What is an axle?
An axle is a rod or a spindle that goes through one or more wheels. An axle can be connected to the wheels in multiple ways. First, the axle could be attached to the wheels and rotate with the wheels and the wheels spin. Second, the axle may be fixed to the main body of the vehicle and the wheels will then rotate around the axle.
For cars, axles are a crucial component. They support the weight of the vehicle. Not only that, but they connect the wheels to the vehicle and also rotate the wheels to move the car. Also, axles come in three main categories, front axles, rear axles and stub axles. There are also live axles and dead axles. Live axles deliver power to the wheels. Dead axles on the contrary are mainly used to support the weight of the vehicle. They also do not transmit power to the wheels.
The main categories of axles:
For the front axles on vehicles, they can either be a live front axle or a dead front axle. Also, steering is connected to the front axles on cars.
Live Front Axle: As mentioned before, these axles deliver power to the wheels. These types of axles are commonly used in Front Wheel Drive (FWD), Four Wheel Drive (4WD) and All-Wheel Drive (AWD) vehicles.
Dead Front Axle: These are used to support the weight of the vehicle and also do not actively spin the wheels.
Similar to the front axle, rear axles also can be either live axles or dead axles. For example, a front-wheel drive vehicle will have a dead rear axle. Also, rear-wheel drive and all-wheel drive will have live rear axles as both types of vehicles send power to the rear wheels to move the car.
There are a few types of rear axles on vehicles. These include Semi Floating Axles, Full Floating Axles, and Three-Quarter Floating Axles. These axles differ based on what support the vehicle needs and where the axle is mounted.
Types of Rear Axles:
- Full Floating Axle: These types of axles do not support the weight of the vehicle, instead they are used to just send power to the rear wheels through the differential. The weight is instead supported by the spindle that is attached to the axle housing. Also, the wheel hub is attached to this spindle. These types of axles are commonly used on heavy-duty trucks. This is because the axle’s load capacity is larger. Also, because of how the wheels are mounted, an axle shaft can be removed if damaged while the wheel is still able to spin unpowered.
- Semi-Floating Axle: Compared to the full floating axle, the semi-floating axle partially supports the weight of the vehicle while also being used to transmit power to the wheels. The wheel housing connects to the axle through a bolted flange. This type of axle is popular on light or medium-weight 4WD trucks and cars.
- Three-Quarter Floating Axle: The three-quarter floating is a combination of the semi-floating axle and the full floating axle. Instead of the axle supporting the weight of the vehicle, the bearings on the wheels are attached to the axle casing and hub. The weight of the vehicle is then moved to the axle casing rather than the axle. Also, this removes any shearing stress from the axle but other loads such as bending loads affect the axle. This type of axle is also used on lighter trucks and cars but is not as popular as the cheaper semi-floating axle.
The stub axle, also known as a stud axle, is an axle that attaches to one wheel. These can be used in vehicles such as front or rear-wheel drive vehicles to support the wheels that do not have power going to them. For example, the rear wheels in a front-wheel drive vehicle may be supported by stub axles. Additionally, these axles have a wheel bearing that supports the wheel hub. These types of axles also attach to an axle through a kingpin.
If you didn’t know, a kingpin is a large bolt that is used as a pivot. And, the cotter is a pin or wedge that goes through a hole in the kingpin to connect it to the axle. It makes sure the kingpin does not come out of the connection between the stub axle and the other axle.
There are four main types of stub axles.
Types of Stub Axles
- Elliot: An Elliot stub axle connects to the axle by fitting inside the yoke of the main axle. Then, the stub axle is connected through the yoke by a kingpin and a cotter.
- Reverse Elliot: For the Reverse Elliot stub axle, the stub axle has the yoke and fits around the main axle. The Reverse Elliot stub axle then connects the two axles with a kingpin and a cotter
- Lamoine: This axle uses an L-shaped spindle that connects to the axle with a kingpin and cotter. The cotter also locks the axle in position. This is a common stub axle on tractors and other heavy vehicles.
- Reverse Lamoine: As the Lamoine stub axle forms an L-shaped spindle, the Reverse Lamoine forms an inverted L shape. It connects in a similar to the Lamoine stub axle with a kingpin and a cotter.