What is a Skid Steer Loader?
A skid steer, sometimes called a skid loader or wheel loader, is a compact, multipurpose piece of construction equipment often used for digging. It's maneuverable, lightweight and its arms can attach to different tools for various construction and landscaping jobs.
A skid loader, skid-steer loader (SSL), or skidsteer is any of a class of compact heavy equipment with lift arms that can attach to a wide variety of buckets and other labor-saving tools or attachments. The wheels typically have no separate steering mechanism and hold a fixed straight alignment on the body of the machine.
Wondering how the skid steer got its name? The wheels (or treads) are fixed in one direction. To turn, the driver applies more speed to one side of the machine, causing the wheels to 'skid' across the ground as the device rotates in the opposite direction. Turning is accomplished by differential steering, in which the left and right wheel pairs are operated at different speeds, and the machine turns by skidding or dragging its fixed-orientation wheels across the ground. This steering function is what gives the machine its name.
The skid steer loader will either have four wheels or two tracks. The front and back axles automatically synchronize their movements, but drivers can operate each separately from the wheels on the other side of the machine.
Skid-steer loaders are capable of zero-radius turning, by driving one set of wheels forward while simultaneously driving the opposite set of wheels in reverse. This "zero-turn" capability (the machine can turn around within its own length) makes them extremely maneuverable and valuable for applications that require a compact, powerful and agile loader or tool carrier in confined-space work areas.
History and Development
This remarkable maneuverability has its roots in a practical farming problem. In 1956, Minnesota turkey farmer Eddie Velo needed a way to clear manure from the second floor of his barn. Standard tractors were too heavy, so inventors Louis and Cyril Keller built a compact, three-wheeled loader that could turn in tight spaces. The Kellers built the loader to help a farmer mechanize the process of cleaning turkey manure from his barn. The light and compact machine, with its rear caster wheel, was able to turn around within its own length while performing the same tasks as a conventional front-end loader.
After testing it on Velo's farm, they began selling the machine—and demand took off. By 1958, the Kellers had partnered with Melroe Manufacturing to produce the first true Bobcat® skid-steer loader. The Melroe brothers, of Melroe Manufacturing Company in Gwinner, North Dakota, purchased the rights to the Keller loader in 1958 and hired the Kellers to continue refining their invention.
As a result of this partnership, the M-200 Melroe self-propelled loader was introduced at the end of 1958. It featured two independent front-drive wheels and a rear caster wheel, a 12.9 hp (9.6 kW) engine and a 750-pound (340 kg) lift capacity. Two years later they replaced the caster wheel with a rear axle and introduced the M-400, the first four-wheel, true skid-steer loader. The M-440 was powered by a 15.5 hp (11.6 kW) engine and had an 1,100-pound (500 kg) rated operating capacity.
Melroe adopted the well-known Bobcat trademark in 1962. By the late 1960s, competing heavy equipment manufacturers were selling machines of this form factor. Some professionals refer to a skid steer as a "Bobcat" or "Bobcat machine." Bobcat is one of the construction manufacturing brands that produce skid steers, like their competitors John Deere and Caterpillar. In the same way that people now say "Google" when they mean "to search," oftentimes people will say "Bobcat" when they mean "skid steer."
How Does a Skid Steer Loader Work?
Now that we understand the origins of this versatile machine, let's explore the engineering principles that make it so effective.
Differential Steering System
Unlike a tractor, wheel loader, or telehandler, skid loaders turn by skidding. The wheels stay straight, but the machine changes direction by powering each side independently through a hydrostatic transmission. This setup gives you tight, controlled turns, which is great if you're working in small spaces or maneuvering around obstacles.
Skid-steer loaders are typically four-wheeled or tracked vehicles with the front and back wheels on each side mechanically linked together to turn at the same speed, and where the left-side drive wheels can be driven independently of the right-side drive wheels. This is accomplished by having two separate and independent transmissions; one for the left side wheels and one for the right side wheels.
Earliest versions of skid steer loaders used forward and reverse clutch drives. Virtually all modern skid steers designed and built since the mid-1970s use two separate hydrostatic transmissions (one for the left side and one for the right side). The differential steering, zero-turn capabilities and lack of visibility often exacerbated by carrying loads with these machines means that their safe operation requires the operator have a good field of vision, good hand eye coordination, manual dexterity and the ability to remember and perform multiple actions at once.
Hydraulic System
A diesel engine creates the machine's initial power using fuel, converting chemical energy into mechanical energy, but that energy is then transformed into fluid energy, harnessed in a closed loop hydraulic system that starts with hydraulic pumps attached to the diesel.
While the diesel engine initiates the power cycle, the true 'hearts' of a skid steer are actually its hydraulic pumps—typically three or four of them. These hydraulic pumps (often high-tech load sensing pumps) work with a system of hoses, reservoirs, filters, regulators, cylinders, directional control valves, actuators, motors and all the necessary electronics to generate and precisely control the pressure, flow and temperature of the hydraulic oil. This circulatory system is used to direct the power for drive operations, boom lifting and attachment usage. These pumps power fluids—compressed oil—to move, spin, lift the boom, curl the bucket and run a zillion different attachments.
