What is a Tandem Axle Bogie Suspension?
“Tandem” means “one unit after another and the units work together”. In case of the heavy duty trucks and trailer, the tandem axle bogie suspension means one unit of axle with suspension system after another work together.
A simple representation of the tandem axle bogie suspension system is shown below:
How really it works?
- As the front wheel hits the hump ( or dip ) in the road, the interconnected shackle will be oscillated with respect to the pivot.
- The interconnected shackle, then, in turns lower (or higher) the rear wheel accordingly.
- In short, both the units of the tandem axle ( with suspension and wheels) work in sync according the road conditions to share the loads and thus prevents a single pair of wheels to take the whole amount of loads.
To get the picture clearer, lets compare the wheel and axle movements of tandem axle spring suspension with an uncompensated (simple) twin axle suspension system. See below:
The above picture is showing the situation where a heavy truck with uncompensated twin axle suspension pass over the hump of the road, the rarest wheel get lifted momentarily and all the payload force applied to the road through one pair of wheels (rear wheel-1). Needless to say that such a situation can cause damage not only to the vehicle but also to the road.
Now, lets see what happened to a truck fitted with a tandem twin axle suspension:
Here, as you can see from the above picture, due to the oscillation of the interconnected shackle about its pivot, the rear wheel-2 doesn’t loose contacts with the ground. The shackle forces the rear (axle) wheel-2 to lower itself and to make contact with the ground.
So, from the comparison it can be concluded that the tandem twin axle bogie suspension distributes loads better than uncompensated twin axle suspension while passing through the uneven roads.