Springs and dampers the dynamic elements of suspension

Springs and dampers prevent the shocks from the wheels of a vehicle to be transmitted to its body. So what is it that we want when we go about looking for the best combination of these dynamic elements of a vehicle?

A spring must be be resilient, that is to say, it must be able to absorb energy when it is compressed and then must also be able to release energy when it expands. While doing so the spring must not become permanently deformed.

It must also be compact and ideally be able to serve as a suspension linkage as well.

The spring rate should increase as we compress it. Here the spring rate is the amount of load required to compress the spring through a unit deflection. So an increasing spring rate would mean that the load required to compress the spring increases as it gets compressed.

In a vehicle the spring experiences repetitive stressing. So it must be able to sustain the fatigue this causes and not fail under such loading.

In Armored Fighting Vehicles (AFVs) the spring must not be vulnerable.

Finally having as spring which gives variable height could be advantages in  AFVs.

Dampers form the other part of the dynamic elements of a suspension.

These must like springs be compact, robust and should be able to act partially as a suspension linkage.

In addition to these they should have the ability to compress softly but rebound quickly. Also dampers should have the ability of working well even under a high frequency of compression and release.

All this movement of the suspension will produce considerable heat in the dampers. They should be able to dissipate this heat well.

An ideal combination of springs and dampers is to be designed for every vehicle. This is vital for comfort of the crew of a vehicle and for the proper functioning of the more delicate of the systems mounted inside and AFV

Why do we need a suspension in a vehicle?

Simply stated, we need a suspension in vehicles, to ensure that the we get a smooth ride and to allow the vehicle to be handled properly.

A supermarket trolley does rattle a lot when we take it to the parking lot on a surface rougher than the store flooring. The vibrations received from the ground are directly transmitted to the basket of the trolley as the wheels are mounted on the basket structure without any suspension.

A vehicle without a suspension would find itself in a similar situation. Riding in such a vehicle would be very uncomfortable.

Engineers while designing a vehicle's suspension focus on making the ride and handling of the vehicle as comfortable as possible. They do this for a variety of ground surfaces and for a range of vehicle speeds.

So suspension design aims to do two main things:

First is to insulate the occupants of the vehicle from shocks and vibrations transmitted from the ground to the wheels.

Second to ensure that the wheels of the vehicle stay in contact with the ground and to enable the control and steering of the vehicle.

These two aims are achieved by having springs and dampers, these being the dynamic elements of suspension, and linkages from the vehicle body to the wheels, which are the kinematic elements of suspension.

The way in which we design and construct the dynamic and kinematic element of suspension shape the ride and handling characteristics of vehicles.

My Thoughts on Main Battle Tank Design

Essentially if you look at a tank it has everything that a vehicle has got and then a lot more. I will talk about the battle tank; ground upwards, something like if you were to  talk about a car tyres upwards.

First and foremost what is in touch with the ground is what we call the running gear which is consisting of the tracks and the bogie wheels which ensure that the tank is able to move. The running gear is getting its drive from a sprocket which is connected from the engine compartment and in order for the tracks to go around smoothly on the other end we have an idler which allows the tracks to go around and lay itself below the road wheels which are also called bogie wheels.

In order to hold the tracks on the bogie wheels we have something called a horn which is there on every track link and the bogie wheels are in pairs; the horns are going through the bogie wheels between the bogie wheels and that’s why when the tank is turning the tracks do not come off or in the language of armoured fighting vehicle the tracks do not shed.

The bogie wheels are in turn connected to the hull of the tank through the suspension system. Typically the suspension system has got axle arms with some sort of a suspension mechanism which absorbs the shocks from the ground. So as the tank moves there is a combination of a spring and a damper in every suspension. The purpose of the spring is to absorb the shock and every time the tank hits a bump the spring compresses to absorb the shock and does not transmit directly to the hull; in addition to this, so that the tank does not keep bobbing up and down we have the shock absorber or what we call the damper which dampens the up and down bobbing of the spring. With this system we get connected to the hull and there are a variety of suspension systems. They can be coil spring pneumatic spring or other designs.

Now we move on the hull. Typically the hull of a tank is divided into three parts. In front is the driver’s compartment, there are tanks which have got the engine right in front, but usually the driver’s compartment comes in front.

Then we have the fighting compartment and in the rear of the tank we have the engine compartment from which the drive goes out the sprocket which I had mentioned earlier.

The driver’s compartment since it is only having the need of holding a driver it normally has space on either side of the driver so this space can be used for storing ammunition or fuel or batteries, things like that.

Behind the driver’s compartment is the fighting compartment. The main element which is there in the fighting compartment is the turret in this compartment you would have three people the commander the loader and the gunner. Certain tanks have got an automatic loading system, in that case in the fighting compartment the loader is replaced by the automatic loading mechanism. In this case the fighting compartment has only the commander and loader. New tanks are coming up which will have no one in the fighting compartment. It will be all automated.

