United States 

Depart men t of 

Agriculture 

Forest Service 

Northeastern Forest 

Experiment Station 

Research 

Paper NE- 495 

the 

hinner 

Cleveland J. Biller 
me Aut 

Cleveland Biller is a Research 

Mechanical Engineer with the Engineering Unit of the Northeastern 

Forest Experiment Station, 

Morgantown, West Virginia. He 

received a B.S. degree in 1967 and 

an M.S. degree in 1970 from West 

Virginia University at Morgantown. 

He joined the research unit in July 

1966 and has written several publications on harvesting systems in 

Appalachia. He is the designer of 

the Appalachian Thinner. 

Manuscript received for publication 26 May 1981 

Abstract 

The Appalachian Thinner, a 

prototype cable yarder, has proven 

capable of harvesting timber on 

steep slopes. Details of the fabrication of the prototype yarder are 

presented. An Appalachian Thinner can be built economically in a 

typical logger's repair shop. 
Figure 1.-The tber stacking logs alongside the truck road. 

A hydraulic knuckleboom 

loader, a hydraulic winch, and a 

small dozer provided the major 

components to build a small 

prototype swing-boom cable 

logging system called the 

Appalachian Thinner. 

The Appalachian Thinner (Fig. 

1) was designed and built by the 

USDA Forest Service's Engineering 

Work Unit in Morgantown, West 

Virginia, to test the concept that a 

versatile yarder could operate 

efficiently on small woodland properties. One of the requirements 

was that the machine be low in 

initial costs. 

Any dozer could serve as a 

carrier for the thinner, but must 

have a mounting bracket on the 

rear so the thinner can be attached. An option on most dozers 

is the backhoe attachment; when 

the backhoe is supplied, the dozer 

comes with a larger hydraulic 

pump and special mounting brackets. Thus, a dozer that is equipped 

to take a backhoe is an ideal carrier for the thinner. 

Dozer Modifications 

The prototype thinner was 

mounted on a JD-450B crawler 

tractor.1 This section records the 

changes made on the JD-450. Other brands of machines may require 

different modifications. Each 

machine should be studied carefully to determine what modifications 

are necessary to make a good yarder. 

1~he 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 23. Department of Agriculture or 

the Forest Service of any product 

or service to the exelusion of 

others that may be suitable. 

The canopy and winch must be 

removed from the dozer. The 

factory canopy is too tall; it will 

interfere with the swing of the 

thinner. The winch on the rear of 

the dozer must be removed so that 

the thinner mounting bracket can 

be attached. 

We used a JD-450 that had 

f actory-installed backhoe equipment. Thus, the dozer had a flow 

divider and selector valve in the 

hydraulic circuit. When the selector valve is in the dozer mode, the 

flow divider allows only part, 15 

gpm max., of the pump flow in the 

dozer circuit to the blade controls. 

The balance is returned to the 

tank. When the selector valve is in 

the backhoe mode, all flow goes 

through the backhoe circuit, which 

we used for the thinner circuit, 

Thus, the thinner has 23 gpm of 

hydraulic fluid available from factory-installed equipment on the 

dozer. A 30 gpm hydraulic pump is 

added to the thinner and powered 

by a short drive shaft from the 

dozer PTO, giving a total flow of 

53 gpm. 

We wanted the dozer to be 

usable without the thinner. Therefore, the hydraulic circuits were 

designed so that fluid would return 

to operating level in the dozer 

tank. Using the factory quick 

disconnects would not allow fluid 

to return to the dozer tank fast 

enough, so all fluid used in the 

thinner is returned to hydraulic 

tanks on the thinner and flows to 

the dozer tank by gravity through a 

2-inch line. A hole was drilled in 

the dozer hydraulic tank, and a 

valve and adapter were attached. 

Likewise, a hole was drilled in one 

hydraulic tank on the thinner. 

These tanks were connected with a 

2-inch hose and clamps. 

The pressure line from the 

dozer pump uses the standard 

backhoe disconnect to supply fluid 

to the thinner. 

