Dimensioning of hollow square and circular rod

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Discussion Overview

The discussion centers on determining the dimensions for hollow square and circular rods when given the material and maximum load, specifically in the context of a telescopic rod supporting a boat. The scope includes considerations of load application, material properties, and structural integrity.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant asks how to determine dimensions for hollow rods given material and load.
  • Another participant notes that the load application method (compression, tension, torque, or sideways deflection) affects the design.
  • A participant specifies that the load is axial compression and bending, describing the configuration of a telescopic rod supporting a boat.
  • JohnnyR provides potential cross-sectional dimensions for the circular rod based on the specified length and load conditions, listing several options for outside diameter and wall thickness.

Areas of Agreement / Disagreement

Participants have not reached a consensus on the exact dimensions needed, as different options are presented and the discussion remains open to further input regarding the design considerations.

Contextual Notes

The discussion does not clarify the specific assumptions regarding load distribution or the exact nature of the bending moments involved, which may influence the final design choices.

JohnnyR
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Hi

Can someone tell me how to determine dimensions for a square hollow rod and circular hollow rod when the material and maximum load is known?
 
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This will depend on the way the load is applied to the hollow member.
Is it axial compression or tension, torque or a sideways deflection ?
There is also a trade-off between outer dimension and wall thickness.
 
The applied load is compression and there is also bending.
It´s a telescopic rod with the circular rod inside the square rod and it´s standing vertically with an angle. The rod has to support a boat standing in a boat rack so it has to support the weight of the boat and the force from wind gust. The material is set to be S235JR Low Carbon Steel.
I hope you can help. Thanks.

http://imagizer.imageshack.us/v2/1024x768q90/833/drpm.jpg
 
Last edited by a moderator:
JohnnyR: If the length of your telescopic rod assembly is 2,26 m, and if your member forces in post 3 are correct, then it currently appears the round tube would need to have cross-sectional dimensions (outside diameter by wall thickness) as listed in any of the following options.

(1) 216 x 5 mm
(2) 197 x 6
(3) 182 x 7
(4) 171 x 8
(5) 155 x 10​
 
Last edited:

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