_ United StatesDepartment of A Program andAgriculture

Forest Documentation forService

N°_htCEen;ra/en t i m u _at i o n of

it_iieeOar_1_1_.22, Grapple kidders_f_"___. and a Who/e-Tree

ChipperSharon A. Winsauer

North Central Forest Experiment StationForest Service--U.S. Department of Agriculture

1992 Folwell AvenueSt. Paul, Minnesota 55108

Manuscript approved for publication April 12, 19821982

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CONTENTSPage

The equipmant studied ................................ 1Model objectives ...................................... 1Simulation language--GPSS .......................... 1Model assumption ..................................... 1Model description ..................................... 3Data input ............................................ 3Data required by model ................................ 7

" Simulation output ..................................... 7• Known differences between systems .................... 10

Conclusions .......................................... 10Literature cited ....................................... 10

Appendix A--Variable lists and definitions .............. 17' Appendix B_Program listing .......................... 19

Appendix C--Complete flow charts ..................... 36

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A PROGRAM AND DOCUMENTATIONFOR SIMULATION OF GRAPPLE SKIDDERS

AND A WHOLE-TREE CHIPPER..

Sharon A. Winsauer, Computer Specialist,Houghton, Michigan

J

Computer simulation of forest harvesting systems /kfter simulating the harvest of a stand, the modelis an efficient tool for resource management. The reports productivity figures for both types of equip-purpose of this paper is to document a computer model ment such as bunches, trees and volume skidded,of a skidder-chipper system. The model was devel- trees and volumes chipped, and number of vans filled. Ioped to provide a detailed study of the interaction Additional output gives the productive and delay jbetween the skidders and the chipper. It allows the times and causes for each type of equipment, etc. tuser to determine cost and productivity, machine ef-

ficiency, and causes of delays for various system con- SIMULATION LANGUAGE--figurations. Complete variable lists, program list-ings, and flow charts are included in Appendices A, GPSS I

B, and C. IThe simulation is written in General Purpose

EQUIPMENT STUDIED Simulation System (GPSS)with output subroutinesTHE written in FORTRAN. GPSS is a discrete event sim-

ulation language developed by IBM (Schriber 1974).The equipment modeled are grapple-type skidders The user constructs a block diagram by arranging

and a whole-tree chipper with a self-loading grapple the discrete events of a system in their logical strut-(figs. 1 and 2). The simulation assumes that the fell- ture. The block diagram is made up from a group ofing was done far enough in advance of the skidders specific GPSS block types. These blocks then becomeso there is no conflict between fellers and the skid- the GPSS program. A basic understanding of theders and that wood to be skidded is always available. GPSS language allows the user to accurately inter-

' pret or modify the simulation.

• MODEL OBJECTIVES Most versions of GPSS have a standard outputformat that contains all the data in a very concise

The primary objective of this model is a detailed form. The FORTRAN subroutines are used to pres-look at productivity and efficiency of a given skidder- ent the. output values of most interest in an orga-chipper combination (size of chipper, number and nized, labeled form.size of skidders). The trees to be skidded are assumedto be bunches left by earlier felling. The number of MODEL ASSUMPTIONStrees in eachbunch can be obtained from the outputof a feller/buncher simulation (Winsauer 1980, Win- The basic time unit used in the model is a centisauer and Bradley [In prep.]), minute; i.e., 1/100 of a minute. The equipment works

one shift a day for the number of days chosen by theFor input, the model requires data on the oper- user. All volume measures are in 1/100 cubic foot of

ating characteristics of the skidders and the chipper, solid wood.the number of trees in each bunch, and stand con-ditions such as diameters of trees cut and skid dis- It is assumed that the trees in the plot have ai-

tances, ready been felled and to some degree bunched by.

Figure 1.--Grapple type skidder.

Figure 2.--Whole-tree chipper.• i• i

. ]

2. I

either man or machine. To obtain simulation results to 1 correspondence between trees skidded andinvolving the interaction of feller and skidders, it trees chipped. This required function DBH andwould be necessary to combine this model with a DIAM to be identical except for the randomfelling model. . number generator; one uses RN4, the other, RN5.

These random number generators must be givenThe following assumptions are made about the identical seed values.

I system:-.

1. The equipment works one shift a day, then is MODEL DESCRIPTIONI turned off for the remainder of 24 hours.

2. Production reports and statistics are produced The model consists of three GPSS segments: .•at the end of each 24-hour day, so they include 1. TIMER SEGMENT

2. SKIDDER SEGMENTany overtime that may have been worked on ashift. " 3. CHIPPER SEGMENT

3. Two 15-minute coffee breaks and one 30-minute and three FORTRAN subroutines for formatted (eas-, lunch break are scheduled each shift. The chip- ily read) output.

per can take a break only when the van is full. The TIMER SEGMENT (fig. 3) controls the dailyThe skidders can break when they reach the schedule, keeps track of the days worked, and sends

• landing if, and only if, the chipper is on break, information to the subroutines to produce the for-4. Each skidder travels from landing to the woods matted output. The TIMER signals the start of the

along a "skid road." It then travels through the day, the rest breaks and lunch (two 15-minute breakswoods to a bunch, grapples it, and hauls it to a a day and 1/2-hour lunch are assumed), and the endcollection point where it can drop trees and re- of the workday. The TIMER then completes the 24-bunch if desired. It also has the option of re- hour day and produces an output report of the pre-turning for a second bunch before hauling to the vious day's operation and production. Output is pro-