Behind the fighting compartment we have the engine compartment. While between the driver’s compartment and the fighting compartment there is really no separation and there is no bulkhead. The driver can exit out of the fighting compartment and the commander and loader can exit out of the driver’s compartment. But in the case of the connection between the fighting compartment and the engine compartment there is a bulkhead. The purpose of the bulkhead is to totally isolate the engine compartment, for obvious reasons, because the engine will have gasses and fuel and fumes which are not good for the crew so the engine and the crew are kept separate.

This bulkhead has various features, for example it will have inspection plates from where we can peer into the engine compartment, specially during maintenance and it will have a number of wires and looms ad pipes going from the fighting compartment to the engine compartment. For electrical connections normally sockets are used.

The engine compartment has the engine, the transmission and the final drives which in turn connect to the sprockets. The sprockets get the drive from the final drive and then run the running gear.

The engine compartment will have the various systems, the engine itself, the lubrication system, the cooling system, the fuel system, the electrical system, the air intake system, the fire fighting system and such like systems.

The engine compartment as I said will be enclosed and the cooling will be achieved through the means of a cooling fan. The cooling fan can achieve cooling in various ways. One way is where it throws out air from the engine compartment creating a low pressure and this results in air being sucked into the engine compartment through the radiators. Normally there will be a number of radiators, water, oil, hydraulic and such like.

The engine compartment will also have an inlet for the air to the air cleaner which will supply air to the engine inlet.

There will also be a passage for the exit of the exhaust from the engine compartment.

Usually tanks have diesel engines but one has a gas turbine engine. Some time tanks have a main engine and an auxiliary engine.

A word over here about the auxiliary engine and the starting system. Normally the starting of a big engine takes a lot of current and drains the battery. So we could have an auxiliary engine which will recharge the battery. This is needed if the electrical starting is the main starting of the tank. However in certain tanks the starting is through air starting in which case the auxiliary engine is dispensed with. And then you have the air starting in which case the main engine keeps the air bottle charged and the stored air pressure is used for starting the main engine thus conserving the electric charge of the battery.

The purpose of the battery here is to give enough power for the tank to be able to operate it’s  electrical systems with the main engine being switched off. If you had the auxiliary engine that could keep running as being smaller it produces very little noise and heat. Starting the main engine would be a give away of your location. So having an auxiliary engine or not is a result of a balance which has to be made.

Tank design is all about balancing one type of requirement with another.

Coming back to the fighting compartment. The main thing which is there is the turret. The turret is mounted on turret ring in the hull. The turret is able to rotate 360 degrees. The electrical connection of the turret to the hull is through some sort of a device like a rotary base junction which is placed at the bottom of the turret from where the turret rotates. In this manner we achieve the supply to the many electrical systems in the turret.

The main thing which the turret houses is the main gun of the tank. The main gun is a huge gun. Main guns of tanks fire very high velocity projectiles. So an important part of the design here is how to contain the recoil of the gun within the space of the turret.

In the turret there are two more important systems. These are the gun control system and fire control system. The purpose of the gun control system is to allow the commander or the gunner to rotate the turret at will and to acquire targets. The purpose is to quickly swivel the turret around and bring the gun onto the target.

The fire control system decides the manner in which the gun will be fired. Nowadays tanks have the stabilising system which means irrespective of how the hull is moving the gun remains locked onto the target. This is what makes the tank a very lethal weapon. A tank can move very fast and at the same time remain locked onto the target and fire accurately. This is the final aim of the designer of the tank.

The gun itself can be rifled or smooth bore. The main purpose of the gun is to be able to fire a projectile which will defeat the adversary tank’s armour. So high velocity rounds are needed and a variety of ammunition has been invented for this.

Coming back to the hull. It is very important for the designer to make a hull which is able to protect the tank from the adversary’s projectiles. Here again the issue of balance comes. Normally the frontal part of the tank, which is known as the frontal arc is heavily protected and the sides, rear and bottom less so. It is impossible to protect a tank heavily from all sides.

A variety of armours have been developed. There used to be the monolithic armour which was a chunk of steel, now new armours have come up which are designed to defeat projectiles without too much of a weight penalty.

The classic balance a tank designer has to achieve is between the firepower and the mobility and the protection. The running gear, the engine the sprocket these all provide the mobility aspect. The firepower is by the gun, it’s calibre’ the speed of the projectile’ accuracy of the projectile and the ability to be able to move and fire.

Protection is through the armour.

It is obvious that if you want a bigger gun it means it will be heavier and the tank’s weight will go up.

Similarly if you want to increase the protection the tank’s weight goes up.

If you want now to put in a bigger more powerful engine you need more space in the engine compartment this will make the tank’s hull bigger which in turn will again require protection.

So in tank design one thing leads to another and you have to strike and optimum balance base on your requirement.

Various armies according to their requirements base on their own situations have designed different tanks. A lot of technology goes in to ensure that you are able to get the optimum firepower, mobility and protection as per your own requirements.

It is expensive technology. Developed after tremendous research and development. 

In spite of the variety of other weapons, both on the ground and in the air, the main battle tank remains the most lethal weapon on the battlefield even today