Balancing a spring and arm at 45 degrees

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Discussion Overview

The discussion revolves around determining the specifications of a spring that can balance a 5m arm at a 45-degree angle, considering the arm as a uniformly distributed load (UDL) of 1.6 kg/m. Participants explore the mechanics involved in the system, including the calculation of moments and the relationship between the arm's position and the spring's tension.

Discussion Character

  • Technical explanation, Mathematical reasoning, Debate/contested

Main Points Raised

  • One participant calculates the total weight of the arm as 8 kN and the moment acting at 45 degrees as 14160 Nm, based on the arm's length and load distribution.
  • Another participant requests clarification on the connection points of the spring, suggesting that a diagram may be helpful for understanding the setup.
  • A later reply proposes that the spring must produce a torque of 138.6 Nm about the pivot, using a different approach to the calculations.
  • There is a note that participants are encouraged to attempt solutions independently before seeking help.

Areas of Agreement / Disagreement

Participants have not reached a consensus on the approach to finding the spring specifications, and multiple viewpoints on the calculations and setup remain present.

Contextual Notes

Some calculations depend on assumptions about the spring's connection points and the geometry of the system, which are not fully detailed in the discussion.

Ziv7
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I need to find what spring will balance an arm at 45 degrees
the arm is 5m and can be considered as a UDL of 1.6kg/m
the situation is that the arm starts upwards at 90 degrees and as it goes down it puts tension on the extension spring


5*1.6 = 8kN
acting 2.5m along the beam
which is 1.77m in direction x (horizontal)
8000*1.77 = 14160Nm (the moment acting at 45degrees)

how do I find the details on the spring? (diameter, length etc)
Maybe I'm approaching it wrong, any advice would be appreciated :)
 
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What two points is the spring connected between ? Diagram might help.
 
Here is what i mean
 

Attachments

Ok. I reckon the spring needs to produce a torque about the pivot of

= 8 * 9.8 * 2.5 * cos(45)
= 138.6 NM

PS: Normally we like you to have a go at the solution first.
 
Last edited:

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