weight transference

Weight transference : 

Weight transference When a tractor is pulling some load either at drawbar or connected to the three point linkage, the weight of the implement along with a part of the weight of the front axle, is transferred to the rear axle. This shifting of the weight to the rear axle is known as weight transference, which adds to the tractive efficiency of the tractor.

The magnitude of the Wight transfer depends upon : 

The magnitude of the Wight transfer depends upon configuration of the tractor It’s total weight Reaction of rear & front wheels Location of C.G. Wheel base Weight of implement Soil reaction Soil weight Size of implement & it’s location of C.G.

Assumption : 

Assumption Rear wheel drive Uniform forward motion on a plane level surface Line of action of drawbar pull “P” Horizontal midway between traction wheel and parallel to the direction of motion Line of action of vertical component ‘R1’ of soil reaction against traction wheel, passing through centre of the Rear axle Line of action of vertical component ‘R2’ of soil reaction against front wheel, passing through centre of the front axle Line of action of Horizontal component ‘R3’ of soil reaction against Traction wheel, tangent to the traction wheel at C

Slide 5: 

Weight Transference of Tractor x1 W1 W2 R2 R1 C Y1 R3 P Drawbar pull P Gravitational force W1 supported by the rear wheel and W2 supported by the front wheel Soil reaction R1 , R2 and R3

Free Body Analyses : 

Free Body Analyses For equilibrium of the tractor the algebraic sum of all the forces acting parallel to the direction of motion should be zero. R3 - P = 0 ……(1) Likewise the algebraic sum of all the forces acting Perpendicular to the direction of motion should be zero R1 + R2 - W1 - W2 = 0 ……(2)

Slide 7: 

The algebraic sum of the Turning moments of all external forces about any axis (say C) must equal Zero W2X1 - PY1 - R2X1 = 0 ……….(3) Solving equation 3 for R2, R2 = W2 - PY1 ………..(4) X1 Similarly Solving equation 2 for R1 R1 = W1 +W2 -R2 ……..(5) Substituting the value of R2 From equation4 in equation 5 R1 = W1 +W2 - W2 - PY1 x1 R1 = W1 + PY1 ….(6) x1

Slide 8: 

The term PY1/X1 Express the Change in soil reaction R1 and R2 resulting from the action of Drawbar pull p This Change in soil reaction is called Weight Transfer Since the tractive capacity of a tractor is to a great extent determined the value of R1, Here R1 gets increased by PY1/X1, means more tractive capacity Stability is determined by the value of R2, if R2 is less tractor becomes less stable Weight transfer = PY1/X1 Weight transfer = Pull x Hitch Height Wheel Base

Increasing the wheel base X1 will Decrease the change in soil reaction R1 And R2 caused by any drawbar pull and will increase the drawbar pull required to lift the front wheels from the ground, on the other way a larger wheel base means more turning radius : 

Increasing the wheel base X1 will Decrease the change in soil reaction R1 And R2 caused by any drawbar pull and will increase the drawbar pull required to lift the front wheels from the ground, on the other way a larger wheel base means more turning radius

Increasing the effective drawbar height Y1 causes the change in soil reaction R1 and R2 due to a given force p and decreases the value of draw bar pull PY1 at which the front wheels will be lifted from the ground thus from the stand point of stability the line of action of draw bar pull should be as low as possible. : 

Increasing the effective drawbar height Y1 causes the change in soil reaction R1 and R2 due to a given force p and decreases the value of draw bar pull PY1 at which the front wheels will be lifted from the ground thus from the stand point of stability the line of action of draw bar pull should be as low as possible. x1 W1 W2 R2 R1 C Y1 R3 P