Help me understand cable housing

[Kbrook]

I don't get it at all, I've searched the Internet including Sheldon Browns explanation. I can't get my head around why you need housing, I know you do and that brakes and gears don't work without housing but why?
The cable moves inside the housing its not connected to the housing so why when I pull my brake lever( or gear lever) is that not enough to move the brakes or derailleur. By pressing the lever I am pulling the cable which in my mind should be enough to apply the brakes, so what does the housing do.
I know I am being stupid but its doing my head in, can't understand it. Help please.

 

[Sharky]

If the brake and lever was in an absolute straight line, when you pull the brake lever, it would shorten the cable and the brake would come on.

But if there are any curves that the cable takes, the cable when pulled would just try and eliminate the slack and would not apply the brake. Imagine if you did have a cable in a straight line from you handle bar to the front brake. When you pull the brake, it would try and turn the handle bars. Thus the housing effectively makes it a fixed distance between the lever and the brake, so when pulled, the only thing that can move is the brake caliper.

And if you don't believe me, you can pull the other one.

Cheers keith

 

[Kbrook]

Just trying to get my head round that Keith, god I'm thick sometimes.

 

[raindog]

Best way to understand it is to set one of your brakes up without an outer cable, then apply the brake and observe what happens.

this mightl help http://en.wikipedia.org/wiki/Bowden_cable

 

[Old Plodder]

The brake caliper acts like scissors to operate the brake, you have to have something to act against the force being applied by the brake lever, this is where the outer stops one side of your caliper from moving so that the cable pulls the other side of the caliper in & onto your rim.

 

[Spinney]

The cable housing is acting a bit like a pulley.
This pulley is only changing the direction of the force.

Your cable housings are doing a similar job.