Download Iowa State University - Agricultural and Biosystems Engineering Homework 4 and more Assignments Business Management and Analysis in PDF only on Docsity! Agricultural and Biosystems Engineering, Iowa State University Fall 2007 T:\Birrell\HWK4_mod.wpd Homework 4 Question 1 Given the following information for a tractor: (Note: Metric values are approximate conversions of the equivalent English values, therefore answers may be slightly different) Rear Axle Weight 15500 lb (7000 kg) Front Axle Weight 4500 lb (2000 kg) Total Weight 20000 lb (9000 kg) Wheel Base 110" (2800mm) Center of Gravity 24.75" (622mm)(Distance from rear axle) Drawbar Height 24" (600mm) a) Determine the weight transfer to the rear wheels if a horizontal pull of 3000 lb (13.2 kN) is attached to the drawbar. b) Under these conditions, is the weight transfer from the front wheels equal to the weight transfer to the back wheels. c) Determine the horizontal pull required for the front wheels to begin lifting of the ground. Question 2: Determine the Drawbar Pull, Drawbar Power, Actual Travel Speed and Tractive Efficiency for an Case 2094 Tractor (See Nebraska Tests) at maximum drawbar power operating in 8th Gear , with full tractor ballast under the following conditions a) mounted plough in firm soil. b) towed plough tilled in tilled soil. Question 3 A double acting hydraulic cylinder has a bore diameter of 4", a rod diameter of 2". The maximum pump pressure is 2200 psi. One cylinder port is connected to the pump, and the return line feeds directly into the reservoir. Assume a pressure drop of 100 psi in both the pressure and return line to the cylinder. Pump delivery rate is 20 gal/min a). What is the maximum load that can be moved when the cylinder is extending. b). What is the maximum load that can be moved when the cylinder is retracting. c). How fast will the cylinder extend. d). How fast will the cylinder retract. e). What is the flowrate of oil from the cylinder when it is retracting. Question 4 Given the following specifications for a gear pump listed in a catalog. Displacement = 1.8 in3/rev (29.5 cm3/rev) Rate Speed = 2500 rpm Rated Pressure = 3000 psi (20.7 MPA) Rated Delivery = 18 gal/min (68.13 l/min) Power Input = 38 Hp (28.35 kW) a). Calculate theoretical delivery. b). What is the volumetric efficiency? c). What is the actual input Torque? d). What is the theoretical input Torque? e). Calculate the overall efficiency of the pump. f). What is the mechanical efficiency. Question 5 Given the following specifications for a motor listed in a catalog. Displacement = 4 in3/rev (65.5 cm3/rev) Rate Speed = 1800 rpm Rated Pressure = 3000 psi (20.7 MPA) Required Delivery = 35 gal/min (130 l/min) Power Output = 48 Hp (35.8 kW) a). Calculate theoretical flowrate for the motor at rated speed. b). What is the volumetric efficiency? c). What is the actual output Torque? d). What is the theoretical output Torque . e). Calculate the overall efficiency of the motor. f). Determine the mechanical efficiency of the motor. Note: Hp = T N / 5252 kW = 2 p T N / 60000 Hp = Q P / 1714 kW = Q P / 60 Agricultural and Biosystems Engineering, Iowa State University Fall 2007 T:\Birrell\HWK4_mod.wpd
