The Rail Industry: Springs in Trains

We encounter springs every day, sometimes without even knowing it!  Because of this, you may not have noticed that they are a vital factor in trains and their functionality. The hydraulics system makes the trains run the way they do and without them, the smooth and comfortable ride wouldn’t be as we experience today.  All the weight of the train is sustained by a hydraulic system, making the movement almost slide, with insignificant friction and abrasion. We have come a long way in engineering terms in the rail industry; from steam trains to spring reliant electric systems. But how does the suspension system work?

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Primary Suspension System

There are two main types of suspensions used in trains, which are all involved with springs. The primary suspension mainly consists of a normal spring damper system which supports the structural suspension of the carriage and entire train. These damper systems are present in every bogie existing between the axle box and the bogie. The bogie of a train is the undercarriage, normally with four to six wheels pivoted beneath the end of the vehicle. It is like a low truck or trolley underneath the train.

Bogie Structure

The bogie is the generic way in which most railway vehicles work. The bogie is divided into the frame, the bolster, the pivot pin, the wheel assembly, roller bearing, the brake beams, brake blocks, brake levers, and the brake cylinders; all vital parts to the structure of the bogie.

Dashpot Arrangement

The primary suspension component in a bogie is through a dashpot arrangement, which comprises of a cylinder piston arrangement. The lower spring seat acts as a cylinder and the axle box guide acts as a piston.

The bogie bolster, or support, is the central section of the area; this carries most of the weight of the coach. The bogie pivots around using the pin which is centred. This uses parts of the secondary suspension system, which is typically coil springs and a spring plank.

Springs in The Bogie

The primary suspension is between the axle box and the bogie and consists of springs and dampers. It is an invariable necessity for all classes of rolling stock, including wagons. Different classes of carriages are provided with different bogie designs with primary suspension, however, they can differ from the eight springs per bogie (classed on each bogie being a three-wheel set). They are all provided with either inner springs or balanced with inner springs along with friction dampers.

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Secondary Suspension System

The Secondary Suspension is between the bogie and the vehicle; the airbag that is present between the car and the frame of the bogie. This is to aid comfort of passengers. The act of secondary suspension is mainly a pneumatic suspension and is even used in trains used for freight.

Bolster Support

The arrangement of this suspension system is through the bolster springs. The bogie bolster or support is not structurally attached to the bogie frame, however is attached through the anchor link (the tubular structure with cylindrical ends) The anchor link is fixed to the bolster and the bogie frame with the assistance of brackets. Both ends of the anchor link then act as a hinge which allows movement of the bolster when the train is in action

Lower Spring Beam

Lower spring beams support the bolster springs.  This lower spring beam is a structure made up of steel plates and the location is marked by circular grooves in the centre of the support. The lower spring beam is also a free-floating structure, but is attached to the bogie frame by the outside, with assistance of a steel hanger. These are traditionally called the BSS Hanger (Bogie Secondary Suspension Hanger).

Equalising Stay Rod

The inside section of the lower spring beam is connected to the bogie bolster, but gets a little help from an equalising stay road. This rod is Y shaped and made from steel sheets and tubes. It is also hinged from both ends with the lower spring beam, along with the bogie bolster. They are all connected by a pin.

The use of springs in Railway and train systems are vital for both smoothness and functionality of the train and the comfort of passengers. Air suspension is for the comfort of boarders and the springs and their suspension uses helps with the structure of the train and support in travel. At European Springs we understand the importance of springs in all types of industries and pride ourselves on supplying the highest quality of springs for them!

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