Weight distribution, multiple points of contact

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Calculating normal forces for a vehicle with three contact points can be challenging due to the lack of sufficient equations. When balancing forces and torques, having three points typically requires an additional equation to solve for the unknowns. If the contact points are collinear, an equation regarding the rigidity of the body may be necessary. However, if the points are not in a straight line, the existing equations might suffice unless there are four contact points. Understanding the geometry and rigidity of the vehicle is crucial for accurate calculations.
Gunnar Larsso
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Hello everyone!

I am struggling with calculating the normal forces for a vehicle that is in contact with the ground at three places (scoop, front wheels, rare wheels).

To calculate the normal forces with two locations (such as front and rare wheel) it is just to balance the forces as well as the torque giving you two equations and two unknowns.

However, with three locations I am one equation short.. Having tried to calculate the torque around all locations I have realized that doing so provide no extra information (i.e. just get back the same equation for angular momentum independent of location or 0=0 after some manipulation). I have the feeling that I have missed something basic, fundamental and simple, but just can't figure out what.. How do I find that extra equation needed to solve the problem? Any help would be deeply appreciated!

Regards,
Gunnar
 
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Welcome to PF!

Hello Gunnar! Welcome to PF! :smile:

If the three contact points are in a straight line, then yes you need another equation (probably one describing how much the "rigid" body bends).

If they're not in a line, then no, but you would need another equation for four points. :wink:
 

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