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Sunday, September 16, 2012

Car wheel alignment, Eigen value problem and excellence

Today morning I was attending a class on dynamics taught by Prof. Rudra Pratap. He explained today in detail the process of mass balancing using simple linear and angular momentum balance theorem. It was basically a disk rotating on a rod with an angle. Refer to the picture below.

It was an enjoyable class and then, he started writing a symmetric matrix (After attending Prof Jog's class, I like to call it as second order tensor. It feels good.) of the moment of inertia of the . The moment of inertia about the three principal axes are the diagonal terms of the matrix. Obviously, the other terms of the matrix are zero. 

Now, from the result of the mass balance problem, it was deduced that if we keep the plate in certain orientations then there is no requirement of torque at the  support points. Subsequently, the orientations were those of the eigen vectors of the moment of inertia matrix.

So, car or bike wheel alignment is essentially a eigen value problem and subsequently any balancing problem involving two masses placed on a rotating rod.

Now, when we go for aligning car or bike wheels, the mechanic does it. He knows by practice that if the wheels are properly balanced and are aligned the support don't feel any reaction force. Even if he knows how to fix the problem better than you and me, he does not have the insight of the problem like we do.

So, what are we going to do with the insight ?

We deduce a lot from the knowledge. As an engineer, we can look at a similar problem and know the solution using this insight and that is where the difference and significance comes. As I mentioned in a previous post about my own hypocrisy, I don't feel that bad about it now.

Now, why the word "excellence" is there on this post title?

It comes from the fact that creativity has a lot to do with knowing something and associating that knowledge correctly to other problems. And that we can learn from this car wheel alignment problem. This skill of associating knowledge requires practice and thinking from the side of the person having that knowledge. To attain excellence we have to practice associating our knowledge to appropriate problems to find solutions.

1 comment:

  1. Thanks for sharing this note. Desire to add up what happens in a vehicle when these two parameters are not correct.
    Due to alignment issue, vehicle pulling towards RH/LH arises which sometime depend on tyres, tyre pressure also.
    Due to in proper balancing, wobbling may arise. Many a time tyre quality also plays a role.



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I am a student [Master of Design - Product Design and Engineering] at Indian Institute of Science, Bangalore. I completed BTech (Mechanical Engineering) from NIT Silchar. My native place is Sipajhar, a small place with rich cultural heritage, in Assam. I am interested in designing products and systems for a better life. I like to collect quotes, read books,blog and surf net, dance and sing Bihu songs and write poems and articles. I don't like to talk while I am eating. But above all, I want to be happy all the time. Contact me at m2n037[at]gmail[dot]com
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