3-19 Design a pin-jointed linkage that will guide the forks of the fork lift truck in Figure P3-5 up and down in an approximate straight line over the range of motion shown. Arrange the fixed pivots so they are close to some part of the existing frame or body of the truck. 3-20 Figure P3-6 shows a "V-link" off-loading mechanism for a paper roll conveyor. Design a pin-jointed linkage to replace the air cylinder driver that will rotate the rocker arm and V-link through the 90 motion shown. Keep the fixed pivots as close to the existing frame as possible. Your fourbar linkage should be Grashof and be in toggle at each extreme position of the rocker arm. 3-21 Figure P3-7 shows a walking-beam transport mechanism that uses a fourbar coupler curve, replicated with a parallelogram linkage for parallel motion. Note the dupli- cate crank and coupler shown ghosted in the right half of the mechanismthey are redundant and have been removed from the duplicate fourbar linkage. Using the same fourbar driving stage (links L1, L2, L3, L4 with coupler point P), design a Watt I sixbar linkage that will drive link 8 in the same parallel motion using two fewer links. *3-22 Find the maximum and minimum transmission angles of the fourbar driving stage (links L1, L2, L3, L4) in Figure P3-7 to graphical accuracy. *3-23 Figure P3-8 shows a fourbar linkage used in a power loom to drive a comblike reed against the thread, "beating it up" into the cloth. Determine its Grashof condition and its minimum and maximum transmission angles to graphical accuracy. 3-24 Draw the Roberts diagram and find the cognates of the linkage in Figure P3-9. forks fork lift truck FIGURE P3-5