' landing. The load is skidded back to the landing duced at the end of 24 hours, not at the end of thealong the skid road. shift, to include the time needed to finish filling the

5. There is limited space at the landing for wood, last van before quitting for the day. If the requiredso the skidder may have to wait for room before number of days have been simulated, the model shutsdropping the load. off. Otherwise, the start of another workday is sig-

6. The skidders can quit for the day only if the naled, and the process continues.chipper has quit. The skidder always drops thebunch before quitting. The SKIDDER SEGMENT (fig. 4) models one or

7. There is room for one van at the chipper. When more identical grapple-type skidders. Each skidderthe van is full, the chipper must wait for it to retrieves bunches of previously felled trees and skidsbe moved out and another van moved in. them to a landing to be chipped.

8. A van is considered full when the volume in the

van--after the last load added--is equal to or The CHIPPER SEGMENT (fig. 5) models a whole-greater than the volume indicated in X$VANCY. tree chipper with self-loading grapple. The chipperSince the model uses hundredths of cubic feet, landing is located in or near the woods so that chip

• this value should also be in hundredths. The van vans can be brought to the chipper.

capacity must also be measured in the same type

of volume used in the models; i.e., solid wood. DATA INPUT9. The chipper can take a break or quit for the day

only after it has finished filling a van. GPSS accepts input data in several forms (table10. One specific chipper delay has been incorporated 1). For additional information on data types and card

into the model. For a certain percent of the chip formats, see a GPSS Programming Manual (Schriberloads, X$PDELY, the chipper is delayed while 1974).the log is bucked to fit into the chipper opening.By setting X$PDELY to zero, the user can elim- Most of the data required in the main programinate this delay source, are expected in the form of VARIABLES. VARIA-

11. To avoid carrying excessive data through the BLES can be defined in terms of the input data avail-model, the skidders and chippers draw d.b.h, val- able at the end of the deck allowing the user flexi-ues for the trees from separate, but identical, bility in data form while avoiding card shuffling indistribution functions. In this way there is a 1 the main program. For example, a skidding time

,

COUNTDAYS

WORKED

j i

TELL CHIPPERTO START |

.. WORK._J

=!V

WATCH QUII'I'ING TFLL CHIPPER --1

. CLOCK TIME _ .IT'STIMEQUITTING_]i

_ REAKTIME

TELL CHIPPER "-I WAIT

IT'S BREAK J UNTILTIME MORNING

!

I REPORTON

t

YES

END RUN

Figure 3._Timer segment--overview.

.

, m

o

" WAIT • NO

TRAVEL TO ]

YESWOODSALONG ,

. SKI D ROAD .i

!• /NEXTBUNCH-X

" i ' / ' DISTANCE,_J ." _NO.TREES, TOTAL ) REBUNCH

_ VOLUHEAND/

.\ DIAMETER/ l ____NO• •

TRAVEL TO SKID TO ]

BUNCHTHROUGH-' WOODS LANDING

l

ALIGN BUNCH CH N YES IPPERIGNI DONE FOR

I _ TOO,,_" GRAPPLEBUNCH UNTIL CHIPPER_o__Ac_ o,__

t I' OLLECTIONPOINT(SKID ROAD)

_--I DROPBUNCH

YES

Figure 4._Skidder segment--overview.,

, 5

CHIPPER

STARTED A VAN WAIT

NO NO YES

WAIT WAIT NEXT LOAD# TREES,

o

GRAPPLE TREES

CHAIN SAWNEEDED DELAY

NO

CHIP LOAD

RECORDCHIPPERUCTIVITY

FULL

YES

SPLITCLOSE AND SUPPLYMOVE OUT VAIl NEW VAN

. TIME TAKE BREAK

NO

' NOTIME

YES

Figure 5._Chipper segment--overview.

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Table 1.'GPSS data input forms

Inputdatatype InputforminGPSS Example

Simpleaveragesorconstants InitializedSAVEVALUES Averaged.b.h. = 6 inches

Rangeofvalues InitializedSAVEVALUESformean.and Sheartime= 0.10to0.14 minutesone-halfwidthofinterval = 0.12 _+0.02minutes

Equations VARIABLES Volume= 0.13d.b.h.2-0.28

I Frequencydistributions . FUNCTIONS PercenttreesD.b.h. (inches) 2341255J3061157185Meanandvariancefora standard SAVEVALUESandFUNCTIONSfor Waittimeis normallydistributedwithdistributionsuchasnormal,Poisson thedistribution Mean= 10exponential,etc. ' Variance= 9

change from a constant (SAVEVALUE) to the prod- The data in the tables are empirical, so they rep-uct of rate times distance is accomplished by simply resent the operating characteristics of this machineredefining the skid time variable and supplying the under given stand conditions. Different harvest con-appropriate input cards, ditions Will require new input data.

