Belt Maximum Tension
Calculate a belt's maximum (tight-side) tension, T₁ = T_e·r ÷ (r − 1), from the effective tension T_e = T₁ − T₂ (the power-transmitting force, N) and the tension ratio r = T₁/T₂ (at the slip limit). Knowing the force the belt must transmit (the effective tension, from power and velocity) and the maximum tension ratio the belt sustains before slipping (from friction, wrap and, in V-belts, the wedge effect), the individual side tensions can be computed. The maximum tension T₁ (tight side) is the larger, and it SIZES the belt's strength (which must not break) and the load on the BEARINGS and pulley shafts (which feel the sum of both side tensions, bending the shaft). Knowing T₁ is essential to: check the belt resists (versus its tensile strength), size the bearings for the radial load imposed by the belt (which can be significant and shortens bearing life), and set the correct installation tension. The LOWER the tension ratio r (worse friction, less wrap), the HIGHER the T₁ needed for the same power — hence the advantage of V-belts (high r) in reducing loads. Enter the effective tension and the tension ratio.
Resultado
—
Tração máxima da correia
A tração máxima (no lado tenso) de uma correia é T₁ = T_e·r ÷ (r − 1), a partir da tração efetiva T_e = T₁ − T₂ (a força que transmite potência) e da relação de tensões r = T₁/T₂ (no limite do escorregamento). Conhecida a força que a correia precisa transmitir (a tração efetiva, derivada da potência e da velocidade) e a relação máxima de tensões que a correia suporta antes de escorregar (que vem do atrito, do abraçamento e, em correias em V, do efeito de cunha), pode-se calcular as trações individuais nos dois lados. A tração máxima T₁ (no lado tenso) é a maior, e é ela que dimensiona a resistência da correia (que não pode romper) e a carga sobre os mancais e os eixos das polias (que sofrem a soma das trações dos dois lados, fletindo o eixo). Conhecer T₁ é essencial para: verificar se a correia resiste (comparando com sua resistência à tração), dimensionar os mancais para a carga radial imposta pela correia (que pode ser significativa e reduz a vida dos rolamentos), e ajustar a tração de instalação correta. Quanto menor a relação de tensões r (pior atrito, menor abraçamento), maior a tração T₁ necessária para a mesma potência — daí a vantagem das correias em V (alto r) em reduzir as cargas. Informe a tração efetiva e a relação de tensões.
Related Tools
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.
Belt Contact Arc
Calculate the contact-arc length of a belt on the smaller pulley, L_arc = (d ÷ 2)·θ, from the smaller pulley diameter d (mm) and the wrap angle θ (radians). The contact arc is the length of the belt portion actually in contact with the pulley (touching it), along the wrap angle — simply the pulley radius times the angle (in radians), the arc-length formula. This length matters for several reasons: it sets the CONTACT AREA between belt and pulley (with the width), governing contact pressure and friction distribution; it influences heating (friction × area) and wear of both belt and pulley; and it is relevant to elastic slip (creep), where the belt, changing tension from T₁ to T₂ along the arc, elastically stretches and contracts, sliding microscopically over the pulley — a small INEVITABLE slip (1-2%) occurring even without gross slipping, making the output speed always slightly below theoretical. A larger contact arc (bigger pulley or more wrap) distributes friction better and reduces the slip tendency. This calculation complements the geometric and friction analysis of a belt drive. Enter the smaller pulley diameter and the wrap angle.
Belt Centrifugal Tension
Calculate the centrifugal tension in a belt, T_c = m·v², from the mass per unit length m (kg/m) and the belt velocity v (m/s). When the belt wraps a pulley at high speed, its own mass, making the turn, generates a CENTRIFUGAL force tending to 'throw' the belt outward, LIFTING it off the pulley. This creates an additional tension throughout the belt (the centrifugal tension), the same at all points and not contributing to power transmission — it only 'steals' part of the belt's gripping capacity against the pulley. Centrifugal tension grows with the SQUARE of velocity, so it is negligible at low speeds but becomes important in fast belts. The effect is harmful: by lifting the belt off the pulley, centrifugal tension REDUCES the normal contact force and thus the friction available to transmit power — there is an OPTIMAL velocity above which increasing speed reduces transmissible power (the belt starts to 'float'). So belt speed has a practical limit (typically 25-30 m/s for conventional V-belts, more for special belts). Centrifugal tension must be added to the tensions to get the total tight- and slack-side tensions. Enter the mass per unit length and the velocity.
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.