Trolley History
Hutnyak Consulting

The following is a brief history of trolley assist for off-highway vehicles. Many thanks to the companies and individuals who contributed photos and technical articles. Anyone wishing to submit additional trolley details are encouraged to contact Dave Hutnyak.

Note: Clicking on each small "thumbnail" photo causes a larger version of the photo to be displayed. Additional photographs are included in the trolley photos page.

Trolley through History:

Pre-1900 - Trolley Buses in the 1800's
1938-1962 - Valtellina Dam Project
1939 - 1964 - International Salt
1956 - 1971 - Riverside Cement
1967 - Kennecott Chino
1970 - 1977 - QCM Lac Jeannine
1980 - 2001 - Palabora
1982 - 2001 - ISCOR
1983 - 198? - Nchanga
1986 - 2001 - Rossing Uranium
1994 - 2001 - Barrick Goldstrike

Early Siemens
Trolley bus - 1882

Trolley bus with
Rigid Boom - 1889

Pre-1900, Trolley Buses in the 1800's

The concept of electrifying vehicles using trolley or pantograph collection is not a new idea. Some say that the trolley concept was first developed by Charles J. Van Depoele, who immigrated to the USA from Belgium in 1869. He developed a trolley car power system that operated a short rail line at the Chicago Industrial Exposition in the years 1882-1883. Van Depoele sold his electric-railway patents in 1888 to Thomson-Houson Electric Company of Lynn, Massachusetts, which was soon absorbed into the General Electric Company.

In Europe it is generally felt that Werner Von Siemens is the "father of the trolley bus", because of his experiments in the Berlin suburbs in 1882. Siemens initially favored a trolley or "contaktwagen" that ran on the top of a pair of wires in horizontal configuration. Initially, a flexible electric cable was used to connect the trolley to the vehicle. Before long, rigid booms replaced the flexible cables. For the last 100 years, designers have been trying to perfect current collecting on trolley buses. Many of the same challenges exist in off-highway trolley applications.

Near Bormio, a new trolley truck in a builder photo of 1940.

Trolley tractor #17 shown in July 1944, during the War. It is painted in "war livery", with white bumpers and mudguards, and eyelids over the front lights.

Crossing between trolley trucks. A frequent scene in the fifties between Tirano and Bormio. The site is one of the six crossing points. The entire trolley line was equipped with single twin wires.

Trolley truck #4 flat body carrying miscellaneous materials, including a bike, in front of the Sondalo hospital.

1938 - 1962: Valtellina Dam Project

The following is based on information received from Mr. Alessandro Albè, who is presently writing a book documenting the history of the trolley truck line that was used to build a dam at Valtellina in northern Italy.

For more information regarding his book, contact Mr. Albè by email at

The Valtellina trolley system was built in 1938 and operated until 1962 by AEM (Milano Power Company), the owner of hydro-electric power plants in Valtellina. A total of 20 trolley trucks were used to carry concrete, sand and equipment for construction of the San Giacomo and Cancano II dams in the high Valtellina valley in northern Italy. The electric power was (and still is) sent to Milano to supply the needs of the city.

There were 16 three-axle trolley trucks, 4 two-axle trolley tractors for pulling heavy loads (i.e. transformers), and 2 trolley buses for transporting personnel. These trucks were straight electrics, operating on 650 volts dc power from overhead lines. Two trolley lines were installed: the original one of 66 km in length from Tirano to Boscopiano for the building of the San Giacomo concrete gravity dam (1940-1950). The second trolley line was a section from Bivio Molina to Digapoli (14 km) for the construction of a second dam, under San Giacomo, called Cancano II (1952-1956). The total length of the these lines was approximately 80 kilometers.

Concrete came by rail, in cylindrical containers, from concrete mills. These containers were transferred to the trolley trucks which transported them to the construction site. From there, cableways were used to carry the concrete containers to the dams. Other goods and personnel were transported directly to the dam. The three-axle trolley trucks were equipped with a removable body. This allowed either a normal flat body to be used, or a special one with rollers to accomodate the concrete containers.

1939 - 1964: International Salt Company

The following is based on reference #9:

The first electric truck application occurred in 1939 when a number of Euclid 20 ton mechanical trucks were converted for electric trolley operation at the International Salt Company's underground mine at River Rouge, Michigan. They were converted by connecting a DC motor directly to the differential. Power for off-trolley operation was provided by storage batteries placed in the area previously occupied by the engine. By 1964 these trucks had successfully operated for 24 years.