The major exception to this convention is theuse

of SAVEVALUES (constants) for the summary val- SIMULATION OUTPUT. ues (average stand d.b.h., average tree height, etc.)

that are entered simply for use in output tables. The The simulation run produces three pages of for-actual input data cards follow the variable defini- matted output for each day of the run (figs. 6, 7, andtions and are supplied as FUNCTIONS or SAVEV- 8). These present a summary of the stand data andALUES depending upon the VARIABLE definition, cumulative productivity reports. Additional output

is produced at the end of the run by the GPSS pro-

REQUIRED BY cessor. This output supplies complete run details.DATAThe first page of standard output (fig. 9) presents

MODEL a simulation "map" listing all the blocks in the modeland the number of transactions that have moved

Input data describing the equipment and har- through each block. This is primarily of value whilevesting operation must be supplied to run the sim- debugging the model. The listing of the QUEUE sta-ulation, tistics provides detailed information on how time is

spent and delays for each type of equipment. TheThereare four types of data to be supplied: SAVEVALUE list contains all the totals necessary

to calculate productivity if the FORTRAN subrou-1. Stand data (table 2) tines cannot be used.2. Machine data for skidders (table 3)

,. 3. Machine data for chipper (table 4) Example:4. Simulation run control (table 5). CPHR = 4,230 = chipper hours x 100

CPTRE = 14,218 = trees chippedThe sample output presented in this paper results CPVNS = 52 = vans filled

from a case study using the data in tables 2-5 as 52/42.30 = 1.23 vans/hour

input. These data were gathered from time studies 14,218/42.30 = 336 trees/hourcarried out during Forest Service projects and are 14,218/52 = 273.4 trees/vanused to illustrate the model and its use. Bunch size

and location data were taken from a simulation run The tables (figs. 10-11) provide additional detailsOf a tracked type feller/buncher (Winsauer 1980). of the machine performance.

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. Table 2._Stand data

FormrequiredDatarequired Casestudy byprogram Name

Averagestanddiameter 5.5 ind.b.h. SAVEVALUE X$AVDBHAveragestandvolume 3,450cuft/acre SAVEVALUE X$AVVOLAveragetreeheight 43ft SAVEVALUE X$AVHGTAveragetrees/acre 844 SAVEVALUE X$TRPACDensityof wood 55Ib/cuft SAVEVALUE X$LBCFTEnergyequivalent-fuel 150,000BTU/gal SAVEVALUE X_IFBTUEnergyequivalent-wood 8,000,000BTU/ton SAVEVALUE X_IWBTUSkiddistance-road/track 300ft VARIABLE W;RDISTSkiddistance-woods Distribution1 VARIABLE V',;WDIST

Distance(ft) 0-5 5-10 10-15 15-20 20-25 25-30 30-35Percenttime 23 12 7 11 10 9 5

J

35-40 40-45 45-50 50-55 55-60 60-1002 3 4 2 2 10

Actualtreediameter Diameterdistribution: FUNCTION FN$DBH• FN$DIAM2

D.b.h(in.) 3 4 5 6 7 8• Percenttrees 5 23 30 24 14 3

Treevolume Volume(cuft) VARIABLE V$TVOL= - 0.283 + 0.0031(d.b.h.2)treeheight

. = 0.283+ 0.133(d.b.h.2)• assumingtreeheight= 43ft

Typeoffeller/bunche" Tracked SAVEVALUE X$FBTYPNumberoffeller/bunchers 1 SAVEVALUE X$NUMFBFeller/buncherfuel

consumption 3.3gal/ton SAVEVALUE X$FBGPTNumberoftreesperbunch Distribution-treesper

leftbyfeller/buncher bunch_ VARIABLE V$NTBUN

Trees/bunch 2 3 4 5 6 7 8 9Percentbunches 0.4 2.1 3.5 3 6 5 4 6

11 12 13 14 15 16 17 184 6 7 6 3 5 4 3

20 21 22 23 24 254 4 3 4 4 6

_Distributionstakenfrom simulationrunof trackedfeller/buncher(Winsauer1980)2FN$DBHandFN$DIAMareidenticaldistributionfunctionsusedbyskiddersandchipper,respectively.

.

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Table 3._Skidder data

Formrequired- • Datarequired Casestudy byprogram Name

Numberofskid(lers 1 SAVEVALUE X$NUMSK

Maximumgappleload(totalsumof 150inches SAVEVALUE X$MXSKDdiameters)

Fuelconsumption 4 gal/hr SAVEVALUE X$SKGPH

Traveltimealongskidroad/track-basedon Distance/speed VARIABLE V$RTRAVdistance Roadspeed= 352ft/min

= 4 mph

Traveltimeinwoods-basedondistance Distance/woodsspeed VARIABLE V$WTRAV• Woodsspeed= 2/3road

speed

Grappletime/bunch Mean = 0.65min VARIABLE V$GRAPL' Std.dev. = .20rain

Timeto alignbunch,if needed Mean = .50rain VARIABLE V$ALIGN, Std.dev. = .30min

Percentof bunchesneedingalignment 1 percent SAVEVALUE X$ALIGNbeforegrappling

Droptimeperload Mean = .30min VARIABLE V$DROP• Std.dev. =.15min

Rebunchtime/load Mean = .50min VARIABLE V$REBUN. Std.dev. = .25min

Percentofsinglebunchesneedingto be 15percent SAVEVALUE X$REBUNrebunchedbeforehauling

