As I wrote, it doesn't really matter. As long as you apply the chosen directions consistently in the equations it will come out fine. Remember that there will be situations where it is not obvious which way the force will act, so it's rather important that it is not necessary to guess it correctly. (An exception to this is friction. You may sometimes need to consider two possibilities separately.)cracktheegg said:haruspex, can you tell me which are the force going the opposite way? I need to learn from my mistake. so please guide me thanks
Where should the cg be?haruspex said:As I wrote, it doesn't really matter. As long as you apply the chosen directions consistently in the equations it will come out fine. Remember that there will be situations where it is not obvious which way the force will act, so it's rather important that it is not necessary to guess it correctly. (An exception to this is friction. You may sometimes need to consider two possibilities separately.)
In the diagram you posted, it's not always clear how a force is being defined. E.g. consider R2y. Is that a vertical force exerted by the girder on the base, or an (equal and opposite) force exerted by the base on the girder? Whichever it is, I assume R3y is defined similarly. Now compare R2y and R3y. You show both pointing down. They must be in fact be in opposite directions to counter the moment from the load.
cracktheegg said:Where should the cg be?
haruspex said:CG of what? Your W1, W2, W3 and W4 look right.
There are forces from the ground surface on both the front and rear sets of wheels. One has to be certain that the vertical force from the ground on the rear wheels is upward, or else the rear wheels would lose contact with the ground and the crane would become unstable and start to tip over.cracktheegg said:Okay Ty, now I just worry about wether should I include the wheel. Because my classmate said the wheel should be in contact with ground, there are no outrigger or hydraulic, it is just stabilizer
A free body diagram is a visual representation of the forces acting on an object. It shows all the forces acting on the object, such as gravity, normal force, friction, and applied forces.
It is important to check the free body diagram for a mobile crane to ensure that all the forces are properly balanced and distributed, and to identify any potential issues or safety concerns.
To check a free body diagram for a mobile crane, you need to first identify all the forces acting on the crane, including its weight, the weight of the load, and any external forces. Then, you need to make sure that these forces are balanced and in the correct direction.
Some common mistakes to look out for when checking a free body diagram for a mobile crane include incorrect or missing forces, incorrect direction of forces, and unbalanced forces. It is also important to make sure that all the forces are drawn to scale.
Yes, there are several online resources and software programs that can help you check your free body diagram for a mobile crane. These tools can help you visualize the forces and ensure that they are balanced and accurate.