Which is stronger....hollow or solid tube??
Discussion
OK,
You have a length of 3 metre cylindrical tubing, similar to a scaffolding pole....
Which would bend easier, if an extremely heavy weight was applied to one end, the hollow pipe, or a solid steel bar..
A guy I know, who has run his own steelworks/sheet metal company for thirty years said the hollow pipe would resist bending the most, and he should know what he is talking about......
What do the PH massive think??...
You have a length of 3 metre cylindrical tubing, similar to a scaffolding pole....
Which would bend easier, if an extremely heavy weight was applied to one end, the hollow pipe, or a solid steel bar..
A guy I know, who has run his own steelworks/sheet metal company for thirty years said the hollow pipe would resist bending the most, and he should know what he is talking about......
What do the PH massive think??...
Wacky Racer said:
Obviously if the load was applied from all sides equally, ie: compressed, the solid bar would be stronger, but I'm meaning if a heavy weight was hung from one end, with the bar locked in a horizontal position......
Are the bars the same in weight or the same in outer diameter?Wacky Racer said:
Obviously if the load was applied from all sides equally, ie: compressed, the solid bar would be stronger, but I'm meaning if a heavy weight was hung from one end, with the bar locked in a horizontal position......
If you were to use the same amount of material the hollow tube would be stronger - obviously if you were using the same amount of material the hollow tube would have a larger diameter, and I think it's easy to imagine how that would affect its strength.When you started getting more alloy framed bikes you may have noticed that they tend to have larger diameter tubing than most cooking steel frames*. This is because alloy is weaker so to get the strength/stiffness they have to increase the diameter (perhaps without increasing material amount). The only downside to this I can think of is that if you hit a tree side on you're more likely to crush and fold the thin walled alloy tube.
- ETA - This is why in mountain biking phrases such as 'oversized tubing' started popping up... They used it on the Raleigh Max, only it was made of 'oversized' steal and weighed a tonne.
Edited by rabw on Wednesday 11th February 13:29
The solid bar is stronger than a tube of equal diameter, but it's a lot heavier too. If its own weight is a significant factor then the tube may have a higher load carrying capacity.
For example if your goal was just to have an unsupported beam sticking out as far as possible, the one that reached furthest before it failed would be a tube because it has better strength-to-weight than a solid bar.
For example if your goal was just to have an unsupported beam sticking out as far as possible, the one that reached furthest before it failed would be a tube because it has better strength-to-weight than a solid bar.
Hollow tube is stronger for equal weight where its larger diameter and different mass distribution (away from the centreline) counts e.g. in torque around its longitudinal axis, like in a torsion bar. The advantage is you can make a hollow bar give the same strength resistance as a solid bar while weighing much less.
I'm not sure if they have an advantage in tension, but I expect hollow ones are also harder to compress, again along the longitudinal axis.
As for hanging a weight from one end, I assume they'd bend less if the outer diameter of the hollow one was greater, but possibly would be weaker if the two bars were the same outer diameter?
I'm not sure if they have an advantage in tension, but I expect hollow ones are also harder to compress, again along the longitudinal axis.
As for hanging a weight from one end, I assume they'd bend less if the outer diameter of the hollow one was greater, but possibly would be weaker if the two bars were the same outer diameter?
monthefish said:
Wacky Racer said:
Obviously if the load was applied from all sides equally, ie: compressed, the solid bar would be stronger, but I'm meaning if a heavy weight was hung from one end, with the bar locked in a horizontal position......
Are the bars the same in weight or the same in outer diameter?
Just an additional point, if you have a tube and want to decrease the deflection so many people go for increasing the wall thickness. This is not so productive because the increase in rigidity is largely offset by the increase in weight.
In this case you should go for an increase in outer diameter retaining the wall thickness, or maybe slightly increasing, it all gets down to the calculation.
Just to be awkward and slightly nerdy, we should have been asking what was the service temperature. It all gets more tricky depending on the hot strength especially whether you are below or above the crossover temperature, ie under creep conditions.
scaffolding poles are somewhere below the Yugo of the tubing world btw.
In this case you should go for an increase in outer diameter retaining the wall thickness, or maybe slightly increasing, it all gets down to the calculation.
Just to be awkward and slightly nerdy, we should have been asking what was the service temperature. It all gets more tricky depending on the hot strength especially whether you are below or above the crossover temperature, ie under creep conditions.
scaffolding poles are somewhere below the Yugo of the tubing world btw.
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