The tractor chassis is the base frame that supports all other components of a tractor. It is built to be very strong to bear heavy loads and shocks from farm work. The chassis frame distributes the load of the engine, transmission, and other components. It also carries the load of any implements and manages forces experienced while working on uneven fields. The location of the center of gravity, hitch point design, and traction surface all impact the mechanics of the chassis. Weight transfer refers to how weight shifts from the front axle to the rear axle, affecting soil reaction and traction. Non-parallel pulling implements introduce additional complexities to the tractor's mechanics and stability.

1. Tractor Chassis
Prepared By:-
Hasanabbas Nedariya(14SOEAG11033)
Yash Savaliya (14SOEAG11042)
5th Semester Agricultural Engineering
School of Engineering, RK University

2. *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.

3. 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.

4. Chassis less Tractor Chassis Frame

5. *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

6. *
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.

7. * 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.

8. 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.

9. *Consider tractor is free
body having all horizontal
forces are balanced and
the algebraic sum of horizontal
forces 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

10. *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.

11. *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.

12. * 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.

13. 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 =
𝑊𝑥2
𝑋1
−
𝑦1 𝑃 cos α + 𝑒𝑃 sin α
𝑥1
;
Also
R1 + R2 = W => R2 = W – R1
R2x1 = [W-
𝑊𝑥2
𝑋1
+
𝑦1 𝑃 cos α + 𝑒𝑃 sin α
𝑥1
]
R2x1 = W
(𝑥2 −𝑥1)
𝑋1
+ P
𝑦1 cos α + 𝑒 sin α
𝑥1

14. *So stability of tractor is Determined by R1 and the
tractive capacity by R2.
*The term P
𝑦1 cos α + 𝑒 sin α
𝑥1
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
𝑊𝑥2
𝑋1
.
*As soon as P
𝑦1 cos α + 𝑒 sin α
𝑥1
becomes more than
𝑊𝑥2
𝑋1
,
then tractor front wheel become up from ground
*The drawbar pull at which tractor become unstable is
given by as P
𝑦1 cos α + 𝑒 sin α
𝑥1
=
𝑊𝑥2
𝑋1

15. 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.

16. *Thank You!