Question

Gradeability Computations for a combine You are developing the propulsion system for a new combine harvester which will need to operate at least part of the time in hills. The field conditions in which this new combine must operate vary widely, but for the sake of analysis, we will assume the combine must climb a 10% grade and also overcome the rolling resistance of the tires as the machine propels up the slope. The coefficient of rolling friction is assumed to bef=0.2. With the given specifications (below), for the combine starting from rest, what is the speed of the combine after 5 seconds and how much wheel power is required to maintain that speed while continuing to dimb the hill? 10000 Vehicle Data Total Vehicle Mass Drive wheel torque Tire rolling radius Grade Coeff. Of Rolling Friction in Max Engine Power mm 136000 1000 10% 0.2. 450 The above photos show combine gradeability testing at White Ranch, California, 2007. Make a free body diagram of the situation described above. Perform the requested calculations and comment on the amount of engine power which must be made available for propulsion of the combine. Realize the engine must supply power to the threshing system, grain cleaning system, residue system (straw chopper/spreader), hydraulic system and other systems. Typically we might target a maximum of 1/2 the engine power going to propulsion is the engine large enough for this combine?

Answer 1

Given information m= 40,000 Fpropulsion T= 1,36,000 nm o r= 1000 mm Frolling Grade = 10% Egrade so ymg f = 0.2 Tam o =01 9825.71° Pengine =450kw since o is small sino=Tano Frorat = Frolling & Egradient = fxmgx coso & mg sino = 02740,000 X9.51COS 5.01 + 40,000 x 9.81% Sin 5:21 = 78090 + 39045 Floral = 117135 N Toral force available = TXr = 1,36,000x 1 = 136000 ma= Favailable - Frelist = 1,36,000 - 1,17, 135 a= 0.4716 m/s² Velocity after 5 sec = v= utat =of 0.471645

V=2.358 m/s I = 8.49 Km/hr Power needed to maintain 8.49 Km/nr. P= Freisrance Xv - 117135x2.358 PE 276209 w P= 276.21 kW power for propulsion, 50% if targer is to use we need engine of 552 kW • power