Front Axle & Stub Axles

Front Axle & Stub Axles

Front Axle

"Front axle is an axle over which the front wheels are mounted. The front axle is fitted with wheels at its end. A part of the weight of the vehicle is transmitted to the wheels through this axle.” 

The front wheels are fixed to the chassis in two ways i.e. either with the independent suspension system or with the help of axle beam with leaf spring.
Functions of Front Axle

The front axle perform the following functions:- 

1. It carries the weight of the front of the vehicle. 
2. It carries the horizontal & vertical loads on bumpy roads. 
3. It works as a cushion through its spring for a comfortable side. 
4. In four wheel drive it also transmits power to the road vehicles. 
5. When brakes are provided at the front wheels, it withstands bending stresses & torsional stresses.

Types of Front Axle

1. According to Load

1. Dead front axle 
2. Live front axle 

1. Dead front axle –

The dead axles are those axle which do not rotate. It have sufficient rigidity & strength to transmit the weight of the vehicle front the springs to the front wheels. 

2. Live front axle – 

It's has a additional function of transmitting the driving power taken from a transfer gear box to the front wheels having a different swiveling mechanism. The live front axles although resembling the gear boxes have some difference at the axle half shaft ends where the wheels are mounted. 

2. According to axle beam 

1. Straight axle
2. Double drop axle
3. Fully drop axle

Construction of Front Axle

Axle beam is a major part of the front axle. It is used to transmit the vehicle weight to the front wheel through the spring. The ends of the axle beam are shaped in such way to assemble the stub axle. The ends of the axle beam are shaped either as a yoke or plain surface with drilled hole to hold a swivel pin connecting the stub axle portion of the assembly. The wheels are connected on stub axles. The inclined steering arms are located to track rod ends. The third steering arm is connected to the drag link. The steering linkage is connected by the drag link to the drop arm of the steering box. The main axle beam is attached to stub axles by king pins. The front road wheels are connected on these stub axles.

Components of Front Axle

The components of the front axle are axle beam, stub axle, swivel pin and track load.

1. Axle beam:

Axle beams are made by drop forging of steel having 0.4% carbon or 1-3% nickel steel. The front axle beam is formed into l-section in the centre portion. The ends are made into either circular or elliptical. l-section construction carries bending loads caused by the load of the vehicle and torque by braking of wheels. The centre portion of the front axle is provided a downward sweep to maintain the chassis height low. This axle beam is already hinged with stub axles. Springs are mounted on the axle beam at equal distance from its centre known Springs pads or seats.
Axle Beam Front | Midatlantic Auto Recycling
2. Kingpin or Swivel pin: 

The steering spindle and steering knuckle assemblies are pinned at the ends of axle beam in order to permit wheels to be turned by (he steering gear. This pin is known as kingpin or steering knuckle pin. It is also called swivel pins. The pins are made of good quality case hardened steels used to secure the stub axle to the axle beam. It is exactly located and locked by cotter pins in position.
New No Ream King Pin Replacement Kit. Fits Many Axle Models ...
3. Track rod:

The two stub axles arms of the front axle are connected with ends of a track rod through knuckle or ball joints known as track rod ends. The connection is done by screws to ensure adjustments. In the stub axle, left hand and right hand threads are formed at each end. Toe-in
is increased by lengthening the rod and it is decreased by shortening the same.

Tie Rods - ZF

4. Pull and push rod or drag link: 

Pull and push rod also called drag link is connected between steering arm of the front axle and drop arm of the steering assemble. But the cross-section is tubular. Spring loaded ball sockets are provided at each end. One end is connected to the steering arm of the stub axle whereas the other end is connected to the steering drop arm.
drag links - Hydrosteer


Stub Axles

“The front wheel are mounted on the stub axles, which are connected to the front axle by means of king pin.” 

The stub axle are forging of 3% nickel steel & alloy steels containing Chromium & vanadium. 

Types of Stub Axles-

The stub axle can have any of four shapes. 

(i) Elliot Stub Axle- 

This type uses a kingpin, a yoke, and a cotter to connect to the front axle.

(ii) Reversed Elliot Stub Axle- 

This type has the opposite arrangement of a standard Elliot stub axle.

(iii) Lemoine Stub Axle- 

This stub axle type has an L-shaped spindle instead of a yoke-type hinge.

(iv) Reversed Lemoine Axle- 

It has the opposite layout of a standard Lemoine stub axle.

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