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.
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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.
On a horizontal road,
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
 Wheel radius = 0.3175m
Hence F=756.21N (at low speed)
Acceleration:
a=(F-R)/m=2.03m/sec²
So, 0-60 km/hr in 8.21 sec.

 

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Comments

  1. Reply
    Prashant

    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??

  4. Reply
    sushant shingare

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

  6. Reply
    Parmeshwar Maske

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

    1. Reply
      Abhishek Upadhyay

      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. Reply
          Abhishek Upadhyay

          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. Reply
    salman

    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. Reply
      Abhishek Upadhyay

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

  10. Reply
    Prashant

    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. Reply
    salman

    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. Reply
      Parteek Kumar Mahey

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

  14. Reply
    vineet

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

  15. Reply
    Arunava Nag

    will there be any change in the above rolling resistance value for 2WD or AWD type vehicles…… please suggest….

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