RE: RE: Rear disk convertion questions...
ricardo_swarez said:
Andrew
2. Pad area has nothing whatsoever to do with force applied, it is down to the area of the piston. Frictional force is independant of area, at least if you are talking about static friction.
since the braking force is dependant on the pressure being delivered........how can u say that the brake pad size doesnt matter!? pressure if force/area.........so if the pad was bigger then there would be a larger area, but less pressure, an if there was a tiny pad then there would be all the pressure accros a small area, so there has to be a ballanced striked between getting the rite amount of pressure and the right amount of friction, you my friend are a grade A retard
You are confusing the issue of pressure in the hydraulic system and pressure between the pad and disc. You do realise that the pad area is not the same as the piston area?
If there is 100psi in the hydraulic circuit, and the piston area is 1 inch^2, then there is 100 pounds of force being exerted on the pad. There are no two ways about this, this is fact.
Frictional Force = Coefficient of Friction x Normal Force
This is another formula that for static friction holds true. There is no concept of area in it. I realise that brakes are not static friction, but dynamic friction is far too complex to deal with.
If you apply a force of 100 pounds on a 1 inch^2 surface, the pressure is 100psi. This pressure will cause a large amount of friction over an area of 1 inch^2. If the surface is 100 inch^2, then the pressure will be 1 psi, causing a smaller amount of friction per unit area, but because the area is proportionally bigger, the total frictional force remains the same. There are other factors, but if you want simple, this is actually pretty accurate.
This lecture gives a relatively good analysis of the torque and power transmitted in a disc clutch. A clutch is the same as a disc brake, except it acts over a fraction of the circle.
http://theduchy.ualr.edu/classes/asci5335/clutches.pdf
Look at the formula - it has force, coefficient of friction, and the inner and outer diameter of the clutch disc (due to angular velocity). Nothing to do with pad area. Even if it did, your maths is flawed.
If you want properly complicated, there are finite element analyses of the entire brake system, including thermal expansion, gassing, dynamic friction, and so on all available on the web.
It's normally pretty widely accepted that the first person to resort to insults, or take the argument off on a tangent, is losing, and can't argue anything relevant anymore.
Andrew MEng (Hons) ACGI (employed by P&O Nedlloyd as a marine engineer).