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Old 1st February 2011, 13:20   #61
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Default Re: Articulating on Articulation

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Originally Posted by Samurai View Post
Spike, can you kindly prove my graph wrong. I am still waiting.

Arka, what is your opinion of my graph in post#45?
Hi Sharath,

I think your Graph is correct just that it needs better labeling.

Had me confused for a while

Regards,

Arka
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Old 1st February 2011, 14:09   #62
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Default Re: Articulating on Articulation

Thanks Arka, I am open to suggestions, I wrote it like a layman. What is the right labeling?

Let's do it before Spike proves it wrong.
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Old 1st February 2011, 14:26   #63
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Default Re: Articulating on Articulation

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Thanks Arka, I am open to suggestions, I wrote it like a layman. What is the right labeling?

Let's do it before Spike proves it wrong.
Hi Sharath,

It is better labeling, not right labeling, to make it self explanatory.

Please
i) Add Min & Max on X & Y Axis.

ii) Label the Y-Axis Lift as Lifting a Tyre.

iii) Label Articulation Curves on/along the curve

Regards,

Arka
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Old 1st February 2011, 14:46   #64
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Default Re: Articulating on Articulation

Ok, I made some changes.

Name:  articulation.jpg
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Last edited by Samurai : 1st February 2011 at 14:47.
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Old 1st February 2011, 14:59   #65
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Default Re: Articulating on Articulation

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Originally Posted by ex670c View Post
Hi Spike,

Are you suggesting that in an IFS there will be not Lateral Shift of CG, since the Front Axle is bolted to the Chassis?

Regards,

Arka
I never said that, did I?

Quote:
Originally Posted by Samurai View Post
Spike, can you kindly prove my graph wrong. I am still waiting.
I have said earlier also, when dealing with lateral weight transfers spring rates and roll stiffness do not play any role then how come the CG begins to shift in a non linear pattern?

Samurai, I don't intend to prove you wrong, at the same time I cannot approve it as right, if it can be convinced with solid reasoning I will agree, that's all. As an Engineer, I simply just don't approve guess work, that's it. I don't know about others, but at-least you yourself being an Engineer must understand. Stop pulling my leg now

Quote:
Originally Posted by ex670c View Post
Hi Sharath,

I think your Graph is correct just that it needs better labeling.

Had me confused for a while

Regards,

Arka
What labeling? Sorry Arka, I disagree with you on this. For anyone who has plotted graph even once in his / her life they will agree that graphs depict a relation between a dependent variable and an independent variable. Here we are sitting and guessing that the relation is linear which becomes non linear after some time, all this with intuition and guess work, WOW!

Spike
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Old 1st February 2011, 15:20   #66
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Default Re: Articulating on Articulation

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Originally Posted by SPIKE ARRESTOR View Post
What labeling? Sorry Arka, I disagree with you on this. For anyone who has plotted graph even once in his / her life they will agree that graphs depict a relation between a dependent variable and an independent variable. Here we are sitting and guessing that the relation is linear which becomes non linear after some time, all this with intuition and guess work, WOW!
Hi Spike,

I agree with Samurai's graph, just wanted the labeling to be clear.

Shift of CG against Lifting of Tyres.

If you disagree with the graph please tell us why and make the necessary corrections.

Regards
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Old 1st February 2011, 15:23   #67
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Default Re: Articulating on Articulation

Arey baba how many times I will explain? See my earlier post.

Spike
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Old 1st February 2011, 15:31   #68
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Default Re: Articulating on Articulation

Quote:
Originally Posted by SPIKE ARRESTOR View Post
...
I have said earlier also, when dealing with lateral weight transfers spring rates and roll stiffness do not play any role then how come the CG begins to shift in a non linear pattern?
...
I tend to agreed with this. I do not see how the CG can shift in a non-linear pattern. Again how will spring rates and other suspension parameters affect the location of the CG. It should only depend on how high one wheel or more is displaced from a flat surface, thereby shifting the CG. Suspension parameters will decide how much the vehicle tyres are displaced from a flat surface given a particular ramp/obstacle. I feel a good IFS setup should contribute to a more stable vehicle, because each wheel will be able to move up and down, without lifting the vehicle off the ground (again depends on the amount of suspension travel possible in any setup).

