A walking excavator, often called a spider excavator or, in the German-speaking world, a Schreitbagger, is a hydraulic excavator that stands on articulated legs instead of a conventional track or wheel undercarriage. Each leg ends in a wheel, a pad or a claw, and the operator can raise, lower, extend and steer every leg on its own. Using the legs and the boom together, the machine can climb steep slopes, straddle obstacles, stand in a riverbed, keep its cab level on very uneven ground and work in places where no other excavator could stand safely.
The walking excavator is a niche machine, much less common than crawler or wheeled excavators, and it is more expensive to buy and more demanding to operate. It is used where terrain rules out standard equipment: mountain slopes, avalanche and torrent barriers, riverbanks, wetlands, forests, rail embankments and steep private gardens. In those conditions it can often replace a combination of cranes, scaffolding and manual labour.
Brief History of Walking Excavators
The modern walking excavator comes from the Alps. In the mid-1960s the Swiss engineer Ernst Menzi and Joseph Kaiser, a designer from Liechtenstein, were involved in developing a prototype excavator meant to work on mountain slopes, where farmers and builders had few mechanical options. From this origin two companies grew up only a few kilometres apart: Menzi Muck in Switzerland and Kaiser in Liechtenstein. For decades they defined the category, and the names “Menzi” and “Kaiser” are still used informally for walking excavators in some countries.
The early machines were simple, with mechanical and hydraulic controls and limited comfort. Over the following decades they gained more powerful engines, longer and telescopic arms, all-wheel drive on the legs, tiltable and rotating cabs, and eventually electronic control of the legs, which made walking movements much easier to learn. Other manufacturers, mostly in Europe, have entered the segment over time, and the machines are now also used in North America, Scandinavia and Oceania for forestry, environmental and utility work.
The large walking draglines used in surface mining, which move by “stepping” on shoes, are a different type of machine and are not covered in this entry.
How a Walking Excavator Works
A walking excavator combines a standard excavator upper structure with a chassis made of independent legs.
- Legs. Usually four legs, two at the front and two at the rear. Each leg can be raised, lowered, spread sideways or extended telescopically by hydraulic cylinders. The front legs often end in pads or claws, while the rear legs carry wheels.
- Drive. On many models the rear wheels, and sometimes all wheels, are driven by hydraulic motors, so the machine can travel short distances on its wheels like a small wheeled excavator.
- Walking. On very steep or broken ground the operator uses the boom and bucket as a fifth leg, pressing it into the ground to lift and pull the chassis forward while the legs are repositioned. This is the movement that gives the machine its “walking” name.
- Levelling. Because each leg can be set to a different height, the upper structure can be kept level on slopes, which keeps the machine stable and makes precise digging easier.
- Upper structure. The cab, engine, hydraulic pumps and slewing ring sit on top of the chassis. Many models allow the cab to tilt or the upper structure to rotate through 360 degrees.
- Front equipment. A boom and arm, often telescopic, carry a bucket, a tiltrotator or other hydraulic tools. The telescopic arm extends reach down a slope or across a watercourse.
Types of Walking Excavators
Compact Walking Excavators
The smallest machines, suited to gardens, vineyards, landscaping and work with tight access. Some can be transported on a trailer and driven through narrow gates.
Standard Walking Excavators
The core of the market, used by contractors for slope stabilisation, torrent and riverbank work, forestry roads, rock fencing and utility lines in mountain areas.
Heavy Walking Excavators
Larger machines with more digging force and reach for bigger civil and environmental projects, including river restoration and large protective structures.
Amphibious and Wetland Configurations
Some walking excavators can be fitted with pontoons, extended legs or special pads for work in shallow water, marshes and reed beds. They sit close to amphibious excavators in their use, though the design is different.
Rail and Remote-Controlled Versions
Versions equipped with rail wheels are used for track maintenance and embankment work, and remote-controlled machines allow the operator to stand away from unstable slopes or hazardous environments.
Size Classes
| Class | Typical operating weight | Typical use |
|---|---|---|
| Compact | about 5 to 9 t | Gardens, vineyards, landscaping, tight access |
| Standard | about 9 to 15 t | Slopes, riverbanks, forestry, utility work in the mountains |
| Heavy | about 15 t and more | Large civil and environmental projects |
Figures are indicative and vary by manufacturer.