Conditionsunderwhichtheskidderwilladd Skidgrappleloadlessthan BooleanVARIABLE BV$ADDanotherbunchbeforeskiddingto landing one/halfitscapacity

Table 4._Chipper and van data

FormrequiredDatarequired Casestudy byprogram Name

Maximumchippergrappleload 12trees SAVEVALUE X$CMAX

• • Roomatlanding 50tree SAVEVALUE X$BUFLM

•, Chipperfuelconsumption 5.7gal/hr SAVEVALUE X$CPGPH

Actualgrappleload Distribution:trees/ VARIABLE V$NGRAPgrappleload '

. Numberoftrees 1 2 3 4 5 6 7 8 9 10

percentof grappleloads 12 19 18 17 15 8 7 3 1 1

Grappleandchiptime/load 0.10rainperstem VARIABLE V$CHIPDelaytimeforsawing mean = 0.48rain VARIABLE V$CHSAW

• Std.dev. = .09min

•Percentof chiploadsneedingsawing 5 percent SAVEVALUE X$PDELY

Vancapacity 1,000cuft (solidwood) SAVEVALUE XSVANCY(approximately30tons)

Timeto closevan 1 minute VARIABLE V$CLSVN

Timeto changevans 4 minutes VARIABLE V$VNWAT

9

Table 5.mSimulation run control

Datarequired Casestudy Formrequiredbyprogram

Randomnumbergenerators Randomnumber Use

1 GPSSscheduler RMULTCARD2 Generatenormalrandomdistributions

3 FUNCTIONSforwooddistance,trees/bunch,chipper-grappleload

4, 5 Diameterdistributions-theseshouldhaveidenticalseedvaluesandnotbeusedfor

' anyotherfunctions

Numberof daysto simulate 5 STARTCARD

Standardoutput Everyfifthday STARTCARD

It should be noted that all of the output was ob- from the standard output. If some form of HELPrained by random processes in the model. Therefore, BLOCKS are allowed, the HELP BLOCKS formatsthe output data are themselves random numbers, and the subroutines may have to be changed. Seeonly a sample of what could happen. If the model is the GPSS manual for your computer installation.run again with different random numbers, the re-sults will be different. An average over several days

• or several runs is the best estimate of an actual sys- CONCLUSIONStern.

The simulation model provides an in-depth look

KNOWN DIFFERENCES at the operation of the system. This makes it possibleto determine the effect on productivity and type of

BETWEEN SYSTEMS delays caused by changes in the system (table 6)orthe stand. It can also be used in conjunction withother models to determine the cost and feasibility of

The program listed in the Appendix is operational a complete harvesting operation.on a UNIVAC 1110 under an implementation of GPSScalled GPSS-XS, obtained through Use Program Li- Some knowledge of GPSS allows the user to mod-brary Interchange (UPLI). It should run under most ify the model to meet his exact needs, making it evenGPSS processors with only minor changes. The fol- more useful and realistic.lowing should be checked for your system.

• INITIAL cards--In GPSS-X8 the INITIAL cards LITERATURE CITEDappear last in the deck. They should be moved to thehead of the deck for most other GPSS processors. Schriber, T. J. Simulation using GPSS. New York:

John Wiley & Sons; 1974. 533 p.JOB CONTROL cards--These are unique to each Winsauer, Sharon A. A program and documentation

computer lab and must be obtained locally, for simulation of a tracked feller/buncher. Res.

HELP BLOCKS--In GPSS-X8 HELP BLOCKS Pap. NC-192. St. Paul, MN: U.S. Department of

(lines 105-152 in the program) are used to pass an Agriculture, Forest Service, North Central Forestarray of up to five integer values to a FORTRAN Experiment Station; 1980. 26 p.

subroutine. Only a one-way transfer is permitted; Winsauer, Sharon A.; Bradley, Dennis P. A programthe subroutine cannot pass arguments back to GPSS. and documentation for simulation of a rubber-tired

feller/buncher. Res. Pap. NC-212. St. Paul, MN:Some versions of GPSS do not allow HELP U.S. Department of Agriculture, Forest Service,

BLOCKS. In this case the program can be run with- North Central Forest Experiment Station; 1982.out.lines 105 to 152 and the data obtained instead 34 p.

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Table 6.--Productivity and delays of two system configurations

• SystemI System2" Oneskidder Onechipper Twoskidders Onechipper

Totalmachinehoursworked 42.39 42.21 81.06 40.42

Percentproductivetime 89.7 56.6 59.6 75.4

Percentnonproductivetime

Totaldelay 10.3 43.3 40.4 24.6

Breaks 10.3 11.8 6.6 12.4

Waitto dropwood 0.0 33.8

Waitforwoodto chip 21.9 0.0

Wait forbucking 3.3 4.6

Waitfor vans 6.3 7.6

Totalirees 14,268 17,843

Totalvansfilled 52 65

Totaltonsprocessed 1,706 2,132

APPENDIX A

VARIABLE LISTS AND DEFINITIONS

IMPLICIT TIME UNIT--centi-minute Segment 3--CHIPPERMODEL SEGMENTS, TRANSACTIONS, AND PA- Transactions--One chipper-loader.When it splits,RAMETERS parent transaction remains as chipper while

Offspring becomes full van.Segment 1--TIMER Parameters

Transactions--1 time keeper. Pl--clock time.Parameters--None. P2--number of trees in chipper-grapple load.

