Thursday, January 05, 2006

Automobile trivia

Over the course of time, I have heard of some insights about automobiles which I've found to be interesting/useful. Thought of sharing it with you all. The first and foremost of all is the tire pressure. Though I've heard about this through all possible means, I've always been lousy about checking my tire pressure. I hoped that the service folks will take care of it and I dont have to really monitor it, till it hit me hard.

I was travelling on a highway one day when I heard a squealing sound which increased rather quickly over time. I realised that there was some problem and I moved the car over to the shoulder. By that time, the car was literally shaking and when I looked over to see what had happened, I found that one of my car tires had almost melted completely. Later, when I realised the physics behind it, I understood what had happened. When a tire loses pressure, its radius becomes smaller. So, it has to rotate more revolutions (more temperature) to keep up with the speed of other tires. In the process, it gets more deflated. Beyond a critical point, the tire with the lesser pressure gets deflated much more quickly and results in the condition that I faced. Sometimes, it could even resulting in bursting of tire. So, be cautious to check the tire pressure regularly.

The second one is more of a real trivia that I heard from radio. Is it possible to predict where the fuel inlet for a car is, just by looking at the rear of the car? It is possible in most cases. Especially, if the car has only one exhaust at the back. The fuel inlet is usually on the opposite side of where the exhaust is. This doesnt work for twin-exhaust cars. But, in most other cases, it is true.

Finally, we all go on long vacations (esp. to India). We end up asking one of our "trustworthy" friends to start the car once in 3-4 days to make sure that the battery doesnt run low. However, there needs to be an explicit instruction. Ask your friend to drive the car for atleast 10 minutes. The reason being, when you start a car, it drains some amount of charge from the battery. If you dont keep the car turned on for atleast 5 minutes, just enough to charge it back to the original value and more, you are actually depleting charge from the battery. So, if your friend doesnt consider the time aspect of charging back, he is effectively making the condition worse. You might return from your long vacation just to find that the battery is drained and your innocent (in this case, ignorant as well) friend will contemplate by saying that he did turn on the car once every few days...He may be right too... If you were the friend and you really forgot to start your friend's car, you can stage a third friend to come and give this explanation and get you out of the trouble..:)

Thats all for now folks !

7 comments:

BrainWaves said...

First and last point is very useful. Especially last one. Never thought about this till now.

Survivor said...

Useful trivia.As long as one person knows and remembers it in a household, I think it is fair enough :-)

Btw, just so that every one knows, the second one regarding the fuel inlet was actually a puzzle in NPR and guess who was the only person who answered it right....OFCOURSE, the great Shoba !!
Cha, Engoyo poyittama !! Pularikudhu ...

Manohar said...

Two points that came to mind, I might be wrong on these:
1. in case of a deflated tire, the major factor of heat increase is because of increase in area of contact patch and hence more friction and less roll.
2. I think most modern car batteries are fine left idle for a few months (my car has gone up to 3 months but I haven't tried longer).
3. An interesting observation you made about starting the car and keeping it on for atleast 'n' minutes to compensate for the drainage of battery to start the car. There is another area i believe this is true- the decision to stop a car in lights to conserve petrol. If you are stopping for less than 'n' seconds- it may be suboptimal- because it takes a certain amt of gas to start the engine and just stopping and starting where the gas saved by stopping is taken up in starting- would yield on savings.

Suresh Sankaralingam said...

All your points are well taken...

During deflation, the increased area will cause more area to be in contact and hence more frictional loss, in addition to the extra revolution which will compound the problem, especially on a freeway...

The second point is also true. If you have a fairly new car, you should be fine. Otherwise, it is a better idea to start the car once in few days...In my friends case, this problem really happened and thats how I got this story to begin with...:)

I agree with your 3rd observation... In India, I've seen auto drivers trying to switch off the engine and switch the gear to neutral before they come to a complete stop, which maximizes the time "n" for which the engine is off..;)

Manohar said...

coasting in neutral has a subtle disadvantage... u can't leverage engine braking.

Suresh Sankaralingam said...

do u think our auto-drivers care about subtle disadvantages? they have their own way...avanga vazhi, thani vazhi..:)

Manohar said...

*rofl* thats true.