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Demands on Agricultural Tires

Demands on Agricultural Tires. Transmission of forces driving and breaking forces lateral guided forces weight-forces Cushioning of unevenness Absorb vibrations. Functions of a tyre. Demands made on farming tractor drive wheel tyres. Economy. Safety. Comfort. Structural durability.

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Demands on Agricultural Tires

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  1. Demands on Agricultural Tires

  2. Transmission of forces driving and breaking forces lateral guided forces weight-forces Cushioning of unevenness Absorb vibrations Functions of a tyre

  3. Demands made on farming tractor drive wheel tyres Economy Safety Comfort Structural durability Load capacity reserves True running Tractive force (traction) Speed reserves Suspension Gentle ground handling Driving stability Absorption Protection of turf Braking distances Vibrations Mileage performance Driving noise

  4. Economy Structural durability • Long service life • Resistance to breaks and impact damage • High load capacity reserves • Usage of light stabilisers and antioxidant agents

  5. Economy Structural durability Deformation of the sidewall through wheel load View of the sidewall: Impact on the tyre through inflation pressure and wheel load

  6. Economy Structural durability Deformation of the tyre through wheel load and driving torque Demonstration of the deformation when tyre is under load through inflation pressure, wheel load and driving torque

  7. Economy Traction • Preconditions for optimum transmission of tractive force • Suitable lug height • Good self-cleaning characteristics • Large tyre diameter • High volume of air for low inflation pressures • Load capacity reserves for add-on weights

  8. Width, diameter, infla- tion pressure, design State, density Ground type, moisture Static and dynamic Contact area pressure Contact patch geometry Firmness Tractive force – Slip – Performance Economy Traction Factors influencing transmission of tractive force Tyre Wheel load Ground Contact area Shearing resistance Pressure resistance Positive fit Grip

  9. Economy Traction – dependent on inflation pressure Traction

  10. Economy • Slip is the loss of distance covered, given as percentage. • Slip is hardly noticeable up to a value of approximately 20%. This value corresponds with normal field work. • Slip can be reduced by • Increasing the tractor weight (add-on weights, filling the tyres with water) • Using high-volume or twin tyres • Using hydraulic controls • Adopted tire inflation pressure Traction Slip

  11. Economy Traction Multi-pass effect • Driving along the same track with both front and rear wheels is referred to as the multi-pass effect.  • Pre-compaction of the ground by the front wheels allows higher tractive forces to be transmitted by the rear wheels. • The use of the widest tyres possible on the front axle improves the multi-pass effect.  • All-wheel drive tractors with four equally large wheels achieve the best multi-pass effect.

  12. 50% 40% 30% 15% Economy Traction Loss of distance covered with different degrees of slip:

  13. Economy Working out the economics Comparison of tractor tyres in heavy tractive work at different slip values Vehicle: 240 hp tractor, operating costs approx. 50 Euro/h Tyre: RA 650/65 R 42, FA 600/65 R 34 Use:Ploughing 300 hectares / 741 acres Slip on loess: 35% 15% Working out the economic data: 7 km/h x 2 m = 1.4 ha/h x 0.65*) = 0.91 ha/h 7 km/h x 2 m = 1.4 ha/h x 0.85*) = 1.19 ha/h a) b) a) 300 ha x h = 330 h x € 50 = € 16,500 0.91 ha b)300 ha x h = 252 h x € 50 = € 12,600 1.19 ha  Savings = € 3,900 *) 35% slip means 0.65 efficiency,15% slip means 0.85

  14. Economy • Save fuel by choosing the right tyre • the reduced track depth of high volume farming tractor and Implement radial tyres means less tractive force is required 1 cm track depth = + 10% fuel • when used on surfaced roads, the lower rolling resistance of radial tyres on trailers and tractors means lower fuel consumption • Avoidance of too high slip Saving fuel

  15. Economy • where plants are cultivated • where equipment and vehicles are used The ground compaction caused by vehicles driving over the fields restricts plant growing. Gentle ground handling In farming, arable land is

  16. Economy • using the ground in a way suitable to the location • conserving and improving the ground structure • avoiding ground compaction • Avoiding damage to the ground by ensuring it is used in a way suitable to the location (hill slopes, wind and water conditions, ground coverage) • conserving and encouraging biological activity through appropriate crop rotation Gentle ground handling Legislative provisions protecting the soil encourage the sustained conservation of ground fertility and productivity as a natural resource through good, professional practices. This includes:

  17. Wheel load Ground contact patch Inflation pressure Slip Compactness of the ground Root growth Yield Economy Gentle ground handling Ground load Influence of the chassis suspension Effects on the ground

  18. Economy Gentle ground handling Comparison of ground contact patches with the same load Switching to the wide tyres allows the same load to be spread across a greater ground contact area at a lower inflation pressure, thereby substantially reducing the specific ground pressure. The larger number of grooves engaged allows higher tractive forces with lower slip. 20.8 R 38 Inflation pressure 1.6 bar 650/65 R 38 Inflation pressure 1.2 bar

  19. 20.8 R 38 650/65 R 38 800/65 R 32 Economy Economy Economy Gentle ground handling Gentle ground handling Gentle ground handling Ground penetration depth with the same wheel load

  20. 1,2 1,0 0,8 0,6 0,4 0,2 Economy Economy • The contact patch pressure between the tyre and the ground creates compressive strain in the ground. • This compressive strain leads to an increase in ground compactness and reduces the proportion of air and water pores in the ground. Gentle ground handling Gentle ground handling Lines of identical pressure

  21. Economy - Gentle ground handling Determining the specific ground pressure with the same tyre diameters and identical wheel load (here 3560 kg at 40 km/h) Specific ground pressure = Tyre inflation pressure [bar] + addition for lateral rigidity

  22. Economy • Ground contact patches at identical load but different inflation pressure Gentle ground handling Source: FH Soest, www.Reifenregler.de 0,6 bar 1,6 bar

  23. Economy Gentle ground handling Lanes Flat lanes not only protect the ground, it also saves fuel, directly at driving and indirectly through less force is needed for loosening the soil late on. Rule of thumb: 1 cm rut depth = + 10% fuel Source: FH Soest, www.Reifenregler.de

  24. Economy Gentle ground handling Wheel loads and inflation pressures Inflation press. [bar] Wheel loads [t] 0,6 to 1,6 Tractor up to 7.0* 1,8 to 3,2 Combine-harvester up to 12.5 1,6 to 2,0 Forage harvester up to 8.0 2,4 to 4,0 Sugar beet harvester > 10.0 1,0** to 4,5 Liquid manure tanker up to 7.0 4.5 2,4 to 4,4 Field sprayer (self-propelled) 2,0 to 5,0 Forage box 2.0 – 4.5 2,0 to 5,0 Forage trailer 4.0 3,0 to 5,0 Dumper truck 6.0 * permitted axle load acc. to German Highway Code: 11.5 t ** with inflation pressure regulator

  25. Economy • High load capacity • Low rolling resistance • Low wear • High driving stability Gentle ground handling Conflict of objectives – tyre inflation pressure High inflation pressure for road use • High tractive force • Gentle ground handling • Protecting the turfs Low inflation pressure for use in the field

  26. Standard tyre 20.8 R 38* Road use 1.6 bar (3650 kg/40 km/h) Field use 0.6 bar (2540 kg) Difference: 1.0bar Wide tyres 650 / 65 R 38* Road use 1.1 bar (3620 kg/40 km/h) Field use 0.6 bar (2880 kg) Difference: 0.5bar Economy Gentle ground handling Conflict of objectives – tyre inflation pressure The following comparison shows how the conflict of objectives can be reduced by using wide tyres: Summary: The use of wide tyres allows convergence of the inflation pressures for road and field use. * Minimum inflation pressure for heavy traction work in the field

  27. 90% 85% 70% 65% Inflation pressures with same load: 1.6 bar 1.35 bar 1.3 bar 1.1 bar Economy Economy Economy Gentle ground handling Gentle ground handling Operation of wide tires Development of height / width ratio with the same outer diameter

  28. 65 er Serie Super Volumen Economy Gentle ground handling Increase of air volume: smaller rim at same outer diameter Ground contact patch Reduction of rim diameter 4600 kg at 30 km/h

  29. Economy Gentle ground handling Comparison of ground pressure Bias Radial

  30. Positive Consolidated farming operations High proportion of time spent on fields Low additional loads Usage of wide tyres Adopted tire pressure Negative High proportion of time spent on roads and in transportation Front loader, front cutter bar Add-on weights High speeds Wrong tire pressure Economy Expected service life / mileage performance Positive and negative influences on mileage performance

  31. Economy • Choose radial tyres • Use wide tyres • Maintain the correct inflation pressures for road use • Choose tyres with a large tread volume Expected service life / mileage performance Increasing mileage performance by choosing the right tyre:

  32. Economy Expected service life / mileage performance Wear tests Testing machine M 1110

  33. Economy Expected service life / mileage performance Wear tests Test parameters The test conditions are defined through a pre-trial. Objective: Determination of wear resistance Test data: Test name: A #IWT Speed: 30 km/h Tyre pressure: 1.3 bar Load: 60% Skew: 0,5 ° Camber: 0 ° Distance involved: 1200 km (750 km) Test room temperature: 20 °C (+/- 3 °C) Talc dosage: 90 g/h Abrasive paper: 80 grit made by 3m

  34. C05384: after 540 km C05384: after 750 km Economy Expected service life / mileage performance Wear tests Test results and evaluation

  35. Economy Expected service life / mileage performance Laser scan of the lug surface Wear reading on the drum test facility AC 85 Competitor Distance covered: 1200 km Distance covered: 750 km Wear: magenta = 0 mm green = 15 mm

  36. Economy Expected service life / mileage performance Measuring tear Field test

  37. Economy Expected service life / mileage performance

  38. Safety • Unlike truck tyre data sheets the technical data sheets for agricultural tyres give the load capacity per tyre. • The load capacity depends on the tyre inflation pressure and the driving speed. Example: When the inflation pressure is reduced from 1.6 to 0.6 bar, the remaining load capacity is 65% if the same driving speed is maintained. Load capacity

  39. Safety Technical Databook

  40. Safety • The overpressure in the tyre is referred to as the tyre inflation pressure. This is measured in bar, psi or Newton/cm². On tractors the tyre inflation pressure affects - tractive force and slip, - load capacity, - ground pressure, - comfort, - rolling resistance and - driving stability. Load capacity Tyre inflation pressure (tyre pressure)

  41. Comfort • Suspension characteristics • Absorption characteristics • True running • Vibrations and driving noise The influence of the tyre on driving comfort:

  42. Comfort Readings taken at the Contidrom Acceleration [g] Speed [km/h] Speed [km/h] Speed [km/h] Distance [m] a_Rear axle [g] a_Passenger compartment [g] a_Front axle [g] a_Seat [g] Speed [km/h] Data aligned Suspended front axle, test date: 07.07.99

  43. Comfort Equipment for measuring tyre true running

  44. Comfort Equipment for measuring tyre true running

  45. Comfort Evaluating the reading

  46. Comfort Marking the tyre’s lowest point

  47. cabine The generation of drone in the cab Vibration and driving noise vibration impulse / sec = 110 Hz The droning noise in the tractor cab, the so-called “booming noise“, results from the interaction between road, rear axle tyre and vehicle. With standard rear tyres the continuous impact of tyre lugs on the road leads to a vibration impulse which is transmitted into the cab. The predominant noise in the cab comes from the the engine and the impact on the road of the lugs as the rear axle tyres rotate. The combination of these noise inputs causes a resonance that generates the unpleasant effect “cab drone”. The front axle tyre does not have perceptible influence on “the booming noise “effect. engine lug of rear axle tyre and road

  48. Booming-Noise-Effect dB(A) measurement of 600/65 R 38 standard tyre, rolling circumference: 5251 mm noise level in dB(A) speed in km/h Example: Vibration and driving noise A tractor, which drives approx. 47 km/h, makes 2,5 rear wheel rotations per second. The lugs (in this example 44) transmits impulses into the operator's cab. 2,5 U/sec. x 44 lug impulses = 110 vibration impulses/sec = 110 Hz At around 110 Hertz (Hz) - in this example at 47 km/h – the air pressure in the cab develops particularly strong oscillations or vibrations. The combination of high levels of vibration generated by the tyre and the engine, result in resonances and consequently to an enormous rise in the noise level. The driver notices this as unpleasant humming/drone. Measured by Continental AG, NVH, 2009

  49. Example: lug excitation frequency depending on number of lugs and speed Vibration and driving noise

  50. Comparison Radial - Bias • Higher mileage thanks to lower wear • Higher load capacity • Better traction • Improved driving comfort thanks to better damping behaviour • Evenly distribution of pressure in ground contact area leads to better soil protection • Less fuel consumption thanks to lower rolling resistance Advantages Radial tyres Advantages Bias tyres • More side stability in slopy application • Less sensitive against damage in sidewall area • Lower price  All in all Radial tyres offer a much higher sevice level

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