Saturday, 8 February 2014

Crash Testing

Automobile manufacturers around the world have devoted R&D teams to work on better and more safer vehicles to put on the roads to ensure customer safety.Companies spend tons of capital into the testing of their cars.There are several standard testing facilities which provide proper infrastructure and equipment for the tests to be conducted, one of the most noted and globally accepted testing center being the Global NCAP.



So How does it Work....?

In the test facility they replicate the kind of accidents that one might have on the road. An artificial real life scenario is created in which an automobile is collided against another automobile/an obstruction . Crash Test dummies are used to find out what effects the collision would have on the driver and the passengers inside the car and in some cases also the people who might be outside the car.In short this is a full proof system to find out the car's safety.


                   Automobile manufacturers from around the world send their new production line cars to the Test Facility to be tested according to the NCAP standards.After the tests are conducted NCAP gives each car a safety rating in stars (max of 5)  based on its performance.Automobile manufacturers look to achieve the highest possible ratings to make it more marketable ,as in developed countries the safety rating is an important yardstick in the sale of a particular variant of a car ..

What kind of tests are conducted...?

Mostly three types of tests are conducted ,among many others ,for accidents that are of  the most common types that one might encounter on the road.The speeds that the test are conducted are generally 40 kmph and 64 kmph (most common driving speeds).
.
  • Frontal Impact (Small Overlap Crash Test) : In this type of testing the automobile is collided against a barrier(which resembles another car) with a 60:40 bias towards the driver's side.


  • Side Impact Test : In the side impact testing the car is collided against a barrier to replicate a side impact by a vehicle. 


  • Rear Impact Test : Rear impact testing is done to ensure safety of the car in the case of a rear end collision.

Other tests include the pole impact test, the incline test,etc.

Do these tests ensure absolute safety of the car...?

Yes, cars which have a high safety rating are less prone to high accident damage and hence when buying a car we should always look at the Safety Ratings of the car.Here is an example of a car with a poor rating and one with a good one.

The  Actual Test :

Well, before the test actually begins, there is an elaborate process of preparing the car for the test.

  • There are several sensors that are fitted to the car  to record impact data during the test.
  • The fuel tank of the car is emptied and the battery acid is also removed.
  • Pre crash measurements are made which are correlated to the measurements that are obtained after the tests.
  • Then the Crash Test Dummies are prepped for the testing to begin.

Crash Test Dummies:

Real humans cannot be used in these tests so the next best things are the crash test dummies.These are figures having identical height and weight characteristics of an average person , moreover they react to accidents also in the same we as we would do .The dummies have several sensors fitted on to different parts of their body to acquire data .



The dummies are generally very expensive but they can be reused and their parts can be changed in case of damage.The dummies are given a special color coded coating in special parts of the faces like the fore head , the nose, the ankles,knees ,etc.these colors help in visual determination of the point of impact of the car to the dummy.



How are the tests conducted...?

The test facility consists of a long hall where the tests are conducted. The cars start at one end of the hall, the cars are not driven during the time of the test but are hurled by hydraulic  Motors coupled to a mechanism attached to the car.



Generally a  4.30 min count down is given before the test ....as the car begins its motion it is pulled with a force of almost .225 Gs until i reaches a speed of 40 k mph.The car travels a total of 538 feet before it comes to a halt 1-2 seconds after the collision.Cameras record the car's movement at every angle .The data acquisition system records a total of more than 50 gigabytes of data in the 20 odd second crash test life , the results of these data give us the safety rating of the car.


This video shows a proper Crash Testing procedure of a Hyundai Santa Fe at The Euro NCAP facility.

So which type of cars do actually pass the test..?

Those cars which provide proper safety to the driver and the passenger during the accident make the cut.
The car needs to be structurally sound, it needs to maintain its structural integrity even after the collision.Some cars are even designed to disintegrate thus absorbing most of the impact energy and providing better safety for the people on board.



Cars like the BMW 1 series (5 door) have done really well in the tests and have received a 5 star rating.

 The proof of the pie is in the 'Testing' ...

So what happened when some of the cars (in small car section) that we see on our roads here in India were tested...?

Firstly we need to remember that only the cars that are in production here in India and for India were included in the tests.the test cars were the base variants of each make...and need less to say none of them had air bags.

  • Tata Nano :The Tata nano ( for India model ) could not get ratings in the Safety Feature, the lack of air bags being its greatest drawback.

  • Maruti Suzuki Alto 800 : The alto 800 Failed to make a mark in the test and was not given recognition in the Star Rating.

  • Hyundai  i-10 : The i10 came out with disappointing results with no stars in the Safety Rating. 

  • Ford Figo :This Ford make did not pass the test along with all the others but one of the positives about the design of the Figo was seen that after the crash it maintained its structural integrity unlike the alto 800 or the Nano.
  • Volkswagon Polo : The Volkswagon Polo turned out to be the safer car among the ones tested...but due to the lack of air bags in the base variant available here in India it did not do well in the test.

But as the car manufacturers were contacted all of them came out positively towards the test results and said that their main objective would always be to manufacture better and more safer cars for its customers,but standing out the Volkswagon India people said that they are looking forward to the test with a variant that includes air bags and are hoping to get better results and they added that their future production cars would include the air bags thus ensuring better safety.


What should be the benchmark..?

Makes like BMW,Mercedes, Bentley and others regularly manufacture cars which have an average of 4 to 5 stars .

How has this kind of testing helped...?

