increasing the bending stiffness of steel pipe or tube?

For info.

Whilst I am sure that users of sophisticated CAD software have such tools readily to hand ... I was very pleased to find this plug-in for SketchUp. ... I use v8, and the plug-in appears [within the idiosyncrasies of SketchUp] to work perfectly.

MichaelG.

The man doth protest too much, methinks

Neil

Got me on this one, but a good exercise . I was looking forward to drawing a Mohr's circle but it didn't get that far!

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Given this Shakespearean accusation from our Moderator, and no comment from anyone else; I wasn't going to bother posting ... but it may useful to someone, sometime:

According to the SketchUp plug-in [mentioned above]: the welded cluster of three tubes [*] is approximately 8.4 times stiffer than the single tube.

MichaelG.

[*] 35mm O.D. x 5mm Wall

Hi Michael, I had also thought of using three tubes as per your drawing, although my first thought was to use seven tubes together which would be more circular but of course would be much more bulky and be very difficult to weld them together with total success.

Regards Nick.

On the subject of welding [of which I know very little] ... I think it would be quite adequate to 'stitch' the joints instead of using continuous welds.

Note: The main stiffening purpose of these welds is to prevent the tubes sliding along each other.

MichaelG.

> According to the SketchUp plug-in [mentioned above]: the welded cluster of three tubes [*] is approximately 8.4 times stiffer than the single tube.

Impressive, clearly a good way to go if you only have small tube, and stronger and more compact than a tube of twice the diameter.

A tube three times the diameter (i.e. with the same amount of tube in it as three smaller ones) would be 27 times as stiff.

I would be keen to see Ady make up a triple tube accurately enough for a yoke to move up and down it smoothly, though

Neil

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It obviously depends upon the quality of the original tube [tolerance on OD and straightness] but the beauty of this arrangement is that it is 'self-jigging' [for want of a better term] ... Try putting a tie-wrap at each end of a cluster of three similar tubes and you will see what I mean.

Again though; I must mention that Ady's original question was conceptual, not specific to the drill pillar.

MichaelG.

Edited By Michael Gilligan on 14/06/2015 17:35:46

I would be keen to see Ady make up a triple tube accurately enough for a yoke to move up and down it smoothly, though

Might be one of my have-a-look-at-that-solution-later jobs...

Thanks for all the input gents