Analysis of Wall Crane: Force & Moment at Pins A & D

In summary, the wall crane in Fig. 3 supports a load of 800 N and the goal is to determine the horizontal and vertical components of reaction at the pins A and D, as well as the force in the cable at the winch W. Using Newton's Laws of Motion, Moment, and Equilibrium of Forces, the attempt at a solution involved drawing a free body diagram at B and calculating the tension in cable WB to be 400N. However, when attempting to find TBD by taking the moment at A, the solution turned out to be 2752N. This discrepancy may have been caused by a mistake in the substitution of the value of TWB. An alternative suggestion was made to find TBD by taking moments at
  • #1
Harmony
203
0

Homework Statement


The wall crane in Fig. 3 supports a load of 800 N. Determine the horizontal and vertical
components of reaction at the pins A and D. Also, what is the force in the cable at the winch
W?
[URL=http://imageshack.us][PLAIN]http://img182.imageshack.us/img182/992/tutorialse0.jpg[/URL] http://g.imageshack.us/g.php?h=182&i=tutorialse0.jpg [Broken][/PLAIN]


Homework Equations


Newton's Laws of Motion, Moment, Equilibrium of Forces


The Attempt at a Solution


First I draw a free body diagram at B. The vertical forces involved are the y component of the tension in rod BD and the y component of the tension of cable WB.

Since the tension of a massless cable is the same throughout the string, the tension of the cable is 400N. Substituting the value of TWB to the above equation, I get TBD=490N.

However, a problem occurs when I attempt to find TBD by taking the moment at A. The solution for TBD turns out to be 2752N.

What cause the difference in the answer?
 
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  • #2
I think it will be easier for us to see where you went wrong if you would show some work with regard to the step on substituting the value of Twb.

My suggestion to get Tbd, now that you have the tension in the rope right is to take the moments at A. The sum of moments must be zero. You have a 800N weight acting at 2 meters CW, and Tbw acting at 1 meter at a 60 degree angle CW. The counter moment CCW then must be Dx.
 
  • #3


As a scientist, it is important to accurately analyze and interpret data. In this case, there seems to be a discrepancy in the calculated value for TBD. It is possible that there may be an error in the equations used or in the assumptions made. It is important to carefully review the calculations and consider all possible factors that may affect the results. Additionally, it may be helpful to double check the given values and ensure they are accurate. Further investigation and analysis may be necessary to determine the cause of the difference in the calculated value for TBD.
 

1. What is the purpose of analyzing the force and moment at pins A and D in a wall crane?

The purpose of this analysis is to determine the amount of force and moment acting on pins A and D, which are crucial components of a wall crane. This information is essential for designing and constructing a safe and efficient crane.

2. What factors affect the force and moment at pins A and D in a wall crane?

The force and moment at pins A and D are affected by various factors such as the weight of the load being lifted, the distance between the pins, the angle of the crane's boom, and the wind speed and direction.

3. How is the force and moment at pins A and D calculated?

The force at pins A and D can be calculated by summing up the individual forces acting on the pins, such as the weight of the load, the tension in the cable, and the reaction forces from the ground. The moment at these pins can be calculated by multiplying the force by the distance from the pin.

4. Why is it important to consider the force and moment at pins A and D in a wall crane?

The force and moment at pins A and D are critical in ensuring the stability and safety of the crane. If these forces are too high, it can cause the crane to collapse or tip over, leading to potential injuries and damages.

5. How can the force and moment at pins A and D be reduced?

The force and moment at pins A and D can be reduced by adjusting the crane's boom angle, using counterweights, and ensuring that the load is evenly distributed. Additionally, regular maintenance and inspections can help identify and address any potential issues that may increase these forces.

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