Well from the time of the Ford Model T we have come a long way...today's cards are more robust and structurally more sound and rigid thus overall providing better safety for the ones on board.

Here's a look at the Crash testing of cars from the 60 s to the 90 s.



And here's one from the current era....You decide for yourself which one you want to be in....






Safe Driving.....!!!

Friday, 24 January 2014

Car Tyres

A tyre is used to provide a cushion between the vehicle and the road , to reduce the transmission of road shocks and also to provide the necessary friction for it to move.However the role of tyres in a car's performance it not limited to this, it also influences the Fuel Efficiency, Steering Resistance, Braking, ride comfort and the overall performance of the car.

Tyres Types based on construction :

Car tyres are divided into two categories based on the mode of their construction.
  • Radial tyres
  • Cross-ply or Bias tyres.
Radial and Cross -ply (bias) tyres

Radial tyres

Radial tyres are the preferred choice for modern day cars, patented by Michelin in 1946.The backbone of the tyre usually consists of  plies of cord or steel. The steel is placed circumferencially as a belt .Over the belt are the plies of reinforcing tyre cords that extend from bead to beadat angle of 90 degrees to the centreline of the tyre hence the name Radial.


Why do we use Radial tyres...?

The reasons for using Radial tyres are extensive,however it boils down to the following ...
  • Its square shaped footprint which is preferred for its even pressure distribution and less soil penetration.
  • Exhibiting superior Traction and good Stability.
  • Even wear
  • High Mileage
  • High durability
  • Resistance to punctures.

Cross-ply or bias tyres :

The main design aspect of bias tyres is its crisscross pattern of  cord design. The cords that reinforce the tyre extend diagonally across the tyre from bead to bead (bead here refers to the bead bundle that properly seals and seats the tyre onto the rim of the wheel.) an angle of 30 to 40 degrees to the centreline of the tyre. As a result of such patterning a successive layering of cords are obtained which run in opposite directions.

Are Cross-ply tyres the best choice..?

Cross -ply tyres have a very simplistic design and hence are very easy to repair. However they have a round footprint and an uneven pressure distribution and hence Radial tyres are preferred over them.

Which tyres do you have in your car..?

Well if you have a car from the production lines of 2000 or later it is mostly probable that you have radial tyres on your car.


Tube and Tubeless tires :

Tube tyres are those which include a tube to seal the air inside the tyre .Whereas tubeless tyres have continuous ribs molded integrally into the bead of the tyre so that they are forced by the pressure of the air inside the tyre to seal with the flanges of the rim of wheel.




Tread Designs : 

The treads of a tyre are the portions of the tyre which actually make contact with the road.The treads provide traction to the wheel for the car to move. Based on tread designs tyres can be categorized as :


  • Directional: Directional tread patterns are used in tyres which are to rotate in a given direction designated by an arrow pointer in the side.
  • Non-Directional :These are the tyres which can rotate in any direction i.e, can be put on any wheel.
  • Symmetric : These have symmetric tread patterns for stable handling and traction.
  • Asymmetric : These have special designs which are not symmetric and have use in specified driving conditions .

How long do the Treads last..?

 The tread wear can be ascertained by the wear indicators on the tyres. Check for the elevated rubber portions in the grooves of the tyre-if they are at the same depths with the adjacent tread ribs then it is time to change your tyre .


Unequal wearing of the treads may be caused by improper alignment of the wheels , incorrect placement of the suspensions and improper tyre inflation. This may lead to bad handling , bad braking and also a bad fuel economy .



Run Flat tyres :
As the name suggests Run flat tyres are the tyres which enable the driver to continue with the journey in case of a puncture within specified speed and distance regulations before the tyre need to be changed .Thus RFT s have a major safety benefit .The RFT technology is a reinforced sidewall that keeps the tyre beads firmly seated to the wheel rim enabling the wheels to support to car's weight in case of a flat.


What are Winter tyres and Summer tyres..?

Based on the climatic situations of a country the tyre technology also changes to adapt to the surroundings.In countries that experience a lot of snowfall , the all season tyres and the summer tyres are of no good.Using the all season tyres would certainly put the safety of the driver and the passengers in jeopardy .



Winter tyres are have specially designed rubber that remain soft even at a very low temperature and complex tread designs that help it to grip to snowy surfaces better.

Some other information about tyres :

  • Speed rating : Speed rated tyres mean that the company that manufactures the tyres have specified that that tyre model is suitable for running at such and such speed ,designated by letters like S,H,V & Z on the tyre sides.
(S-upto 180 kmph, H-upto 210kmph, V-upto 240kmph, Z- 240 kmph+)

  • Load index : The load index of a tyre tells us how much load the tyre is designed to support according to the manufacturer's guidebook .The load index chart gives us the necessary details.
  • Car Specification : Tyres are specified by the manufacturer for consumer use by Letters like P,LT,C,T etc.
(P-Passanger car,LT-Light Truck,C-Commercial Vehicle,T-Temporary tyre.)

  • Radius of tyre : The tyre radius can be obtained from the markings like R-14 on the tyre sides.
  • Section width of the tyre : The section width of the tyres can be ascertained from the markings on the sides of the tyres by the three digit numbers eg-240 , which denotes that the section width of the tyre is 240 mm. 

Are tyres really of this much importance ...?


Yes,they are....a Car with the right set of tyres for the road is much safer and a far better performer than a car with bad tyres.So go get the correct ones....

Happy Driving...!!!