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Old 26th October 2012, 07:22   #16
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Default Re: Understanding Seat Belts : Layman Language

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Originally Posted by shankar.balan View Post
I wonder why we in India have even more primitive and archaic rules and enforcement than the chaps out there in Africa.
I insist that everyone in the vehicle wears their seat belts. The front passenger most certainly ( no getting away because the warning light and sound keeps on at it to remind one to wear the belt), and the rear passengers because it is simply safer. However, there are very few occasions where we have four people in the vehicle.
I will not allow 5 people in my car because it is too much of a tight squeeze.
For the simple reason that most of our political leaders are very uneducated people and they can't or won't understand the value of such rules. Look at the number of blue collar criminals in politics. Add to it the fact that Indians in general don't like obeying any rules and have a major fate attitude (if it is my time, nothing can save me and so be it) and it is next to impossible to implement. Even educated people in India refuse to use seatbelts or for that matter helmets (properly), except for when they see police checking on this.
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Old 26th October 2012, 11:19   #17
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Default Re: Understanding Seat Belts : Layman Language

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Originally Posted by torquecurve View Post
Hi Everyone, .......

I am starting this thread to make an attempt at explaining why we
And, yes, they come for free with the Car, why not use it if it is free?

A very good topic Indeed Torquecurve, And really appreciate you taking the efforts to bring in the numbers and make very very logical comments here.
One more observation is once you start using seat belts, One just does not feel comfortable without them !! Most of the times I even wear seat belts while in the rear seat and doze of without a worry

While we are at this guys, I am dumb (and dont kill me for this) Any pointers to save the shirts from getting creased, I have tried my best to buckle up without the shirts getting creased, hasnt helped so far (doesn't deter me from weaing one though) !!
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Old 26th October 2012, 11:30   #18
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Default Re: Understanding Seat Belts : Layman Language

Just received an SMS from PTP (Pune Traffic Police) group.

"Hug your kids at home but belt then in Car! Last week,3 people without seatbelt did but 2 with Seat belt survived in accident in Saangavi,Pune.Take Care"

This SMS service was initiated recently to give updates on traffic, accidents, areas to avoid for safety reasons, etc in Pune.
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Old 26th October 2012, 13:01   #19
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Default Re: Understanding Seat Belts : Layman Language

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Originally Posted by torquecurve View Post
Seat belts save lives. Please wear them.
And, yes, they come for free with the Car, why not use it if it is free?
Excellent initiative, sir! I am very bad at math, physics or whatever else you have put up so would not delve into the numbers part. I would liek to add two things here.

The first that I remember is that at 40kmph its like Usain Bolt running at full speed into a wall. Someone had mentioned this in the accidents thread and it has stood out for me.

The second is my own experience in an accident when the driver side front wheel ran over a divider stone (in the fast lane/ removed for easy access) at about 50kmph. Of what I clearly remember in the next couple of seconds was the seatbelt tightening around me and preventing my head from hitting the roof or going through the windshield. What I want to state here is that the forces acting may not be in only one direction and the primary restraint needs to be in place (not by sitting over a buckled seatbelt) to save life and limb.

Quote:
Originally Posted by Swanand Inamdar View Post
Im sorry, but how does it matter, what the equation says?
The point he is trying to make is, wear your seatbelts. Regardless of the weight, the speed, the time taken to stop etc etc.
Just wear the belt!
For someone who is bad at the math part, that comment totally sums it up for me!
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Old 29th October 2012, 11:09   #20
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Default Re: Understanding Seat Belts : Layman Language

Thread moved from the Assembly Line (The "Assembly Line" Forum section) to the Technical Section. TorqueCurve has made changes to the opening post! Thanks for sharing
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Old 30th October 2012, 13:49   #21
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Default Re: Understanding Seat Belts : Layman Language

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Originally Posted by ecenandu View Post
Because in race cars they are not using a 3point seat belt but a 5 point one. Once properly strapped in those your body won't move an inch. It will be impractical to use those for daily purpose.
Would it be possible for installing this 5 point seat belts in regular streetcar without any modifications? And why would it be impractical? I am strapping a 3 point one now, if I have an option, I might as well strap a 5 point one.
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Old 30th October 2012, 14:42   #22
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Default Re: Understanding Seat Belts : Layman Language

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Originally Posted by shipnil View Post
Would it be possible for installing this 5 point seat belts in regular streetcar without any modifications? And why would it be impractical? I am strapping a 3 point one now, if I have an option, I might as well strap a 5 point one.
Without modification, I don't think so. For the Baja buggy we built, it had a 5 point seat belt and the two straps of the seat belt which goes over the shoulder has to properly strapped to a rigid member. It will be easy to do that in a race car, by means of a horizontal pipe connecting the roll cage.

