MV mulimi is a multi-purpose tractor designed by the department of Agricultural and Bio-systems engineering, Makerere university, Uganda.

1. MAKERERE UNIVERSITY
AEN 4107: DESIGN OF AGRICULTURAL MACHINERY
A CASE STUDY ABOUT MV MULIMI AT MUARIK

2. GROUP MEMBERS
NAME REG_NUMBER
NTEGE IVAN 12/u/12827/ps
KISUULE NOAH 12/u/462
MUTEBI FAIZAL 12/u/9341/ps
SSEMPIJJA DIRISA 12/u/13470/Ps
LEMYE IBRA 12/u/7686/ps

3. INTRODUCTION
 MV mulimi is a low cost mobile utility tractor which was developed
purposely
• For transportation
• For powering small devices such as irrigation pumps, threshers,
grinders, etc.
• For field operations such as ploughing, and
• Additional uses such as phone charging, power generation
This was a collaborative project between MUK and Purdue University

4. STUDY OBJECTIVES
Main objective:
To study about the design and construction of MV mulimi
Specific objectives:
• To find out how the different components of MV Mulimi
were designed
• To find out the fabrication and assembling procedures
• To assess its performance

5. COMPONENTS OF MV MULIMI
 The MV mulimi is comprised of several smaller component
assemblies which include:
• The frame
• The suspension
• The transmission
• Clutch and engine
• Ergonomics and woodwork

6. TYPICAL SPECIFICATIONS OF THE DESIGN
Empty Weight <500 kg
Payload 700-2 tonnes
Transmission Belt clutch
Engine 3500 rpm ,12.5 hp diesel
engine
Length/Width 3.61 m/1.45 m
Top speed 30-50km/hr
Brakes Hydraulic brakes on each
wheel
Suspension Coil springs on each wheel
Frame Light weight truss
Required Tools/Skills Constructed by cutting and
welding angle iron, limited
bolted joints, with no custom
tooling required
Source: MUARIK, ABE (2015)

7. TOOLS AND EQUIPMENT USED
Source: John Lumkes, ABE (2015)

8. MATERIAL SELECTION AND PROCUREMENT
• Ensuring the procurement of quality material correlates directly
to increased lifespan, durability, and safety of the end product
• Good material selection may result in higher upfront costs in
vehicle construction but it will ensure a product that safely and
effectively meets the needs of the community and will save
cost in the long run

9. MATERIAL SELECTION CONT’D
1. Mild Steel Angle bars
• These were used in vehicle frame construction because MS is
Commonly available
Cheap compared to other materials
And can endure much of the stress on the vehicles

10. HOW POOR AND GOOD QUALITY ANGLE BARS WERE
DIFFERENTIATED
Poor quality Good quality
• Inconsistence in dimensions, thickness
in particular
Clean, smooth surfaces with constant and
precise dimensions
• Mushroomed ends have a square outer corner and a distinct
rounded inner angle.
• Deep pitting or excessive rust Water markings or slight surface rusting
left from production hot working
• Ability to twist or bend steel over a
short distance
Resistant to twisting or bending over
short distances
• Fragile (brakes or cracks when
hammered, instead of bending)
Non-fragile
MATERIAL SELECTION CONT’D

11. 2. Car parts
MATERIAL SELECTION CONT’D
Source: John Lumkes, ABE (2015)

12. 3. Engine
• A 12.5 Hp diesel engine was used to meet the drive-
train requirements of the vehicle.
• The engine spare parts are also readily available
4. Bearings, Shaft and sprockets
• New bearings, Shaft and Sprockets were purchased.
• Ensured that pillow block and flange mount bearings
had lock collars and/or set screws and grease ports
with fittings
MATERIAL SELECTION CONT’D

13. Discussion include ;
 Frame designs (wood, steel space frame, ladder frame, recycled
truck frame, etc.)
 Driveline options (chains, gears, belts, transmissions, hydraulic,
etc.)
 Layout (front/rear wheel drive, 3 or 4 wheels, seating, steering,
cargo bed, etc.)
DESIGN APPROACH

14. DESIGN APPROACH CONT’D
1. Frame design
• The frame was designed with straight
pieces of mild steel angle bar
• 3D modelling and simulation was used to decide
on different truss frame members and frame load
paths
• Multiple coil springs were mounted across the
rear to achieve the desired load capacity
• Benefits however, of a single front wheel are
that the frame torsional loads are significantly
reduced

15. DESIGN APPROACH CONT’D
2. Driveline
 A three-speed driveline was designed using
standard size B V-belts, two chains and
sprocket reductions
 A pedal-actuated belt tensioner acted as the
vehicle clutch
 Spring loaded idlers on the differential belts
allowed one tire to rotate faster than the other
during a turn, while providing limited-slip
 The vehicle speed was measured using GPS
and correlated very well with simulated data

16. DESIGN APPROACH CONT’D
Driveline
The PUP driveline: engine (A), belt-pulley reduction/clutch (B), jack shaft (C), chain-
sprocket reduction (D), RWD transmission gearbox (E), drive shaft (F), and rear
differential (G)

