Friction Torque
Calculate the friction torque in a shaft or bearing, T = μ·F·r, multiplying the friction coefficient μ by the normal force (load) F and the radius r where friction acts. The result, in N·m, is the moment friction opposes to rotation — the torque the motor must overcome just to turn the assembly, without doing useful work. Reducing friction torque (with lubrication, rolling bearings and good finishes) saves energy and lowers heating. Multiplied by the angular velocity, it gives the power dissipated by friction. Enter the friction coefficient, the force and the radius.
Resultado
—
Torque de atrito
Todo contato que desliza ou rola sob carga gera atrito, e quando esse contato acontece a uma certa distância do eixo de rotação, o atrito se opõe ao giro com um torque. O torque de atrito é T = μ·F·r, o produto do coeficiente de atrito μ (que depende do par de materiais e da lubrificação — de ~0,001 num mancal hidrodinâmico ou rolamento bem lubrificado a ~0,5 em contato seco metal-metal), da força normal F (a carga que pressiona as superfícies) e do raio r onde o atrito atua (o raio do munhão, do rolamento, da superfície de contato). O resultado, em N·m, é o momento que o sistema precisa vencer só para girar, antes de realizar qualquer trabalho útil — é energia pura desperdiçada como calor. Em máquinas reais, a soma dos torques de atrito de todos os mancais, vedações e engrenagens representa as perdas mecânicas que separam a potência de entrada da potência útil de saída, reduzindo o rendimento. Minimizá-lo — escolhendo rolamentos em vez de buchas, lubrificando bem, reduzindo cargas e usando raios menores onde possível — economiza energia e diminui o aquecimento. E há um vínculo direto com a potência: multiplicando o torque de atrito pela velocidade angular (ω), obtém-se a potência dissipada por atrito (P = T·ω), o calor que precisa ser removido. Informe o coeficiente de atrito, a força e o raio.
Related Tools
Hersey Number
Calculate the Hersey number of a bearing, H = μ·N ÷ P, from the dynamic viscosity μ, the rotational speed N and the specific pressure P. The dimensionless result is the horizontal-axis variable of the Stribeck curve, which maps the lubrication regimes: very low values indicate boundary lubrication (metal-to-metal contact, high friction and wear); intermediate values, mixed lubrication; and high values, full hydrodynamic lubrication (complete film, minimum friction). Tracking the Hersey number helps keep the bearing in the hydrodynamic regime, away from contact. Enter the viscosity, the speed and the pressure.
Bearing Power Loss
Calculate the power dissipated by friction in a bearing, P = T × ω, multiplying the friction torque T by the angular velocity ω (rad/s). The result, in watts, is the mechanical energy converted to heat per unit time by friction — a loss that reduces efficiency and heats the lubricant and components. This heat must be dissipated (by convection or oil circulation) to keep a safe operating temperature, since overheating degrades the lubricant and can cause seizure. Estimating the dissipated power is essential to size the cooling and the oil flow. Enter the friction torque and the angular velocity.
Bearing Radial Clearance
Calculate the radial clearance of a journal bearing, c = (D_bore − D_shaft) ÷ 2, subtracting the shaft diameter from the bearing bore diameter and dividing by two. The result is the radial space between shaft and bearing, where the lubricant oil film forms. Clearance is a critical design parameter: too small hampers film formation and heat dissipation (seizure risk); too large reduces load capacity and increases vibration and noise. A rule of thumb uses a radial clearance of about one thousandth of the diameter. Enter the bore and shaft diameters.
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.