International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056

Volume: 06 Issue: 04 | Apr 2019 www.irjet.net p-ISSN: 2395-0072

“Design, Development and Manufacturing of CVT for ATV through Real

Time Tuning”
Kulkarni maithili1, Pawar hrushikesh2, Nashte kailas3, Uttarwar shivam4,Pratik Tikar5
1B.E. UG Student,Dept. Of Mechanical Engineering, Dr.D.Y.Patil Institute of Technology, Pimpri-411018, Maharashtra,India
2B.E. UG Student,Dept. Of Mechanical Engineering, Dr.D.Y.Patil Institute of Technology, Pimpri-411018, Maharashtra,India
3B.E. UG Student,Dept. Of Mechanical Engineering, Dr.D.Y.Patil Institute of Technology, Pimpri-411018, Maharashtra,India
4B.E. UG Student,Dept. Of Mechanical Engineering, Dr.D.Y.Patil Institute of Technology, Pimpri-411018, Maharashtra,India
5Assistant Professor, Dept. Of Mechanical Engineering, Dr.D.Y.Patil Institute of Technology, Pimpri-411018, Maharashtra,India

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Abstract - As the government enacts new regulations for
automotive fuel economy and emissions, the continuously
variable transmission, or CVT, continues to emerge as a key 2. PROBLEM DISCRIPTION AND BAGROUND
technology for improving the fuel efficiency of automobiles
with internal combustion (IC) engines. CVTs use infinitely The TEAM DURGYANAS is a student engineering project
adjustable drive ratios instead of discrete gears to attain team at the SPPU University that designs, builds, tests, and
optimal engine performance. Since the engine always runs at competes with a fully custom off-road racing vehicle in the
the most efficient number of revolutions per minute for a Baja SAE racing series. The Baja SAE series restricts teams to
given vehicle speed, CVT-equipped vehicles attain better gas the use of a common engine that is not allowed to be
mileage and acceleration than cars with traditional modified. This forces teams to concentrate on the efficient
transmissions. The project aims at designing and power delivery to the wheels. The Baja team uses a custom
manufacturing the Continuously Varying Transmission Continuously Variable Transmission (CVT), similar to those
(CVT). The CVT is designed considering the requirements of used on commercial ATV’s and snowmobiles. One large
SAE BAJA event and the engine used in the event i.e. B&S 10 drawback to CVTs, as compared to a traditional gear based
hp engine. This CVT provides better acceleration and ease in transmission, is the inherent efficiency loss with the
handling as compared to the manual transmission and cost transmission of torque through friction and belt slip. We are
effective as compared to the other transmissions available in the group of four members working towards improving
the market. acceleration and general driveline performance in the 2018
vehicle by reducing these inefficiencies. Thus, the racing
Key Words: SAE BAJA, CVT team has tasked us with creating a Continuously Variable
Transmission (CVT)
1. INTRODUCTION
3. ACTUATING MECHANISM OF CVT
With growing demand for environment friendly
technologies, automobile manufacturers today are Different types of variators are used to have desire
increasingly focusing on ‘Continuously Variable movement of the pulley, they are roller based, slider based
Transmissions’ (CVTs) as an alternative to conventional and cam base, these all are mechanically actuated variators,
gearbox transmission; to achieve a balance between fuel while hydraulically operated and electrically operated
economy and vehicle performance. By allowing for a actuators are also available. Basically all the variator is used
continuous band of gear ratios between the driver shaft and to actuate the pulley to have the required speed ratio.
driven shaft, a CVT permits the engine to operate for the Mechanical variators are simple in construction but less
most part in a region of high combustion efficiency resulting accurate while the other variators are complex but accurate.
in lower emissions, and higher fuel economy. In this CVT mechanical variator is used with cam based
actuator, which is smoother than the roller and slider type
Because there are no steps between effective gear ratios, actuators. Cam is designed base on the displacement of the
CVTs operate smoothly with no sudden jerks commonly driving pulley required. This displacement is converted into
experienced in manual transmission. Since drivers expect a the rotating motion of the cam and the CG location of the
car to jerk or the engine sound to change as they press the cam. Profile of the cam is generated in such a way that the
accelerator pedal further, it is very confusing for them when cam is always being in contact with the slider roller. Cam
the car smoothly accelerates without the engine revving push the movable pulley of the primary clutch to make them
faster. Drivers have unfortunately perceived this as the car closer to each other while the belt and the primary spring
lacking power which is causing a marketing problem for the resist the motion of the pulley and try to expands the pulley.
transmissions. So cam has to produce enough force to overcome the belt
force and the spring force. But forces in cam is generated

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 International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 06 Issue: 04 | Apr 2019 www.irjet.net p-ISSN: 2395-0072

only due to centrifugal action. Forces generated and Maximum R.P.M=3800 RPM
transmitted in primary clutch is shown
Minimum R.P.M =1750 RPM

Maximum Speed= 60KMPH

Tyre Diameter=.5842m

Design of CVT

Step (1)

Gear Ratio Calculation as per the Requirement of Vehicle

1) Speed of Tyre (N)

