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Old 19th September 2007, 23:14   #106
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Stuttgart-West™: The Physics of Racing, Part 1: Weight Transfer, Porsche models 356, 911, 912, 914, 914-6, 924, 944, 928, 993, 986, 968, carrera, cabriolet, speedster, targa, twin turbo including porsche repair, porsche restoration, porsche parts and
Maybe this article on weight tranfer substentiates what I have said.
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Old 20th September 2007, 03:22   #107
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Originally Posted by binz View Post
I believe that is not the case in the baleno.Because,even at peak torque my car wont wheelspin.I don't really think my 195's have anything to do with this.See stumpy's car used to wheels spin with 15"ers .. neovas also if im not wrong,so did memos car,and it used to wheelspin at the redline.

Except that,Memo's car had an exedy stage two clutch,stumpy's had an imported valeo clutch from an esteem's parts bin and my car had very new stock baleno clutch.
Maybe this is because your car is slow. My car wheelspun with the stock clutch anywhere over 4000 rpm. Now of course, my clutch is a distant memory.

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Originally Posted by anupmathur View Post
Revvedup, I beg to dis-agree with this!

FWD DOES NOT load the rear at acceleration, it loads the front! Which is why a FWD car can NEVER do a 'wheelie'.
As for loading the front suspension at braking, I think it depends entirely on the brake force distribution, which, in almost all modern cars is heavily biased toward the front wheels with disc brakes. My old HM Landmaster never had any significant nose-dip even in the hardest of braking conditions. Of course we used to be 'thrown' forward, but that was because of momentum being broken and not because of nose-dip.
Please enlighten with the aid of 'physics', if required. Even deep physics is welcome.
Nothing in the history of automobiles ever loads the front while accelerating. Simple physics, and a bit of inertia, means the rear is loaded. Which is why you are thrown back in your seat during acceleration. Your point about the brakes is self-negating. The fronts are better brakes because on decelerating, the front is loaded. Thus logically, on acceleration the rear is loaded. QED.
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Old 20th September 2007, 08:07   #108
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Originally Posted by v1p3r View Post
Nothing in the history of automobiles ever loads the front while accelerating. Simple physics, and a bit of inertia, means the rear is loaded. Which is why you are thrown back in your seat during acceleration. Your point about the brakes is self-negating. The fronts are better brakes because on decelerating, the front is loaded. Thus logically, on acceleration the rear is loaded. QED.
Sir, what you are saying is essentially correct. To me, it seems we MIGHT be saying the same thing but not making it clear, and also suffering from inadequate knowledge. Simple physics would not be up to the job of explaining all of this.
When acceleration is in fwd direction, undoubtedly all masses are 'pushed' backwards, and the reverse occurs during braking. That to me is 'intuitively' very clear too.
These forces would act purely backwards and forwards, if you look at them only as acceleration and deceleration as applied to a point object.
However, application of such acceleration at the particular point where it is applied to a 3D object generates moments with respect to fulcrum points. These are generated because the application of acceleration is not IDEAL. Torque is applied at the wheels to achieve the acceleration: ie. only a component of the total force would translate into forward motion. Many other components would also be generated.
I think it is these we are trying to figure out. These, or components of these, create forces that act in the up or down directions. So, in the dynamic condition, there are torques and there are moments at work also.
What are these components? What are the effects?
In this context, how would one explain that a FWD car will NOT do a wheelie?
Further, intuitively, you can figure out that it might do a 'reverse wheelie' (bucking) if the acceleration at front wheels is large enough!? Would it? Or does that violate the laws of physics?
For braking, if ONLY the rear wheels are used, there is no nose-dip. How is that to be explained? And anyway the act of braking should only create a forward acting force (to do entirely with momentum) and nothing upwards or downwards. But it does. That is because the simple physics we do at school is only limited to point objects, to keep the principles clear. In real life, and applied at a point on a large 3D object, there are many more attributes that complicate the situation. That physics, and for dynamic conditions, is quite beyond me. So I just observe the effects.
Considering you too are not going into deep physics (for possibly the same reason as I), I would leave it at observation of the actual effects of such manoeuvres performed by us.