Drive System
For the skid steer loader, each side of the machine is powered by a hydraulic motor. Each of the two motors (one for each side) connects to a sprocket, and each sprocket is connected by two chains to each wheel. The sprockets and chains serve two purposes: They distribute the power from a single hydraulic motor to both wheels, and they provide a gear reduction to increase the torque at the wheels.
Each hydraulic motor has a sprocket on it which connects the front and back wheels through a pair of heavy-duty chains, forming a chain and sprocket system. The chains serve two unique purposes. First, they evenly distribute the power to both wheels while making sure that the wheels are being driven at the same speed. The chains and sprockets are usually in a sealed compartment and immersed in an oil bath. This protects them from the elements and keeps them optimally lubricated.
The chain system keeps the wheels on each side synchronized, e.g., the left side wheels are in sync with each other and the right side wheels are in sync with each other. The drive sprockets connect to the wheel hub through a relatively short shaft. The shaft, in turn, passes through some seals before it connects to the actual hub. The hub, of course, holds the wheel.
Weight Distribution and Operation
Skid steer loaders, both wheel and track models, operate most efficiently when they are imbalanced – either the front wheels or the back wheels are more heavily loaded. When equipped with an empty bucket, skid steer loaders are all heavier in the rear and the rear wheels pivot in place while the front wheels slide around. When a bucket is fully loaded, the weight distribution reverses and the front wheels become significantly heavier than the rear wheels. When making a zero-turn while loaded, the front wheels pivot and the rear wheels slide. Imbalanced operation reduces the amount of power required to turn the machine and minimizes tire wear.
Main Parts of a Skid Steer Loader
With a solid understanding of how the machine operates, let's examine the key components that make up a skid steer loader.
1. Engine
The engine is the lifeblood of the skid steer, providing the necessary power to drive the machine. It typically varies in power output from 25 to 90 horsepower, depending on the specific model. This crucial component dictates the machine's lifting capacity and operational speed, making it a key factor in the skid steer's overall performance.
The drive motor provides sufficient power and torque to propel the loader under different working conditions. Its design and performance directly affect the machine's operational efficiency, fuel consumption, and reliability. An efficient drive motor can provide strong power while maintaining low fuel consumption and emissions, reducing operating costs and environmental impact. Regular maintenance and upkeep are crucial for ensuring the long-term reliability and performance of the drive motor.
2. Hydraulic System
The hydraulic system is at the core of skid steer functionality. A skid steer loader's components work together to create a useful machine. The lift arm system uses two hydraulic cylinders to control lifting and lowering operations with one cylinder on each side. The main hydraulic pump takes mechanical energy from the engine and converts it to hydraulic power that feeds various components through hydraulic fluid.
Starting with the hydrostatic system, the transmission and drives system, pressures are pretty high, upward of 6,000 psi. These are heavy-duty components to get the speed and torque you want. When it comes to the hydraulic system, bucket, boom and aux, typically you're running between 3,000 and 5,000 psi. Most manufacturers run right around the 3,500-psi range, which allows the use of reasonably sized cylinders and boom geometry to get the breakouts needed, while still maintaining the speed required.
Hydraulic flow to the auxiliary circuit and the attachment will be determined in gpm (gallons per minute) and as standard- and high-flow configurations. High flow systems boast a considerably higher GPM range, typically falling between 30 to 45 GPM. This translates to more hydraulic horsepower, enabling the machine to handle demanding applications that require powerful movements or operations, such as lifting heavy loads or powering high-performance attachments like brush cutters and rock saws.
3. Lift Arms
The lift arm system is critical for the skid steer's lifting capabilities. Two hydraulic cylinders, one on each side of the lift arm, control the lifting and lowering of the boom. These cylinders must be sufficiently powerful to lift heavy loads and designed for frequent use. A loader operator must take care to prevent damage to lift cylinders during lifts and when the boom is subject to forces from the side.
The original skid-steer loader arms were designed using a hinge near the top of the loader frame towers at the rear of the machine. When the loader arms were raised the mechanism would pivot the loader arm up into the air in an arc that would swing up over the top of the operator. This is known as a radial lift loader. This design is simple to manufacture and lower cost.
Radial lift loaders start with the bucket close to the machine when the arms are fully down and start moving up and forward away from the machine as the arms are raised. This provides greater forward reach at mid-point in the lift for dumping at around four to five feet, but less stability at the middle of their lift arc. As the loader arms continue to raise past mid-height the bucket begins to move back closer to the machine and becomes more stable at full lift height, but also has far less forward reach at full height.
Machines with vertical lifting will raise their arm straight upwards. A radial-lift will give you more of a forward reach, which is better for lifting materials over certain heights or unloading flatbed trucks.
4. Wheels or Tracks
Skid steers are equipped with either wheels or tracks, each offering distinct advantages. Wheels provide swift movement and agile handling on solid surfaces, while tracks deliver superior traction and stability on soft or uneven terrain, ensuring the machine's grip and balance in challenging conditions.
