A Comparison of TwoRoad Reconditioning

Systems:Roto Trimmer and

Forester C-2000

United StatesDepartment ofAgriculture

Forest Service

Technology &DevelopmentProgram

7700—Transportation SystemsSeptember 19989877 1205—SDTDC

Information contained in this document has been developed for the guidance ofemployees of the Forest Service, USDA, its contractors, and cooperating Federaland State agencies. The Department of Agriculture assumes no responsibilityfor the interpretation or use of this information by other than its own employees.The use of trade, firm, or corporation names is for the information and convenienceof the reader. Such use does not constitute an official evaluation, conclusion,recommendation, endorsement, or approval of any product or service to theexclusion of others that may be suitable.

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A Comparison of TwoRoad ReconditioningSystems:

Roto Trimmer andForester C-2000

James R. Bassel, P.E.Civil Engineer

USDA Forest ServiceSan Dimas Technology and Development CenterSan Dimas, California

September 1998

CONTENTS

INTRODUCTION................................................................................................................................ 1EQUIPMENT DESCRIPTION ............................................................................................................ 2

Roto Trimmer ......................................................................................................................... 2Forester C-2000 ..................................................................................................................... 2

CREW, PROJECT OPERATION, AND PRODUCTION RATE .......................................................... 2Roto Trimmer System ............................................................................................................ 2Forester C-2000 System ........................................................................................................ 4

SYSTEM APPLICATION, LIMITATIONS, AND RESULTS ................................................................. 4Roto Trimmer System ............................................................................................................ 4Forester C-2000 System ........................................................................................................ 4

PAST USE, AVAILABILITY, AND COST ............................................................................................. 6Roto Trimmer .......................................................................................................................... 6Forester C-2000 ..................................................................................................................... 6

CONCLUSION ................................................................................................................................... 6LITERATURE CITED ......................................................................................................................... 7APPENDIX ......................................................................................................................................A-1

Contacts ..............................................................................................................................A-3

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INTRODUCTIONThis report compares the performance, capabilities,and cost of two road-reconditioning systems: theRoto Trimmer, owned and constructed by Triple TreeIncorporated located in Missoula, Montana, and theForester C-2000 rock crusher, developed by FAHRIndustries located in New Brunswick, Canada. Eachpiece of equipment has specific attributes andcapabilities that make each machine appropriate forspecific road surface conditions.

The information in this paper was gained fromdiscussions with manufacturers, reviews of completedprojects, and discussions with USDA Forest Servicepersonnel who have detailed knowledge of themachines’ capabilities and costs. The study focusedon determining the performance of each machine forvarious road and geologic conditions.

This paper provides a cursory review of both roadreconditioners with the objective of assisting fieldpersonnel in selecting the best equipment to matchthe specific road-surface conditions for their project.Table␣ 1 provides a summary of performance and cost

• Limestone, dolomite, quartzite, igneousintrusion

• Outcrops and boulders with fracturedexposed bedrock

• Fractured/brittle rock, layer rock• In rock easily fractured by teeth (i.e.

limestone, dolomite, quartzite, igneous)• Round rock imbedded in surface• Ledge rock/bedrock intact in surface• Angular rock that can be fractured (indepen-

dent of size)

• Cobbles, boulders, angular rock• Rock that can be ripped and windrowed• Rock less than 16-inch diameter• Rhyolite, sandstone, shale, igneous

volcanic,breccia, andesite

Roto Trimmer System Forester C-2000 SystemCategory

Material, Rock and GeologicTypes

Operates best in:

Least efficient in: • Hard non-fracturable round rock• Hard metamorphic rock• Competent rock, difficult to fracture

* Bedrock* Material that has a significant amount of

oversize rocks (greater than 16-inch diameter)

(Lane for Roto Trimmer, up to 15 feet)

$4,900 - $9,700

$7,000

$5,000

$10,000

Cost independent of lane-mile if greater than3 miles

NA

NA

(Note: based on 1998 contract cost)

(Lanes for Forester, up to 14 feet)

$6,500 - $17,000

$8,500

NA

NA

$6,500

$17,000

$10,000

(Note: Based upon government ownershipusing force account crew)

Operating Cost (per lane-mile)

Range

Average

Easily fractured rock

Hard rock

29 lane-mile project,

medium hardness rock

5 lane-mile project,

medium hardness rock

8 lane-mile project,

medium hardness rock

Production Rate (lane-mile per 8-hour day)

Range

Average

Hard rock

Easily fractured rock

Project less than 6 miles

Project greater than 10 miles

0.75 to 1.25

1.0 (manufacture estimate)

0.75

1.25

NA

NA

0.7 to 0.9

0.8

NA

NA

0.7

0.9

(Note: Because of different crews there is a timeto learn the project coordination among them)

• Triple Tree, Inc. (Missoula, MT) has the onlymachine. It is subject to their schedule andoperations.