Last edited by anupmathur : 20th September 2007 at 08:08.
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Old 20th September 2007, 10:03   #109
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Originally Posted by anupmathur View Post
Sir, what you are saying is essentially correct. To me, it seems we MIGHT be saying the same thing but not making it clear, and also suffering from inadequate knowledge. Simple physics would not be up to the job of explaining all of this.
When acceleration is in fwd direction, undoubtedly all masses are 'pushed' backwards, and the reverse occurs during braking. That to me is 'intuitively' very clear too.
These forces would act purely backwards and forwards, if you look at them only as acceleration and deceleration as applied to a point object.
However, application of such acceleration at the particular point where it is applied to a 3D object generates moments with respect to fulcrum points. These are generated because the application of acceleration is not IDEAL. Torque is applied at the wheels to achieve the acceleration: ie. only a component of the total force would translate into forward motion. Many other components would also be generated.
I think it is these we are trying to figure out. These, or components of these, create forces that act in the up or down directions. So, in the dynamic condition, there are torques and there are moments at work also.
What are these components? What are the effects?
Overhead transmission! Components - friction, heat? Total torque or power is not converted into forward motion is that what you mean to say? Up and down motion is not directly related to the torque in this context. It is caused by the weight shifting for which torque is responsible.

Quote:
Originally Posted by anupmathur View Post
In this context, how would one explain that a FWD car will NOT do a wheelie?
Further, intuitively, you can figure out that it might do a 'reverse wheelie' (bucking) if the acceleration at front wheels is large enough!? Would it? Or does that violate the laws of physics?
When you accelerate the weight shifts to the rear causing the front end to lift up and rear end to squat down. If the car is a rwd the weight transferred over to the back will help to push down the rear wheels more firmly into the ground, this helps the rear wheels to transfer more power into the ground without breaking traction.

In the case of a fwd when the weight shifts to the back the front end is unloaded. The front end lifts up, same happens in rwd too, but since the driving wheels are lifted up and since there is no weight over the driven wheels to press it down into the ground the traction is broken.

So in fwd as the nose lifts up traction comes down and effective transfer of power to the ground is not happening. If the wheels clear the ground then there's no power being transferred to the ground to hold the nose up.

In rwd the more the nose lifts up the more the rear wheels are pressed down into the ground, the front wheels can stay in the air coz the driven wheels are still on the ground keeping the front wheels up.

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Originally Posted by anupmathur View Post
For braking, if ONLY the rear wheels are used, there is no nose-dip. How is that to be explained?
Ineffective braking. Too less a speed. Stiff suspension. Or a combination of these factors.

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Originally Posted by anupmathur View Post
And anyway the act of braking should only create a forward acting force (to do entirely with momentum) and nothing upwards or downwards.
Braking causes a force that opposes the forward motion. The downward force you say that causes the nose dip is caused by the weight transfer to the front. It happens naturally due to momentum.
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Old 20th September 2007, 10:57   #110
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Sankar, thanks. Most of it sounds pretty good. I'm still trying to assimilate it!
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Old 20th September 2007, 11:21   #111
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You should not mistake inertia with torque..
Its because of Inerita that a FWD car pushes you back and its the same force that tends to lift the front wheels and load the back wheels. So if you have a stiff rear suspension, you might be able to counter this force and allow more % of torque to be transferred to the front wheels. infact more torque on the front wheels cancels out the force of inerita and pegs the car to the ground. but again you need to have broader tyres on the front to put all the torque to ground and prevent torque steer.
In a RWD car, the front lifts up because of torque on the rear wheels.the same happens in any bike. the back wheel is rotating more than the front and once again inertia puts a lot of load on the rear suspension. This is why a rear wheel car with hughe torque tends to lift the car up ( torque + inertia loading on the rear)
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Old 20th September 2007, 11:53   #112
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Originally Posted by doomsday View Post
If you are talking about power-to-weight ratio
You, got my point

Can we have P to W ratio of all three cars, it might lead to some thing concrete.
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Old 20th September 2007, 18:29   #113
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Originally Posted by vivek_pinkoo View Post
You, got my point

Can we have P to W ratio of all three cars, it might lead to some thing concrete.
I feel that P to W ratio has nothing to do with this. However, here you go.
M800 56.9 bhp/tonne
Ikon 92 bhp/tonne
Baleno 96.4 bhp/tonne

Please enlighten us how these figures have a bearing on the 1st to 2nd gear wheelspins. Thank you.

P.S. All figures taken from Indiacar.com - Buy/ Sell Cars, Prices, Research, Car Buyers Guide, Car Site, Questions, Car Quotes and much more
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Old 21st September 2007, 11:32   #114
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Originally Posted by doomsday View Post

Please enlighten us how these figures have a bearing on the 1st to 2nd gear wheelspins. Thank you.
I can not get deep into this, but as per my observation (feeling) if some how decrease (more people in a car) the ratio of Baleno to Ikon level or better less than Ikon then Baleno wheels also will start spinning while shifting from 1 to 2.
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Old 21st September 2007, 16:35   #115
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Originally Posted by anupmathur View Post

I think it is these we are trying to figure out. These, or components of these, create forces that act in the up or down directions. So, in the dynamic condition, there are torques and there are moments at work also.
What are these components? What are the effects?

