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The Pros and Cons of Straight Cut Gears

The Pros and Cons of Straight Cut Gears

A car wouldn’t be complete without gears. These gears are in the gearbox which is an essential part of the car’s overall mechanism. The power from the engine is supplied to the gearbox making its series of gears to provide the car with more power and less speed or more speed and with less power, depending on where you are driving. Whether you are on an uphill climb, driving on slow traffic, or speeding on a highway. The gearbox is the one that provides you the torque and speed you need on whatever surface you drive on or the driving situation you are in. It is also the gearbox that allows you to shift reverse so the vehicle can move backwards. The gearbox as a whole has four main components that work together to do its required function. Its main components include the counter shaft, the main shaft, the bearings, and the gears. As for the gears, there are different types of them and the most commonly used ones are the straight cut gears and the helical gears. 

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While a straight cut gear is more popular in motorsports application, it is the helical gear that has a more positive image to the consumers than the straight cuts. Let us find out if that is really the truth as we learn about the pros and cons of the straight cut gears.


The Pros

  • One of the advantages of the straight cut gears is that they don’t create axial load. These gears create less side to side torque which lets the engine deliver more torque through them. With no axial load or thrust load, the gears put no restrictions on the torque. It is the reason why racing cars usually use straight cut gears since they can use all the torque they need. 


  • The absence of the axial load, the straight cut transmission does not produce any heat that causes losses of energy.


  • Straight cut gears remove the complexities of its transmission case design and so are the types of the bearings used. This makes way for a less heavy transmission structure making it ideal for car racing. It is also easier to replace. Aside from that, the thrust load adds a significant amount of transmission to the car which adds another unnecessary weight that the car racers are trying to avoid. This is because when you are putting more torque, the thrust load gets too high. And when it does, you have to have a very sturdy transmission case and shafts to contain the said load. For this reason, the race car drivers prefer straight cut gears since they are not only lightweight, they are also efficient. The additional weight that the other types of gear give will just slow them down and being fast is a car racer’s number one priority.


  • It also makes it possible to place a larger powertrain in the vehicle without risking the bearings and output shafts from being torn apart. It does not only protect the torque even at a great force, it also ensures safety.


  • The straight cut gears are also easy to assemble due to their simple structure. You won’t need the output shafts or bearings because it doesn’t have an axial load. Straight cut gears are efficient since the energy is applied instantly and directly and there is only one contact point between the gears for each tooth on every revolution. If ever you encounter failures caused by these gears, it will be less disastrous.


  • With the straight cut gears having simple structure, its minimalist style cuts down the costs of all the extra parts the other types of gears have like the bearings and output shafts. You won’t also need a synchronizer making it less expensive. 


The Cons

  • No matter how great the advantages of the straight cut gears, it also has some disadvantages. First on the list is that it produces a lot of noise. Its straight cut teeth mesh with each other fully and all at once. It does that for a longer period of time which gives a very distinctive whining sound. The straight cut gears rams into place rather forcefully after each change making it difficult to pull away smoothly or getting a good launch.


  • Though straight cuts are relatively cheaper in price, using it as your daily ride is impractical. It is primarily used on race tracks and some other places where you can test its speed. It would probably attract some unwanted attention if you drive it around the city with its noisy driving. 


  • Aside from the whining sound it produces, it is also not capable of carrying heavy loads. This is because the force of the straight cut gears are not distributed efficiently due to its weaker, vertical teeth. 


Straight Cut Gears Vs Helical Gears

Straight cut gears and helical gears are two of the commonly used gears in the automotive world. Many are confused between the two since both can be utilized in many similar types of applications. Let us go through the differences between each gear and what makes the other more special, or not. 


  • Just like its name, the straight cut gears have teeth that are cut in straight form while the helical ones have slanted teeth, giving it a curved appearance. 


  • The helical gears hold more teeth than the straight cuts making it a good choice if you want a vehicle with a stronger or bigger load bearing capabilities. Straight cuts might not be able to carry heavy loads but it makes up its disadvantage by providing more power and high performance abilities. 


  • The angled teeth of the helical gears give a quieter and smoother ride. A smooth ride is also possible since the gears shift power through parallel and straight angle axis. 


  • The helical gears have a larger contact area which gives more allowable stress making it strong and reliable but it comes with an axial load making it susceptible to axial displacement. A straight cut gear on the other hand has no thrust load but weaker because it  holds less contact area for stress. 


