Designing a Trailer: Determining Steel Square Tube Size

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Discussion Overview

The discussion revolves around the design of a trailer, specifically focusing on determining the appropriate size of steel square tubing to support a load of 350lbs with a safety factor of 3. Participants explore various aspects of load distribution, shear stress, and structural integrity, with an emphasis on the materials and calculations involved in the design process.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant seeks advice on formulas or methods to determine the size of steel square tubing required for a trailer that must support a total load of 1050lbs.
  • Another participant inquires about how to determine the shear stress on square tubing made from ASTM A500 Grade B steel.
  • A suggestion is made that more specific geometry details, such as a diagram, would help in providing useful feedback.
  • There is a request for formulas related to shear stress given the yield point of the material.
  • A participant questions why the load is supported by only two points instead of being distributed across the trailer's frame.
  • One participant speculates that the design might be for a jet ski, noting that most weight would be on the two keel supports, with side supports likely bearing little load.
  • Another participant suggests that if the project is personal, it might be wise to over-design the trailer, while for academic purposes, they recommend researching "bending and shear in beams" and "shear at welded connections."
  • A participant lists several questions regarding specific measurements related to the trailer's structure to better understand the design requirements.

Areas of Agreement / Disagreement

Participants express various viewpoints on the design considerations, with no consensus reached on the best approach or specific calculations needed. The discussion includes both technical inquiries and speculative comments, indicating multiple competing views on the design process.

Contextual Notes

Limitations include a lack of specific geometric details and assumptions about load distribution, which may affect the calculations and recommendations provided.

sgmech1
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I am working on designing a trailer that will hold a load of 350lbs on 2 centered posts. It needs to have a safety factor of 3, so 1050lbs plus trailer weight. I am trying to determine the size of Steel square tube I must use. Any advice on formulas or methods of determining this? I would greatly appreciate it.

Thanks
 
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How would I determine the shear stress on sqaure tubing if I am using ASTM A500 Grade B steel
 
Without some better specifics for your geometry (like a picture) it's hard to give you any useful feedback. Remember: a picture is worth 1000 words.
 
What formulas are there for shear if I have a yield point of the material?

appreciate the help
 

Attachments

Why is load of the trailer supported by just those two points, instead of distributed across the trailer's frame?
 
I'd imagine that it's for something like a jet ski. Most of the weight will be directed on the two keel supports. There will be side supports to keep it straight probably, but they won't bear much load.

Is this for a personal or academic project? If it's personal, then just over design it. If it's for school or something, well, just look up "bending and shear in beams", "shear at welded connections"
 
sgmech1: (1) What is the distance between the centerlines of the tires? (2) What is the distance from the back tube centerline to the trailer hitch ball? (3) What is the distance from the back tube centerline to the front load point shown on your diagram? (4) What is the distance from the back tube centerline forward to the apex of the diagonal tubes?
 
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