For braking, if ONLY the rear wheels are used, there is no nose-dip. How is that to be explained? And anyway the act of braking should only create a forward acting force (to do entirely with momentum) and nothing upwards or downwards. But it does. That is because the simple physics we do at school is only limited to point objects, to keep the principles clear. In real life, and applied at a point on a large 3D object, there are many more attributes that complicate the situation.
Okay. It took some time for me to assimilate all these facts. Reason: Last studied Physics in Std X I think the key word here is all these forces being applied to a 3D object as Anup said. Also as per observation there is another thing to be kept in mind. This 3D object is not a rigid object but a flexible one. An example would clear this.

From what I have observed, the nose dive that a car undergoes while braking is dependent on the stiffness of the front suspensions. For those who have seen the track esteems race at the MMST and/or the KMS, will notice that the suspension setup is so stiff that the car hardly nosedives even under heavy braking. I say hardly because it is still not completely neutral. So optimally, if we remove the springs entirely from the front strut, the nosedive will be absent completely since the point where the forces are acting will not be flexible at all.

Taking this example further, if we setup a car that has no flexible points except the tires (which rotate) i.e. a car with no roll/pitch and zero rebound damping, these forces will not have these effects (by-products) but will effect the car as they effect a point i.e. only in one plane (forward/backward) in simple physics.

Of course it is all a theory, in practice there might be some factors which we cannot think of in practice.

Quote:
Originally Posted by shazikon View Post
You should not mistake inertia with torque..
Its because of Inerita that a FWD car pushes you back and its the same force that tends to lift the front wheels and load the back wheels. So if you have a stiff rear suspension, you might be able to counter this force and allow more % of torque to be transferred to the front wheels. infact more torque on the front wheels cancels out the force of inerita and pegs the car to the ground. but again you need to have broader tyres on the front to put all the torque to ground and prevent torque steer.
In a RWD car, the front lifts up because of torque on the rear wheels.the same happens in any bike. the back wheel is rotating more than the front and once again inertia puts a lot of load on the rear suspension. This is why a rear wheel car with hughe torque tends to lift the car up ( torque + inertia loading on the rear)
Very well explained.

Quote:
Originally Posted by vivek_pinkoo View Post
I can not get deep into this, but as per my observation (feeling) if some how decrease (more people in a car) the ratio of Baleno to Ikon level or better less than Ikon then Baleno wheels also will start spinning while shifting from 1 to 2.
Is it an observation or a feeling? Because observation is something which you have actually seen taking place and feeling is something which you have not seen in real but you think it will happen the way you expect.

So you are saying that reducing the power to weight ratio of the Baleno to match it with the Ikon will enable it to wheelspin. I am sorry to say that this is not even close to the solution. Your feeling/observation is going in an entirely different (read wrong) direction.

FYI, the power-to-weight ratio of a car denotes the relative amount of power one car has to move the mass of the car. It is measured in bhp/tonne, i.e. how much relative bhp does that car produce to move a tonne of weight.

For example if there are two cars; A & B. Car A weighs 500 kgs and produces 100 bhp. while car B weighs 1000 kgs and produces 150 bhp. Even though car B produces more power than car A, its power to weight ratio is lesser than the car A which produces less power than B.

To calculate P to W ratio. (Power/weight in kilograms) * 1000

So we get:

Car A: 200 bhp/tonne
Car B: 150 bhp/tonne.

So in effect, car A will have better performance (0-60, 0-100, 1/4 mile, top speed etc. etc.) than car B; even though it produces less power on paper.

As per your post, if the power to weight ratio of the Baleno is reduced by adding more weight to the car, its performance will drop, which I am sure will not be reflected by spinning wheels from 1st to 2nd. This among other factors like: A fully loaded car will sit lower to the ground due to the added weight and also the springs will be loaded due to the additional weight will definitely not aid wheelspin.
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Old 21st September 2007, 17:31   #116
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Originally Posted by doomsday View Post

As per your post, if the power to weight ratio of the Baleno is reduced by adding more weight to the car, its performance will drop, which I am sure will not be reflected by spinning wheels from 1st to 2nd. This among other factors like: A fully loaded car will sit lower to the ground due to the added weight and also the springs will be loaded due to the additional weight will definitely not aid wheelspin.
Give one answer

What will happened when you hook rear of a car with a pole and try to accelerate? (wheel will spin)

Means if friction ( deciding factor are tire size, tire age, engine weight , speed of the wheel etc ) between wheels and surface is lower than the weight, the car has to pull then car will spin.



Why I used observation? Because I have seen vehicle wheels spinning while stuck in the mud so observation word came from here.

Why I used feeling ? Because I have not seen exactly the same thing which you did and raised the question. So in that case feeling came.
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Old 22nd September 2007, 12:29   #117
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From what I have observed, the nose dive that a car undergoes while braking is dependent on the stiffness of the front suspensions.
But the fact that the weight is thrown forwards onto the front wheels and off the back wheels does not depend on the suspension.

