by Brad Harris March 10, 2021

How Does A Compound Bow Work?

In modern archery, there are two main types of bow that are used; the recurve bow, which is more reminiscent of a traditional bow and the compound bow which is a more mechanical and modern piece of equipment.

Many archers opt for a compound bow due to their ease of use and great build quality. However, if you really want to get to know your equipment well, learning how it works is a great step forward.

In this article, we will be looking at how a compound bow works as well as everything you need to know before using one.

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What Is A Compound Bow?

A compound bow is a modern piece of archery equipment that is used to shoot an arrow at a target; they are frequently used in both target archery as well as out in the field for bowhunters.

This type of bow operates on a system based around a series of cables and pulleys; this might sound complicated, but the technology behind it might not be as mind-boggling as you might first think.

What Is The Difference Between A Compound Bow And A Traditional Bow?

Humans have been using a bow and arrows for as long as 60,000 years, potentially more so it stands to reason that when we talk about ‘traditional’ bows, we could be referring to a vast number of items. For the purposes of this article, the traditional bow is a longbow or a recurve bow. These pieces of archery equipment are very useful and are favoured by many archers the world over. However, the energy is stored within the bow and in short, the further back you draw the bow, the more energy is transferred into the arrow; thus sending it further. However, if you have ever used a recurve bow, you will know that you, the archer, are responsible for taking the entire weight of the draw and this can be something of a challenge, especially if you aren’t going to release the arrow right away.

In contrast, a compound bow features an intricate system of pulleys and cams, and these will take much of the weight of the draw. This makes it far easier to hold the bow steadily and release an arrow that hits the target. In most cases, a compound bow will take as much as 80% of the total draw weight, so it isn’t difficult to see how much simpler it can be to use one.

Where Did The Compound Bow Come From?

As far back as time itself, men and women have been using bow and arrow equipment for hunting and for sport. However, it was not until quite recently that the compound bow was developed and it has undoubtedly changed the way that we shoot.

In the 1960s, a man named Holiss Wilbur designed the compound bow and in 1969 was given a patent for this design. Since this time, the compound bow has grown in popularity, so much so that in the Olympic games, archers are required to use this type of equipment if they want to compete.

But the original compound bow differed rather significantly from the compounds bows that we are used to working with today. Initially, Mr Wilbur simply removed the curved ends from the recurve bow and attached a simple pulley system. Unfortunately, this did not function in the way he had imagined, and he needed to go back to the drawing board. At this point, he started working on the pulley system that we are familiar with today, and despite having undergone several updates throughout the last fifty years, the compound bow he created then is much the same as what archers are using in modern times.

What Are The Benefits Of Using A Compound Bow?

There are people who prefer to use a more traditional type of bow, and this is mainly because they choose to go for a more conventional type of archery, and there are many benefits to this.

However, there is no denying that the unique and modern technology that is used on a compound bow delivers an incredible number of advantages.

Primarily, you will notice that when shooting a compound bow, the speed at which the arrow travels is far greater than a recurve bow. Furthermore, a compound bow has a much more significant amount of power, and this directly translates to arrows being able to travel over a further distance. In fact, it is commonly accepted that while a recurve bow can fire an arrow to around 30 yards, an archer using a compound bow might be able to fire their arrows double this distance, with an average of 60 yards.

In addition to this, a compound bow offers a much more accurate shot, and this is mostly in relation to how the bow works. When you draw your compound bow, the cams and pulley system takes much of the draw weight. With you less focused on maintaining this weight, you are able to hold the bow more steadily and for a longer time. This gives you the chance to perfect your aim and keep each arrow precisely on target.

A compound bow is far easier to use, and many modern archers go straight to this type of equipment when starting out in the sport. You would not need anywhere near as much practice when using a compound bow, and this relates, once again to how the bow functions.

Finally, since these bows are built with the modern archer in mind, they are a lot easier to customise meaning that you can add a variety of different sights and other accessories far more easily than on a recurve bow.

How Does A Compound Bow Work?

Admittedly a compound bow is a little more complex than any other sort of bow, but in order to understand how it works, it is essential that we look at the various parts of the bow. Once you have an understanding of these, it can be far easier to get to grips with the operation and function of the bow.

The Pulley System

As we have discovered, the compound bow uses a pulley system which is hugely adept where shooting arrows is concerned. The reason for this is that regardless of the poundage of the bow, you won’t need to take the draw weight, at least, not the pull draw weight and this is where the pulley system comes in.

Where a recurve bow would have the archer taking the weight of the draw, a compound bow has what is known as a ‘let off’ and this is the amount or percentage of the draw weight that it will take. The pulley system takes a lot of the stress off the other parts of the bow and therefore, off the archer.

The Cams

When you go to purchase a compound bow or move in archery circles, you will frequently hear talk of cams. The cams can be found at the tip of the limbs and in general, are asymmetrical in shape. These are small mechanisms which slide as you draw the bow.

Whilst these are small components of the compound bow, they are potentially one of the most important. The reason for this is that the shape of the cam can drastically affect several things. Primarily, the shape of the cam will determine the speed of the arrow, but it can also count towards how comfortable the bow is to use. This means that when making a compound bow, manufacturers must think carefully about the shape of the cams.

The cams further contribute to an overall lower drawing weight but also make it easier to continue drawing the bow as it reaches its peak. Conversely, when you use a recurve bow, you will notice that the draw begins relatively easily but the further back you draw the bow, the more difficult it becomes.

This makes compound bows an excellent choice for archers who are lacking in strength, younger archers or those who do not want the added pressure of drawing a high-poundage recurve bow.

One of the most important aspects of purchasing a recurve bow is choosing the right cam; there are a lot of factors to consider, and this is something that should take priority.