To be honest, its not at all required(5 point seat belt) for a street car. A regular one will do the job.
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Last edited by ecenandu : 30th October 2012 at 14:55. Reason: Adding picture
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Old 30th October 2012, 21:03   #23
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Default Re: Understanding Seat Belts : Layman Language

Quote:
Originally Posted by torquecurve View Post

Seatbelts don’t just help in case of accidents, they also help when you suddenly have to slow down (e.g. another vehicle/ person comes in your way).
....
Lets say you are driving at a speed of 60 Kmph. You weigh about 80 Kgs (I weigh 100 ) And you suddenly have to slow down (Brake) from 60 to 0 kmph very quickly and this happens in 1 seconds. 60 Kmph = 16.67m/s
Simple physics - Force = Mass X Acceleration(Deceleration)
To calculate Decelaration I use another formula = (0-16.67)/1 = -16.67 m/s square.
So the total force exerted is about = 80x16.17 = 1293.6 (Newtons)
Okay before you say, this is not laymans language, I will try to make sense of these numbers.
I have considered that your car is braking (not crashing) just to show what are the effects of this. 1293.6 Newtons of force is approximately equal to a weight of about 132 Kgs kept on the ground. Imagine that on your hands in this case).
If you change the weights, you get the below (for same speeds).

At 100 kgs, the force is 100X16.17 = 1617 N (165 Kg weight!)
At 90 Kgs, the force is 90 x 16.17 =1455 N (~150 kg weight!).

.......
I dont think my bones are as strong as concrete, or neither do I train to be a martial artist/ boxer. My bones can easily fracture under these stresses. So unless you are, well.
Many times, you will not get major fractures but there will surely be minor stress fractures which sooner or later will lead to major issues. The seatbelt in this case will take this force and transmit it to the body shell of the car through the B-Pillar and the lower support strut. The car is designed to take this kind of force.

Another thing, with increase in speed, this factor changes drastically.
For an 80 kg person in a car at
80 kmph the force is 80 X 22.22 = 1776 N and at
100 kmph = 80 X 27.77 = 2221 N

This is Way beyond what your hands can support and can easily break your hands. And I am considering just Braking.
Hi,
Not to take away from the focus of the article, but braking causing wrist/ arm/ hand fractures is surprising. To me at least. To put the forces in form which we laymen can relate to, could you rework your equations to work out the stopping distances in your example above, and to express the deceleration in terms of g. We can then compare it against our real world figures.

Once again, I am talking only of braking, and your illustrative examples.

Regards
Sutripta
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Old 31st October 2012, 19:09   #24
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Default Re: Understanding Seat Belts : Layman Language

Quote:
Originally Posted by Sutripta View Post
Hi,
Not to take away from the focus of the article, but braking causing wrist/ arm/ hand fractures is surprising. To me at least. To put the forces in form which we laymen can relate to, could you rework your equations to work out the stopping distances in your example above, and to express the deceleration in terms of g. We can then compare it against our real world figures.

Once again, I am talking only of braking, and your illustrative examples.

Regards
Sutripta
Speed = distance/ time.
so, distance travelled = Delta of speed/ delta of time = -16.66/1 = 16 metres.

The force will equate to about 1300 Newtons ( as calculated earlier).

To convert the Newtons to G forces.

For an 80 Kg person, he is exerting 80*9.8m/s = 784N in terms of mass.
So Force on the body = 1300/784 = 1.66 G.

This is also equal to a person jumping from a height of 16 meters (which I believe is 3 storeys of a building.

This is an approximation and will vary by stopping distance of your car.

Also, if you are not wearing a seatbelt and ONLY using your hands to stop yourself from crashing into the steering (or move ahead) this ENTIRE force is on your wrists, elbows and shoulders. Also, normally your body dissipates the forces on it by moving the force to the ground (which according to the body is not accelarating). However in this case, your feet which most probably will be on the pedals will also experience the same forces and the body will transmit the force towards your back or through your joints. Try this, tightly roll a magazine. Next fold this roll into half. Use the pointed end thus formed to hit an empty can. The effect of the hit is multiplied as it is on a small contact area.

The forces will NOT fracture your hand or other joints (unless you have a bone disorder) however it will potentially create micro fractures, which over time will weaken your bones.
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Old 31st October 2012, 20:33   #25
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Default Re: Understanding Seat Belts : Layman Language

Hi,
I had asked for
Quote:
Originally Posted by Sutripta View Post
....
To put the forces in form which we laymen can relate to, could you rework your equations to work out the stopping distances in your example above, and to express the deceleration in terms of g. We can then compare it against our real world figures.
So I take it that

Quote:
Originally Posted by torquecurve View Post
Speed = distance/ time.
so, distance travelled = Delta of speed/ delta of time = -16.66/1 = 16 metres.
16.7m is what the vehicle will travel while braking from 60 Km/hr to 0 Km/hr in 1 sec.
You sure? This does not seem right.
dv/dt = distance?


