Tractor ChassisPrepared By:-Hasanabbas

Nedariya(14SOEAG11033)Yash Savaliya (14SOEAG11042)

5th Semester Agricultural EngineeringSchool of Engineering, RK University

*What is Chassis?*Chassis is the base frame of a tractor on which all the

components and assemblies like Engine, Transmission, Tires, Front Axle, Steering Systems and Electrical Systems are attached. So, the overall structure which binds all these components together in a tractor is called tractor chassis.

*It is built very strong to bear the heavy load and shocks received while working on the farms.

*

Functions Of Tractor Chassis Frame

• The load of assemblies like engine, transmission, steering etc. is supported by chassis frame design.• The rear and front wheels are connected to each other using tractor chassis.• The load of implements is also carried easily by this frame.• The working on an uneven field normally causes more load production. This extra load is managed by the frame efficiently.• The load incurred when tractor is working on the field along with an implement is also managed by this frame.

Chassis less Tractor Chassis Frame

*Weight Transfer

*Definition:-Shifting of weight from the first axle and the implement to the rear axle is called the weight transfer.

*Application:-1. To avoid the lifting of front axle.2. To increase the tractive efficiency.3. To reduce the slippage of rear wheel.

Principle:- Based on Law of Mechanics

*

If 1kg load is added at far end of the 0.5 m from the fulcrum then to balance it 0.5 kg of

should be added to far end of 1 m distance from fulcrum. So at fulcrum the weight gain

should be of 1.5 kg.

*Mechanics of Tractor under simplest operating

*Factor affecting chassis of tractor.1. Gravitational force (Weight of Tractor W1,W2).2. Soil Reaction (R1, R2).3. Traction force (F).4. Draw bar pull (P).*Factor affecting mechanics of chassis.1. Location of C.G.2. Type & Design.3. Design & location of Hitch point.4. Type of implement pull.5. Traction surface.6. PTO Torque.

Assumption of simple operating Mechanism :-1. Rear wheel drive tractor.2. Uniform forward travel and leveled surface.3. The line of action of the drawbar pull is at the center

of rear wheel and midway from the ground and parallel to direction of travel.

4. Line of action of vehicle soil reaction R1 and R2 is passing through center of front axle and rear axle respectively.

5. Line of action of tractive force (F) is tangential to traction wheel at point B.

6. Rolling resistance is Zero.

*Consider tractor is free body having all horizontal forces are balanced andthe algebraic sum of horizontalforces should equal to zero. so F – P = 0*All the algebraic sum of vertical forces it should be zero. So W1 + W2 - R1 - R2 = 0…………….. A. Where W1 = Weight on front axle. W2 = Weight on rear axle. R1 & R2 are soil reaction

*The algebraic sum of moments should be zero while taking all moments from point B.

W1x1 – Py1 – R1x1 = 0……….. 1.*From above equation soil reaction can be obtain as

R1 = W1 – Py1/x1………………… 2.

*Likewise from equation A.R2 = W1 + W2 – R1 …………… 3.

*Substituting value of R1 from equation 2. in Equation 3

R2 = W2 + Py1/x1…………………… 4.

*The stability of tractor is determined by R1 and R2.

*P is directly proportional to R2 and inversely proportional to R1.*The term Py1/x1 expresses the change in soil

reaction R1 and R2 resulting from drawbar pull P.*The R1 supporting the front wheel decrease as P

increase and R2 increase.*The above reaction is true till the P become large

such that Py1/x1 to become equal to Zero. So any further increase in P will cause the front wheel up from ground.*So in actually there is no shift of weight from front

axle and implement to the rear axle but the change in Py/x1 will effect R1 and R2 soil reaction and this is actually weight transfer.

*Mechanics of Tractor chassis under nonparallel pull condition

*When the implement is added to the Drawbar is non parallel so under this condition the equation.

*As shown in figure point B is the interaction of the resultant supporting and traction components of the soil reaction against the rear wheel.

* So to make simple W(Weight ) is acted through C.G..

* Same way as we resolve for simple operation this also

resolve in same way.

The algebraic sum of all horizontal forces is zero.F – P cos α = 0………….. 1.

*Now algebraic of all vertical forces is equal to Zero.

R1 + R2 – W – P sin α = 0…………… 2.*Taking Moment about Point B,Wx2 – R1x1 – y1 P cos α – e P sin α = 0……….. 3.*Solving equation 3. for R1

R1 =Also

R1 + R2 = W => R2 = W – R1R2x1 = [W- + ]R2x1 = W + P

*So stability of tractor is Determined by R1 and the tractive capacity by R2.*The term P is known as weight transfer and

indicates the change in soil reaction between R1 and R2. *In order to avoid overturning of the tractor this

factor must b less than .*As soon as P becomes more than , then tractor front wheel become up from ground*The drawbar pull at which tractor become

unstable is given by as P =

Centre of Gravity (C.G.)*Centre of Gravity is the point on the body

where body of tractor at which its total weight may be considered as acting.*Since tractors are composed of irregular

shaped parts so it is difficult to find out its C.G. point.*So there are three method to find out the C.G.

of tractors.1. Suspension Method.2. Balancing method.3. Weighing method.

*Thank You!