Road-rail mini-excavator UNAC 8TRR

The UNAC 8TRR mini-excavator can carry out lifting and earthwork operations on roads as well as on HST tracks, conventional tracks, and tram networks.



The UNAC 8TRR is a self-propelled hy-rail mini-excavator with hydrostatic transmission. The 8TRR was inspired by a basic Caterpillar mini-excavator for which the boom kinematics were completely maintained, apart from rail-road limitations. On the road, the mini-excavator has the same characteristics as a standard mini-excavator, except its stabilisation and backfilling blade is retractable thanks to a quick mechanical attachment system. On rail-roads, the 8TRR moves at speeds of up to 20 km/h thanks to its rail-road lorries. The UNAC 8TRR mini-excavator has the following features:

  • A comfortable, hermetic, heated and air-conditioned cab.
  • A caterpillar frame with rubber tracks that are controlled independently by levers inside the cab.
  • A single-block boom with boom leg rotation The boom's height is limited when working under high-voltage wires.
  • Two UNAC-HDX type lorries with a lifting system.
  • A turret rotation movement that can be restricted at two places in order to secure traffic on an adjacent lane.
  • A sophisticated UNAC-SMARTCS that includes a rear-view camera and operator indication system to receive real-time information concerning the machine, its load, and tilt, and to configure limits.




  • Secured by electronic management for the boom kinematics (different catenary heights) and for the rotation according to the work situations, backed up by mechanical stops.
  • Ergonomic controls in a premium  Caterpillar cab that combines comfort, soundproofing, air conditioning, and high visibility.
  • Robust, reliable and easy maintenance.
  • Can work in either lane direction thanks to the turret’s full rotation and rear-view camera.
  • Caterpillar warranty officially maintained The excavator benefits from the UNAC after-sales service and from Caterpillar’s dynamic after-sales network.
  • Maintains the original excavator’s lifting and earthwork capacities. The Rail/Road excavator can lift over 1 T up to 2.5 m from the centre of the track. The mini-excavator can thus lift very large loads in comparison to its size.
  • Very safe system, satisfying the most stringent rail-road standards, authorising work under live powerlines and leaving adjacent lanes open for incoming traffic
  • Electric emergency pump included, allowing significant autonomy in electric mode at about 80% lifting capacity and 20% kinematics.
  • Machine certified for the French network.
  • Caterpillar frame for easy manoeuvring with zero turning radius, making getting onto rails easy.
  • Angle of attack for all-terrain transfer greater than 50°.
  • Very stable thanks to its very low centre of gravity.
  • Possibility of using the blade by installing it via the quick mechanical attachment directly on the lorry.
  • Boom kinematics providing great liberty with the possibility of making trenches parallel to the rail-road using the boom leg rotation.
  • Great digging depth, even from the rail-road track.
  • Wide range of usable tools: auger, hydraulic rock breaker, buckets, hammers, universal pliers, hydraulic shears, mechanical pliers, compactor, clips with claws, loading bin, earthwork bin, and stripping beam.
  • Significant digging depth.
  • Automatic selection of lorries while lifting or getting on rails.
  • Ultra-short rear radius to work in smaller zones such as tunnels.
  • Significant rate of speed when on tracks.
  • Great acceleration and deceleration when on tracks to optimise time spent on work sites.
  • Indication of lane inclination and load in real time.


Technical Data

  • CATERPILLAR C2.4 Diesel
  • Gross horsepower 47.7 hp / 34.1 kW at 2,400 rpm
Road transmission
  • Caterpillar frame with rubber caterpillar tracks
  • Hydrostatic transmission with 2 gears and automatic transmission
  • Gear 1: 0 to 2.8km/h
  • Gear 2 : 0 to 4.6km/h
  • Ground pressure: about 32 kPa
  • Maximum slope allowes: 30°
Rail transmission
  • Hydraulic, 4 wheel drive
  • An engine per iron tire: POCLAIN
  • Speed: 0 to 20km/h
Hydraulic circuit
  • A load-sensing pump and piloting pump
  • Hydraulic tank: 68L, 95L circuit
  • Oil cooler
  • Hydraulic steering via 2 levers, 1 per track
  • Mini turning radius: 0m
Accessible road-rail track characteristics
  • Track spacing: 1,435mm
  • Maximum slope available: 35
  • Maximum track inclination: 180mm

On rails, deceleration and immobilisation are controlled using the Hyd-rev UNAC hydrostatic. Furthermore, the hydraulic motors controlling iron wheels are equipped with positive action pads. Brakes are automatically engaged if the driver cab armrest is lifted, if the emergency stop button is pressed, if the parking brake button is pressed, or when the engine is turned off.


Premium range, soundproof, ventilated, heated, air-conditioned. Electronic dashboard with digital display devices managing tools, controlling the excavator status in real time, showing the rear facing of the machine, and controlling the load and inclination. Work lights.

Fuel Tank Capacity
  • Fuel tank: 63L
  • Average autonomy: 12/14 hours, depending on the type of work
Boom kinematics
  • Adjustable single-block boom
  • Maximum range: 5,790mm with standard arm, 6,170mm with long arm
  • Maximum digging depth: 3,470mm with standard arm, 3,870mm with long arm
  • PTC: 6,700kg with standard