An electric throttle was designed for the dozer so that it 

would not have to be run at high 

rpm all the time. This throttle has 

a control box on the dozer and one 

in the operator's cage on the thinner. 
Loader Modification 

A yarder can be made out of 

any hydrauf ic knuckleboom loader. 

The lightest loader that will safely 

handle the logs should be selected 

to make the yarder as light and 

mobile as possible. This section 

records the modifications made to 

the Savage Model 100 hydraulic 

knuckleboom loader1 (rear mount) 

to convert it into a yarding attachment (Fig. 2). Twenty inches was 

cut off the bottom of the support 

frame to give ground clearance and 

allow the boom to swing above the 

dozer operator's seat (Fig. 3). Two 

smaller hydraulic tanks replaced 

the original hydraulic tank (Fig. 4) 

to give clearance for a 30 gpm 

hydraulic pump. Figure 5 shows 

the hydraulic tanks, pump, and 

hoses. 

Most hydraulic loaders are not 

equipped with an operator's cage. 

One was built for the thinner to 

protect the operator from broken 

winch cable (Fig. 6). 

The grapple was removed from 

the loader along with the hydraulic 

controls. If one were going to load 

logs with the machine, he might 

want to consider leaving the grapple on and adding a sheave on top 

of the boom. The grapple would 

handle logs on the landing and load 

trucks faster than the tongs. The 

design would have to be such that 

the cable or tongs would not interfere with the hydraulic hoses. 

The sheave on the end of the 

boom needs to be enclosed so the 

cable cannot slip off the sheave. 

At the hinge point in the center 

of the boom, a roller was added so 

the cable would have something to 

move over when the boom is 

knuckled under (Fig. 7). 

A 7/8-inch-thick steel pltzte 

was welded to the main boom and 

reinf oreed near the opera tor's cage 

for mounting the winch. The features of the winch are covered in 

another section. 

The outriggers originally were 

to be mounted under the support 

frame of the Savage loader. Since 

the support frame was shortened, 

the outriggers had to be mounted 

at a different location. A mounting bracket was welded on the 

lower part of the support frame 

and the outriggers were bolted to 

it (Fig. 8). When the outriggers are 

folded, the thinner is 8 feet wide 

for legal highway travel. 

The mechanism that secures 

the yarder to the dozer is critical. 

The yarder support frame should be 

slightly wider than the mounting 

bracket. A standard John Deere 

backhoe mount was used; the only 

modification to the mounting 

bracket was to enlarge the mounting pin holes to 1-314 inches. Figure 8 shows the mounting bracket 

on the dozer. Figure 9 shows the 

pin mounts that are fastened to the 

yarder support frame. It and a 

piece of steel plate straddled the 

mounting bracket; the 1-314 pin 

goes through all three pieces. In 

(Text continued on page 6) 

Figure 2.-Savage Model 100 hydraulic knuckleboom loader, 
e 3,-Twenty-ineh section eat off the bttom of the Savage loader. 
e .Q.-N(ydrafle tanic: removed from Savage loader. Figure G.-Operator*s cage for protection if cable br 

Figure 5.-Thinner's two hydraulic tanks, 30 gpm pump in 

the center of the two tanks, and return line to the dozer Figure 7.-Thinner placing logs on truck road (Note the 

tank. roller in the center of the boom). 
e 8,-Loader taken apatt afld 

mounted on dozer piece by piece. 

Figure 9.-Revised mount of Appalachian Thinner (top mount 

shown). 

HOUSING PLATES ON APT - 1/2" THRU 518"THICK A 

SPACER BLOCKS -WELDED BETWEEN 

HOUSING PLATES TO ADD -STRENGTH 

MOUNTING BRACKET-ON DOZER 

SETSCREW-TO LOCK PIN IN PLACE 

MOUNTING PIN-1 3/4"COLD ROLL 

STEEL-TAPERED ENDS FOR 

EASIER STARTING 

COLLAR-WELDED TO HOU 

PLATE FOR REINFORCEM 

NOTE: BOTTOM MOUNT SIMILAR 

EXCEPT PIN SITS IN CRADLE 
previous design the yarder mount 

did not straddle the dozer mount, 

and stress cracks occurred in the 

yarder mount. 

