Fixed end hydrualic cylinder with a pulley on top

  • Thread starter Thread starter gjshafer
  • Start date Start date
  • Tags Tags
    Cylinder Pulley
Click For Summary

Discussion Overview

The discussion revolves around the mechanics of a hydraulic cylinder with a pulley system designed to double the lifting height of an object. Participants explore the relationship between the pulley diameter and the lifting height, focusing on the technical aspects of achieving a 2:1 lifting ratio.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • Glen describes a setup using a hydraulic cylinder with a pulley to lift an object from the ground to 48 inches, seeking to understand how to determine the appropriate pulley diameter.
  • One participant notes that similar arrangements have been used in hoists and hydraulic elevators, emphasizing the need for the pulley diameter to exceed the cylinder width and accommodate load factors.
  • Glen questions how the pulley diameter affects the lifting ratio, specifically asking for guidance on sizing the pulley to achieve a 2:1 height ratio.
  • Another participant asserts that the pulley diameter does not influence the lifting ratio, stating that it only needs to be large enough for clearance.
  • Glen expresses confusion about how the cylinder achieves a 2:1 lifting height if the pulley diameter is not a factor, seeking clarification for future applications.
  • A suggestion is made to look up pulleys in simple machines for further understanding.
  • A link to a diagram illustrating a 3:1 pulley system is provided, although its relevance to the current discussion is unclear.

Areas of Agreement / Disagreement

Participants exhibit disagreement regarding the role of pulley diameter in achieving the desired lifting height. Some assert that diameter is irrelevant to the lifting ratio, while others, including Glen, question this assertion based on practical experience.

Contextual Notes

There are unresolved assumptions regarding the mechanics of the pulley system and how the lifting height is achieved, particularly in relation to the design of the hydraulic cylinder and the pulley configuration.

gjshafer
Messages
4
Reaction score
0
I am using a hydraulic cylinder with a pulley on top. The bottom of the cylinder is fixed and the top has the pulley mounted on it free to rotate. I am trying to double the lifing height of the cylinder. The cylinder stroke is 24inches and I need to make if lift something from the ground up to 48inches. I am using a chain that one end is connected to the base of the cylinder, the chain is draped over the pulley and back down to the ground where it is attached to the object I am lifting up 48 inches. I am trying to figure out how to determine what diameter pulley to use to double the lifting height of the cylinder. Any help at all would be greatly appreciated.

Thanks,
Glen
 
Engineering news on Phys.org
Such an arrangement has been used in a number of hoist and jacks. I also think it has been used in some hydraulic elevators, but probably no longer.

The pulley needs to have a diameter greater than the width of the cylinder plus any chain guides, load rails, etc. Then the teeth need to be sized to carry the load and of course fit a chain that can handle the load. Typically speed is not an issue. Non-axial loads, due to asymmetries in the load support and guidance also would play a factor, although probably more in the pulley's attachment and the cylinder's guide bushing.
 
Ok, thanks for the information, but doesn't the pulley diameter have an effect on the ratio in which it doubles the cylinder? I guess that's what I'm truly asking is how can I size the pulley? Like you said it obviously has to be bigger than the width of the cylinder but how can I find the diamter to achieve the ratio lifting height of 2:1?
 
It only needs to be as large as required for clearance. Diameter means nothing as far as ratio goes.
 
Ok, so what is giving the cylinder a 2:1 lifting height? We already use this application else where so I know it works. The initial cylinder stroke is 24 inches and the object that is lifted, is lifted from the ground to the its stopping point of 48 inches from the ground. How is the cylinder doubling its lifting height if the pulley diameter has nothing to do with it? The engineer that designed this application is no longer here so I am just trying to understand how it works for future applications. Any help on this is greatly appreciated
 
Look up pulleys in simple machines.
 

Similar threads

Hydraulic Cylinder Held In Place Until Needed
  • · Replies 19 ·
Replies
19
Views
2K
Air Cylinder connected to a Lever that drives a Pulley for Applying Belt Tension
  • · Replies 4 ·
Replies
4
Views
3K
How Is Cylinder Force Calculated to Rotate a Beam with a Horizontal Load?
  • · Replies 4 ·
Replies
4
Views
2K
Calculating Force Needed to Raise Steel Tower
  • · Replies 5 ·
Replies
5
Views
3K
Time to empty gas cylinder (problem worked, but would like feedback)
  • · Replies 7 ·
Replies
7
Views
4K
Hydraulic Car Ramps...... need to make them go up and down
  • · Replies 15 ·
Replies
15
Views
4K
Can a Pulley System Replace Hydraulic Rams for Mechanical Lifting Without Power?
  • · Replies 35 ·
2
Replies
35
Views
6K
How Can I Connect Two Cylinders Coaxially to Transfer Pulling Force?
  • · Replies 2 ·
Replies
2
Views
2K
Pneumatic safety valve question
  • · Replies 4 ·
Replies
4
Views
2K
Calculating pump to cylinder pressure ratios
  • · Replies 1 ·
Replies
1
Views
2K