Belt Transmitted Power
Calculate the power transmitted by a belt, P = (T₁ − T₂)·v, from the tight-side tension T₁ (N), the slack-side tension T₂ (N) and the belt velocity v (m/s). In a belt drive, the driving pulley drags the belt by friction, creating a DIFFERENCE in tension between the two sides: the side that 'pulls' (tight side, T₁) is more tensioned than the side that 'follows' (slack side, T₂). This difference (T₁ − T₂), the effective tension or tangential force, is the net force that actually transmits motion; times the belt velocity, it gives the transmitted POWER. The larger the tension difference the belt can sustain without slipping (depending on friction, wrap angle and, in V-belts, the wedging effect of the pulley walls), the greater the transmissible power. Power also grows with belt velocity — so high-power drives use large pulleys and fast belts (up to a limit, since centrifugal tension reduces available friction at very high speeds). This is central in belt-drive design, present in almost every rotating machine: motors, fans, pumps, compressors, machine tools and vehicles. Enter the tight- and slack-side tensions and the belt velocity.
Result
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Potência transmitida por correia
A potência transmitida por uma correia é P = (T₁ − T₂)·v, a partir da tração no lado tenso T₁, da tração no lado frouxo T₂ e da velocidade da correia v. Em uma transmissão por correia, a polia motora arrasta a correia por atrito, criando uma diferença de tração entre os dois lados: o lado que 'puxa' (lado tenso, T₁) fica mais tracionado que o lado que 'segue' (lado frouxo, T₂). Essa diferença (T₁ − T₂), chamada tração efetiva ou força tangencial, é a força líquida que de fato transmite o movimento; multiplicada pela velocidade da correia, dá a potência. Quanto maior a diferença de tração que a correia consegue suportar sem escorregar (que depende do atrito, do ângulo de abraçamento e, em correias em V, do efeito de cunha das paredes da polia), maior a potência transmissível. A potência também cresce com a velocidade da correia — por isso transmissões de alta potência usam polias grandes e correias rápidas (até um limite, pois a tração centrífuga reduz o atrito disponível em velocidades muito altas). Este cálculo é central no dimensionamento de transmissões por correia, presentes em quase toda máquina rotativa: motores, ventiladores, bombas, compressores, máquinas-ferramenta e veículos. Informe as trações nos lados tenso e frouxo e a velocidade da correia.
Related Tools
Belt Transmission Ratio with Slip
Calculate a belt's real transmission ratio accounting for slip, i = (D ÷ d)·(1 − s/100), from the driving D and driven d pulley diameters (mm) and the slip percentage s (%). A belt's THEORETICAL transmission ratio is simply the pulley diameter ratio (D/d) — a large driving pulley turning a small driven one multiplies the rotation. But in practice, a belt drive is NOT exact like a gear drive (which has interlocking teeth): the belt transmits by FRICTION, and there is always a small SLIP between belt and pulleys. This slip has two components: ELASTIC slip (creep, inevitable, ~1-2%, from the belt stretching and contracting as tension changes between the two sides) and GROSS slip (occurring under overload, when the belt loses grip — undesirable and harmful). Slip makes the driven pulley's real rotation SLIGHTLY LOWER than theoretical, and the real transmission ratio a bit different from nominal. In applications needing exact synchronism (engine timing shafts, positioning), V-belt slip is unacceptable, and TIMING (toothed) belts or chains, which do not slip, are used. This calculation quantifies the slip effect on the transmission ratio. Enter the driving and driven pulley diameters and the slip percentage.
Number of V-Belts
Calculate the number of V-belts needed in a drive, N = P_design ÷ P_belt, from the design power P_design (the power to transmit times the service factor, kW) and the power each individual belt can transmit P_belt (kW, corrected by the wrap-angle and length factors). When a single V-belt lacks capacity to transmit the needed power, SEVERAL belts are used in parallel, running in parallel grooves of the same pulleys (multi-groove pulleys). The belt count is the design power divided by one belt's capacity. The design power includes the SERVICE FACTOR (1.0 to 2.0+), amplifying the nominal power to cover real operating conditions — shocks, frequent starts, hours of daily use, type of driving and driven machine (a crusher has a high factor, a fan a low one). The power per belt comes from the maker's tables for each profile and speed, corrected by the wrap angle (less wrap → less capacity) and belt length. When several belts are used, they should be a MATCHED SET (with identical lengths) to share the load equally — belts of different lengths overload some and idle others. This is the final step of selecting a V-belt drive. Enter the design power and the power per belt.
Belt Installation Tension
Calculate a belt's installation (static) tension, T_i = (T₁ + T₂) ÷ 2, from the tight-side T₁ and slack-side T₂ tensions (N). The installation tension is the INITIAL tension applied to the belt when mounting it (with the machine stopped), tensioning it between pulleys — it is the average of the tensions that will exist on both sides during operation. Setting this initial tension correctly is one of the most important and most neglected maintenance tasks in belt drives: a SLACK belt (low tension) slips under load — losing power, generating heat, wearing fast and even burning; an OVER-TIGHT belt (high tension) overloads the bearings and shafts (drastically shortening bearing life), stretches and fatigues the belt, and wastes energy. The correct installation tension is the one that, under operating load, keeps the slack side with enough tension not to slip, without overdoing the tight side. In practice, the installation tension is measured by belt deflection under a standard force, or by the span natural frequency (sonic meter). Tension 'settles' in the first hours (a new belt stretches), so re-tensioning after the run-in period is recommended. Enter the tight- and slack-side tensions.
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.