Beer Can

[Jason Musgrave]

Somebody 'splain the beer can effect to me (I don't mean what happens on Friday nights). Is it the ratio of diameter to wall thickness that causes it to crumple?

Is a 35mm DT with .65/.45/.65 walls less likely to beer can than a 38mm DT with the same walls?

[Don Walker]

Hope this can help....

DW

[marten]

Is a 35mm DT with .65/.45/.65 walls less likely to beer can than a 38mm DT with the same walls?

Yes.

Engineering rule of thumb is do not go over 50:1, but with high strength bicycle tubing 80:1 or so is possible. Too thin and tube looses it's round shape if you load it in compression, and then the tube buckles

[dbohemian]

Actually there are examples in the bike world of ratios over 100 to 1.

Marten is correct as to the action but this is one of those area's where I think traditional engineering is falling a bit short for what we do.

One thing to consider is that the diameter of the tube is important in also reducing this tendency. A 1'' tube for instance drawn very thin has a higher probability of failure do to localized collapse than a larger diameter tube of the same thickness because there is much more stress per unit area on it's surfaces. A 1.5'' inch tube carrying the same stresses will have that stress distributed across a larger surface area and therefore will have a lower stress per sq/cm than the smaller diameter tube.

This is one reason why you can see a 2'' .8.5.8 tube work on a tandem even though it's ratio is 101 to 1 in the center.