Do not think (Maybe you weren't) that the suspension can alter this weight distribution; it can only alter the way the body responds.

I guess that's why people put bookshelves ...err, spoilers on the back end of their cars.
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Old 22nd September 2007, 16:15   #118
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Originally Posted by vivek_pinkoo View Post
Give one answer

What will happened when you hook rear of a car with a pole and try to accelerate? (wheel will spin)

Means if friction ( deciding factor are tire size, tire age, engine weight , speed of the wheel etc ) between wheels and surface is lower than the weight, the car has to pull then car will spin.
Okay. I'm guessing here that you are talking about F-R weight distribution. I am sorry I am unable to comprehend your point sometimes. Yes, if the car's weight distribution is biased towards the rear and the car is a FWD then the tires will spin while shifting. But this theory is ruled out for two reasons.

1. The weight distribution would be almost equal for the Baleno and the Ikon since they both are three box sedans and even though the Ikon is heavier by a few kilos; I think it is because of its motor. AFAIK, the Baleno is an aluminum motor while the Ikon comes with an aluminum head only. So this makes the Ikon even more forward biased with more weight over the front wheels.

2. The weight distribution for the M800 is forward biased since it does not have a boot. But it still spins up. So the weight distribution theory does not hold good.

What I am understanding is that it has something to do with the clutch spring back action. Thats all.

[/quote]

Quote:
Originally Posted by Thad E Ginathom View Post
But the fact that the weight is thrown forwards onto the front wheels and off the back wheels does not depend on the suspension.

Do not think (Maybe you weren't) that the suspension can alter this weight distribution; it can only alter the way the body responds.
As I mentioned earlier, I was just thinking that if the an object is rigid, the forces acting on it will act only on one plane i.e. forward/backward. instead of acting (forward+downward) or (backward+upward). I understand that it would not alter weight distribution since it acts in the plane I mentioned i.e. forward/backward or front/rear.

Quote:
Originally Posted by Thad E Ginathom View Post
I guess that's why people put bookshelves ...err, spoilers on the back end of their cars.
You might be aware of the fact that spoilers act in a way exactly opposite what wings act in an airplane. At speed, the wings on a plane help it to take off. In a car, a spoiler prevents the car from taking off at high speeds and induces downforce which work to help the car grip the tarmac better. I think the spoiler affects the weight distribution of the car in someway. That is the very reason that race cars have spoilers both in the front lip and the rear opposed streetcars which only have the rear spoiler (which mostly works to enhance cosmetic look) and have little role to play in increasing aerodynamic efficiency if not ruining it.
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Old 22nd September 2007, 19:13   #119
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Yes, spoilers are upside-down wings. Did you know that, if you carry a big surf-board on your car it really matters which way up it is? Apparently some people learnt that the hard way!

Here's an interesting demo of 'aero'-dynamics, though I confess it may be entirely off-topic! turn on the tap, hold a spoon by the tip of its handle, closed (bottom) side towards the water flow, and move it sideways into the flow. You'd expect it to be pushed away by the water, yes? but... well, try it.

You can't have your weight distribution working in just one plane, forwards or backwards: the very idea of weight is that it acts down, surely! but then, I guess it isn't really 'weight' that moves, it is force.

BTW... having driven to Pondy and back from Chennai this week, I gave a little thought to my driving style and realised....

1. I only push it in 1stif I have to. That would mean eg getting in front of and away from something fast-moving as I join traffic, both for my safety and not to be a pain to another driver.

2. When I really need power I'm far too busy to look at the tachometer!

3. But my main acceleration will be done in 2nd and third. 4th will be a quickie before 5th for cruising.

2. Not much more than 4,000 in 3rd will do me fine even for a hurried overtake.

Totally off-topic: I'm impressed with my diesel Swift's ability to have some acceleration left even in 5th.
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Old 23rd September 2007, 10:47   #120
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Originally Posted by doomsday View Post

As I mentioned earlier, I was just thinking that if the an object is rigid, the forces acting on it will act only on one plane i.e. forward/backward. instead of acting (forward+downward) or (backward+upward). I understand that it would not alter weight distribution since it acts in the plane I mentioned i.e. forward/backward or front/rear.

when you have a soft suspension, the joints of the suspension become pivot (also the rear wheel, to a large extent) to convert the linear force into rotational.

in the ideal condition you mentioned, there is no suspension, hence the contact point of front wheel with ground becomes the pivot, and can still make the car nosedive.

imagine your imaginary setup having a high center of gravity, travelling at 100 mph, then braking hard. you will get a different kind of a nosedive.
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