• A forest can contract only for the completeRoto Trimmer system.

• Mainly used within 300 miles of Missoula.Company states they can mobilize anywheredepending upon size and complexity ofproject.

• Company has stated they can build anothermachine depending upon sufficient demand,but will not sell it.

Availability: • Coronado and Rio Grande NFs ownmachines. Equipment and crushing crew canbe contracted through the two Forests.

• Part of crew to be supplied by host Forest(organization)

• Use of machines and crew subject to Forestavailability and schedule

• Forester C-2000 can be purchased from orcontracted through FAHR Industries

• Purchase price as of 1998 was $250,000(with additional parts).

Table 1—Capabilities, performance, and cost of Roto Trimmer and Forester C-2000.

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information for both machines, based upon fielddemonstrations and experience. Table␣ 2 is aqualitative comparison of both machines, based upondetailed field knowledge gained duringdemonstrations of the equipment.

The Pettibone P-500 Mobile Hammer Mill, usedextensively in Region 6 over the last 20␣ years, wasoriginally to have been evaluated in this report.However, the machine has not been used innumerous years, and there are no plans to do so;therefore, it was not considered further. The machineis currently in Baker City, Oregon, on theWallowa-Whitman National Forest and has beencompletely refurbished. When it was operating, itspurported production was similar to the ForesterC-2000, and it operated on the same principle asthe Forester, with revolving hammers. Forestsinterested in using the machine can call theWallowa-Whitman engineering section. The Centerhas published two reports in 1974 and 1979 aboutits use and results.

EQUIPMENT DESCRIPTION

Roto Trimmer

The Roto Trimmer Mobile Rock Processor (Figure␣ 1)is a self-contained unit that mounts to a CAT␣ 966front-end loader. The machine has a rotary drumwith 184␣ carbide-tipped teeth in knuckle holdersmounted in a spiraled-inward pattern. The drum ispowered by a CAT␣ 3406 diesel engine rated at400␣ hp.

Forester C-2000

The Forester C-2000 Road Crusher (Figure␣ 2) is alsoa self contained unit and mounts on the front of aCAT␣ 950F front-end loader or equivalent. TheForester C-2000 is powered by a CAT␣ 3208 dieselengine rated at 255␣ hp, and consists of eighthammers bolted through a solid steel rotor.

CREW, PROJECT OPERATION, ANDPRODUCTION RATE

The Forester C-2000 and the Roto Trimmer systemsrecondition roads based upon different physicalprocesses. The roads being processed thereforerequire different preparation and post-processingtreatments. Each machine, along with its particularpre- and post-processing needs, will be referred toas a “system.”

Roto Trimmer System

Pre-processing: Prior to operating the RotoTrimmer, a hydraulic rock hammer mounted on aBobcat prebreaks large rocks (over 6 inches indiameter) that are imbedded in the roadway and thatare not easily fractured with the machine. Thisoperation is not absolutely necessary, but it doesallow the Roto Trimmer to get an easier bite on rocks,thus improving overall performance. Ditch anddrainage repairs are also completed before the RotoTrimmer starts operations. No further pre-processingof the road surface is necessary with this system.

Roto Trimmer Operation: After completion of thepre-processing activities, the Roto Trimmer isbrought to the site. For a 15-foot-wide road anddepths of 4␣ to␣ 6␣ inches, the Roto Trimmer makes four

Roto Trimmer System Forester C-2000 SystemCategory

Driveability by passenger cars

Production of erodible fine material

Quality of finished project after 5 years

Quality of finished projects after 3 years

Ability to process boulders less than 12 inches

Ability to process ledge rock

Impact to local forest personnel

Production rate

Excellent

Poor

Good

Good

Good

Excellent

Low

Very good

Excellent

Poor

Unknown

Good

Excellent

Very poor

High

Good

Table 2—Qualitative Assessment of finished projects (by author).

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Figure 1—Roto Trimmer Mobile Rock Processor

Figure 2—Forester C-2000 Road Crusher

R9800150

R9800153

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passes: two passes for width, and two for depth.The most efficient method has been to operate themachine against the grain of the rock.

Post-processing: A grader reshapes the processedmaterial to achieve the desired road prism: inslope,outsloped, or crowned. A water truck then applieswater for compaction. A vibratory roller with Elliotgrids compacts the roadway, making several passesuntil desired compaction is achieved. The gradermakes another pass to fill in voids. The road is thenrolled again with a smooth drum to remove the gridmarks from previous rollings with the Elliot Grid.