Total Electric Truck
30 ton Kenworth

On the Road
Power from Trolley Line

At the Shovel
On an "Extension Cord"

GE 762 Traction Motor

Motor in Truck
Driving Rear Axle

Cable Reel
Side View

1956 - 1971: Riverside Cement Company

The following is based on reference #1:

In 1956 the Riverside Cement Company of Crestmore, California purchased four Kenworth 30 ton end dump trucks for electric trolley operation. A 350 hp DC traction motor was used to drive the rear axle differential. Power was collected from a 550 volt, two-wire overhead catenary system using a rigid pole collector assembly. The electrical equipment was built by the Locomotive & Car Equipment Department of the General Electric Company (Erie, Pennsylvania) and was installed in the trucks by Kenworth.

The trucks hauled limestone from an underground mine up a 10% grade to a crusher located at the cement mill. The total haul length was about one mile, of which approximately 4,000 feet was at a 10% grade. When descending the 10% grade, the speed of the empty truck was held at approximately 14 mph with the dynamic brake, excepting on sharp curves when the the control lever was moved from "brake 1" to "brake 2". This reduced the speed to about 9 mph. The air brake was used only when bringing the truck to a complete stop.

At the entrance to an underground room, the truck's cable reel was plugged into a wall-mounted receptacle which supplied 550 volt current to the truck's traction motor through the cable reel. The truck then backed away from the trolley wire until it reached the shovel. After being loaded it ran forward until the trolley wire was again reached, at which point the cable reel was unplugged and the trolley poles put up again. With a 30 ton load, a speed of 10-12 mph was maintained on the 10% grade during the uphill run to the crusher. This speed on grade was approximately double the speed attainable if a diesel engine were used.

A General Electric 550 volt auxiliary motor was used to drive the hydraulic system (steering & dumping), the 24 volt generator (headlights and control power), and the air brake compressor.

An economic evaluation, conducted in 1954, indicated that it would be cheaper to purchase electric power than diesel fuel. Other anticipated savings included engine oil, engine maintenance, powertrain maintenance (no transmission, no shock loads), brakes and tires. Although increased tire life was not originally anticipated, it did occur and was attributed to the smooth application of torque.

The drive motor was the GE762B1 traction motor, which was originally designed for heavy duty railway service. The motor frame was equipped with brackets used to support the motor in the truck's chassis. The motor was of the "open frame" type, and could be used for either forced ventilation or unblown operation. At Riverside, the unblown version was used. No external blower or fan was needed. Resistors, used during acceleration and retarding,were enclosed in a cabinet located behind the operator's cab.

The cable reel had a diameter of 60 inches, and could carry from 300 to 470 feet of cable - depending on the size of cable used. The reel was driven, through a single reduction pinion and ring gear, by two GE 500 volt cable reel motors. After pulling down the trolley pole and plugging the cable into the receptacle, the driver would operate the cable reel switch in the truck's cab. The system was designed to keep sufficient tension on the cable as the truck backs away (unreeling) but not sufficient to damage the cable as the reel pays it out. The motors developed higher torque when reeling in the cable as the truck accelerates forward toward the trolley wire.

These trucks operated for 15 years before being retired from service. To view additional photos, click here.

Unit Rig M100

1967- Kennecott Copper, Chino Mine

The following is based on references #3 and #5:

In 1967 Kennecott Copper Corporation at Chino, New Mexico, conducted the first feasibility study and prototype test of trolley-assisted large mining trucks. The truck used was a Unit Rig Model M100 with a 700 hp diesel engine, General Electric motorized wheels, and 2400X49 tires. The testing indicated that the truck, carrying a payload of 123 tons up a 1,300 ft ramp at 7%, was able to increase its maximum speed from 6 mph to 13.5 mph by using trolley assist. The maximum voltage that could be maintained was only 634 volts and it was reasoned that a higher speed would have resulted if a higher trolley line voltage could have been supplied.

Unit Rig M100

Power Collected
by Trolley Pole

Entrance to
Overhead Bus Bar

Truck on Line

1970-1977 - Quebec Cartier Mine, Canada

The following is based on references #3 and #5:

QCM at Lac Jeannine, Quebec, is located at the extreme southwestern end of the Quebec Labrador Trough. An iron ore mine, the typical haulage route from shovel to crusher at mid-1971 was anticipated as 8,000 ft with a vertical lift of 400 feet and a cycle time of 26.6 minutes. They were looking for ways to reduce their cycle time, and felt that their trucks needed more horsepower.

