Linkages are an essential part of machines with moving parts. And it’s a collection of rigid bodies linked together by joints that can transfer forces and movement.
A bell crank, also known as an idler arm, is a type of linkage that is used to transfer force and movement through an angle.
For example, take an L-shaped lever, which has a 90-degree angle between the links. Then, let’s pivot the lever at the joint. So, we can see that both force and the movement transfer through a 90-degree angle.
Types of Bell Cranks
Considering the angle, we can simply classify bell cranks. However, we can make bell cranks from many different angles. For that reason, we can only look into the most common ones.
The most common angles for the bell crank are 90 degrees (L-type) and 100 degrees (straight line) bell crank.
The L-type bell crank is used to transfer power, force, and movement at a 90-degree angle. The above image shows an L-type bellcrank used in automobiles.
The straight-line bell crank is used to transfer power at a 180-degree angle. And the above image is a straight line bellcrank used in automobiles.
Bell Crank Suspension
Bell Crank Suspension as a tandem axle is doing an important role in auto suspension systems. It is used in multi-axle trucks and other vehicles.
Bellcrank suspension works when the road is rough and all the tires are not contacting with the ground. When it happens the rear axle of the vehicle gets overloaded. Then the crank mechanism keeps the balance, by dividing the load equally between axels. So, it can keep both tires on the ground.
Advantages
Not like many other power transmission mechanisms that can transfer power at an angle, the bell crank mechanism is simple and operates in a small space. Furthermore, it has the ability to change direction without adding a mechanical advantage.
But, we can still design a bellcrank that can provide a mechanical advantage.
Applications
A common application of the bell crank mechanism is the brake system of a normal bicycle. When you pull the brake, the cable pushes the crank in the vertical direction, and the brake is applied in the horizontal direction.
Other than that, it’s commonly used in automobiles, as the clutch and accelerator pedals. In some automobiles, it’s used for the suspension system.
When it comes to aircraft, this simple mechanism is the one that is used to control the movement.
References
- Redesign of a Bell Crank to Ensure Compliance with Von-mises Failure Criterion
- Bell Crank Design
- Bell Crank Systems
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