7.3 Combining Road Sections
7.4 Combining Skidding Systems
The standard applications of PACE were discussed in Chapter 6. Occasionally, you may want to model other situations. In this section we present several advanced applications of PACE. These applications will assist you in thinking up additional ways to model situations you are interested in studying.
The PACE program is designed to build upon machine rates so that the analyst can trace back a harvesting cost-road cost analysis to the set of underlying assumptions. Occasionally you might want to get unit costs quickly without making a number of machine rate files and road cost files. In this situation, it may be useful to keep a .UCD file on your disk. You only need to build this file once and save it. When you recall this dummy file, it satisfies the input requirements for PACE. You can then change machine costs in the various screens. The only thing you need to remember is that PACE uses the proportions derived in the original machine rate files to divide any revised machine rates between ownership, operating, and labor costs. If all you are interested in is the total unit cost for any activity, it does not matter.
Often the road from the landing to the mill may have two or more road standards or other factors which affect the travel speed of the truck. PACE only permits entry of one truck speed.
If you want to calculate a truck transport cost which includes the total route you will need to derive the average loaded and average unloaded speed outside of PACE and use these average speeds in PACE. The example below shows how to do this for a road divided into three sections.
The speed on section 1 is V1, on section 2 is V2 and on section is V3. The length of the sections are L1, L2, and L3 respectively.
The average speed is calculated by dividing the total travel distance by the total travel time, or
This calculation would be repeated for the loaded and unloaded direction.
In some cases, PACE can be used to combine two skidding systems. The Unit Cost program can then be used to solve for the optimal skidding distance for each system simultaneously. For example, consider a situation where oxen are being used to skid along trails perpendicular to tractor skid trails, and the tractors swing the wood to truck roads. If we consider the oxen to be the "lateral skidding cycle" for the tractor skidding system we can model this system in PACE by deriving an equivalent lateral skidding speed and equivalent hook and unhook time which takes into account the difference in machine rates for the oxen relative to the tractor. The formulas for the equivalent skidding speed and equivalent hooking time are given below:
V = equivalent speed for lateral yarding to be used in Skidding Screen with tractor machine rate in Row (1) and V in Row (5) or Row (7).
C1 = machine rate for tractor
L1 = load for tractor
C2 = machine rate for oxen
L2 = load for oxen
V2 = speed for oxen
T = equivalent hook or unhook time to be used in Skidding Screen with tractor machine rate in Row (1) and T in Row (6) or Row (9).
T1 = hook or unhook time for tractor.
T2 = hook or unhook time for oxen.
Other skidding combinations which could be modeled in this way are (1) skidding by tractors and forwarding by rubber tired skidders and (2) manual forwarding and swinging by skyline.