Cam Systems

There are various setups that can be used where cams are concerned on a compound bow and which you choose will largely depend on your personal preference. However, it is worth being aware of each of them so that you can understand the benefits or drawbacks associated with them.

To begin with, there is a single cam system, and this is widely accepted to be the least complex setup owing to the low amount of maintenance that is required. In this system, the compound bow would feature a unique cam that is located at the top limb and a conventional cam located on the bottom limb. The cam at the top is generally referred to as an idler, and this is because it does not take any of the draw weight but rather unravels as you pull the bow back. In contrast, the bottom cam will take much of the draw weight and stabilise the bow.

This is a good option for bowhunters as it will deliver an exceptionally quiet shot when the arrow is fired. However, the arrow will travel at much slower speeds.

Secondly, there is the twin-cam system, which, as its name may suggest, makes use of two cams at either end of the bow – located on the ends of the limbs in much the same way as the single cam system.

Whilst this is a superior setup where speed and accuracy are concerned, you will likely notice the increased noise when shooting the arrow, therefore, if you are shooting wild game, this may not be a preferable setup.

Furthermore, if you are not experienced in archery, this type of system may serve as more of a hindrance. This is because it requires far more maintenance than the single cam system. If you do not perform this maintenance when it is needed, this could mean that the cams do not move in unisons and this can be disastrous for the arrow.

A binary cam system uses a similar setup to the twin system but rather than the cams being attached to the bow limbs, they are connected to one another. This is great if you want to make use of the speed and accuracy of such a system but want a quieter shot. Furthermore, where you may have issues with the cams syncing up with one another in a twin system, this problem is eliminated when using a binary system.

Finally, archers have the option to use a hybrid cam system which gives the best of both worlds – it would seem insane, would it not, not to use this system? And whilst this is true to a degree, this could be seen as the most complex setup and therefore, not ideal for less experienced archers.

This type of system uses both the idler from the single cam system as well as the linked nature of the binary system which, when combined, come together to deliver one of the most accurate and speedy shots out there.

The Limbs

Since a compound bow operates on a pulley system, it is essential that the limbs are durable and able to withstand an incredible amount of pressure. These lengthier parts of the bow are responsible for storing the energy that is built up when the archer draws the bow.

The Riser

The riser can be seen as the backbone of the bow. It is the point at which everything is held together and is positioned in the centre of the equipment. Everything comes back here, the limbs, the pulleys, the sight – everything.

For this reason, it is crucial that the riser is solid yet flexible and able to withstand the incredible amount of pressure that is put on the bow.

Other Essential Parts Of The Compound Bow

When you purchase a compound bow, you are getting exactly that; a bow. However, any experienced archer will tell you that there are some optional accessories on the recurve bow that when using this type of equipment, could be seen as mandatory.

An arrow rest is a small accessory that attaches to the bow and keeps the arrow in place while you draw the bow. There are several types of arrow rest, and we have written a more in-depth guide on this. But in the main, if you are practising target archery, you will need a minimal contact arrow rest, whereas bowhunters will do well with a whisker biscuit.
A D-loop is used to nock the arrow.
A peep is attached to the bowstring and can be used as a rear sight which will allow you to align the bow correctly.
A release is not a crucial piece of equipment for any type of archery, but it certainly does make the process far simpler. There are two main types of release; the hand release and the wrist release, but for the most part, archers using a compound bow will fare better with a wrist release. In short, this small accessory is attached to your wrist and can connect to the bow, releasing it as opposed to using your fingers to draw.

The Process Of Shooting A Compound Bow

Now that you are familiar with the various components that make up the compound bow, you are ready to start shooting. If you have ever used a traditional bow before, you will be familiar with the overall process of firing an arrow; that being said, shooting a compound bow is vastly different, and you will likely notice this.

To begin with, you will arm the bow with the arrow. For the most part, you will have installed an arrow rest, and this makes it far easier to keep the arrow in place while you find your aim. However, there are some cases that archers prefer not to use an arrow rest, and in this case, you would arm the bow using a traditional method.
The next step to firing a compound bow is to bring it to full draw. Unlike a recurve bow which will rely on your strength and power to draw it, your compound bow will likely feel much easier. This is because, as you pull the bowstring back, the cable which is connected to the cams, moves back as well, therefore dispersing the energy across the entirety of the bow. As this happens, the limbs are compressed, and these take a huge portion of the draw weight.
You might imagine the limbs as being similar to a spring, the energy is stored within them, and this causes them to flex. In a similar way to a coiled spring releasing its energy and bouncing back, the limbs of your compound bow will spring back to their default position once the arrow is fired and the energy is released.
This is the point at which you will notice the let off; this is the amount of weight that the compound bow can hold. If you have been used to using a traditional bow, this can feel strange at first but try to go with it. This is all basic physics and is thanks to the cams moving with the bowstring and taking that high poundage, making it easier for you to gain control over the shot.
Once the arrow is released, you will notice that the limbs flex once again. This is down to the energy being transferred into the arrow and what is responsible for the extreme speed that can be achieved when using a compound bow. But potentially the most exciting thing about this process is that in the few minutes that it has taken you to read these steps, this process could have been repeated multiple times. That is down to the fact that this process happens over an extremely short amount of time; that’s quite incredible when you think about it.

Conclusion

The compound bow was invented in the 1960s, so has not been around all that long, especially when we compare it to the more traditional styles of bow that have been around for many thousands of years.

However, due to modern technology and the use of a simple yet effective pulley and cam system, the compound bow is much easier to work with and will take most of the draw weight, leaving the archer free to concentrate on his or her aim.

This system works because when the bowstring is drawn back, this causes a system of cables and cams to move with it, therefore dispersing much of the weight across the limbs of the bow. This allows for more incredible speed, accuracy and consistency, all of which are important elements of archery.

About Brad Harris