AREA 1: AB POWER, ENERGY, AND MACHINERY ENGINEERING AND ALLIED SUBJECTS PROBLEM SOLVING

 If the speed ratio of the groundwheel over seedplate of a two-row corn planter is 5.0, determine the plant population per hectare.  Row spacing is 75 cm.  Groundwheel diameter is 60 cm.  Ave. no. of seeds per hill is 2.  No. of cells of seedplate is 25.  Ave. emergence of seeds is 85%.

Determine the no. of days (8hrs/day) to plow a 10-ha field using a 3-bottom moldboard plow drawn by a 4-wheel tractor at a speed of 5 kph and field efficiency of 76%.  Width of cut of one bottom is 33 cm.

Using the results of the calibration test of the 8X20 cm drum seeder, determine the seeding rate (kg/ha) if Qmedium is used.  Row spacing is 40 cm. Groundwheel diameter is 50 cm.  Discharge of one row per 10 revolutions of the groundwheel: Qlow = 16 gms, Qmedium = 22 gms, and Qhigh = 38 gms. 

A 3-ha field was plowed using a 15-cm wide animal-drawn plow at 4 kph and field efficiency of 75%.  The draft required to pull the plow is 60 kg. Find the time required to plow the field: 

A 9-tooth sprocket operating at 200rev/min drives a 23-tooth sprocket. The pitch of this chain is 41.4 mm and the ultimate strength is 9.34 kN. Calculate the average linear speed, recommended maximum power and average torque applied to the drive shaft at recommended power.

A 540-rpm tractor PTO will be used to power a hydraulic pump. The pump is equipped with an 15-tooth sprocket. If the pump must turn 2,400 rpm, determine the size of the driver pulley. What is the speed ratio?

A water pump running at 900 rpm is driven by a 20-hp, 1250 rpm, diesel engine. The pulley mounted on the shaft of the diesel engine is 12 inches. Center to center distance is 1.4 meters. Determine the minimum angle of wrap, tensions on the tight and slack side, and length of belt. Use coefficient of friction of 0.35.

Compute the deflection of a 18 coils 10-cm diameter helical spring having a load of 100 kg. Wire diameter of spring is 9.5 mm. Use G=90 GPa.

 A helical spring attached in the baling mechanism of a baler machine is designed for an operating range of 100 to 150 N. Spring deflection should not be more than 2 inches. Determine wire diameter of spring and the no. of active coils. Use C=10, design stress of 170 Mpa and G-= 80 Gpa.

A 10-x 10-mm key was used in a 45-mm diameter shaft of a 30 kW diesel engine rotating at 1200 rpm. Calculate the shear stress in the key and the torsional stress in the shaft. Assuming length of key to be 1.5 times shaft diameter.

A 0.5-m long solid shaft of a rice thresher is stressed at 100 MPa during operation. If the torsional deflection is 2 degrees, compute the shaft diameter. What power is transmitted by the shaft at 20 Hz? Use G = 83 GPa.

Calculate the diameter of a SAE 1030 steel shaft is used to transmit 10 hp at 1100 rpm. Torsional deflection was found to be 0.08 degrees in a length of meter. G (modulus of rigidity) of steel is 82.7 Gpa. Use a safety factor of 2.

A 35.5 cm long SAE 1030 solid steel shaft is used to transmit mechanical power from an engine to a biomass shredder at a rate of 25 kW at 1450 rpm. Torsional stress during operation was 7.4 Mpa. Calculate the diameter of the shaft.