As any other mechanism, the lever mechanism is used to do certain jobs in an easier way. It consists of a beam located on a fulcrum which works as a pivot for the rotational movement. Snap hooks and carabiners use this principle in order to make it quick and easy to lock and unlock the hook in a critical situation.
The main or general purpose of a lever is escalating a force with a little effort; however, this may be different according to the final objective and the type of lever used. There are three types of levers: class 1 (first-order lever), class 2 (second-order lever) and class 3 (third-order lever). Each type depends on the position of the load to be moved, the effort to be made and the fulcrum or pivoting element.
Types of levers
Class 1 or first-order lever: in this case, the fulcrum is located between the load to be moved and the effort. The load and the effort forces work in the same direction. This type of lever results in less effort to move the load, although the movement of the effort will cover more distance. Some examples of the use of this type of lever mechanism are scissors, a seesaw or a crowbar.
Class 2 or second-order lever: This type of mechanism locates the load between the effort to be made and the pivoting element. This time, the effort is applied in the opposite direction of the load force, and some advantages are that the effort is even smaller than the effort needed in a class 1 lever and the distance between the load and the effort can be reduced. Some common and simple machines using this type of lever mechanism are a nutcracker, a wheelbarrow and a bottle opener among others.
Class 3 or third-order lever: finally, this type of levers locates the effort between the fulcrum and the load, and is the one which has a different purpose. Instead of escalating the force, it magnifies the distance of the movement, but the effort needed is bigger than the load being moved. Some examples are fishing rods, tweezers, shovels, etc.
(photo source: wikipedia.org)
Fasteners are a key element in everyday life. They are present in any structure or device in order to hold their parts working together.
In the automobile industry, this key elements take a higher level of importance, since they form part of important systems which involve the security of the driver and its passengers.
Some of the critical systems where fasteners are frequently selected and used very carefully and with a very demanding criteria are: security systems, electrical mounting, brake systems, airbags, fluid carrying components, transmission components, among others.
Among the most common fasteners used in the automobile industry, there are bolts, nuts, studs, washers, screws, rivets and tie rods.
Let’s take a closer look to each one of them.
They comprise a threaded pin or a threaded rod and a head at one end, and they need a matching nut in order to fulfill their function.
In the automobile industry, the most important ones are the engine mounting bolts, the suspension bolts and the connecting rod bolts.
Being such a dedicated industry, with many specialized systems, these bolts are normally fabricated according to the cars manufacturer specs. However, the most common materials used are steels, ranging strengths that can reach the 1500 MPa.
As mentioned in the previous point, these are the complement for the bolts. Again, there are different types according to their function, such as hex nuts, plate nuts and self-locking nuts.
The material requirements of these elements for their use in automotive and related industries are mainly covered by the standards SAE J482 and ASME B18.2.2, although they normally match the material of the corresponding bolt.
These type of fasteners are mainly used in the engine and wheels systems. There are different materials, being those made of stainless steel the most common ones. However, due to the different needs from cars manufacturers, there are also brass studs, copper studs, aluminum studs and even plastic studs among others.
The way they work is by being fastened at both ends with an unthreaded shank.
Although they do not look as important as the rest of the elements, they really are. Just to mention one of their important functions, they can prevent leakage which is a very important aspect in the automobile industry.
The most relevant ones are known by the name of the system where they are used, such as the cylinder head washers and the radiator washers (here’s the leakage prevention importance mentioned before).
They are very similar to bolts, with the difference that they do not need the use of a nut. Normally, they are used to hold to parts which are already threaded in order to match with the screw. Furthermore, some of the screws used in the automobile industry can be driven through some materials without deforming or breaking. These are called tapping screws.
Considered one of the oldest fastener in the industry it is being used across a wide range of applications.
They are very fast and easily placed which makes them a good option for a high paced industry as the automobile one. However, it is important to select it correctly according to the application in order to ensure its correct operation. A good practice to achieve the best results would be checking SAE J492 standard which comprises a complete guide for rivet selection and design consideration.
Their main use lies on the steering system. There, they are used to join the pitman arm and the idler arm to the steering knuckle arms. Having a flexible coupling at the end, they are able to turn the wheels with the force coming from the rack gear to the steering knuckle.
Since all of these elements are so important for the correct operation and smooth performance of the systems mentioned before, the general recommendation is to use those parts which are certified under the international standards.
(photo sources: wikipedia.org and pixabay.com)
Mechanical engineering involves a group of disciplines also known as branches where we can find thermo-systems, manufacturing and design. Talking about the latter, we can say is the branch where the engineer can combine a series of components to create a new element or machine which shall be manufactured in a future. In order to achieve such creation, the engineer must go through very detailed calculation to determine the best components for the purpose of the design. A very important part of this entire process are the fasteners, which allow us to join together different parts or components and also make sure they will not have any undesirable movement while in service.
There are different types of fasteners with specific properties and uses, which should be selected according to the application. Among them, we find bolts, nuts and grub or set screws as the most common ones.
Let’s get to know a little more about the fasteners that were mentioned above.
First of all, the use of the words “bolt” and “screw” is widely unclear and the difference commonly misunderstood. A good way to have a better idea on this matter is that a bolt is described as any threaded fastener that is used together with a nut in order to assembly two unthreaded components, and that a screw is described as the same threaded fastener, but in this case being used to assembly two components where one of them has an internal thread where the fastener is fitted. Now, you can be sure that every time you use a bolt you will be needing a nut to complete what is known as a bolted joint. In this type of joint, the nut provides a fastening axial force at the time the bolt provides the needed resistance against shear forces.
As mentioned before, the nut is the element providing the fastening force in a bolted joint. The main feature of its structure is the threaded hole where the bolt is fitted, and its profile can be squared or hexagonal, being the latter the most common one. The bolted joints are frequently used because many applications makes it difficult to have a threaded hole in one of the parts being assembled. However, there are applications that involve a lot of movement and vibrations which can get the nut loose; thus, creating a major problem. This kind of problems are solved by adding other locking mechanisms.
Grub or Set Screws
Also known as “blind” set screws, this type differs from the rest for not having a head, but only a hole with a specific shape which suggests the type of tool that should be used in order to drive it. The most common ones are hexagonal (Allen), squared (Robertson) and star shaped (Torx). This kind of screw are frequently used as “safety” holders, together with a detent in order to resist or transmit high torque, which is why they are used in applications where parts are attached to a shaft, such as couplings, bearings, pulleys, among others.