Last edited by pjbiju : 1st February 2011 at 15:40.
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Old 1st February 2011, 16:14   #69
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Default Re: Articulating on Articulation

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Originally Posted by pjbiju View Post
I tend to agreed with this. I do not see how the CG can shift in a non-linear pattern. Again how will spring rates and other suspension parameters affect the location of the CG. It should only depend on how high one wheel or more is displaced from a flat surface, thereby shifting the CG. Suspension parameters will decide how much the vehicle tyres are displaced from a flat surface given a particular ramp/obstacle. I feel a good IFS setup should contribute to a more stable vehicle, because each wheel will be able to move up and down, without lifting the vehicle off the ground (again depends on the amount of suspension travel possible in any setup).
Quote:
Originally Posted by SPIKE ARRESTOR View Post
^^ Thank God, I can sleep in peace tonight, Amen!
Hi Spike & Pjbiju,

The Please explain why the Thar was lifting wheels, where other JEEPs had all 4 Wheels on the Ground.

Does the Thar CRDe have a better RTI than Thar MDI & NGCS MM550XD.

In a heavy articulation section, don't you think the Thar will be lifting it's body more since the IFS is Bolted to the Chassis, and in a Solid Axle setup the Body and Chassis ride above the suspension, which flexes, the axle, to track the undulations.

Regards,

Arka
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Old 1st February 2011, 17:43   #70
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Default Re: Articulating on Articulation

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Originally Posted by SPIKE ARRESTOR View Post
As an Engineer, I simply just don't approve guess work, that's it. I don't know about others, but at-least you yourself being an Engineer must understand. Stop pulling my leg now
No, I am not pulling your leg. Any observation will have a scientific explanation. Since this is not my field, I am at a disadvantage. But I know what I am seeing.

Quote:
Originally Posted by SPIKE ARRESTOR View Post
For anyone who has plotted graph even once in his / her life they will agree that graphs depict a relation between a dependent variable and an independent variable. Here we are sitting and guessing that the relation is linear which becomes non linear after some time, all this with intuition and guess work, WOW!
A complex equation need not be constantly linear or non-linear. What about torque curve or power curve? Is it constantly linear or non-linear? Nope, it isn't.

Am I guessing all this? No! I drew a graph based on my observation, and Arka has agreed that is correct in principle. And he is a master artisan when it comes to Jeeps.

If you know something, you should be able to explain in layman terms. You can't really hide behind jargon. Let your inner engineer come out and explain why we are wrong in simple terms. Leave jargon and buzz words to MBA types, let's hear the engineer.
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Old 1st February 2011, 18:09   #71
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Default Re: Articulating on Articulation

Quote:
Originally Posted by SPIKE ARRESTOR View Post
I have said earlier also, when dealing with lateral weight transfers spring rates and roll stiffness do not play any role then how come the CG begins to shift in a non linear pattern?

Hey spike,

Please explain why the spring rates and roll stiffness would not play any role in a "roll".

I think that as the CoG starts shifting, the suspension will try and push it back/resisting (layman terms, sorry) and hence the spring rates and roll stiffness is relevant.

Also, I think Samurai is correct in assuming it is better represented by a non-linear curve as when the CoG starts shifting, the resistance by the CoG will be greater and slowly reduce as the weight shifts further (changing angles w.r.to spring + momentum) till finally there's no resistance (acute angle/CoG beyond the Axles) which would result in a "topple"

Does that make any sense at all? or am I just rambling?

Last edited by '72 Bullet : 1st February 2011 at 18:12. Reason: addition
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Old 1st February 2011, 20:10   #72
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Talking Articulating on Articulation- Spike's view

Quote:
Originally Posted by Samurai View Post
A complex equation need not be constantly linear or non-linear. What about torque curve or power curve? Is it constantly linear or non-linear? Nope, it isn't.

Am I guessing all this? No! I drew a graph based on my observation, and Arka has agreed that is correct in principle. And he is a master artisan when it comes to Jeeps.
Samurai, you are right, a complex equation need not be constantly linear or non linear, so is the torque and power curve which is derived from lots of variables which keep on changing.

Since the master artisan has already spoken, poor me will try and speak a few things, May I??

Ok, I will first explain in simpler terms then complicate it with a free body diagram followed by resolving the forces about a point (considering the system to be in equilibrium).

For a layman- There are four forces which play a role here:-

1. Weight of the vehicle
2. Force due to lateral acceleration (read Rolling in off-road parlance)
3. Height of Center of gravity (C.G.)
4. Wheel track

On a banked vehicle these forces resolve into various horizontal and vertical forces but basically the forces remain the same (only these 4). So if you change all these the amount of weight transfer will change; in other words the nature and type of suspension does not determine how much weight is getting transferred to the inner and outer wheels it is only these 4 and not the spring rates and roll stiffness.