Quote:
So Force on the body = 1300/784 = 1.66 G.
Convoluted, but 1.7 G does seem right. In what sort of cars can we expect this braking performance?

Quote:
This is also equal to a person jumping from a height of 16 meters (which I believe is 3 storeys of a building.
Puzzled. What is equal to what?

Quote:
Also, if you are not wearing a seatbelt and ONLY using your hands to stop yourself from crashing into the steering (or move ahead) this ENTIRE force is on your wrists, elbows and shoulders. Also, normally your body dissipates the forces on it by moving the force to the ground (which according to the body is not accelarating). However in this case, your feet which most probably will be on the pedals will also experience the same forces and the body will transmit the force towards your back or through your joints.
Next topic for discussion!

Regards
Sutripta
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Old 31st October 2012, 23:25   #26
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Default Re: Understanding Seat Belts : Layman Language

Quote:
Originally Posted by Sutripta View Post
Hi,
I had asked for

So I take it that


16.7m is what the vehicle will travel while braking from 60 Km/hr to 0 Km/hr in 1 sec.
You sure? This does not seem right.
dv/dt = distance?
My mistake.

S=D/t so Delta S=DeltaD/ Delta t
hence, Delta D = Delta S * Delta T.

In this case however the Delta T is considered to be about 1 second and so didnt make a difference to my further calculation.

Quote:
Convoluted, but 1.7 G does seem right. In what sort of cars can we expect this braking performance?
I dont know why does that sound convulted to you. You can look up some websites and I am sure you will find calculations such as these.

Otherwise, you can use the OpenSource Math software.

Cars on dry tarmac with all discs maybe provide this stopping power. In case of a crash you would slow down in less than 0.1 of a second in less than 1-2 metres probably.

Quote:


Puzzled. What is equal to what?

The G force is equivalent to a distance travelled by a person. I was just trying to make my point.


But I think you are digressing from the whole point. I am just trying to make people aware that wearing a seatbelt does really help.
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Old 1st November 2012, 05:15   #27
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Default Re: Understanding Seat Belts : Layman Language

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Originally Posted by shipnil View Post
Would it be possible for installing this 5 point seat belts in regular streetcar without any modifications? And why would it be impractical? I am strapping a 3 point one now, if I have an option, I might as well strap a 5 point one.
Technically it is not very difficult. A five point seat belt just requires 5 holes drilled in the body where the belts are held in place. The front three (groin and across your thighs are easy enough. The floor below your seat. The two over your shoulder are tougher. A simple jugaad is to fit them on the floor behind the seat and then bring them up and over the seat. Need to ensure it does not interfere or get interfered with by the rear seat passenger and that it comes over the seat in an effective manner.

Of course one of the reasons people prefer the three point seatbelt is ease of use. Just pull from one place and pop in and pop out and let it go. A five point does take more time to put on and take off, which is not ideal in a city.
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Old 1st November 2012, 18:36   #28
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Default Re: Understanding Seat Belts : Layman Language

What are the pretension belts and are they really effective in comparison with regular ones?
How height adjustments contribute to safety?

Thanks for this thread.
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Old 1st November 2012, 18:41   #29
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Default Re: Understanding Seat Belts : Layman Language

I agree to the need for seatbelts in saving lives. i myself always put it on whenever i drive on major roads/highways/expressways. in the case of hitting a barrier/car they go a long way in helping reduce damage to the body.

my contention is regarding their use and utility along the slow twisty/curvy roads in the hills. major accidents in hills happen when vehicles go down a hill and in this case a 3-point harness is almost useless. only a 5 point harness coupled with a rollcage can help in saving from severe harm.

also "people" claim its easier to get out of a car(when it is rolling down a hill) if a person is not wearing a seatbelt although i don't know how accurate that is(no i have never tried that myself )
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Old 1st November 2012, 18:48   #30
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Default Re: Understanding Seat Belts : Layman Language

Torquecurve, thank you so much for such a "silly-sounding" topic you've stressed on!

I always wear my seat belts even for the shortest distance. It's become a habit actually. Sadly, there are people whom I know who drive Beamers and Mercs, and laugh at me for doing this (on my Zen Estilo), stating that some "advanced" electronic whatever (they don't even know the names of these safety technologies) can prevent them from any sort of serious injuries.

I think, even for the most sophisticated cars, all the other safety mechanisms are built upon the underlying advantages of the seat belt, without which many of their efficiencies are reduced, including ABS!

Oh and yes, silliest thing, cops here (in Chennai) catch you for sun-films and such lamer things, but no one including them bothers about seat belts or helmets. So much for claiming that we're from a land of intelligent and educated people.
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