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.
Hydraulic Jump Energy Loss
Calculate the specific energy dissipated in a hydraulic jump, ΔE = (y₂ − y₁)³ ÷ (4·y₁·y₂), from the upstream y₁ (supercritical) and downstream y₂ (subcritical) sequent depths. The hydraulic jump is one of the most efficient energy dissipators in hydraulics: intense turbulence in the transition converts kinetic energy to heat and sound, removing excess flow energy. This head loss ΔE is exactly what is sought downstream of spillways, gates and bottom outlets — water arrives with very high energy (able to scour the riverbed and undermine the structure), and the stilling basin induces the jump to 'burn' that energy in a controlled way. The higher the incoming Froude number, the greater the dissipated fraction — jumps with Fr > 9 dissipate up to 85%. Enter the upstream and downstream sequent depths.
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.
Prestress Friction Loss
Calculate the prestress force loss from friction along a curved tendon, ΔP = P_0·(1 − e^(−(μα + k·x))), from the jacking force P_0 (kN), the tendon-duct friction coefficient μ, the sum of tendon deviation angles α (radians), the wobble coefficient k (loss per metre, 1/m) and the tendon length x (m). In POST-TENSIONING (where the tendon is tensioned after the concrete hardens, sliding inside a duct embedded in the member), the force applied at the end by the jack does NOT arrive full at the other end: FRICTION between tendon and duct consumes part of it along the path. There are two effects: friction in the tendon CURVES (μα term — the more the tendon curves, the more it 'squeezes' the duct and the greater the friction, like a rope on a pulley — the capstan effect) and 'wobble' friction in straight runs (k·x term — from small undulations and duct misalignment). Friction loss makes the prestress force DECREASE progressively from the active end (jack) to the passive (dead anchorage), which is why long tendons are sometimes tensioned from BOTH ends. It is an immediate loss, computed tendon by tendon. Enter the jacking force, friction coefficient, sum of angles, wobble coefficient and length.
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.