The crew consists of four people: One person onthe Roto Trimmer, one on the grader, one on theroller, and one who operates both the Bobcat andwater truck. Production rate of the Roto TrimmerSystem averages 0.75 to 1.25 miles per 8-hour day.This rate depends largely upon the level of energyrequired to fracture the material.

Forester C-2000 System

Pre-processing: Before the crushing operationbegins, the rippers on a motor grader or tractorloosen the top 4␣ to␣ 6␣ inches of the road surface anddislodge embedded rocks. The ripped material,along with loose rock on the shoulder and ditches,is windrowed in the center of the roadway. Windrowsthat are 5␣ feet wide by 1␣ foot high are efficientlyhandled by the machine. The water truck wets thewindrow for dust abatement immediately before theForester C-2000 processes the material.

Forester C-2000 Operation: The machine makesone pass crushing the material in the windrow. Large16-inch diameter rocks are typically broken into3-inch minus material. Rocks are crushed betweenthe rotating hammers and steel anvils bolted to thetop of the crusher box. The rotor spins in the directionopposite to the travel of operation. A heavy-dutychain drapes the opening in front of the box keepingrocks in line for crushing rather than allowing themto be pushed out as the loader moves forward(Figure␣ 3). When the rock material is crushed smallenough to fit through the spaces between thehammers and the anvils, the crushed materialpasses out the back under a flexible belting screeninto a new windrow.

Post-processing: A second grader works behindthe Forester C-2000 spreading the crushed materialon the roadway,and watering as needed. To achievebest production rates, two motor graders are needed:one for ripping and windrowing prior to crushing, the

other to spread the processed material after crushing.An Elliot grid roller or other compaction device isoften used to compact the surface.

Five people have been used for the Forester C-2000System: a loader/crusher operator, two graderoperators, and two water truck drivers/mechanics.However, later projects have used a four-personcrew just as efficiently with the elimination of one ofthe graders and associated operators. The averageproduction rate is 0.8 mile per 8-hour day to completethe entire operation. The Forester C-2000production rate is most dependent on the size of awindrow and the amount of rock material in thewindrow. An overly large windrow with a significantamount of rock material clogs the crusher and stallsthe engine, and a small windrow producesinsufficient crushed material.

SYSTEM APPLICATION, LIMITATIONS, ANDRESULTS

Roto Trimmer System

The Roto Trimmer System works best when grindingeasy-to-fracture ledge rock embedded in the roadsurface. Material that is embedded in the roadwayor that shows weathering, joint lines, or internalfracturing can be efficiently processed by the RotoTrimmer. The teeth impact the road surface with a“striking” action as the rotary drum moves along theroadway. The rocks are fractured and ripped alongwith other material. The loose rock revolves in thedrum’s casing, which further fractures and blendsall the material (Figure␣ 4). The finished product is awell mixed, 4-inch minus material, resulting in asignificant increase in fines. Rock that was noteffectively fractured with the rock hammer is eitherre-incorporated into the surface, windrowed alongthe side of the roadway, or cast beyond the roadway.Since post-processing with this system includesdouble compaction of the road surface, the finishedproduct is a hard, smooth drivable surface. The RotoTrimmer is less effective on rock that is notembedded in the roadway or is not easily fractured.

Forester C-2000 System

The Forester C-2000 works best on cobbles andboulders that are either angular or rounded up to amaximum size of 16-inch diameter. If the materialcan be windrowed, the Forester C-2000 can usuallycrush it. The resulting material generally consistsof 2-inch minus, with occasional 3-␣ to␣ 4-␣ inch minusas the hammers and anvils wear down. Largeboulders are deliberately sought after and carriedinto the windrow for processing by the Forester

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Figure 3—Forester C-2000 heavy-duty chain

Figure 4—Roto Trimmer drum casing

R9800154

R9800149

6

C-2000. As with the Roto Trimmer, the ForesterC-2000 increases the amount of fines material in theroad surface, sometimes significantly. In-placebedrock cannot be crushed with the Forester C-2000.

Both systems usually increase the amount of erodiblesilts and sands on the road surface, as comparedwith pre-processing conditions. Additionally, neithersystem will produce an engineered material, nor canthe final gradation be controlled. Both systems,however, do produce a very smooth, drivable surfacethat can be maintained with a grader and used bypassenger cars.