For others (even Gurus can also read this):-

On a flat road the forces acting (laterally are) represented like this-
Name:  1.jpg
Views: 646
Size:  9.9 KB

Unless there is a lateral acceleration (read Rolling in off-road parlance) it has only a static component of the total forces, once it starts tilting ( read Rolling in off-road parlance) there is an additional component of force called as dynamic component. The amount of weight on the wheels is dependent only on these two components namely Static and Dynamic. The representation is as shown below:-
Name:  2.jpg
Views: 690
Size:  31.7 KB


This shows one wheel looses weight and another gains weight, OK Sam ??

Next consider a situation where the vehicle is banked / articulated (read Rolling in off-road parlance), here the force components remain the same but they get resolved in accordance to the roll angle (phi). See this pic:-

Name:  3.jpg
Views: 652
Size:  28.6 KB

The resolved forces turn out like this:-
Name:  4.jpg
Views: 639
Size:  18.2 KB


Now can someone tell me if there is any term which mentions about spring and suspension stiffness? NO! So what I had been harping continuously was correct, the graph is wrong. Since no terms related to suspension feature in these equations, there is no relation between Suspension characteristics and the amount of weight transfer when on road and off- road. Weight transfer-> CG Shifting

Hence Proved.

Lets take it one step further can anyone tell me when the vehicle will begin to roll over? (I am not trying to ridicule anyone, I just want people to know what the truth is, contrary to what is being told here)

Quote:
Originally Posted by '72 Bullet View Post
Hey spike,

Please explain why the spring rates and roll stiffness would not play any role in a "roll".

I think that as the CoG starts shifting, the suspension will try and push it back/resisting (layman terms, sorry) and hence the spring rates and roll stiffness is relevant.
Dear 72 Bullet, poor me has tried to explain with whatever limited knowledge I had, now it is up to the Gurus and Jeep Gods to approve. Please let me know if you are OK with the explanation, otherwise I will explain in more detail. I had to use pictures and equations otherwise people will again get a reason to crib that all these were framed.

This is my last post on this thread, I think I have had enough, no point in breaking my head. I rest my case here. :-)

Spike Arrestor

PS- Arka, regarding vehicle toppling at the "Robinson Point" (pardon me Robi, I have to be specific), it had nothing to do with articulation. I was keeping quiet on this as it would hurt others sentiments, as I am being questioned, I have to answer this. It was purely driver error, I did not see it but I have Eye witness account on this. The eye witness is a very Senior, experienced and respected Jeeper in Indian offroading scene.

Last edited by SPIKE ARRESTOR : 1st February 2011 at 20:16. Reason: attachments not visible at first instance
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Old 1st February 2011, 20:59   #73
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Default Re: Articulating on Articulation- Spike's view

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Originally Posted by Samurai View Post
No numbers, just behavior. If you want to get any more technical, only Sutripta will understand and discuss, rest of us will back off.
Thrown into the den of warring lions! Methinks I'll run for cover.

Quote:
Originally Posted by SPIKE ARRESTOR View Post
Ok, I will first explain in simpler terms then complicate it with a free body diagram followed by resolving the forces about a point (considering the system to be in equilibrium).
........
Hence Proved.
Prateesh, as weight shifts from one wheel to another, I think suspension travel will have to be factored in. Because at its limits the car essentially becomes a tricycle.

I would prefer to do my initial thinking with vehicle stationary (no dynamic component) and think through its behavior as we jack up a wheel. Seen in this light, I think what others are trying to say is that in a car with good articulation as we keep on jacking up one wheel, the frame (chassis) will move less than in a car with less articulation. I think this point is more easily thought through.

Over to you. I'm retiring to lurking mode.

Regards
Sutripta
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Old 1st February 2011, 22:25   #74
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Default 4Wheels

Quote:
Originally Posted by SPIKE ARRESTOR View Post
Samurai, you are right, a complex equation need not be constantly linear or non linear, so is the torque and power curve which is derived from lots of variables which keep on changing.

Since the master artisan has already spoken, poor me will try and speak a few things, May I??

Ok, I will first explain in simpler terms then complicate it with a free body diagram followed by resolving the forces about a point (considering the system to be in equilibrium).

