Disc Clutch Torque
Calculate the torque transmissible by a disc clutch (or brake), T = μ·F·N·r_m, from the friction coefficient μ, the axial clamping force F (N), the number of friction surfaces N and the mean friction radius r_m (m). A disc clutch transmits torque between two shafts by FRICTION between surfaces pressed together: an axial force F clamps the discs, and the friction at that interface, acting at the mean radius, generates the torque. The number of friction surfaces N multiplies the capacity — a single disc clutch has N=1 (one face) or N=2 (disc between two faces); MULTI-PLATE clutches (motorcycles, automatic transmissions) stack several discs with high N, transmitting large torque in compact space. The same principle applies to disc and clutch BRAKES: the braking (or transmitting) torque is μ·F·N·r_m. This is central in clutch and brake design: it sets the actuation force (pedal, spring, hydraulic actuator) needed to transmit/brake a given torque, and the area and number of discs. The design torque includes a service factor (1.2-3) over the nominal, to cover peaks and wear. Enter the friction coefficient, axial force, number of surfaces and mean radius.
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Torque de embreagem de disco
O torque transmissível por uma embreagem (ou freio) de disco é T = μ·F·N·r_m, a partir do coeficiente de atrito μ, da força axial de aperto F, do número de superfícies de atrito N e do raio médio de atrito r_m. A embreagem de disco transmite torque entre dois eixos pelo atrito entre superfícies pressionadas uma contra a outra: uma força axial F aperta os discos, e o atrito nessa interface, atuando no raio médio, gera o torque. O número de superfícies de atrito N multiplica a capacidade — uma embreagem de disco simples tem N=1 (uma face) ou N=2 (disco entre duas faces); embreagens multidisco (motos, câmbios automáticos) empilham vários discos, com N alto, transmitindo grande torque em espaço compacto. O mesmo princípio vale para freios de disco: o torque que freia (ou transmite) é μ·F·N·r_m. Este cálculo é central no dimensionamento de embreagens e freios: define a força de acionamento (pedal, mola, atuador hidráulico) necessária para transmitir/frear um dado torque, e a área e o número de discos. O torque real de projeto inclui um fator de serviço (1,2 a 3) sobre o torque nominal, para cobrir picos e o desgaste. Informe o coeficiente de atrito, a força axial, o número de superfícies e o raio médio.
Related Tools
Mean Friction Radius (Clutch)
Calculate the mean friction radius of a disc clutch or brake by uniform-wear theory, r_m = (D + d) ÷ 4, from the outer D and inner d diameters (m) of the friction annulus. The mean radius is the EFFECTIVE radius at which the resultant friction force is taken to act for torque calculation (T = μ·F·N·r_m). There are two classic assumptions for this radius: UNIFORM WEAR (assuming the disc has 'bedded in' and wears evenly, concentrating pressure at the inner radius; gives r_m = (D+d)/4, the simple mean of radii) and UNIFORM PRESSURE (new disc, constant pressure; gives r_m = (2/3)·(D³−d³)/(D²−d²), slightly larger). Uniform wear is most used in DESIGN, being conservative (slightly lower torque) and representing the run-in steady state. The mean radius shows an interesting design point: discs with a narrow friction annulus (D close to d, thin ring at large radius) have a high mean radius, transmitting more torque per unit force — so high-performance disc brakes use calipers acting near the disc edge (large radius). Enter the outer and inner diameters.
Shoe Brake Torque
Calculate the braking torque of a simple shoe (or drum) brake, T = μ·F·r, from the friction coefficient μ, the normal force applied by the shoe F (N) and the drum radius r (m). The shoe brake presses a friction-lined shoe against the surface of a rotating drum (or cylinder); the friction between shoe and drum generates a tangential force (μ·F) which, acting at the drum radius, produces the braking torque. It is the principle of vehicle drum brakes, hoist and industrial drum brakes, and rotating-machine brakes. The torque is simply the friction force times the radius. An important effect in shoe brakes is SELF-ENERGIZING: depending on the shoe pivot geometry, friction itself can HELP press the shoe against the drum (leading shoe), raising the effective force and torque for a given actuation force — or HINDER it (trailing shoe). This amplifies braking (an advantage) but makes it sensitive to the friction coefficient (which varies with temperature and moisture), possibly causing unstable behavior. This basic formula gives the torque without the self-energizing factor, considered separately per geometry. Enter the friction coefficient, the normal force and the drum radius.
Brake Contact Pressure
Calculate the contact pressure between the shoe/pad and the drum/disc of a brake, p = F ÷ A, from the normal force F (N) and the friction material contact area A (m²); the result is in kPa. Contact pressure is the normal force distributed over the friction surface area, and one of the most important parameters in a brake's or clutch's DURABILITY and PERFORMANCE. It must be below the friction material's ALLOWABLE pressure (linings, organic, semi-metallic, ceramic or sintered metallic pads — each with its limit). Pressures ABOVE the allowable lead to accelerated wear, overheating and friction loss (fading), reducing material life and impairing braking. Very LOW pressures underuse the material (a bigger, costlier brake than needed). Contact pressure also relates to the p·v product (pressure × velocity), the key indicator of the friction contact's thermal intensity — friction materials have a p·v limit above which they overheat, and that limit often governs design. This simple check — comparing contact pressure with the material's allowable — is essential in brake and clutch design and in choosing the right friction material for the application. Enter the normal force and the contact area.
The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.