P3--volume of load.Segment 2--sKIDDER(S) P4--sum of diameter of load (inches).

Transactions--One for each skidder. P5--1oop counter.ParametersPl--nbt used.P2--clock time. FACILITYP3--total number of trees in skid load.P4--total d.b.h. (inches) in skid load. CPBUF Chipper buffer--area where skidders dropP5--total volume of skid load. logs within reach of chipper.P6--number of feller/buncher bunches com-

bined in this skid load. FUNCTIONS] P7--road distance.

PS"woods distance. DBH Distribution of diameters in the stand--

P9--number of trees in feller/buncher bunch, used by skidder.P10--counter for d.b.h, loop. DIAM Identical diameter distribution--used byP11--total sum of diameter in feller/buncher chipper.

bunch. NGRAP Distribution of the number of trees perP12--total volume of feller/buncher bunch, chipper--grapple load.

-

17

NTBUN Distribution of number of trees in each CPTIM Total chipper time (centi-minutes).. bunch left by feller/buncher. CPTRE Total trees chipped.

SNORM Used to obtain a normal distribution for CPVNS Total vans filled.

sampling. CPVOL Total volume chipped (cubic feet x 100).WDIST Distribution of bunches in the woods. DAYS Number of current day.

DBH Diameter of current tree (inches).

QUEUES DROP1 Time needed for skidder to drop bunch--mean (centi-minutes).

ALIGN Time skidder spends aligning bunches. DROP2 Time needed to drop bunch--standard de-BFEMT Time chipper waits for wood. viation (centi-minutes).CHIP Chipping time. FBGPT Feller/buncher fuel usage (gallons/ton).CHSAW Time spent bucking logs. FBTU Btu's in fuel per gallon.CPBRK Time chipper spends on break. FBTYP Feller/buncher type. 0 = tracked; 1 = rub-CPBUF Skidder time .waiting to drop load. ber tired.

GRPL1 Skidder grapple time/bunch--mean (centi-EVCPR Chipper time waiting for empty van.GRAPL Skidder grapple time. minutes).RDIST Skidder travel time on road. GRPL2 Grapple time/bunch--standard deviation

REBUN Time spent rebunching a skid load. (centi-minutes).SKBRK Time skidders spend on break. HALF Skid load limit to add more to the loadWTRAV Skidder travel time in woods. (sum of diameters).

" LBCFT Density of wood (pounds/cubic feet).

I SAVEVALUES MXSKD Maximum skidder grapple load--total sum• . of diameter (inches).I NTBUF Current number of trees at the chipper.I ALGN1 • Time to align bunch_mean (centi-min- NUMFB Number offeller/bunchers used to fell trees.

utes). NUMSK Number of skidders in operation.. ALGN2 Time t_ align bunch_standard deviation PDELY Percent of chipper loads requiring sawing.

(centi-minutes). NOTE: Must be three digits in terms ofALIGN Percent of bunches needing alignment, thousandths.

NOTE" Must be three digits in terms of RDIST Skid road/track distance (feet).thousandths. REBN1 Time needed to rebunch skid load--mean

AVDBH Average stand diameter (inches x 10). (centi-minutes).AVHGT Average tree height (feet). REBN2 Time needed to rebunch--standard de-AVVOL Average stand volume (cubic feet x 100). viation (centi-minutes).BUCK Chipper delay time due to bucking (centi- REBUN Percent of single bunches needing re-

minutes), bunching before hauling. NOTE: Must beBUFLM Available room at chipper (number of logs), three digits in terms of thousandths.CHSWl Chain saw time to buck log--mean (centi- ROAD Skid distance along road/track (feet).

. _ minutes). SDIST Total skid distance (feet).CHSW2 Chain sawtime_standarddeviation(centi- SKADD Number of feller/buncher bunches col-

minutes). " lected into this skid load.• CLSV1 Time to close van_mean (centi-minutes). SKBRK Skidder time on break (centi-minutes).

CLSV2 Time to close van--standard deviation SKBUN Total bunches skidded.

(centi-minutes). SKGPH Skidder fuel consumption (gallons/hour).CMAX Maximum chipper load (number of trees). SKHR Total skidder time on job (hours x 100).CNPVN Chipper nonproductive time waiting for SKLND Skidder time spent at landing (centi-min-

vans (centi-minutes). utes).

CNPWD Chipper nonproductive time waiting for SNLN Skidder time at landing--nonproductive.wood to chip (centi-minutes). SKTIM Total skidder time--all machines (centi-

CPBRK Chipper time spent on breaks (centi-min- minutes).utes). SKTRE Total number of trees skidded.

CPGPH Chipper fuel consumption (gallons/hour). SKVOL Total volume skidded--all machines.

CPHR Total chipper time (hours x 100). SPEED Skidder travel speed on road/track (feet/CPLOD Total number of chipper-grapple loads minutes).

chipped. TRPAC Trees per acre.

I.i. 18I,

VANCY Van capacity (cubic feet x 100). VARIABLESVNCON Van contents (cubic feet x 100).

VNWT1 Time needed to replace full van with empty ALIGN Time needed for skidder to align bunch ifvan---mean (centi-minutes). needed (centi-minutes).

VNWT2 Time needed to replace van--standard BREAK Time between breaks (centi-minutes).deviation (centi-minutes). BUCK Total delay due to bucking logs (centi-min-

WBTU Btu's in wood per ton. utes).

WDIST Total distance skidders have traveled CHIP Time to chip this load (centi-minutes).through the woods (feet). CHSAW Time needed to buck a log (centi-minutes).

WDTIM Skid time in the woods (centi-minutes). CLSVN Time to close full van (centi-minutes).WKDAY Length of workday (hours). CNPVN Chipper nonproductive time spent wait-

ing for vans (centi-minutes)._YVII_rI__r_'T_'_TT_=_'_ CNPWD Chipper nonproductive time waiting for

• wood (centi-minutes).CBRK Set by chipper to tell skidders that chipper CPBRK Time chipper spends on break (centi-min-

is on break, utes).CI-IIPR Set by chipper to indicate it is on the job. CPHR Total chipper time (hours x 100).COFFE Set bytimer to indicate coffee break time. DROP Time for skidder to drop bunch (centi-min-DAY • Set by timer to indicate start of shift, utes).

EVCPR Setby vans to indicate empty van avail- GRAPL Skidder-grapple time per bunch (centi-able. minutes).

LuNcH Set by timer to indicate lunch time. NGRAP Number of trees the chipper-grapple takes• each load.

• NIGHT Remainder of 24 hours after work shiftTABLE S (centi-minutes).

• - NTBUN Number of trees feller/buncher left in eachBNDIA Total sum of diameter of skid bunch bunch.

(inches). RDIST Skid road/track distance (feet).BNTRE Number of trees per skid bunch. REBUN Time needed to rebunch skid load (centi-BNVOL Volume of skidder loads (cubic feet x 100). minutes).

CPTIM Time to chip each load (centi-minutes). RTRAV Skidder travel time along skid road (centi-CPVOL Volume in each chip load (cubic feet x 100). minutes).

SKILN Time skidder is at landing on each trip(centi-minutes). SKBRK Time skidders spend on break (centi-min-

WDTIM Time skidder is in woods on each trip (centi- utes).minutes). SKHR Total skidder time--all machines (hours

x 100).

BOOLEAN VARIABLES SKNLN Total nonproductive time for skidders atlanding (centi-minutes). -

ADD Conditions under which the skidder will SKTIM Total skid time--all machines (centi-min-

• add another bunch before skidding to utes).chipper. TVOL Volume of each tree in terms of d.b.h. (cu-

DROP Allows skidder to drop trees if there is bic feet x 100).• room at chipper or if chipper is done for VNWAT Time needed to change vans (centi-min-

' the day. utes).WDIST Distance from skid road/trail to bunches

• (feet).WKDAY Length of work shift (centi-minutes).WTRAV Skidder travel time through woods (centi-

minutes).

APPENDIX B

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too o oo ooo e ooo o ooo oo ooo oe oooo eo eeeo oo oooooooooeoooo o

0(_0'_'_ - :- - :r:-- :- :- :_,l,,1,,l'kJlrUf_dNlf_drMl_dNIlIMl_d_i--_r.-ii, l._r--ii--__qr _ __qrqr_ll'lltlttllrlllll_ll_ I

I

t

29

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i

I

30I

* C;_* 20 CONTINUE

.- C NUMFB = NU OF FELLER BUNCHER$

(=* C FBT_):;{_{!ER BUNCHER TYP! 0 = DROT? I • RUBBER-TIRED TYPE

-|!'1 c ,_x, , I,i 30 CONTINUE

, M X, C MXSKDKD MAXIMUM SUM OF DIAMETER PER BUNCHkb, .u:s_.x

'I: . C NUMSKWRILoI_i!_Ei O, 8KIDD,$_, _;'K E

_9, WR KD90, X9_, C CHIPPE

l!! 'R_TEIb _I_IM TXL_DLM

_[ URC

g5, _0 _ONTINU

9 , X X2 N OF WOOD

" 99, C LB" oFNWuOD _--u_O _uFT

FBGPT • X ' 'FBT UiX_

0 , RETURN

0 • 50

: c .ou_l_cR.o_E_' " b S HR m Xl/I$_ H =_P x2,_88

_9, O0O* C SKIR_;_RPRODUCTION IN _8_$N

I: c, bO C__TINUE

9, c c.x_'_ " "_ F°_o.oU..T.o.._,L,.ou.N$ m X3*XO 1200000

O* C CALCU A FUEL CONSUHPTION

2 • ! == PHR • CPGPH

.. PTNS

T8 p = FBGPT+$KGPT+CPGPT

MP _ E WHEN ADDED129, FBTF = GPT, TONS|_0" SKTFC m SKGPT*TONS

• TFC = TFC+SKTF T

"I , C ;!oo UEL PER TON

C _L A 0_ O AS FUEL• }5, BT T PT * FBTU

BC IT RAT;8, C;9, .C

_0, wRITE (6_ 13)FBGPT_ SKGPT_ CPGPT_ TGPT

• • WRITE 6_I_)BTUTF_WBTUeE, BC• _., RETUR

_, END

31I

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32

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35

I

i

i

" APPENDIX C

" COMPLETE FLOW CHARTSi

i

!

' COMPLETEFLOWCHARTS- PART1 OF 7-.

I, TIMERSEGMENT

i

, CREATEONE' ,,,1,12 TIMER

COUNTNUMBER ,LOGIC SIGNAL'(NXDAY) SAVEVALUE OF DAYS SET COFFEEBREAK

I

, COFFE

DAYS+,1- ill

WORKUNTILADVANCELOGIC _'1 TIIIE TO V$BREAK ENDOFSHI_

SET _J START WORKDAY

LOGIC TIME TO'- ' RESET QUIT FOR

ADVANCE WAITUNTIL DAY TODAYVSBREAK TIME .FORCOFFEEBREAK

I

ADVANCE WAIT UNTIL

LOGIC _'1 SIGNAL V$NIGHT MORNING

SET _ COFFEEBREAKCOFFE

L )• , SAVEVALUE PRODUCTIVEAND' ADVANCE WORKUNTIL

VSBREAK TIME FOR | REPORT! NONPRODUCTIVELUNCH IVARIABLE TIMES

' LOGIC SIGNAL SKIDR,CHIPR FORTRAN. SET LUNCHTIME PRODUCTION

LUNCII _ REPORTi

• V$BREAK TIME FOR ,_ (NXDAY) ,SECONDBREAK 1

TERMINATE

, ""

36

COMPLETEFLOWCHARTS- PART 2 OF 7

SKIDDERSEGMENT

CREATESKIDDER(S)

.. (NDBH)

DI3HOFSAVEVALUE EACHTREE

(START) I S CHI PPERWORKING?

YES

" C ""'_START ASSIGN F.INDTOTAL

MARK __2s) WOODS DBH AND VOLUMETINE 11+,X$1}IH! OF BUNCHm _

+ 12+,VSTVOL

ASSIGN DETERMINEROAD/TRACK REPEATFOR

• 7,V$RDIST DISTANCE LOOP ALL TREES, IN BUNCH

• IQUEUE ASSIGN

' RDIST /f 3+,P9

_ ,Pll 6+

,, , ,5+, 12

ADVANCE TRAVELTOWOODS

I I REINITIALIZE, V$RTRAV ASSIGN STORAGEFOR

+ ,0 _ NEXTFELLERRDIST TRAVEL 12:8

TIME

QUEUE

• SAVEVALUE TRAVEL WTRAVDISTANCE

I TRAVELTHROUGHADVANCE WOODSTO

' V$WTRAV FELLERBUNCHJ..

(WOODS) ASSIGN DEFINENEXT + ,FELLERBUNCH _ RECORD

9,V$NTBUN NUMBEROF TREES, DEPART _WOODS TRAVE10,P9 WOODS DISTANCE WTRAV "

8,V$WDIST. • TIME

, 1 &-(NDBH) PART3

37

i

COHPLETEFLOgCHARTS- PART3 OF 7 ""Ih

' - _ SKIDDERSEGHENTW

i . (SAVEVALUI " . HOODS _'

ISDIST+,P81 TRAVEL (SAVEVALUE )TRAVEL

I

_IDIST+,Pq DISTANCE DISTANCE

I

' (ALIbi)m

, ADDMOTHERBUNCH?

(WOODS)QUEUE _'_VSADD'NE'I_.----Ib PART2' ALIEN

BUNCHBI G.ENOUGH?. N.I_

I, ADVANCE BUNCH P6'LE' 1ALIGN I F NEEDED

NEEDTO

..... Q REBUNCH?

DEPART. ALIGN

,X$REBUN, _ (REBi

i " • QUEUE

QUEUE RE UNGRAPL

ADVANCE REBUNCHi ii

I ADVANCE GRAPPLE VSREBUN MHENNEEDED|

I VSGRAPL BUNCH

DEPART_ , _ DEPART _. Lf"_ RECORD REBUN

" • GRAPPLE |

(SKLND)

QUEUE ' "_ QUEUEHTRAV _ } RDIST

i

TRAVELTO [ ADVANCE I SKID BACKADVANCE COLLECTION V$RDIST TO LANDINGV$MTRAV POINT

i i QDEPART TRAVEL DEPART RECORDHTRAV TIHE . RDIST SKID TIHE

38

r

o

COMPQETEFLOgCHARTS- PART4 OF 7

SKIDDERSEGMENT

..... Q RECORD

RECORD DEPART WAIT TIME" i SAVEYALUE SKID CPBUFDISTANCE TO DROPWOOD

i ii i i i

ADVANCE DROPV$DROP LOAD

TABULATE•WOODTIMES

ADDTHIS LOAD(.LAND) SAVEVALUE TO AREABY

START CHIPPERMARK LANDING

TIME UF+,

RELEASEIS CHIPPER CPBUF

LS ONBREAK?

YESLANDING

SAVEVALUE. QUEUE TIRE

SKBRK SKLND+,MP2

SKIDDERCAN TABULATELR BREAKUNTILCHIPPER LANDINGTIME

RESUMESWORK

RECORD COLLECTDATADEPART SKIDDER SAVEVALUE ON CHIPPERSKBRK BREAKTIME PRODUCTIVITY

•. QUEUECPBUF

• ASS.IGN REINITIAL I ZE

3,0 6,0 _ SKIDDERSKIDDERWILL DROP 4,0 7,0 BUNCHDATALOADIF ROOMAT 5,0 8,0

' E'l CHIPPEROR CHIPPER "_ '' HASQUIT

J J_ ONESKIDI,ER, , SEIZE l/ _ ATA TIME

CPBUF _ .\CAN DROPWOODi i ii i i..

.(START) PART2

39

I

|

COMPLETEFLOWCHARTS- PART•5 OF•7

CHI PPERSEGHENT

•CREATECHIPPER

-.

+ +LOGICS h STARTFIRST DAY " ASSIGN DE_'ERMiNE

EVCPR _J HI.ill VAN NUI_EROFAVAILABLE ' TREESIN DESIP,ED2,V$NGRAP CHIPPERLOAD +

(CSTRT) SHIFTSTARTED?

LESS THAN.XSNTBUF FULLLOAD

AVAILABLE?

LOGICS h CHIPPERIS YES ,

CHIPR _ WORKING?'' ASSIGN. TAKE ALL(NEWLD) _ " TREES

_' _--_ AVAILABLE:2,X$NTBUFHARK 11

J

' l COURTERQUEUE '(GRAPE) ASSI GN TO ASSI GNEVCPR -- DBH

5,P2 " '

GATE EMPTYVAN LOAD)

LS AVAILABLE? • . SAVEVALUE ...YES • • • .

DBH, "DEPART _'_ RECORDWAIT FN$DBH

EVCPR _ FOREMPTY ", VANASSIGN ADDTREE. .I

, ' 'Lf-')(_ TO LOAD

L_) 4 �”�X$DBH" "• 3+,V$TVOL ,.

.-.

REPEATFOR, _. XSNTBUF_ 'LOOP ALL.TREES

DEPART | _ RECORDWAIT " 6

,lJ( mRwoo.+

•40

ICOHPLETEFLONCHARTS-'PART 6 OF 7

o

CHIPPERSEG_NT

SAVEVALUE PI CK UPTREES

UF-,

RESTARTSCAN i TABULATE_VOLUEANDBUFFER SOSKIDDER CPVOL CHIP TIRE

CANDROP CPTIt4 RECORDS

. TREES

( _ CHIPPERPERCENTOF TREESNEEDING SAVEYALUE PRODUCTIVITY" PDELY SAWING

CPLOD+,I(CHSAM) CPTRE+,P2 ADDCH1PS I

TO VANI ° )CHS_REINITIALIZE I

ASSIGN CHIP_R-G_PPLEz zi

, I ADVANCE DELAYDUE 2,0

• [ V$CHSAN TOSA.ZNS 3,0 4,0 I, n _ •

F

.... _ j' DEPART Q

CHS_ (N_LD) I• I

(CHI P) _'_ YES ,,

QUEUE LOGICR VANIS 1. CHIP EVCPR FULL l

IADVMCE CHIP SPLIT (LNKVN) 'V$CHII) LOAD ]

i-i -_,__- PART, leEcoms_LL VAN

.ECORO i•. ' DEPART CHIPCHIP- -TIME

• ' lPART 7

REI*,AINS ASSAVEVALUE CHIPPER,

' CeTI_t II

' I' I

!q,

, F

I• 41 I

I

[

o

COMPLETEFLOWCHARTS- PART7 OF 7

" CHIPPERSEGMENT

' " C NARK " _ %_• sI &

QUEUE SAVEVALU'E

- NO BREAK

TIME? (NEWLD)• PART5

D TELL SKIDDERSLOGICS "CHIPPERISCBRK ON BREAK" LOGICR h CHIPPER

CHIPR QUITPii

ADVANCE 15-MINUTE1500 BREAK

ill i I i

. fLOGICR BACKTO

COFFE,CBRK WORK

(CSTRT)PART5

p(eOB LUNCH?

'--_ 1 NO'- (LNKVN) FULLVAN.. _, YESLOGICS TELL SKIDDER_. REINITZALiZE

CBRK THEYCAN VANCONTENTSBREAK COUNTFULLVANS

ADVANCE 30-NINUll_ l. 3000 LUNCH ADVANCE CLOSEVAN

V$CLSVN

LOGICR BACKTO I TIMETO

. LUNCH,CBRK WORK I ADVANCEV$VNWAT HOVEIN ENPTY(CPDON) r_,_, VANAT CHIPPER

DEPART CHIPPER ] LO C. CPBRK BREAKTI HE EVCPRi

I_'U.S.GOVERNIENT PRINTING OFFICE: 1982--566-950/99

42

Winsauer, Sharon A.A program and documentation for simulation of grapple skidders and

a whole-tree chipper. Res. Pap. NC-221. St. Paul, MN: U.S. Depart-ment of Agriculture, Forest Service, North Central Forest Experi-ment Station; 1982. 42 p.

Presents a computer model written in GPSS (General PurposeSimulation System) designed to simulate a skidding-chipping op-eration.

KEY WORDS: GPSS (General Purpose Simulation System), com-puter, harvesting, productivity, modeling.