Having reviewed the trolley experiment at Kennecott Chino, which utilized a truck similar to those in use at the Lac Jeannine Mine, a study was carried out which indicated that trolley-assist would be feasible for Quebec Cartier's operation. Chino's experiment had established the technical feasibility of a trolley-assist system, but did not address the many factors required to operate a full size trolley fleet in a high production mode. To address this, Quebec Cartier, Canadian Johns Manville Company, and Unit Rig and Equipment Company agreed to participate in a program to develop and test the prototype of a trolley assist system which would satisfy the severe operating requirements of an open-pit mine.

Considerable effort was expended to optimize the power distribution system. Steel towers on anchored concrete bases were designed to support two aluminum bus bars on a span of 40 feet. Segments of bus bars capable of carrying large currents were bolted together. An entrance pan at the bottom of the haulage road was used to guide the contact shoes onto the bus bars.

During the initial test period, a 1,000 ft long ramp at 10% was constructed, and an 1,800 hp diesel-electric locomotive was used as a DC power supply. It was learned that modifications to the onboard truck hardware and to the trolley entrance pan were needed. Once these issues were resolved, additional tests were conducted. An economic evaluation indicated that trolley-assist should produce the desired productivity increase, while saving a lot of fuel.

As a result, all of QCM's trucks were converted to trolley in December 1970 - including KW Dart 85 ton, Unit Rig M85 (85 ton), and Unit Rig M100 (100 ton) trucks. Trolley continued to operate successfully until the iron ore deposit was depleted and mining activity ceased in 1977. Over the life of the system, QCM realized a 23% improvement in productivity and an 87% decrease in fuel consumption on the grade.

To view additional photos, click here.

Unit Rig Mk36

Entering Test Line
with Pole Collector

Prototype Pantographs
Replaced the Poles

Final Pantograph

Palabora Open Pit

1980-2001 - Palabora Mining, South Africa

The following is based on reference #8:

The practicalities of installing and operating a trolley assist truck haulage system at Palabora was confirmed by a feasibility study in 1979. Acting on the study's recommendations, a three-phased approach was adopted. Phase I was a test program to prove the technical and operational feasibility of the system. A test line was constructed on an 8% ramp leading to one of the waste dumps. The trolley line design was of compound catenary construction and totaled 720 meters in length. Two single copper contact wires were used, one for each of positive and negative supply.

Electric power was provided to the overhead lines via a roadside rectifier substation, which was designed along the lines of modern railway practice having a continuous output of 5,000 kW at 1,200 volts DC. This selected substation size was based on supplying electricity to 3 fully laden trucks on a continuous basis while they travel up an 8% grade.

Current collection from the overhead trolley line to the trucks' onboard equipment was via 2 trolley poles mounted on a platform supported immediately ahead and above the driver's cab. Upon selecting trolley mode, the poles would automatically unlatch from their stowed position and extend upward by the action of pneumatic cylinders. An "entrance pan" was used to guide the trolley pole onto the conductor wires.

In June of 1980 the Phase I trolley line was commissioned and the first converted truck made its maiden run. Although the system was functional and achieved many of the design goals, it was decided that the current collection system needed improvement. Thus, the trolley poles were replaced with two railway type pantographs which were much larger and heavier than the trolley poles. The trolley line was converted to accommodate this concept.

Sufficient confidence was gained during the Phase I test to recommend that Phase II be installed. By October 1981 all 75 of the 170 ton Unit Rig trucks were converted to trolley, and 2.7 kilometers of overhead lines were installed along selected in-pit ramps. Installation of Phase III trolley ramps began in June of 1982.

General Comments:

As of February 2001, Palabora was operating a fleet of 19 Euclid R190 trolley haul trucks, 4 Unit Rig M36 trolley water trucks, and 2 Unit Rig M36 trolley fuel trucks.

To view additional photos, click here.

ISCOR Trolley

Unit Rig M36

MLT 2200

Euclid R280

Lots of Trucks

1982-2001 - ISCOR Mining, South Africa

The following is based on reference #12:

During 1979, the South African Iron and Steel Company Ltd. (ISCOR) conducted a trolley-assist feasibility study. The incentive was the unrealistic escalation in the cost of diesel fuel, and the appeal from the South African government to reduce the use of fossil fuels. Tests and economic evaluations proved the system to be technically feasible and economically attractive. Construction of 7.7 km of trolley line and the conversion of 66 @ 170 ton trucks at the Sishen mine was completed in March 1982.