PAST USE, AVAILABILITY, AND COST

Roto Trimmer

Triple Tree is the sole owner of the Roto Trimmer,with services that can be contracted only throughthe company. The machine cannot currently bepurchased on the open market. It has been usedmainly on road projects within a 300-mile radius ofMissoula, Montana, where Triple Tree is located.This company has its own transport equipment, iscompletely mobile, and states they can go almostanywhere. The company can and will build anotherRoto Trimmer if the demand warrants, but they willnot sell it. Triple Tree has been using the RotoTrimmer since 1990 and has processed over300␣ miles of roadway. Much of this business hasbeen contracted with the same clients. Typical jobsize is 10 ␣ miles, and the minimum job size is 3␣ miles.

In 1998 the Lolo National Forest (Montana)contracted with Triple Tree to re-establish nativesurface on 23␣ miles of road at six different locations.The total cost was $158,000; average cost was$6,900␣ per mile. The unit cost for each locationranged from $4,900 to $9,600 per mile.

Forester C-2000

The Forest Service purchased and owns twoForester C-2000s. One is located on the CoronadoNational Forest in Arizona; the other is located onthe Rio Grande National Forest in Colorado, whichis shared between Regions␣ 2␣ and␣ 3. The ForesterC-2000 is available for purchase from FAHR at aprice of $250,000 (August␣ 1998), or it can be leasedfrom FAHR for $5,300 per mile, which includes thecrusher and loader, crusher operator, and mechanic/assistant (includes transportation anywhere inContinental U. S. or Canada). Alternately, Forestsinterested in using the Forester C-2000 system can

contact the Coronado or Rio Grande National Forestsfor possible sharing arrangements. Both Forestshave indicated a desire to lend their machines, andpossibly part of the crew, to perform work in otherareas during slack periods. It may be possible tocombine the local road maintenance crew with anexperienced crew from the Coronado or Rio Grandeto help defray the cost of the project. To date, theForester has processed about 100␣ miles of roadway.Minimum job size is the key factor in determiningthe unit cost of the project. Longer projects havelower costs. Projects with fewer than 8␣ lane-mileshave unit costs that may exceed importing materialfrom local sources.

Over the last three years, the Coronado, Rio Grandeand Plumas National Forests completed three road-reconditioning demonstration projects totaling42␣ miles using the Forester C-2000 system. Thetotal cost was $356,000, with an average cost permile of $8,500.

CONCLUSION

Both the Roto Trimmer system and the ForesterC-2000 system can make a rough, rocky road intoa good road, with a hard, smooth, maintainabledriving surface. The Roto Trimmer works bestgrinding ledge or layered sedimentary rocks or easilyfractured imbedded boulders, while the ForesterC-2000 crushes hard, large boulders up to 16␣ inchesin diameter. Each machine occupies its own specificniche of projects. The Roto Trimmer is more efficientand economical than the Forester C-2000 forprocessing road surfaces composed of ledge rockand easily fractured well embedded rock, while theForester C-2000 is the right machine to process roadsurfaces composed of harder cobbles and bouldersthat need a real crushing action. It is important tonote that the Forester C-2000 cannot process roadsurfaces composed of ledge rock that cannot beripped with ordinary rippers, while the Roto␣ Trimmerhas difficulty processing road surfaces composedof loose, hard cobbles and boulders. Neither systemproduces an engineered material of uniformgradation. However, both produce a better roadsurface when the quality and expense of a standardcrushed aggregate is not economically justified.

NOTE: Since these demonstration projects wereconducted, FAHR has patented and trademarkedthe Forester C-2000 as the “FAHR Roadcrusher,”and this model is called the Forester C-2000.

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LITERATURE CITED

Bassel, J., and S. Clements. “Forester C-2000 Road Reconditioning- 3 Demonstration Projects.” Report98771206-SDTDC. September␣ 1998. USDA Forest Service.

Fischer, A., T. Pasqual, and J.Bassel. “Forester C-2000 Demonstration Project.” Report 9671 1212-SDTDC.November 1996. USDA Forest Service.

Northrup, J. “Development of Cusion Aggregate on Native Surface Roads by Use of the Roto Trimmer.”USDA Forest Service, 1994.

Sheehy, D. “Recycling of Road Surfaces with the Roto Trimmer Mobile Rock Processor.”

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APPENDIX

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APPENDIX

Contacts

Contact for Roto TrimmerTriple Tree, Inc.Bob Greil6205 Pine Grove LaneMissoula, MT 59802406/258-6273

Contact for Forester C-2000FAHR Industries, Inc.Brian BouleyP.O. Bax 254Madawaska, Maine 04756-0254506/735-4179 or 888/983-7333

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