manchild wrote: ↑
Fri Aug 10, 2018 9:59 am
An old idea of mine which I've never presented. I was thinking of a lock that would connect disc instantly when pedal is touched and unlock it when foot is raised so that disc spin freely without actually adding the weight to the wheel during acceleration, and have no intertia before braking. It would improve both the braking effectiveness and acceleration.
It would also enable the disc to maintain its speed during slowdowns without braking, thus maintain its cooling.
And possibly, if accordingly designed, the air pressure from the brake inlet could do the spinning of the disc and level up in a way, likely reducing the drag.
4 discs x approximately 1kg = 4kg less to accelerate, with ditched inertia under braking.
There are some problems with that idea.
The wheel assembly has about 10kg. If we assume the mass distribution can be approximated as a disc we get an inertia of about
. With the same approximation for the disc (1kg, r=139mm) we get about
. That means the brake disc contributes to the total inertia of the wheel assembly only 2.5%.
When we assume the only relevant inertia for our purposes comes from the 4 tyres we can calculate the effective mass during acceleration as
Or in other words the total rotating mass of the wheels reduce the acceleration by 2.7% and the inertia of the brake discs only 0.0675%.
So in short even if it would work as intended it had barely any effect on the performance
Additionally the freewheeling part would need to withstand all of the breaking forces (ergo heavier than the bolts used now), would need to be able to accelerate a standing brake disc within a fraction of a second and fit into an already cramped space.