The yarder has to be transported on a lowboy, because even with 

the cage removed it is 10 feet 

high, and adding the height of the 

lowboy approaches the maximum 

legal road height of 13 feet. Total 

weight of the prototype including 

dozer is about 10 tons. 

The controls and hydraulic lines 

for the grapple were removed, but 

trs mentioned earlier, it is possible 

to leave these on and make the 

yarder an efficient loader, also. A 

view of the yarder controls from 

the operator's cage is shown in 

Figure 10. 

The small box in the upper right 

corner is the electric throttle control. The three levers on the right 

control the main boom, jib, boom, 

and boom rotation. The short lever 

in the eenter combines all flow 

from both pumps to the winch, 

The long lever on the left is the 

winch control, The Huseo control 

valve for the winch is open center 

so that the supply to the winch 

motor will not eavitate, 

The hydraulic circuit for the 

dozer and the thinner is shown in 

Figure 11. The selector valve can 

combine the flow Prom the pump 

on the f rant of the dozer with the 

flow from the pump on the rear of 

the dozer and supply this combined 

flow to the control valve of the 

winch. When the pump on the 

front of the dozer is not supplying 

the winch, it operates the other 

functions of the yarder. 

The winch mounted on the rear 

of the main boom is a Gearmatie 

GH-85, Specifications for the 

winch are: hydraulic fluid supply-- 

60 gpm at 2500 psi; weight-I40 lb; 

line puLf--8510 lb (bare drum), 6089 

drum (full drum); line speed-244 

fpm (bare drum), 352 fpm (full 

drum). The winch operates under 

power in and out, and "ns a brake 

applied in neutral, 

The pressure relief for the 

winch is set to release at 8,000 

pounds of pull in the winch line. 

The drum has 1,500 feet of cable on 

it, and the speed sf the cable is 

near the rated maximum of 351 

fpm, The winch has been used lo 

yard logs up lo 400 feet. The eable 

is very high strength Bridon American 3/8-inch cable with a published breaking strength of 18,000 

pounds. 
e 11.-Hyeaulie circuit diagram, 

I-----' BLADE ANGLE 

JIB 

I 

BOOM 

MAIN BOOM 

I SWING 

WINCH $3 BLADE LIFT I 

I I FLOW DIVIDER SELECTOR 

WITH RETURN /SPEED co t . 

MODE SELECTOR 

VALVE 

I I STABILIZERS I 

THINNER 0 

DOZIER DIAGRAM 

t .S. GOVEKMIEhT PRISllUG OFFICE: 1982-505-0 12 3 12 
Biller, Cleveland J. Fabrication of the Appalachian Thinner. 

Broomall, PA: Northeast. For. Exp. Stn.; 1982; USDA For, Serv. 

Res. Pap. fdE-495. ? p. 

The Appalachian Thinner, a prototype cable yarder, has proven 

capable of harvesting timber on steep slopes. Details of the fabrication of the prototype yarder are presented. An Appalachian 

, 

Thinner can be built economically in a typical logger's repair shop. 

ODC: 377.4 

Keywords= Logging, Timber production, Forest engineering 
Headquarters of the Northeastern Forest Experiment Station are in 

Broomall, Pa. Field laboratories are maintained at: 

@ Amherst, Massachusetts, in cooperation with the University of 

Massachusetts. * Berea, Kentucky, in cooperation with Berea College. 

@ Burlington, Vermont, in cooperation with the University of 

Vermont. 

@ Delaware, Ohio. 

, New Hmps~m, hi cmpratisn with the University of 

New Hampshire. 

@ Hamden, Connecticut, in cooperation with Yale University. 

Morgantown, West Virginia, in cooperation with West Vi 

University, Morgantown. 

Omno, Maine, in cooperation with the University of Maine, 

Orono. * Parsons, West Virginia. 

@ Princeton, West Virginia. 

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

New York College of Environmental Sciences and Fo 

Syracuse University, Syracuse. 

@ University Park, Pennsylvania, in coopration with the