V=
Fig-2 Actuating mechanism of cvt 16.66=

4. CVT Vs STEPPED TRANSMISSION N=544.64 RPM

Maximum Rpm of engine is 3800 Rpm and in the
The CVT is designed and tuned to maintain an optimal ratio drive train two stage reduction gear box is also
between the engine and drive train to keep the engine used with reduction ratio 7
operating at its peak power. The diagram below depicts the 2) So , speed reduction required in CVT is Calculated
difference between a standard “stepped” speed transmission as
and a CVT. For the Baja SAE India Racing vehicle, the =
competition specified engine has a very narrow speed range
where it produces the maximum power. Therefore, the CVT =
is used to avoid operating outside of the maximum power
range. =.9
So, Minimum gear Reduction Required to have a
maximum speed 60KMPH is = 0.9

3) Torque Required at wheel (TW)

Torque Required=

To calculate total resistance effort 1stup all we calculate

the total resistances which are coming on vehicle

4) Air Resistance (RA)

RA= µAR*A*V2
= 0.5*1.22*.778*16.662
=132.26 N
Fig-3 CVT vs Stepped transmission 5) Rolling Resistance (RR)
RR=µRR*W
4. ANALYTICAL DESIGN OF CVT COMPONENTS
=0.05*250*9.81
Data Available =122.62 N
6) Gradient Resistance (RG)
Engine power= 10HP = 7.45Kw RG= W*sinθ
= 250*9081*sin(35)
Frontal area of Vehicle=0.778m^2 (θ=35 Because of Maximum Gradient in Hill climb
/sled pull Event is 350)
Weight of Vehicle=250Kg (With driver) = 1406.69 N
7) Acceleration Resistance (RAc)

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 International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 06 Issue: 04 | Apr 2019 www.irjet.net p-ISSN: 2395-0072

RA c = a* From equation (3) HGR3= = 3.5

Acceleration of Vehicle (a) As per above result 3.5 is the lower gear
Total torque of Wheel as per rated engine Torque and two reduction ratio is selected
stage reduction gear box and transmission efficiency
8) Torque at Wheel = Rated engine Torque *
Reduction Ratio of GB STEP (2)
= 19*7*4
=532 N.M Diameter calculation of primary and secondary
9) Torque =Force*Radius of Wheel pulleys as per gear ratios
T = F*R
F= Higher gear ratio = 0.8

= Lower gear ratio = 4

= 1821.29*.75
Then assume the dia of primary pulley
F =1365 N
This is the force required at wheel
DP = 155 mm
F=m*a
a= dP = 45 mm
a=
( these dia are selected as per packaging space of vehicle )
a= 5.74 m/sec2 then

So, RA c=a* Calculation of dia. of secondary pulley

=5.74*  The power transmission through pulley at pitch

dia. of pulley at which v belt in direct contact
= 146.02 N So when we calculate the all dia. considering pitch
dia.
10) Then Total Resistance  For pitch dia. 1st up all we select the belt cross
(1) Considering air and rolling resistance only section so according to power rating and max
TE= RA + RR RPM we select the V Belt with C-Cross Section
= 132.2+122.62 Which have Following Dimension.
=254.88 N …………..(1)
 So We have also consider the pitch thickness of
(2) Considering air , Gradient and rolling
belt while calculating the pitch dia. of secondary
resistance
TE= RA + RR+ RG
= 132.26 + 122.62 +1406.69 (1) L.G.R=
= 1661.57 N …………..(3)
(3) Considering air , Gradient, Acceleration and
rolling resistance 3.5
TE= RA + RR+ RG +RA c
= 132.26 + 122.62 +1406.69 +146.02 Ds =220.5 mm
=1807.59 N …………..(3)
So Torque Required at Wheel
(2) H.G.R=
Torque =Total resistance*Radius
TW = 1807.59*0.2921
TW = 527.99 N.M
0.8
11) So, speed reduction required
Higher Gear Ratio =
0.8
=

From equation (1) HGR1= =.55 dS = 98.5mm

From equation (2) HGR2= =3.24 So final dimensions of primary and secondary

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 International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 06 Issue: 04 | Apr 2019 www.irjet.net p-ISSN: 2395-0072

(1) Pitch dia. Of secondary and primary pulley Then C-section with 890 mm belt length is selected
from manufacturing catalogue of V.B Bhandari.
dp=59mm
Step (4)
Dp=141mm
Axial displacement of sheave (total) for transferring
ds=112.5mm belt lower to Higher Dia. Pitch dia.
( considering edge to edge dia of pulleys )
Ds=206.5 mm
(1) Axial Displacement of movable primary pulley
(2) Edge to Edge dia. Of secondary and primary Xp=2*(Rp-RpMin)*tan(α)
pulley
α=half wedge angle=110
dp=45mm Xp=2*(68-27)*tan(11)

Dp=155mm Xp=15.93mm
Xpe= 2*(75-20)*tan(11)
ds=98.5mm Xpe=21.38mm

Ds=220.5mm Xp=2*(68-27)*tan(11)

Step (3) (2) Axial Displacement of movable Secondary pulley

(3)
Belt Length Calculation Xs= 2*(Rsmax-Rs)*tan(α)

(1) Considering lower dia of primary and higher dia. = 2*(108-61.2)*tan(11)

Of secondary
D=216mm =18.193mm
d=54mm
Step (5)
L = 2C+
calculation of maximum and minimum centrifugal force
C=centre to centre distance =215mm
C.F= mrw2
L = 2*215+
N max=3800 Rpm
L=884.63mm
N min=1750 Rpm 100 Rpm
(2) Considering higher dia of primary and lower dia.
Of secondary r max =65mm
(3)
D=136mm r min =45mm

d=122.4mm w max= =397.93 rad /sec

L = 2C+
w min= =183.25 rad /sec
C= centre to centre distance =215mm
m=0.06 kg
L = 2*215+
C.F max=
L=836.10mm

So maximum length of above is considered and C.F max=617.5*8

calculate the actual length of C-section belt from
manufacturing catalogue =4940 N

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C.F min= Nt =5+2

=7
C.F min=90.66*8 Actual deflection=20.135

=725.28N
Medium (soft) BetN black and orange
Step (6)
d=4mm
spring design
D=40mm
(1) Spring in primary side
Material- Aluminum Spring (SW --Grade) K=10N/mm
Sut =1440 N/mm2
‫=ﭐ‬.5Sut N=4
=570 N/mm2
Nt=4+2=6
Whals Factor
Solid length=24+16+7.5
K=
=74mm

C=8 for spring clutches Spring in secondary pulley

K= d=4mm

D=56mm
K=1.184
K=1.962N/mm
Wire Diameter
N=4
‫= ﭐ‬K( )
Nt=N=4
=K( Solid length=24+16+7.5

d=4.241mm =74mm

d≈5mm Free length= 92+22

D=c*d Solid length=24mm

=8*5
5. PROCEDURE FOR TUNING
= 40mm
There are several methods and recommended processes for
Deflection “ideal” clutch tuning. however, if one is looking for optimum
output instead of simple performance improvement ,trial
= and error iterations is the only key.
These steps can sum up the primary procedure:-
17 =
 Check the engine parameters : The entire working
of CVT setup depends upon the continues input
N=4.22 from engine and the feedback from CVT. we need to
N=5 assure that the CVT feedback keeps the engine at
N= No of active coil power peak with increasing RPM .check first the
rpm where you obtain maximum torque and
Total no of coil=N+2 maximum power. This rpm band will be where you
have to operate your cvt within. For briggs and
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 International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 06 Issue: 04 | Apr 2019 www.irjet.net p-ISSN: 2395-0072

Stratton engine, its generally 2300-2700 rpm for

torque peak and 3500-3700rpm for power peak.
 Engagement rpm: it is preferred to have CVT
engagement rpm at torque peak rpm. this helps
your vehicle to propel at max possible torque to
wheels and hence provide optimum thrust for
further acceleration. thus, you need to set your
primary clutch spring pretension and flyweight
such that primary clutch sheaves come together to
clutch and engage the belt at torque peak rpm.
 Shiftout rpm : the ideal shiftout should take place at
power peak due to obvious reason as your
transmission should reach to its least opposition to
engine at power peak rpm to harness optimum
efficiency.
 Coarse tuning parameters: They cause maximum
impact and hence need to be checked first
:1)flyweight 2)ramp profile .iterate within
tolerances till you get best performance.
 Fine tuning: change the secondary spring twisting
rate and helix. Continue iterations till you get best
performance . Fig-4 CVT performance curves

 Super fine tuning : try various combinations like 7 .MODELING OF CVT BY USING CATIA V5R19
low weights, low spring stiffness, high weight-high
spring stiffness; high weight low –low spring
stiffness ; high weight low spring stiffness to make
sure your vehicle weight and its dynamic opposition
is collaborating with your engine performance.
6. RESULT ANALYSIS FOR TUNING

Fig-5 Catia model of cvt

CONCLUSIONS
From the above research work our team concluded that CVT
has potential to increase fuel efficiency of the vehicle as well
as decreasing the emission of harmful gases from exhaust

The research on CVT gives us increased acceleration and

torque by using various tuning option like flyweights, helix
optimization in secondary pulley and spring stiffness.

Further design and development of CVT laid to increase in

safety of vehicle and reduction in maintenance cost of
engine.

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 International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 06 Issue: 04 | Apr 2019 www.irjet.net p-ISSN: 2395-0072

REFERENCES

[1] Kevin R. Lang- Continuously Variable Transmissions An

Overview of CVT Research Past, Present, and. Future, SAE
International, February 1998

[3]K VINOD KUMAR- study and design of automobile

continuously variable transmission Science Direct 2010

[4] Akshay Kumar, Sayan Karmakar Nasit Malay-

performance optimization ofcontinuously variable
transmission (cvt) using data acquisition systems Scientia
Iranica 23 Jule 2011

[5]Nur Cholis, Sugeng Ariyono, Gigih Priyandoko-Design of

single acting pulley actuator (SAPA) continuously variable
transmission (CVT),Science Direct

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