Drawbar Pull
Calculate the available drawbar pull of a tractor, F = W × μ, multiplying the weight on the driving wheels W (kN) by the traction coefficient μ of the tire-soil pair. The result, in kN, is the pulling effort the tractor can exert on implements (plow, harrow, planter) — limited by soil grip, not engine power. The traction coefficient depends on soil and tire type (0.5 to 0.7 on firm soil; much less on loose or wet soil). Increasing the adhesive weight (ballast) raises the available force. Enter the adhesive weight and the traction coefficient.
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Drawbar pull
One misconception is widespread: assuming that the force a tractor can pull depends only on engine power. On farm soil the limit is almost always traction — how firmly the tyre grips the ground before it starts to slip. The force available at the drawbar is F = W × μ, the product of the adhesive weight W (the share of tractor weight carried by the driving wheels, in kN) and the traction coefficient μ (which characterises the tyre-soil pair). The physics matches ordinary friction: maximum tractive force is proportional to the normal force (the weight) times a coefficient. The traction coefficient swings enormously with conditions: on firm dry soil with an agricultural tyre it reaches 0.5-0.7; on ploughed, loose or wet soil it collapses to 0.3 or less; on concrete it climbs past 0.8. This explains why the same tractor power delivers far less pull on poor ground. The practical consequence is direct and at times counterintuitive: to pull more, the answer often lies in more adhesive weight rather than more power — adding ballast (cast iron weights, water in the tyres) raises W and therefore the force available, up to the point where wheel slip settles into its optimum band. A trade-off remains: too much ballast wastes fuel and compacts the soil (see wheel slip). Drawbar pull multiplied by speed gives drawbar power — the useful power that actually hauls the implement, always lower than engine power (losses occur in the transmission and in wheel slip). Matching a tractor to an implement starts by making sure the force available at the drawbar exceeds the draft of the implement (plough, harrow, seed drill) in the soil at hand. Enter the adhesive weight and the traction coefficient.
Related Tools
Tractor Wheel Slip
Calculate the wheel slip of a tractor, slip = (1 − D_loaded ÷ D_unloaded) × 100%, comparing the distance traveled in a number of wheel revolutions under load (D_loaded) and unloaded (D_unloaded). The result, in %, measures how much the wheels spin without advancing, by slipping on the soil. Excessive slip wastes power and fuel and compacts the soil; zero slip indicates lack of traction. The ideal range for farm tractors is typically 8 to 15% on firm soil, adjusted with ballast and tire pressure. It is a key traction efficiency indicator. Enter the loaded and unloaded distances.
Fuel Consumption per Hectare
Calculate the fuel consumption per hectare of a mechanized operation, consumption = hourly consumption ÷ field capacity, dividing the tractor's hourly consumption (L/h) by the effective field capacity (ha/h). The result, in liters per hectare, is the practical indicator to budget the fuel cost of a farming operation and compare the energy efficiency of machines and settings. Heavy operations (subsoiling) consume far more L/ha than light ones (spraying). Combined with the diesel price and the total area, it gives the season's fuel cost. Enter the hourly consumption and the field capacity.
Adhesion Tractive Effort (Locomotive)
Calculate a locomotive's maximum tractive effort limited by adhesion, F = μ·W, from the wheel-rail adhesion coefficient μ (typically 0.25-0.35 dry, less with rain, ice or leaves) and the adhesive weight W (N, the locomotive weight on powered axles). Tractive effort is the force the locomotive applies to pull the train, with two limits: power (engine) and adhesion (wheel-rail friction). At low speed and starting, ADHESION limits — however powerful the engine, if the demanded force exceeds μ·W, the wheels spin, losing traction and wearing wheels and rails. So locomotives concentrate weight on powered axles (adhesive weight) and use anti-slip systems and sand application to boost friction. The steel-on-steel railway contact has very low rolling resistance (the train's great energy advantage) but precisely therefore limited adhesion — the fundamental paradox of rail traction. This defines the maximum train a locomotive can start and pull on a grade. Enter the adhesion coefficient and the adhesive weight.
Effective Field Capacity
Calculate the effective field capacity of a mechanized farming operation, FC = (v × L × Ef) ÷ 10, from the working speed v (km/h), the effective working width L (m) and the field efficiency Ef (decimal). The result, in hectares per hour, is the area the machine actually works per hour, already discounting time losses with turns, refills and overlaps (efficiency). The factor 10 adjusts the units. It is central to mechanization planning: it sets how many machines and hours are needed to complete an operation (planting, spraying, harvesting) in the available window. Enter the speed, the width and the field efficiency.
Hoist Rope Tension
Calculate the resultant force in an elevator's hoist rope, F = (Q + M_car − M_counterweight)·g, from the payload Q, the car mass and the counterweight mass (kg). The result, in newtons, is the unbalanced effort the steel ropes must transmit, already net of the counterweight's balancing effect. It is the basis for sizing the ropes (number, diameter and safety factor, typically ≥ 12 in elevator codes) and the traction sheave. When the load is such that car + load ≈ counterweight, the force tends to zero (balanced system). Enter the load, the car mass and the counterweight mass.
Rail Thermal Force (CWR)
Calculate the axial thermal force in a continuous welded rail (CWR), F = E·A·α·ΔT, from the steel elastic modulus E (Pa), the rail section area A (m²), the thermal expansion coefficient α (1/°C) and the temperature change ΔT from the neutral temperature (°C). In CWR — where rails are welded into hundreds-of-metre or kilometre strings, removing joints — thermal expansion is PREVENTED by track fastening, so a temperature change, instead of changing length, generates a huge internal axial force: compression in heat (risk of track buckling, which misaligns the rails) and tension in cold (risk of rail or weld fracture). Since the force does not depend on length (only section and ΔT), it can reach hundreds of kN. So CWR is installed at a neutral (stress-free) temperature chosen mid-range, minimizing compression and tension extremes. This is essential to modern track safety and to set the laying neutral temperature. Enter the elastic modulus, section area, expansion coefficient and temperature change.
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.