Although the truck conversions of the GE drive system were similar to what was done at QCM Lac Jeanine mine in Canada, the unique operational requirements at Sishen rendered the already proven trolley pole system unacceptable. Minimum loss in truck mobility and flexibility was required. Overhead lines and substations were required to be of a relatively light construction and portable, enabling fast and easy repositioning of a line with no loss in material. These unique specifications set the base for the design of the Sishen system.

The overhead line was constructed using steel I-beams mounted on base plates. The masts were erected at about a 50 meter span and the base plates covered with approximately 12 tonnes of iron ore to keep them stable. It was decided to suspend each polarity of overhead conductor wire from an independent cantilever arm. These conductors were kept under constant tension by means of weights acting through a 2:1 pulley tensioning arrangement. For each overhead conductor, a standard grooved copper railway conductor was used. To obtain the necessary current carrying capacity, 2 of these conductors were used in parallel for each polarity.

The rectifier stations consist of an 11 kV to 860 V three phase transformer and a three phase diode bridge rectifier. The output voltage was (originally) 1200 volts DC, earthed through a current limiting network so that the line potential to earth is +600 V and -600 V. The output capacity of each station was adequate to supply 1 truck.

A scaled-up version of the railway type of pantograph was used to collect the current from the overhead lines. Each pantograph head is 3 meters wide, equipped with 2 strips of current collecting graphite brushes in parallel. With the Sishen system, a truck can exit at any point along the line, pass a disabled truck that is blocking the line and re-enter at any point.

General Comments:

ISCOR has been a great proponent of trolley assist, and has continually developed innovations in overhead lines, substations and pantographs. Trolley has been applied to other ISCOR mines, including the Grootegeluk mine in South Africa.

As of February 2001, the Sishen mine was operating a trolley haulage fleet consisting of 32 Komatsu 730Es and 9 Unit Rig M36s. The Grootegeluk mine was operating a trolley haulage fleet consisting of 14 Komatsu 730Es, 11 Marathon-LeTourneau 2200s, and 1 Euclid R280 AC.

To view additional photos, click here.

Haulpak 120C

Poles Raised
Ready to Enter Trolley

Closeup of
Pole Arrangement

Closeup of
Collector Shoe

1983-198? - Nchanga Mine, Zambia

The following is based on reference #14:

Diesel-electric haul trucks were introduced into the Nchanga open pit in 1967, and the possibility of employing trolley-assist was proposed in 1968 by consultants from Anglo American Corporation. Ten years later the rising cost of diesel fuel proved to be a good incentive for conducting a trolley feasibility study, which recommended that trolley-assist be installed in stages. Introducing trolley in this manner allowed for the partial conversion of the truck fleet - 33 out of the fleet of 100 trucks - during the first two or three years.

Construction of Stage I was completed in February 1983, with 15 of the mine's 120 ton capacity trucks being modified for trolley operation. All trucks were equipped with GE drive systems. Current collection employed bus bars and trolley poles.

The Nchanga trolley system has been decommissioned and is no longer in operation.

To view additional photos, click here.


170 ton Haulpak

1986-2001 - Rossing Uranium, Namibia

Rossing was a "sister" mine to Palabora, and when they installed their trolley system (sometime around 1986) they patterned it after Palabora's.

As of February 2001, Rossing was operating a trolley haulage fleet consisting of 11 Komatsu 730Es.

Haulpak 685E

Siemens Substation

Trolley Line

1994-2001 - Barrick Goldstrike, Nevada

The following is based on reference #16:

Barrick conducted numerous trolley feasibility studies and in 1993 gave the go-ahead to proceed with the installation of a system at their Goldstrike mine in Nevada. The system was patterned after Palabora's, except that the equipment was upsized to accommodate Goldstrike's larger trucks (190 ton vs. 170 ton).

Overhead lines and substations were supplied by Siemens, and were of a full catenary heavy-duty design. Pantographs, from TransTech of South Carolina, were used for current collection. Their "half-scissor" design differed from the "full-scissor" design used at Palabora.

By October 1994 five trolley lines, which totaled 2.9 miles in length, were in service - along with 50 Komatsu 685E haul trucks that had been converted for trolley operation. Barrick continued to expand the trolley system, with a total of 74 trucks and 4.5 miles of trolley lines in service.


Barrick decided to decommission the trolley system in early 2001. This was reportedly due to major changes to the mine plan. To view additional photos, click here.

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Hutnyak Consulting
2122 Colonial Drive
Elko, Nevada 89801