  • Straight cut gears can only transfer power between parallel shafts while the helical gears can transfer power between the parallel and non-parallel ones. 


  • The helical gear’s axial load can limit the transmission’s torque capacity.


  • A helical gear produces a lot of heat because of its axial load. Since it generates a lot of heat, it requires more maintenance. It is prone to wear and tear and will constantly be needing a good lubrication system to keep it in a good running condition. 


  • Straight cut gears have a simple design making it economical and easier to manufacture while the helical gears have a complex design plus with it needing more parts such as thrust bearings and other hardware to handle its thrust load makes it more costly than the straight cuts.


  • Helical gears mesh their teeth together in small segments at a time while the straight cut gears meet their parts all at once and for longer periods. This is the reason why the helical gears are more quiet and smooth while the straight cuts are annoyingly loud. But if you are a motorsport enthusiast, the loud sound of the straight cuts won’t probably bother you.


  • Straight cut gears have less practical uses than the helicals. Although it is very efficient and produces high power, with it producing a loud and whining sound which increases when you increase the speed makes it not ideal to drive around the city. 


Can Any Transmission Be Converted to Straight Cut Gears?

There are lots of car enthusiasts who chose to convert their gear system to a straight cut gear mechanism to improve its speed, performance, and efficiency. You can convert a helical gear to a straight cut gear. In fact, converting it is fairly easy but converting a straight cut gear to a helical gear is not possible. Changing your vehicle’s gearbox really depends on what you are trying to achieve. There are a couple of things you need to consider in making the decision whether to have your gearbox converted or not. Or if you are planning on getting or building your next vehicle and deciding what gearbox you should use and install.


One of them is practicality. If you are using your car in city driving, then helical will be the best choice. You won’t need the additional torque and speed and definitely you don’t want to deal with the whining sound every time you drive around. Helicals also have a stronger bearing surface with a structure that allows you to take on heavy loads. But if you use your car for racing, straight cut gears will be the best option. It suits well for that purpose. Because when you are hitting the track a lot, the absence of the thrust force and your gears not creating excess heat and weight will make your vehicle more efficient and will fare better for a long period. Racers also utilize the use of the straight cut gearboxes because it is easier to replace. Racing sometimes needs quick gear changes. More importantly, they can also use the reduced weight of the gearbox and the reduced friction to their advantage. The reduced friction sends more engine power to the wheels and it helps decrease the fuel consumption. It also reduces the need for added cooling capacity that usually has a cost in aerodynamic drag


There are also people who don't like the limited transmission torque capacity which the helical cut gears provide. In order to drastically increase the torque capacity of the transmission, they opt to install an aftermarket straight cut gears in exchange for their factory-equipped helical cut gears. They could install or set it into the case that came from the factory with helical gears. As a result, they get to enjoy the increased torque. They probably don’t mind its loud sound as most motorsport enthusiasts do. 


There are some applications where converting your helical gears into straight cut gears won’t be necessary to achieve increased torque capacity. You can increase the torque capacity of your transmission a lot more than the power your engine produces. This can be done by simply reducing the helix angle of the helical gear. Doing this not only increases the transmission capacity, it also can keep the whining noise at a more acceptable level. 


There is also another gear design called the double helical gear. It eliminates thrust loads and has a possibility of providing smoother operations. Though this gear offers many positive outputs, there is no available data or any additional information that confirms that this design can be used in an automobile. The double helical gears are usually wide and it might not be suitable for a car transmission. 


Understanding the differences of each gear setup and what they can do to your vehicle will help you decide whether you really need it or not. If you are still torn between converting to a straight cut gear or not, it is better to take your time in deciding and do some research about the gears and make sure that it is what you want. It has been stated that changing from a helical gear to a straight cut gear is easy, but changing it back is impossible. Or if it's not, it would probably cost more and will require more maintenance and service. If you are already determined to have your gear changed, it will be best to pay a visit or call a trusted professional and inquire about its procedures and its possible outcome.


With the advancements of technology, more and more people are experimenting the transmissions of their cars with the hopes of increasing their car’s performance and overall capabilities. Straight cut gears probably make the cut as a great choice for this purpose. Many cars use this gear and they are usually winning their races with its improved efficiency and speed. The decision is all yours.  



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