Download : CALCULATIONS FOR FNR GEAR BOX AND CVT COMBINATION

Gear Reduction Selection

Power Requirements against:

 

Fr: Wheel Resistance

FL : Air resistance

Fs: Gradient resistance

Fa: Acceleration resistance

 

Wheel Resistance= Rolling resistance + Slip Resistance + Road Resistance

Tr: Brake Torque

 

Assumption taken

 

Unmade road coefficient of friction fr= .16

mass of vehicle being=Mf

 

CALCULATIONS

 

Fr=fr*Mf*g*Cosαst     where αst=30˚

 

Fr=0.16*200*9.81*Cos 30

Fr=280N

 

Total Load R=113kg(driver)+200kg (vehicle)

R=313*9.81=3070.50N

 

Static Resistance=µR

=0.65*3070.5=1995.84N

 

Vmax=60kmph

Wheel Radius r=221.875mm

= .221m

Air Resistance

 

FL:0.5ρCwAv2

Ρ=Air Density

Cw=Drag Coefficient

A=Area

V=velocity

 

FL =0.5*1.99*0.0315*(16.66)2

=0.52N

 

 

Gradient Resistance:

Fst=Mf*g *Sinαst

 

Putting the corresponding value

Fst=131.725N

 

Acceleration resistance:

Fa=m*a

=956N

Ftotal=2662.247

 

Power Required: Ftotal*v/(Nrpm*η)

Comments

  1. nikhil singh

    can you share a sample calculation of max torque which can be applied on wheels so that it doesn’t slip . Actually I know how to do it just want to verify as i am getting very low value. Pls reply soon I have to finalize my baja report

    1. Baja Tutor

      1.) Calculate normal force: F = M* 9.81 = X N
      2) Multiply normal force by a friction coefficient – (Rolling resistance not static one, lets say its 0.6) and wheel radius: T = X * 0.6 * 0.4394 = Y Nm
      3) Divide by number of wheels: T/4 = Z Nm.
      Note : A BAJA buggy will have a different load on the front and rear wheels, so they have different required torques.

  2. sushant shingare

    can you give a sample calculation for calculating efficiency of transmission including all the resistances

  3. Rohit Garg

    hey,
    you have calculated the aero drag at 60kmph and also considered the acceleration resistance, so when ur car is already at top speed, e.i. 60kmph than how can it accelerate?

  4. Santosh Kumar.S

    Hello mate…
    In calculating Air resistance…..what do u infer by “area”… On what basis you’ve taken it as 0.0315..?

    …… eagerly waiting for reply

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