# Manual Transmission calculations – 2 | Tractive forces, accelaration and gradability

Some basic formula for the calucation of various dynamics of vehicle…..for gradability the force component will be resolve in two component one is along the road and one is perpendicular to the road. only along the road component will help in climbing and perpendicular to the road will cause the vehicle to topple. there are various losses in engine , tranmission due to various friction so the result which is gonna come is gonna be in ideal case(i.e no friction etc) so what ever you get after calculation the actual result will be only 60-70 % of that. so calculate accordingly.

here is sample calculation(  ideal case)

At hill climbing, tractive force available at an inclination of 45°,
F=Wsinθ- μWcosθ ≈2081N
Power =10hp=7460 Watt =F*V
V=3.58m/sec=12.9km/hr
So, our vehicle can climb the hill of inclination 45° with this velocity.
Air resistance (Ra)= Ka*A*(V)²
 Ka= 0.004725 – 0.005 ,depending upon type of vehicle we have considered it to be 0.005
 Area (A) = Projected front area= 1.025 m²
 Velocity = 59.06km/hr
Hence Ra=17.88N
Rolling Resistance (Rr) = K*W
 W=total weight of vehicle= 300kg
 K is a constant and depends upon the nature of surface
 We have considered the road surface to be loose mud whose rolling resistance is 0.0435
Hence Rolling resistance (Rr) = 128.02N
Total resistance= Ra + Rr =145.9N
Traction –
F= (Te* Gear ratio* Transmission efficiency)/wheel radius
 Te=engine torque= 19Nm
Hence F=756.21N (at low speed)
Acceleration:
a=(F-R)/m=2.03m/sec²
So, 0-60 km/hr in 8.21 sec. ## 30 thoughts on “Manual Transmission calculations – 2 | Tractive forces, accelaration and gradability”

1. Prashant says:

Thanks. That helped a lot. There’s a doubt related to gradability. As per definition ,Gradability is the highest grade or ability a buggy can ascend at a speed. And I have considered gradability in terms of angle of inclination. So if my vehicle goes upto a hill climb of 60 deg , is it 100% gradable?? Am I correct? I have no particular formula for gradabilty, but just an approximation. Need help for this. Or can I calculate it from the traction vs speed diagram??

1. Baja Tutor says:

Prashant, Pleasure is ours 🙂 you can calculate from Traction vs Speed Diagram !

2. Parteek Kumar Mahey says:

this might help u 🙂

3. Mohak Sheth says:

i.e. tan45=1*100=100% and tan30=.577*100=57.7 %

2. nikhil singh says:

great

3. Shubham Saraswat says:

Can u explain how can I calculate the efficiency of transmission….???

4. sushant shingare says:

i would like to know how to calculate the overall efficiency of transmission including all the resistances.

5. nikhil singh says:

F=Wsinθ- μWcosθ ≈2081N
Is this surely correct?

1. chetan badsar says:

how do i calculate the hill climb angle

6. Parmeshwar Maske says:

Yet i am not cleared the meaning of IBJ and OBJ .Is it cocept of ball joints or removing the problem of vibrations…….?????

1. Prashant says:

IBJ and OBJ are not related to vibrations for sure..

7. mayur kava says:

8. nikhil singh says:

how to ensure we are not providing extra torque to wheels ? then they will start slipping.

1. Abhishek Upadhyay says:

The overall efficiency you want to calculate is the research subject. there are lots of losses which we neglect during the calculation. and if you want to calculate all of that losses then it will take time and lots of research. still you want to calculate then…..you can go on internet where you can find some paper which were submitted on this topics.

1. salman says:

bt in above calculations by baja tutor..the resistance is coming near about my value

1. Abhishek Upadhyay says:

the acceleration you got is the maximum acceleration that can be achieved by the vehicle. the drag you have consider is at 60 km/hr. the torque you have consider i.e 19Nm is the maximum torque output of engine…. and engine torque is vary with the RPM of engine. the rolling friction is high when vehicle is at rest and decreases as the vehicle starts moving. So, the calculation is shown above by bajatutor is purely ideal case. the true way to define acceleration of the vehicle is like this (0-60 km/hr in 8.21 sec). So, if you want to know the actual acceleration of vehicle consider all above points then start calculating. The above solution given by the bajatutor is for the basic idea that how acceleration should be calculated. there is no exact and precise way to calculate the acceleration because, we wont be able to account all the losses.

9. salman says:

above in traction, u haven’t divided the wheel radius such that if u ll divide then the traction force will come as 2381.76N which will give acc. as 7.45m/s2 which is pretty high….so plz tell me the soln fr the same

1. Abhishek Upadhyay says:

yes IBJ and OBJ is not related with vibration. NVH is related with vibration. IBJ and OBJ is relates with the ball joint.

10. Prashant says:

1} First calculate torque on wheels by using engine torque and your gear ratio.
2}Torque on wheel and radius of wheel will give you force on wheel i.e. total force= Torque on wheel/ radius.
3} Now calculate drag and rolling resistances, add them up to get total resistance.
4} (Total force-total resistance) will give you available traction, or tractive force.
5} Tractive force / weight of vehicle will give you acceleration.
This was how I calculated my vehicle’s acceleration. Baja experts correct me if I am wrong anywhere.

11. salman says:

actually i hv done the same thing but what i m getting is….
1.firstly i hv calculated the total resistance(drag rolling)=130.54N
2.secondly i hv calculated the torque on wheels=18.65*13.25*3.7*0.8=731.45Nm
3.nw taking out the traction force by dividing it wid wheel radius=731.45/0.3=2438.17
4.acceleration=(2438.17-130.540/280=7.45m/s2……….
so the acceleration which m getting is quite high…so plzz correct me coz i knw m wrong smwhere

1. Parteek Kumar Mahey says:

i think u doesn’t use the rotational inertial coefficient that’s why acceleration value is coming out to be soo large…

1. nikhil singh says:

Anyone?

2. Prashant says:

Check out your value of resistance . Its much lesser than what I have calculated. Its about 534 N.

12. Prashant says:

What is the assumed weight of your buggy????

13. salman says:

280

14. vineet says:

Sir how to determine engine torque for Electric vehicle? And how to calculate transmission efficiency and weight and gear ratio?

1. Shubham Sugandhi says:

yes
15. Arunava Nag says:
16. Shubham Sugandhi says:
17. Kirtan patel says: