United States 

Department of 

Agriculture 

Forest Service 

Northeastern Forest 

Experiment Station 

Research Paper NE-664 

Cycle-time Equations for Five Small 

Tractors Operating in Low-Volume 

Small-Diameter Hardwood Stands 

Chris B. LeDoux 

Neil K. Huyler 
Abstract 

Prediction equations for estimating cycle time were developed for five small tractors 

studied under various silvicultural treatments and operating conditions. Skidding 

costs were estimated based on the cycle-time equations. Using these equations to 

determine the incremental effect of log size on cost shows that hooking a 30-ft310g 

cost $0.1 03At3 while hooking six logs to form a 30-cubic foot turn cost $0.234/ft3, an 

increase of 127 percent. Cost relationships are illustrated for each tractor. 

The Authors 

CHRIS B. LEDOUX, supervisory industrial engineer, is engaged in forest 

engineering research at the Northeastern Forest Experiment Station in Morgantown, 

West Virginia. He received a B.S. degree in forest management from the University 

of Idaho, and M.S. and Ph.D. degrees in forest engineering from Oregon State 

University. He joined the USDA Forest Service in 1983. 

NEIL K. HUYLER, research forester, is engaged in research on the economics of 

fuelwood harvesting at the Northeastern Station's George D. Aiken Forestry 

Sciences Laboratory at Burlington, Vermont. He received B.S. and MS. degrees in 

wood industry from West Virginia University, and joined the Forest Service in 1963. 

Manuscript received for publication 14 April 1992. 

Northeastern Forest Experiment Station 

5 Radnor Corporate Center 

100 Matsonford Road, Suite 200 

P.O. Box 6775 

Radnor, Pennsylvania 19087-4585 

July 1992 
Introduction 

Several small tractors have entered the commercial 

market in the last decade. Designed for light farming, land 

cultivation, and forestry operations, they are relatively low 

cost with low horsepower (12 to 60). 

Interest in using these tractors on small-scale logging 

operations in the northeastern and north-central regions 

has increased in recent years. Owners of small tracts of 

land see small tractors as an alternative to large skidding 

machines that may damage their woodlots. Also, fuelwood 

often is processed from small low-quality trees from stand 

thinnings, and harvesting such material with large equipment usually is not economical. 

To evaluate and develop alternative harvesting systems, a 

series of time and motion studies were conducted on 

small-scale logging operations in the Northeast. Several 

small tractors were studied for a wide range of silvicultural 

treatments and operating conditions. The small tractors 

included the Pasquali 933, a Holder A60F, a Forest Ant 

Forwarder, a Massey-Ferguson, and a Sam6 Minitaurus.' 

This paper summarizes attributes, operating conditions, 

and cycle-time equations for these machines. 

'The use of trade, firm, or corporation names in this 

publication is for the information and convenience of the 

reader. Such use does not constitute an official endorsement or approval by the U.S. Department of Agriculture or 

the Forest Service of any product or service to the 

exclusion of others that may be suitable. 
Table 1.-Characteristics of the study sites 

Study Average 

site tree Basal area 

Tractor no. d.b.h. Precut Postcut 

Loaded 

Ave. skidroad slope skid 

Primary Secondary direction Type of cut 

/n&= -------- fp/acre ---------. 

Massey-Ferguson 1 9.4 1 09 80 

Massey-Ferguson 2 10.3 90 0 

Massey-Ferguson 3 10.3 90 0 

Same 4 11.0 110 85 

Pasquali 4 8.6 116 76 

Holder 4 8.6 1 16 76 

Forest Ant 5 8.4 96 71 

--------a- Percent------- 

4 22 Downhill Selection 

6 17 Uphill Regeneration clearcut 

6 2 Uphill Regeneration clearcut 

5 15 Downhill Selection 

0 14 Uphill Low thinning 

0 14 Uphill Low thinning 

0 12 Uphill Low thinning 

Table 2.-Summary of cycletime elements for five small tractors 

Time 

Item Outhaul Hookup lnhaul Unhook Hook Productive Delay Total 

Average time (minutes) 5.31 

Standard deviation 2.02 

Percent of total time 15.55 

Average time (minutes) 11.58 

Standard deviation 5.63 

Percent of total time 18.94 

Average time (minutes) 2.50 

Standard deviation 0.57 

Percent of total time 10.60 

Average time (minutes) 2.70 

Standard deviation 1 .08 

Percent of total time 10.70 

Average time (minutes) 2.50 

Standard deviation 1.03 

Percent of total time 8.90 

MASSEY-FERGUSON (1 191878)" 

HOLDER (45/627)8 

10.30 2.50 4.20 

2.45 0.65 1.20 

43.60 10.60 17.40 

FOREST ANT (301237)" 

13.50 2.00 1.00 

4.24 1 .OO .58 

48.20 7.10 3.50 

"Number of observationslmean skidding distance (ft). 

bMachine utilization rate. 

2 
Logging Equipment and Sites 

The Pasquali 993 tractor is manufactured in ltaly and was 

designed for use on small farms, landscaping projects, and 

light construction work. It is powered by a 30-hp engine 

and has an articulated frame with four-wheel drive. The 

tractor was equipped with a three-point hitch, live power 

takeoff (PTO), and a JL-25 Farmi logging winch. The 

winch has a 5,500-pound line-pulling capacity, spooled with 

100 feet of 318-inch cable. The Pasquali tractor is 4-112 

feet wide and 8 feet long, excluding a 4-foot bucket. 

Safety options include liquid-loaded front and rear tires, 

rollbar, skid pan, and wheel chains. 

The Holder A60F tractor is manufactured in Germany and 

was designed for farm use and light forestry operations. It 

is powered by a 48-hp engine with an articulated frame. 

The tractor is equipped with a 3-point hitch, live power 

takeoff, and an lgland Jones 3000 double-drum winch. The 

winch has a 6,600-pound line-pulling capacity, spooled with 

120 feet of 318-inch cable. Safety options include wheel 

weights, forestry cab, rollbar, and skid pan. 

The Forest Ant is manufactured in Sweden and was 

designed to forward stems to the main skid trails in large 

forest operations. This small four-wheel drive tractor has a 

12-hp engine with an articulated frame. It is equipped with 

a knuckleboom loader and clam bunk. The tractor steering 

and speed are controlled by a tiller bar in front. The 

machine has no cab and the operator walks at a comfortable speed with the machine following. 

The Massey-Ferguson 184-4, manufactured in the United 

States, is a medium-size, four-wheel drive farm tractor. It 

has a 60-hp diesel engine and is equipped with a threepoint hitch and live power takeoff, and a JL-456 Farmi 

winch with a line-pulling capacity of 10,000 pounds. Tire 

chains were used on the rear tires and extra weight was 

added to the front tires. All tires were loaded with calcium 

chloride for weight. 

The Same Minitaurus 60 is manufactured in Italy and is 

designed for use on small farms. It is a medium-size, fourwheel drive tractor with a 60-hp engine. It is equipped with 

a three-point hitch, live power takeoff, and a JL30 Farrni 

logging winch. The winch has a 6,600-pound line-pulling 

capacity, spooled with 165 feet of 318-inch cable. Safety 

options include a bucket loader, front wheel weights, 

loaded rear tires, wheel chains, and rollover protection. 

Attributes of the study sites are shown in Table 1 and 

detailed in Huyler et al. (1984); Turner et al. (1987); Huyler 

and LeDoux (1989); and Huyler and LeDoux (1991). 

Skidder Production Rates 

Table 2 summarizes cycle-production data for the five 

machines studied. The data were recorded by two technicians trained in continuous time-study techniques. One 

technician was located in the woods at the hookup site 

and the other was at the landing. Work-cycle elements 

were timed to the nearest 1/10 minute with a stopwatch, 

two-way radio communication was used. Individual logs 

were scaled at the landing or at the hooking point on a 

turn-by-tum basis. Other turn attributes such as slope 

yarding distance, were similarly recorded. Table 3 surnmarizes mean production data for each tractor. Figure 1 

summarizes operating delays during the time-study operation as a percentage of total observed time. 

Regression analysis was performed on the time-study data 

of each machine to develop prediction equations for 

estimating cycle time, excluding delays. Variables were 

selected such that each equation would be similar. Variables included slope yarding distance, turn volume, logs 

per turn, and volume per log. Table 4 lists the prediction 

equations obtained by regression analysis of the skidding 

production cycle for each of the five machines. The 

equations were chosen by comparing overall R~ values 

and levels of significance of the estimated regression 

Table 3.-Mean production data for each tractor 

Volume Volume1 

production1 scheduled 

Tractor Stemstturn Volumehurn houra hour 

Massey-Ferguson 3.78 46.9 1.32 1 .04 

Same 3.98 66.2 1.12 .80 

Holder 5.67 48.4 1.85 1.54 

Pasquali 3.94 22.8 1 .O1 .68 

Forest Ant 7.10 34.9 1.39 .94 

aWitho~t delay time. 
Massey -Ferguson Same 

I Holder Pasquali Forest Ant 

Productive 

67 

elay Time elay Time 

16 33 32 

Figure 1 .-Yarding delay as a percentage of total time observed. 

coefficients. Although not all of the regression coefficients examples that follow to illustrate the 

were statistically significant, we found-it useful to include 

some of these variables in the equations for comparison 

purposes. 

Skidding Costs 

Skidding costs for each system listed in Table 5 are based 

on the total hours worked and the purchase of all new 

equipment. The costs do not include an allowance for 

profit and risk. Results for the Holder A60F are used in the 

incremental effect of 

each variable on the cost of skidding small-diameter trees. 

Data from Tables 4 and 5 were integrated using a 

computer program. The output was used to develop Figure 

2, which shows the incremental effect of each respective 

variable in the regression equation on cost per volume 

produced. The variable of interest was allowed to change 

in value while other variables were held constant at the 

observed mean value. 

Table 4.-Prediction equations obtained by regression analysis, excluding delays (estimates of cycle time in minutes) for 

five small tractors 

Equation 

Turn 

Slope yarding volume Logslturn Volume/turn 

Tractor Constant distance (ft) (fi3) (no.) (fi3) R2 

Pasquali Y=8.99OW + 0.009,,** + 0.318," - 0.1 10, - 0.307,, 51.2 

Massey-Ferguson Y14.346 + 0.01 I,,'* + 0.351, + 0.810, - 0.1 11, 29.0 

Holder Y=l5.574** + 0.007,,'* + 0.141, - 0.473, - O.54Ox4** 64.2 

Forest Ant Y=4.948 + 0.005,, - 0.107, + 1.762,," + 2.672," 59.2 

Same Y=l9.451 + 0.01 I,," + 0.138, - 0.894,, - 0.325, 33.6 

aSignificant at 0.10 percent level. 

-p<0.01. 4 
Figure 2A suggests that as slope yarding distance increases, cost per volume produced increased. For example, skidding costs at the average turn volume and logs 

per turn would be $0. 194m3 for a slope yarding distance 

of 500 feet. However, a distance of 1,000 feet would 

increase the cost by 21.1 percent to $0.235flt3. 

Figure 26 shows the effect of varying the number of logs 

and volumeAog skidded per turn while the other variables 

are at their mean values. For example, hooking one 30-ft3 

log would cost $0.103flt3. By contrast, hooking six logs to 

form a 30-ft3 turn would increase the cost by 127.2 

percent to $0.234/ft3. The relationship illustrated is the 

result of holding turn volume constant and increasing the 

number of pieces to make up that volume. 

Incremental costs associated with skidding various volumes 

per turn are shown in Figure 2C. The cost to skid a 20- 

cubic foot turn is $0.683m3. Skidding a turn volume of 

60 cubic feet would lower this cost by 67.9 percent to 

$0.219fi. 

Figure 2D shows the incremental effect of skidding logs of 

different sizes. The cost of skidding logs that average 5 ft3 

with all other variables at their mean values is $0.234/ft3. 

Increasing log size to 20 ft3 lowers the cost by 30.3 

percent to $0.1 63m3. 

Table 5.-Owning and operating and labor rates for 

five small tractors 

Own and Total 

Tractor operatea LaboP hourly 

----------------- Dollars -------------..----------- 

Pasquali 5.77 6.75 12.52 

Forest Ant 4.27 6.75 11.02 

Massey-Ferguson 5.62 6.75 12.37 

Holder 14.42 6.75 21.17 

Same 5.41 6.75 12.16 

"Based on 1988 new equipment cost, depreciation, 

insurance, taxes, interest, storage, operating cost (fuel, oil, 

lubricants, maintenance, and repair). 

bLatwlr rate at $5.001hour plus 35-percent fringe benefits. 

Slope Yarding Distance [ft 1 Turn Volume [ft31 

Logs per Turn [no.\ Volume per Log [ft3) 

Figure 2.-Incremental effects of skidding variables on costs for Holder Tractor for 

following conditions (mean values): (a) slope yarding distance, 800 feet; (b) number of 

logs per turn, 3; (c) turn volume, 30 ft3; (d) volume per log, 10 ft3. 
Discussion Literature Cited 

Besides the prospect of increased revenue from the sale of 

selectively removed small-diameter stems, there are other 

benefits from removing wood of this size: fuel loadings on 

the site are reduced; one can enter young stands and 

conduct silvicultural thinnings and cleanings; habitat that 

promotes forest insects and diseases is removed; and 

visual management is enhanced. Additional research should 

focus on matching specific machines to stand and site 

conditions. 

Cycle-time and production estimators by machine, along 

with the range of stand and forest conditions, could be 

used as input to select simulation models. Simulators would 

be run repeatedly over the range of conditions of interest. 

The resulting cost or production data points by machine 

and forest condition could be summarized in a mathematical equation suitable for incorporation into generalized 

stump-to-mill models that can be used by managers, 

planners, and loggers to estimate logging costs. 

Forest-land owners and users are placing increased 

demands on the forest for a variety of uses. Often, the 

silvicultural treatment needed to bring the woodlot or forest 

to the desired condition generates associated logging and 

harvesting costs. Generally, the revenues needed to offset 

these costs are derived from the value of the wood harvested. The results presented here along with the results of 

research in progress should provide managers, planners, 

loggers, and landowners with detailed and accurate logging 

cost estimators that can be used to evaluate and quantify 

the tradeoffs posed by different forest uses and allow for 

comparison and selection of equipment. 

Huyler, Neil K.; Koten, Donald E.; Lea, Richard V.; Quadro, 

Anthony P. 1984. Productivity and cost of three small 

fuelwood skldders. Journal of Forestry. 82(11): 671 -674. 

Huyler, Neil K.; LeDoux, Chris B. 1989. Small tractors for 

harvesting fuelwood in low-volume small diameter 

hardwood stands. In: Proceedings of the 12th annual 

meeting of the Council on Forest Engineering; 1989 August 

27-30; Coeur d'Alene, ID. Atlanta, GA: US. Department of 

Agriculture, Forest Service, Southern Region: 61-66. 

Huyler, Neil K.; LeDoux, Chris B. 1991. A comparison of 

small tractors for thinning central hardwoods. In: 

McCormick, Larry H.; Gottschalk, Kurt W., eds. Proceedings, 8th central hardwood forest conference; 1991 March 

4-6; University Park, PA. Gen. Tech. Rep. NE-148. Radnor, 

PA: U.S. Department of Agriculture, Forest Service, Northeastern Forest Experiment Station: 92-104. 

Turner, Terry L.; Bousquet, Daniel W.; Huyler, Neil K. 1987. 

Productivity and operating cost of two medium-size 

tractors harvesting northern hardwoods in Vermont. 

Burlington, VT: University of Vermont, School of Natural 

Resources. 23 p. 
LeDoux, Chris B.; Huyler, Neil K. 1992. Cycle-time equations for five smali 

tractors operating in low-volume small-diameter hardwood stands.. 

Res. Pap. NE-664. Radnor, PA: U.S. Department of Agriculture, Forest 

Service, Northeastern Forest Experiment Station. 6 p. 

Prediction equations for estimating cycle time were developed for five small 

tractors studied under various silvicultural treatments and operating conditions. 

The tractors studied included the Pasquali 933, a Holder A60F, a Forest Ant 

Forwarder (Skogsman), a Massey-Ferguson, and a Sam4 Minitarus. Skidding 

costs were estimated based on the cycle-time equations. Using these equations to determine the incremental effect of log size on cost shows that hooking 

a 30-fP log cost $0.1 03/ft3 while hooking six logs to form a 30-cubic foot turn 

cost $0.234/ft3, an increase of 127 percent. 

Keywords: Harvesting, thinning, cost, production 

* U.S. GOVERNMENT PRINTING OFFICE: 1992--648-139140,022 
Headquarters of the Northeastern Forest Experiment Station is in Radnor, Pennsylvania. Field laboratories are maintained at: 

Amherst, Massachusetts, in cooperation with the University of Massachusetts 

Burlington, Vermont, in cooperation with the University of Vermont 

Delaware, Ohio 

Durham, New Hampshire, in cooperation with the University of New Hampshire 

Hamden, Connecticut, in cooperation with Yale University 

Morgantown, West Virginia, in cooperation with West Virginia University 

Orono, Maine, in cooperation with the University of Maine 

Parsons, West Virginia 

Princeton, West Virginia 

Syracuse, New York, in cooperation with the State University of New York, 

College of Environmental Sciences and Forestry at Syracuse University 

University Park, Pennsylvania, in cooperation with The Pennsylvania State University 

Warren, Pennsylvania 

Persons of any race, color, national origin, sex, age, religion, or with any handicapping condition are welcome to use and enjoy all facilities, programs, and services of 

the USDA. Discrimination in any form is Jrictly against agency policy, and should be 

reported to the Secretary of Agriculture, Washington, DC 20250.