Attachments
Walking excavators use most of the attachments found on conventional excavators: digging and ditch-cleaning buckets, tiltrotators, grabs, hydraulic breakers, augers and drilling units for anchors and micropiles, mulchers and felling heads for forestry, and lifting hooks for placing barriers and nets. The combination of a tiltrotator and a telescopic arm is common, because it allows the machine to reach a work area from a stable position without constantly walking.
Main Manufacturers
- Menzi Muck, one of the two historic Swiss and Liechtenstein makers.
- Kaiser, the Liechtenstein manufacturer that shaped the category together with Menzi Muck.
- Euromach, an Italian manufacturer of walking and multipurpose excavators.
Other manufacturers and specialist converters exist, often supplying regional markets, but the segment remains small and concentrated.
Main Uses of Walking Excavators
- Slope stabilisation, rockfall protection and avalanche barriers.
- Torrent control, riverbank protection and river restoration.
- Forestry work, including road building, thinning and stump removal on steep ground.
- Utility lines, pipelines and cable routes in mountainous areas.
- Wetland, reed bed and pond work where ground pressure must stay low.
- Landscaping, vineyards and gardens with steep or restricted access.
- Railway embankment and track maintenance in rail versions.
Planning a Walking Excavator Job
- Survey the terrain. Slope angle, soil type, rock and water depth determine whether a walking excavator is needed and which configuration fits.
- Plan access and transport. Machines are usually delivered on a low loader or trailer and then walk to the work area. Check the route from the unloading point, including gates, bridges and tree cover.
- Choose the right feet. Wheels, pads and claws behave differently. Claws grip rock and steep slopes, while wide pads and pontoons reduce ground pressure in soft soil.
- Consider operator experience. Walking movements take training and practice. Many contractors keep the same operator on the same machine, and some rental companies supply the machine only with an operator.
- Match attachments to the work. A tiltrotator, a drilling unit or a mulcher can remove the need for a second machine on a difficult site.
- Allow for the environment. In rivers and protected areas, use biodegradable hydraulic oil where required and plan spill protection.
Safety
The main risk with a walking excavator is loss of stability. The machine is designed to work on slopes, but every configuration has limits, and those limits change with leg position, arm extension, load and ground conditions. Operators must follow the manufacturer’s stability and load charts, keep the upper structure as level as possible, and avoid sudden swings with heavy loads on the downhill side. Seat belts, rollover and falling-object protection and a well-defined exclusion zone are essential. On slopes, loose rocks and debris can roll towards people below the machine, and working in water adds risks from currents and hidden obstacles. Remote control and camera systems are increasingly used to keep the operator away from the most dangerous positions.
Trends and Technology
Walking excavators are becoming easier to operate thanks to electronic control of the legs, programmable positions and levelling functions that reduce the number of separate movements the operator has to coordinate. Remote-controlled and teleoperated models allow work on very unstable ground without a person in the cab. Machine control and GNSS guidance, already common on standard excavators, are appearing on walking machines for slope profiling and river engineering. Manufacturers are also working on engines that meet the latest emission standards and on electric or hybrid drives for sensitive environments.
Key Terms
- Schreitbagger: the German name for a walking excavator.
- Spider excavator: a common informal name that refers to the leg layout.
- Telescopic arm: an arm that extends hydraulically to increase reach.
- Claws: pointed feet at the end of the legs that grip rock and steep ground.
- Levelling: adjusting the legs so that the upper structure stays horizontal on a slope.
- Tiltrotator: a tool between arm and attachment that allows it to rotate and tilt.
Frequently Asked Questions
How steep a slope can a walking excavator work on? Much steeper than a conventional excavator, but there is no single figure. The limit depends on the machine, its configuration, the ground and the load, and is set by the manufacturer’s stability data.
Can a walking excavator drive on the road? Some models can travel short distances on their wheels and may be approved for road use in certain countries. Most are moved between jobs on a trailer or low loader.
Why are walking excavators so expensive? They are built in small numbers, the leg chassis is complex, and the machines are designed for extreme conditions. Their price is usually justified only where no standard machine can do the job.
Is it difficult to learn to operate a walking excavator? Basic digging is similar to other excavators, but walking and positioning on steep ground require specific training and experience.
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