Steel Tube Bending: Gai Abraham's LEV Automotive Engineering Question

  • Thread starter Thread starter ga5aq
  • Start date Start date
  • Tags Tags
    Bending Steel
Click For Summary

Discussion Overview

The discussion revolves around the bending of steel tubes for automotive applications, specifically focusing on the interpretation of original length during the bending process and the implications for material properties, particularly for stainless steel ASTM 301. Participants explore various methods and considerations related to tube bending in the context of low emission vehicle (LEV) design.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Gai Abraham questions whether the original length of a bent steel tube should be considered as the midline or the inside radius during bending, given the material properties of stainless steel ASTM 301.
  • Some participants suggest that if the tube is supported on the inside during bending, the inside radius could be considered the original length, but this raises questions about practical implementation.
  • One participant proposes a method of filling the tube with sand to provide internal support during bending, which could help maintain the tube's shape.
  • Gai mentions modeling the bending radius in AutoCAD and notes that using the midline as the original length aligns better with elongation percentages, while also expressing concerns about cracking if the bending radius is too small.
  • Another participant recommends visiting the Pirate4X4 website for additional tubing fabrication hints, indicating that there are resources available for practical guidance.

Areas of Agreement / Disagreement

Participants express differing views on the definition of original length during bending, with no consensus reached on the best approach or method for supporting the tube during the bending process. The discussion remains unresolved regarding the implications of these definitions on the bending of steel tubes.

Contextual Notes

Participants acknowledge the limitations of their understanding of bending machine mechanics and the practical challenges of supporting the tube during the bending process. There are also concerns about the material properties and potential for cracking based on bending radius.

ga5aq
Messages
3
Reaction score
0
My name is Gai Abraham, an automotive engineer trying to build a little LEV (low emission vehicle)

I have contacted you previously and I wish to ask further help on the bending of steel tubes.

Namely I have designed a chassis from bent steel tube, the technical sheet on S.S. astm 301 allows, depending on the hardness of the tube, to have elongations ranging from 40% (for annealed) up to 9% (for full hard) from original length.

The issue I am trying to solve is whether the original length is the midline of the tube, giving during bending, compression on the inlay and tension on the outlay for final plastic bending

or the original length is the inside radius of the curved tube and gradually all the tube stands deformation up to a maximum value on the outer side?

I think that if the tube is held in position and supported on the inside while curving it, the original length is the inside radius since it was not able to compress.

thank you
Gai
ga5aq@yahoo.com
 
Engineering news on Phys.org
I got to ask: How would you support the inside of the tube? If you could do that, you are correct in saying the inner radius would be the length. But, I've never seen anything even close to that.
 
Uhm
that's the real question, I don't really know how the bending machine works, I guess that there is a concave roller on either side of the tube and the roller turns on a radious predefined supporting the inner tube while the outer roller goes on bending it on the outside.

what's your e-mail add?

Cheers
Gai
 
An old trick to consider, is to fill the tube with sand, pack it as tight as possible, plug both ends,( you might need to have a pair of plugs machined, kind of like thermos bottle stoppers) this will make the tube almost as solid as a rod. After bending the end plugs are removed and the sand will pour out.
 
Probably for your application, I'd suggest you go to the Pirate4X4 website and find tubing fabrication hints.
 
thank you all
as I will try to take this Lev to production I am hoping to use the Stainless steel ASTM 301 in its 1/2 or 3/4 hard modes.

the limit of bending of these two is bound by the percentage of longation so if I use a too small a radius I might crack it.

on the autocad program I have modeled the bending radius of 90 deg. and I have found that if I take the values of the inner radius and th outermost radius of the bent I am out of the elongation percentage stated but if I use the midline, then I pretty close.

as such I was wondering if the tube is being supported from the inside, then the midline stretches and the outer line stretches even more, on the other hand I might just as well take the midline as being stable i.e. original lebngth, and on either side I have got a compression and an extension.
but as I don't want to buy a stock load of steell tubes of one grade to then find out it doesn't cope with bending I thought to hear some views about it.

BTW I like it the PIRATE 4X4 stuff, Thanks TVP45