Curved Top tubes

[BrumJim]

I had always thought that the intention behind bending the top tube was to make the connections at either end of the tube closer to 90 degrees, which would reduce the propensity of the tubes to tear apart at the top when the bike is compressed front to back - the crudest example I can think of would be a rear end impact. The Spesh top tube to head tube connection is broad, and, I would imagine, very stiff and strong. I don't particularly care to think about this, but it might be better able to resist the tension force that gave me a small crack in the lug of my conventionally framed bike.

My guess would be that on a welded aluminium bike the major design consideration at the joins is fatigue adjacent to the weld, rather than maximum load seen in an accident. Therefore design in this area would reduce the stress at the joint by making it larger in the plane of most stress, improving fatigue.

 

[gaz]

Why are dam walls curved?

So the pressure of the water that is building up behind it actually makes it stronger.

Obviously that is your classical dam shape, some dams are not curved

 

[nmcgann]

For some reason I like this one:

head-on crash into a lamp post.....

 

[slowmotion]

Why are dam walls curved?

They bulge towards the contained water because it means that the curved dam wall is in compression
rather than tension. Tension means that you have to stuff in a whole heap of reinforcing steel. Expensive. Look at an arch in virtually any church built before 1850 and they just rely on the "stuff" taking compression forces.

Sorry, that wasn't very well explained.

 

[slowmotion]

A dam.

[media]
]View: http://www.youtube.com/watch?v=Qdk3b7sHdPA[/media]

 

[rowan 46]

As far as I can see they are an abomination and should be banned. Look what they lead to. By all accounts the ride on this is very hard and as you can see the top tube is very curved.