In this case, we have a bicycle which has removed the rear brake from its traditional place to underneath the bottom bracket. Gets it out of the air flow alright!
In the image here you see a cover which directs whatever air is flowing around down here by the brake mechanism cleanly. (Never mind that whirling crank set and that spinning rear wheel!)
|Kinda like how Charlie would have done it...|
Here we have a view with the cover off. Doesn't look like a typical road brake, does it? That's because it has more in common with a mountain bike brake from about 30 years ago than it does any road brake we know from today. And that mountain bike brake is a take off from a design used early in the 20th Century.
The two pivots are easy to find here. If you follow up from there, each brake arm cants inward to the center line of the bike until the arms terminate where you see the two small circular elements at the ends of each arm. These are pins that ride the edges of the triangular shaped "cam" plate you see which has the brake cable emanating from its top, and a bolt near its base above the spring. The bolt anchors the brake cable.
When the brake is activated, the cam plate moves upward, (as we look at the view here), and forces the two arms outward along the cam's profile, which the two pins ride on that are anchored in the ends of the brake arms. The arms pivot, in turn, and like a see-saw, they push the brake pads into the rim as the arms pivot on those silver colored bushings. When the brake lever is released, the spring attaching both arms above the tire pulls the tops of the arms back in, and the brake comes to its resting state as seen here.
It is also notable here that you can see the front derailleur cable on the right, and the rear derailleur cable on the left on either side of the brake cable above the brake itself. All cables are internally routed for better aerodynamics.
This brake is very reminiscent of the 80's "under-the-chain-stay" "Rollercam" style brakes which this looks like a miniaturized version of with a cross spring instead of the two wire linear springs that Rollercams used.
And there is your look at the "guts" of a tri-bike brake.