Piston problem -- Method to increase the force against a spring

In summary, the conversation discusses designing a device to close sun-blocking window-shutters using a liquid-vapor mixture and a piston that moves 6 inches. The suggested approach is to use R-134a as the working fluid and vary the temperature from 70 degrees F to 100 degrees F. The conversation also explores the mechanical details and dimensions of the piston chamber needed to achieve this task, as well as determining the maximum force and pressure required.
  • #1
Hsol
3
0
Hi people, I need help to this problemSomeone has suggested that the device shown in the figure below be used to improve the maximum force F against the spring, which has a spring constant of k. This is accomplished by changing the temperature of the liquid-vapor mixture in the container. You are to design such a device to close sun-blocking window-shutters that require a maximum force of 0.5 lbf. The piston must move 6 inches to close those shutters completely. You elect to use R-134a as the working fluid and arrange the liquid-vapor mixture container such that he temperature changes from 70 degrees F when shaded from the sun to 100 degrees F when exposed to the full sun. Select the sizes of the various components in this system to do this task. Also select the necessary spring constant and the amount of R-134a to be used.
 
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  • #2
No figure attached to post.
 
  • #3
Someone has suggested that the device shown in the figure below
... need the figure.

Just reading it over suggests several approaches - how have you been thinking about this so far?
 
  • #4
ImageUploadedByPhysics Forums1385982749.769889.jpg
 
  • #5
Good - so, do you have a list of the properties of the liquid in question?
Have you translated the design parameters into terms appropriate to the mechanism?
 
  • #6
I assume that when the system is 100 degrees F is not applying any bone strength the system is in equilibrium. I was able to determine that the saturation pressure of R-134a table are as follows:

100 degrees F the saturation pressure is 138.93 psia.
70 degrees F the saturation pressure is 85,858 psia.

That's what I've been able to determine so far.
 
  • #7
OK - so how does this work: you warm the gas reservoir (the small container), what happens?
This is the basics of the operation that you have to work with. Make sure you understand it.

Do you have no idea how the piston should move to open and close the shutters?

Never mind about the gas part just yet - just get the mechanical details down.
How would you rig a piston so that it moves the shutters?

Once you know that, you can get an idea of the dimensions of the piston chamber.
What shape should it be? How long should it be?
What determines the cross-section area?

What is the maximum force needed?
Can you turn that into a pressure?

Start to see how to proceed?
 
  • #8
Is there any solution to this problem?
 
  • #9
barney said:
Is there any solution to this problem?
No. Do you want to try it?
 
  • Love
Likes Tom.G

1. How does a piston increase the force against a spring?

A piston works by using a confined space to compress a fluid or gas, which then exerts pressure onto the spring. This pressure increases the force against the spring, making it more difficult to compress or extend.

2. Is there a specific method to increase the force against a spring using a piston?

Yes, there are several methods that can be used to increase the force against a spring using a piston. These include increasing the size or pressure of the fluid or gas within the piston, using multiple pistons in a series, or increasing the weight or force applied to the piston.

3. Can a piston be used to decrease the force against a spring?

Yes, a piston can also be used to decrease the force against a spring. This can be achieved by creating a vacuum or decreasing the pressure within the piston, which will result in less force being exerted on the spring.

4. What are some common applications of using a piston to increase force against a spring?

Pistons are commonly used in many mechanical systems, such as car engines, pumps, and hydraulic or pneumatic systems. They are also used in various industrial applications, such as presses and cranes, to increase the force against a spring for lifting or compressing heavy objects.

5. Are there any limitations to using a piston to increase the force against a spring?

While pistons are effective in increasing force against a spring, there are some limitations to consider. These include the maximum pressure and weight capacity of the piston, as well as the potential for leaks or malfunctions in the system. Additionally, the size and design of the piston must be carefully chosen to ensure it is suitable for the specific application.

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