The average of allsubgroups becomes the centerline for the lower plotting area. Average of Ranges Example Step 7 - Calculate the upper control limit (UCL) and lower control limit (LCL)for the averages of the subgroups. At this point, your chart will look like aRun Chart. Now, however, the uniqueness of the Control Chart becomes evidentas you calculate the control limits.
Ford Motor Company recommends that the Crown Vic limit its towing to a trailer with a gross vehicle weight of 1500 lbs or less with a tongue weight not to exceed 150 lbs. See HERE.
Letâs say you have a 5,000 pound trailer. A tow vehicle with a 6,500 towing capacity would be a great choice. Its capacity is a little bit more than what you need, and thatâs just what you want. Tongue weight should be 7 to 8 percent of overall trailer weight, which means a Class III hitch would be best.A Class III hitch is rated from 350 to 600 pounds of tongue weight, which, again, is a little more than what you need, and thatâs just what you want.Choose the hitch-ball size based on what your trailer requires.The draw bar, however, requires a bit more thought.ts capacity is a little bit more than what you need, and thatâs just what you want. Tongue weight should be 7 to 8 percent of overall trailer weight, which means a Class III hitch would be best.