17. DESIGN APPROACH CONT’D
3. Cargo Bed and Ergonomics
 The cargo bed, two seats, driveline shielding, and engine cover
were integrated using a wood structure
 The cargo bed was constructed with a width of 1 m and length
of 2 m (2 m2)

18. DESIGN APPROACH CONT’D
Dimensions for MV Mulimi

19. DESIGN APPROACH CONT’D
4. Wheels
MV mulimi is a three wheel design due to the following
considerations below;
• Costs are reduced due to fewer components
• It’s steering mechanism is a simple mechanical tiller
• It’s frame experiences very little twisting even under heavy
loads as opposed to 4 wheel vehicles

20. MV MULIMI FOR TRANSPORTATION
 Available transportation options are either
unreliable, have a small load capacity, or are
expensive to purchase
 Affordable motorbikes imported are excellent for
carrying a few people or goods quickly to and
from the markets, but their capacity is very limited
 People are forced to carry loads manually: a job
that often falls to women and children
 Because of poor transport, many rural people
remain primarily subsistence farmers, with little
impact on the regional economy

21. MV MULIMI FOR TRANSPORTATION
 Commercial farming was approximated to yield 1.5 tonnes of farm
produce
 Together with agricultural inputs (0.5 tonnes), it required a cargo
bed of capacity 2 tonnes
 From the eqn 𝑽 =
𝒎
𝝆
,
 where ρ 𝑜𝑓 𝑡ℎ𝑒 𝑚𝑜𝑠𝑡 𝑑𝑒𝑛𝑠𝑒 agricultural produce
 m, mass of agricultural produce, and
 V, volume of the cargo bed

22. ATTACHMENT OF DIFFERENT DEVICES
1. Water pump (Centrifugal impeller
pump)
 The pump is bolted onto the plate attached to
the frame
 Belt/pulley set transmission provides the
necessary power reduction (N1D1 = N2D2)
 The smaller the pulley, the more pump
discharge
 Gravity tensioning with a PTO belt as well
as power transmission
 Engine speed allows high flow rates by use
of the throttle
 The pump discharges (optimal) 500 l/min

23. ATTACHMENT OF DIFFERENT DEVICES CONT’D
2. Agro processing equipments
 These include maize grinder,
threshers, pelleting machine etc
 Bolted on a plate that is
attached to the frame
 Gravity tensioning
 Belt/Pulley reduction of 4.6
from the engine
 Integrated on the opposite side
of the exhaust pipe

24. ATTACHMENT OF DIFFERENT DEVICES CONT’D
3. Agricultural machinery
 These include Planters, ploughs,
rippers etc
 It provides draft power to a two
wheeled caddy
 A scissor jack from a small car was
used as the height control

25.  Small attached devices
o The tractor has both a belt/pulley set and sprocket/chain set
reduction which provides a power reduction ratio
o In case of any device, the farmer only varies the size of the
pulley to obtain the necessary speed (N1D1 =N2D2)
 Pulled agriculture implements
o The tractor pulls up to 900 Kg with less resistance in the field
since it is a rear wheel drive
o Stability of the implements is provided by a wheeled caddy
o Small implements are fastened on the wheeled caddy
FOR SMALL HOLDER FARMERS

26. FABRICATION
TIPS AND TRICKS USED
• Cleaned up edges of all pieces after cutting
• Edges of angle bars were rounded when they butted up on the
inside of another piece to allow for contact on all faces. An
example which required rounding can be seen below

27. FABRICATION CONT’D
• Checked positions of all pieces before welding to
insure all dimensions were correct
• To insure that frame members were square, the
diagonals were measured as seen below
Tips and Tricks cont’d

28. FABRICATION CONT’D
 The frame was entirely constructed of 40mm x 40mm x 4mm 90 degree mild steel
angle bars
A Total Length Of Angle mild steel: 120 meters (recommended that an extra 5 to 10
meters is purchased for errors
STEPS
• Different mild steel bars were marked and cut to the required dimensions for
constructing the frame
• The cut mild steel bars were welded together on a level surface
• Holes were then drilled through parts which required mechanical fasteners
• The frame was built and periodically checked for straightness on a level surface
• The welded joints were smoothened using a grinding machine
• The frame surface was finished by painting
1. Frame Assembly

29. FABRICATION CONT’D

30. 2. SUSPENSION ASSEMBLY
• It consists of two smaller assemblies, the trailing-arm rear assembly and the
front strut assembly
• Each wheel was designed to have hydraulic brakes and spring suspensions for
comfortable operations
FABRICATION CONT’D

31. FINDINGS
 During the performance test which was done at MUARIK, the tractor was stable
with minimal slippage
 Good steering mechanism using motorcycle handles

32. REFERENCES
• Frame, X. X. M. M., Anselm, B. T., Coverdale, K.,
Robison, J., & Roush, D. (2015). 2014-2015 A SSEMBLY
M ANUAL.
• Jr, J. H. L. (2006). Design of a Sustainable , Locally
Manufacturable , Agricultural Utility Vehicle for
Developing Countries.
• Transportation, A., & Mechanization, A. (n.d.). Practical
Utility Platform ( PUP ).