For a layman- There are four forces which play a role here:-

1. Weight of the vehicle
2. Force due to lateral acceleration (read Rolling in off-road parlance)
3. Height of Center of gravity (C.G.)
4. Wheel track

On a banked vehicle these forces resolve into various horizontal and vertical forces but basically the forces remain the same (only these 4). So if you change all these the amount of weight transfer will change; in other words the nature and type of suspension does not determine how much weight is getting transferred to the inner and outer wheels it is only these 4 and not the spring rates and roll stiffness.

For others (even Gurus can also read this):-

On a flat road the forces acting (laterally are) represented like this-
Attachment 493805

Unless there is a lateral acceleration (read Rolling in off-road parlance) it has only a static component of the total forces, once it starts tilting ( read Rolling in off-road parlance) there is an additional component of force called as dynamic component. The amount of weight on the wheels is dependent only on these two components namely Static and Dynamic. The representation is as shown below:-
Attachment 493806


This shows one wheel looses weight and another gains weight, OK Sam ??

Next consider a situation where the vehicle is banked / articulated (read Rolling in off-road parlance), here the force components remain the same but they get resolved in accordance to the roll angle (phi). See this pic:-

Attachment 493807

The resolved forces turn out like this:-
Attachment 493808


Now can someone tell me if there is any term which mentions about spring and suspension stiffness? NO! So what I had been harping continuously was correct, the graph is wrong. Since no terms related to suspension feature in these equations, there is no relation between Suspension characteristics and the amount of weight transfer when on road and off- road. Weight transfer-> CG Shifting

Hence Proved.

Lets take it one step further can anyone tell me when the vehicle will begin to roll over? (I am not trying to ridicule anyone, I just want people to know what the truth is, contrary to what is being told here)

PS- Arka, regarding vehicle toppling at the "Robinson Point" (pardon me Robi, I have to be specific), it had nothing to do with articulation. I was keeping quiet on this as it would hurt others sentiments, as I am being questioned, I have to answer this. It was purely driver error, I did not see it but I have Eye witness account on this. The eye witness is a very Senior, experienced and respected Jeeper in Indian offroading scene.
Hi Spike,

You very effectively explained your point.

Kindly apply this to RTI Ramp and explain this effect for all 4 wheels, 2 Axles and the Chassis.

In an OTR situation, the vehicle is not necessarily "Banked" perfectly to roll-over, hence the RTI Ramp was devised to checkout "Articulation"

What if one Axle is Banked Left and another Banked Right, what if the vehicle was climbing up or climbing down, along with the bank.

I don't have enough experience "within the realms of scientific engineering" to draw out such equations, and explain with reason or experience.

The original question was why was the Thar, lifting its wheel, I tried to explain it with RTI as reference.

Sharath further went to explain it in terms of Shifting of CG & Lifting a Wheel.

If you add further variables as
i) Effect of all 4 wheels
ii) Chassis/Body -- Torsional Rigidity
iii) Type of Suspension Front & Rear
iv) Vehicle Speed.

The RTI & Sharath's graph make sense, yes it we have not expressed it very eloquently, and you misinterpreted it as purely academic Wheel Lifting vs Shifting of CG.

Regards,

Arka

PS - All Roll-Over's are purely driver error, but to analyse, speed, camber of the steepest slope, additional weight in vehicle, type of suspension, helps us laymen.
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Old 1st February 2011, 23:10   #75
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Default Re: Articulating on Articulation

Reloading a different version of Samurai's graph. I think the graph would be true for Vehicle lift vis--vis the height of the ramp/obstacle based on the suspension characteristics. But it will not be true for shifting of the CG. The vehicle lift will not be linear to the obstacle height upto the point where the suspension is able to adjust itself. But once it reaches its limits, then the graph should be linear, as if there was no suspension at all. Does this make sense?

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Quote:
Originally Posted by ex670c View Post
Hi Spike & Pjbiju,

The Please explain why the Thar was lifting wheels, where other JEEPs had all 4 Wheels on the Ground.

Does the Thar CRDe have a better RTI than Thar MDI & NGCS MM550XD.

In a heavy articulation section, don't you think the Thar will be lifting it's body more since the IFS is Bolted to the Chassis, and in a Solid Axle setup the Body and Chassis ride above the suspension, which flexes, the axle, to track the undulations.

Regards,

Arka
From what you and Sharath are telling, I can only conclude that the Thar has less articulation compared to the other vehicles you observed. I think a vehicle with less articulation will tend to lift its wheels more. In doing so, it will futher shift the CG, because the more weight you have closer to the ground, the lesser will be the shift in the CG.

Last edited by pjbiju : 1st February 2011 at 23:23.
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