Why you should not use a laptop on bus or train.

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Why you should not use a laptop on bus or train.

Postby SemiconductorCat » Mon Feb 18, 2013 9:57 pm

It's seems like many people are using their laptops and computer equipment while traveling on the train.
This probably saves your time. Even you got an android complete linux running device , there are still situations where
you need to open your laptop and work.

Some trains are also provide power to the passengers who are traveling in the train and also wifi to internet
access. But still it isn't a good idea to use your laptop when you traveling on the train.


REASON:
The reason comes from classical mechanics. In other words it's acceleration. Yep acceleration does harm your
laptop hard disk drive.

Adaptive servo mechanisms may lead to learn incorrect friction parameters.

HOW?
So as I explained above , hard disks could failed due to two reasons.
1. Acceleration.
It's not the velocity is the problem. Hard disk disks are rotating more higher speeds than we think. But the problem
is acceleration. Simple equation comes here,F=ma. It is said that head surface could be damaged due to the
force or contract between disk surface and the head. When your bus is breaking ,it's nothing but very high
acceleration for a short time. It's somethings more than 10g but it's transient and short so we don't feel it.
But hard disk does. Because it's sensitive to it and it wasn't designed to withstand to that acceleration.

The second reason is because it uses adaptive neural network learning mechanisms on it's servo-mechanical
controls. Mechanical friction is a complicated function which depends on temperature, and with lots of other
parameters. And also the environment , think about engine vibration environment. Sometimes if you brought a
hard disk of a computer near to a milling machine on a workshop and fix it to your home computer , it may
fail to work. Or large seek time or CRC errors.Why? The same reason, it's neural networks are already learned
how to work on that environment. So simply when you using your mechanical hard disk drive on bus, it will
adopt to it's environment and may failed to work in your typical environment.

DEFENSE
The only defense technology against his is dampers. You could see rubber dampers around hard disks.
In CD roms drives used in those cars and vans you could see rubber dampers. Dampers does not do a magic
it's just acts like a friction and absorbs the vibration energy. In hard disks and CD roms we typically use
rubber vibration isolation techniques.
Image

Dampers could also exists on the vehicle itself. Some idiots think they are unnecessary but they are necessary.
Even human brain can't withstand if you remove dampers from your vehicle.
Image

Image

Vibration isolation is a complete different subject. I'm still a level 3 engineering student ,even not a
mechanical engineering ,but computer eng. So let give this wiki-page for you to future studies.
http://en.wikipedia.org/wiki/Vibration_isolation
There may be many technologies such as oil , magnetic, eddy current based mechanical vibration isolation techniques
and some new technologies that I even never heard about. fair enough since I'm not a mechanical engineering
student know.

Anyway shock absorbing is not the only method of reducing such transient acceleration effects and vibrations.
In electrical engineering like we reduce ripple of a rectifier through a capacitor, adding mass will do the same.
In trains , we could see this. On each train truck there is a heavy weight which is free to alternate , and it
smoothness the transient vibrations of rail cars.

Image
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Re: Why you should not use a laptop on bus or train.

Postby Lafountain » Sat Aug 12, 2017 6:14 am

That's interesting, I use my laptop on the train every morning and I've never had a laptop last longer than 6-12 months. Maybe the acceleration is messing them up.
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