure you can then establish the coupling sizing torque by calculating as follows:

Design Torque = Application Torque x Service Factor = Coupling Sizing Torque (in-lbs)

 Most flexible couplings have a couple of flanges

In most instances, flexible couplings are constructed with two flanges or two hubs that connect to the shafts during pairing. The materials the couplings are made from can differ depending on the product, including spring discs, nylon or mechanical connections such as universal joints or gear couplings.     

Operating conditions will affect your choice of coupling

The company is the world’s best Cardan Shaft Coupling supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.

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Depending on the environment, couplings can be affected by changes in temperatures, operating conditions, and movement in machinery. This is why it’s essential you choose the right type of product for the task to suit the equipment and the application. Consider the environment where the couplings will be working and take into consideration what might affect them. Think about the operating temperature of the room, what type of run cycle the couplings will be experiencing, and whether they are going to be exposed to unusual elements such as chemicals or minerals.      

Think about the factors when choosing couplings

Knowing the difference between a flexible coupling and a rigid coupling is one thing, understanding the factors to help you choose a coupling size is something else. To help you narrow the search we suggest you think about these five fundamentals:

• The total horsepower of the motor
• RPM at the coupling connection
• The shaft and keyway size
• The distance between the shaft ends
• Type of equipment used   

Couplings improve the efficiency of your equipment

Select the right type of flexible or rigid coupling and you reduce stress on motors, pumps and shaft mounted tacho generators. This will help to lower your spare parts bill and prevent you having to replace shafts and couplings sooner. By sourcing the appropriate coupling for your machinery, you will improve the operating efficiency of pumps and motors, which in turn will help to extend their life.     

Choosing the best coupling supplier will make things so much easier for you!

Give yourself as much scope as possible when you are choosing couplings for motors, pumps and shaft mounted tacho generators.  A reliable and reputable couplings supplier will be able to give you advice and help you choose the right type of coupling for the application you have in mind.

As a leading supplier of tachogenerator spares, incremental encoders, sensors and shaft couplings, we can guide you here at Greenbank Machinery & Plant and help you make informed decisions about new products and spares.

Special attention to the friction couplings

Friction couplings in cardan shafts are exposed to pressure from the springs all year round. However, if the couplings are not used for a longer period of time – which can happen in the winter months, for example –, the friction disks can “stick” to the counter plate. In the worst case, they no longer move – which could result in damage to the machine.

These problems can be avoided however, if you observe a few basic notes:

In the non-tensioned state, the coupling must be able to be turned independently of the hub. If this is not possible the frictions disks are “stuck” and must be mechanically separated.

You should also make sure that the hub does not have too much clearance on the power take-off in order to avoid increased wear and prevent the coupling from starting to knock.

Which cardan shaft should I select?

The selection of the right cardan shaft (drive shaft) is always based on the conditions under which it will be used. The cardan shaft must be suitably robust in order to transmit the generated torques under all operating conditions.

In agricultural machinery drives such as those of tractors, torques are highly variable depending on the machine type and operating conditions. They also depend on which product is being processed and the speed at which the machine works.

Based on these general conditions, the cardan shaft can be selected. The angle of articulation, required service life of the universal joints, rotational speed and required lubrication interval must also be determined. The following factors must be observed:

Cardan shafts are also called drive shafts and propshafts. They facilitate the transmission of power (more precisely, the transmission of torque) between offset axles. They are used in almost all motor vehicles, from tractors and trucks to cars.

Most cardan shafts contain universal joints mounted on both sides in order to accomplish transmission between the drive axles. Two cardan joints are used in order to avoid the “cardan problem:” when only one universal joint is used, the result is uneven, fluctuating rotational speed transmission.

Changes in distance or length during operation can also be compensated for by a length compensator, a sliding piece inside the cardan shaft.

Joints in cardan shafts are usually jacketed with collars or another suitable cardan shaft guard to prevent contamination or water from penetrating into the joint. At the same time, thorough relubrication at regular intervals with high-quality lubricating grease is essential for smooth functioning.

The right type is crucial

Numerous factors are important for power transmission effectiveness, including the cardan joints’ angle of articulation. It also has a decisive impact on the joint’s service life. The joint must also match the rotational speed at which the cardan joint will be used.

As you can see, many factors must be considered when you are selecting the right cardan shaft. One of our technical specialists would be happy to provide you with technical support.

Contact us to discuss your requirements of Pin Bush Coupling. Our experienced sales team can help you identify the options that best suit your needs.