Lift capacity of a spring loaded arm

In summary, the problem is that the lift capacity is not as high as expected. The spring has the following parameters: Spring rate: 32 N/mm deflection: 58mm (for rotation of 40 deg above n below horizontal) Spring length: 450mm Spring set length: 363mm(set for 40deg above horizontal) 2790N for the spring set length and 4670N generated for 58mm deflection.
  • #1
MayZ91
23
0
Hello all,

Yet another problem on engineering mechanics. This time I have a spring loaded; counterpoised arm:
Something like this- http://www.akwmedical.com/files/imagecache/cart/SK2323_1.jpg
http://t3.gstatic.com/images?q=tbn:ANd9GcTUCvnSKhKEbs4uNiOLg2TGU3p0quUrSp8Uh4QXqt5m4eIEf6_ISA
What it consists of is a compression spring which compresses on articulation to keep the arm in place. Just like the old table lamps.
The set up goes like this:

upload_2015-1-16_11-2-47.png


AB is a link which is connected to BD(spindle). The spindle BD is held concentric with the arm EF, which is a circular tube. The spindle BD has a sliding contact with arm EF. Similarly; link CD is connected to the same spindle at D. There is another sliding contact between the spindle BD and arm EF at D. The pin joints C and F are on a plate which carries a load W. Due to the sliding joints, when the arm EF rotates about E, the weight W is always perpendicular to the ground(these links behave like a parallelogram). To counterbalance the system, a spring is introduced between a stopper and joint D. The stopper is connected to the arm EF and welded. This spring is concentric with the spindle BD.

BELOW images(with spring) can be assumed for understanding the articulations only, it does not depict the actual scenario.
upload_2015-1-16_14-28-21.png


upload_2015-1-16_14-29-34.png


The problem is to identify the lift capacity for the system. The load is attached to point F (in the first figure) (all references are for figure 1)
The spring has the following parameters: Spring rate: 32 N/mm deflection: 58mm (for rotation of 40 deg above n below horizontal) Spring length: 450mm Spring set length: 363mm(set for 40deg above horizontal) 2790N for the spring set length and 4670N generated for 58mm deflection.
Not to worry about the wire dia and OD of the spring just yet.


Attached is the excel sheet with attempt to solution.
I am getting 800+N as the lift capacity. However, its not as high 350N. Need to know where I am going wrong.

Kindly help.
Thank you.
 
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  • #2
I'm not seeing the spreadsheet...
 
  • #3
Extremely sorry for missing the spreadsheet.

What I have done is, i have built the geometric relations between the angles made and spring deflection. And hence calculated the force on the link AE. Resolved for its components and using moment equation about the stopper, have found the link force CD. By calculating the moment arm distance, have found the lift capacity.
 

Attachments

  • Calculations.xlsx
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  • #4
Hello all,

I am stuck in this problem, kindly help me resolve.

Thank you.
 
  • #5
I have updated my calculations, also have put the equations: (sorry for a change in notations)

upload_2015-1-23_18-19-4.png
 

Attachments

  • Calculations_updated.xlsx
    773.1 KB · Views: 240
  • #6
Please help!
 

FAQ: Lift capacity of a spring loaded arm

What is the lift capacity of a spring loaded arm?

The lift capacity of a spring loaded arm refers to the maximum weight or load that the arm can lift without breaking or failing. This capacity is determined by the strength of the spring and the materials used in the arm's construction.

How is the lift capacity of a spring loaded arm calculated?

The lift capacity of a spring loaded arm is typically calculated by determining the maximum force the spring can exert and factoring in the arm's mechanical advantage. This can be done through mathematical equations or through physical testing.

What factors can affect the lift capacity of a spring loaded arm?

The lift capacity of a spring loaded arm can be affected by various factors, including the strength and quality of the spring, the materials used in the arm's construction, and the design and mechanism of the arm. Environmental factors such as temperature and humidity can also impact the arm's performance.

Can the lift capacity of a spring loaded arm be increased?

Yes, the lift capacity of a spring loaded arm can be increased by using a stronger and more durable spring, as well as by using high-quality and sturdy materials in the arm's construction. Additionally, optimizing the design and mechanism of the arm can also improve its lift capacity.

What are some common applications of spring loaded arms with high lift capacity?

Spring loaded arms with high lift capacity are commonly used in various industries, such as automotive, aerospace, and manufacturing. They are often used in lifting and moving heavy objects, as well as in machinery and equipment that require precise and controlled movements.

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