Automotive Calculations

Index-Vehicle Performance Calculations 1.  Calculating Torque at wheels 2.  Calculate Tractive Effort at wheels-TE 3.  Finding Engine torque value 4.  Max permissible Tractive effort due to   Ground Adhesion- TEGA 5.  Vehicle Speed calculation 6.  Wheel slip Condition based based on Tractive effort. 7.  Power to weight ratio : PWR

Power to weight ratio : PWR Power-to-weight ratio  is a measurement of actual performance of any engine or  power  source. It is also used as a measurement of performance of a vehicle as a whole, with the engine's  power  output being divided by the  weight  (or mass) of the vehicle, to give a metric that is independent of the vehicle's size. It is defined as per requirement of vehicle performance. It can be defined in terms of (in SI Units) HP/Tonne Kw/Tonne Kw/Kg Example Engine Power= 350 Hp Vehicle GVW=18000 Kg= 18 Tonne PWR= HP/Tonne 350/18= 19.5 Article Contribution by Sandeep Bhasme.

Wheel slip Condition based based on Tractive effort. To determine wheel slip condition we will need to compare Tractive Effort due to Ground adhesion vs Tractive effort produced due to power train aggregates. TEGA =  Tractive Effort due to Ground adhesion TE= T ractive effort produced due to power train  aggregates. condition: TEGA > TE ; No slip TEGA < TE ; wheel will slip - Not favorable condition for design . TEGA Calculation Formula https://autocal1.blogspot.com/2020/06/max-permissible-effort-due-to-ground.html TE calculation Formula https://autocal1.blogspot.com/2020/06/calculate-tractive-at-wheels-inputs.html

Vehicle Speed calculation By using Prescribed method you will be able to find vehicle speed at any Gear  you will need to have these inputs to perform the calculation: 1) Engine RPM (N)=2500 2) Tyre revolution/Km (M)=398 3) Total reduction of power train (Rg)=14.3856:1 vehicle Speed formula is given by V =Vehicle Speed in Km/hr. V= (N X 60) / ( M x Rg)   =(2500 x 60)/(398 x 14.38)   =26.19 Kmph

Max permissible Tractive effort due to Ground Adhesion- TEGA To Calculate Max TE due to ground adhesion  you will need to have following data as input. Mue =Coefficient of friction between road and wheel =0.7 (Dry road) =0.4 (wet surface) GUV( Gross vehicle Weight)= 9500 Kg Formula: Tractive effort= GVW X Mue=9500 x 9.81 x 0.7 = 65236.5 N

Finding Engine torque value You must have Engine Torque and power curve data sheet, You can get this from engine manufacturer or from their website. Engine torque and power is mapped against Engine RPM. A typical example can be seen here. Torque curve sample Image