A haul fleet of trucks having a heaped capacity of 15 cy. is to be loaded by a hydraulic backhoe excavator (CT=.48 min.) with a 3 1/2 cy. heaped capacity. Assume the material is a wet loam that weighs 3380 lb/cy in the bank state and has a swell factor of 1.2 and the bucket fill factor is 95% with this material. Assume that the haul and return times together are 10.5 minutes (this does not include load and dump times) and a 45 min.- hr. is worked. The project has to move 24,000 LCY, the backhoe cost $600 per day, the trucks $40/hr, and operators cost $20/hr for both trucks and backhoe. Assume the swing depth factor is 1.0. Assume truck dump time is 1.4 minutes.
1. Calculate the Excavator Production using the process in your text. Remember, the cycle of the backhoe was given above. Use equation 9.2 from page 271 to calculate excavator production. You don’t need to convert to BCY. You don’t have to calculate a cycle time for the backhoe. It is given above.
a. 260 LCY/hr b. 477 LCY/hr c. 312 LCY/hr d. 156 LCY/hr
2. Determine the cycle time of the trucks, including load, haul, dump, and return. The haul and return times are given above. When calculating load time, round up the number of MINUTES to the nearest whole number.
a. 11.3 min/cycle b. 12.3 min/cycle c. 16.1 min/cycle d. 13.9 min/cycle
3. How many trucks are needed to service the backhoe? Assume the trucks limit production. Round up your answer to the nearest whole number.
a. 4 trucks b. 5 trucks c. 6 trucks d. 7 trucks
4. How many trucks are needed to service the backhoe? Assume the excavator limits production. Round up your answer to the nearest whole number.
a. 4 trucks b. 5 trucks c. 6 trucks d. 7 trucks
5. What would be the cost per LCY at 75 % efficiency if the trucks limit production? Assume an 8-hr work day and round up your “DAYS” example = 9.52 = 10 days.
a. $1.29/LCY b. $2.15/LCY c. $1.01/LCY d. $1.71/LCY
6. What would be the cost per LCY at 75% efficiency if the backhoe limits production? Assume an 8-hr work day and round up your “DAYS” example = 9.52 = 10 days.
a. $1.46/LCY b. $2.15/LCY c. $1.13/LCY d. $1.96/LCY