Wheeled Skid Steers: Wheels generally require less maintenance and do not break as easily as tracks go through a lot of wear and tear, primarily due to the harsher environments they work in. It is also much easier to clean the undercarriage of a wheeled skid steer than a tracked one meaning that preventative care is easier to maintain. Wheeled skid steers are best for flat, hard surfaces. They tend to run faster and are more flexible.
Tracked Skid Steers (Compact Track Loaders): Also commonly called compact track loaders, tracked machines are better for certain terrain types. For example, snow, mud, and sand are easier to drive over with powerful track models. They were built to master uneven terrain and slopes since they disperse their weight across the tracks instead of isolating it to four wheels. Compact track loaders have broader weight distribution due to their two tracks, making them ideal for working in wet, snowy and muddy conditions.
A skid steer's weight is distributed among four main points — its tires. This can throw out its balance and sturdiness in wet and muddy terrain. It runs the risk of sinking into fresh mud and getting stuck. However, compact track loaders don't have the same level of maneuverability as a skid steer because they lack zero-radius turning capabilities.
5. Cab and Controls
The cab on a skid steer or compact track loader is the control center for the machine and, in today's newest machines, the cab can be loaded with advanced technology to maximize the abilities of the machine and its operators. A rigid chassis on which the cabin is mounted; it is from here that the movements are controlled, and it can be open or covered. Its structure is resistant and supports significant weight.
To operate a skid steer loader, the driver must position the seat high enough to have good visibility over what is being done with the bucket. Proper handling of the vehicle is necessary so that its operation is as optimal and safe as possible. To this end, it is necessary to identify the controls and levers in the cab. These may vary depending on the type of skid steer loader and the manufacturer's brand, but there are usually two levers located on the armrest of the machine, each with control buttons.
Many models have moved away from the traditional lever and pulley system to a modern joystick control. Some even come with electronic dashboards. Modern skid steer loaders are also equipped with electronic control systems, allowing precise control of various functions, thus enhancing operational precision and efficiency.
Since small loaders so often work in busy and compact areas, cabs are outfitted with features to protect the operator and ensure their safety as they use the machine. When controls are activated, the loader or lift arm attachments can move and crush individuals who are within the range of the machinery. To prevent injuries, operators should always fasten the seatbelt and lower the safety bar to stay securely in the cab.
6. Bucket and Attachments
The bucket located on the front of the machine with which loading is done. The conventional bucket of many skid loaders can be replaced with a variety of specialized buckets or attachments, many powered by the loader's hydraulic system. The list of attachments available is virtually endless.
The bucket can operate in two ways: Taking a single load of a mound of material, or making a frontal displacement flush with the ground to accumulate the material on the surface. The bucket is controlled by hydraulic cylinders. This is the hydraulic ram that powers the tilting action of the bucket.
The hallmark characteristic of this loader is the variety of skid steer attachments and accessories available, making it possible to perform a wide range of jobs using the same piece of equipment. Some examples include:
- Buckets and blades: Dura Graders, dozer blades (various sizes for moving and transporting material)
- Digging attachments: Backhoe, trencher, auger
- Breaking and demolition: Hydraulic breaker, ripper, wheel saw, pavement miller
- Material handling: Pallet forks, grapple, dumping hopper
- Landscaping: Stump grinder, tree spade, mower, angle broom, sweeper
- Agriculture: Bale spears, tillers, feed pusher
- Snow removal: Snow blower, snow blade, snow pusher
- Construction: Cement mixer, roller, wood chipper
Some models of skid steer now also have an automatic attachment changer mechanism. This allows a driver to change between a variety of terrain handling, shaping, and leveling tools without having to leave the machine, by using a hydraulic control mechanism to latch onto the attachments.
Skid Steers that are HIGH FLOW compatible will have 3 hydraulic quick coupler fittings (Usually mounted in line with the loader arms on a steel bracket). Standard hydraulic flow skid steers typically have 2 Hydraulic fittings. The bucket coupler is the mechanism that allows the skid steer to quickly and easily attach and detach different attachments.
7. Additional Components
Radiator: A radiator is a heat exchanger that transfers heat from a fluid to the air. In a skid steer or compact track loader, the radiator transfers heat from the engine coolant to the air, cooling the engine and preventing it from overheating.
Main Control Valve: The main control valve in a skid steer or compact track loader controls the direction of flow and pressure of the hydraulic system and each of the loader's hydraulically-powered parts.
Lighting: Lighting on a skid steer or compact loader serves two purposes: highlighting the work area and increasing the visibility of the machine to other machines and their operators. Loader operators often work in tight quarters and need to perform their work to exacting measurements. Under these constraints, proper lighting and good visibility can mean the difference between success and failure on the job.
Axle: The axle is a key component that connects the wheels and the drive system of the skid steer loader, supporting and transmitting power to the wheels to propel the machine. A high-strength axle design can withstand the heavy loads and varying motion stresses encountered during work while ensuring wheel stability and reliability.
Size Classifications
Understanding the different size classes helps you choose the right skid steer for your specific needs.
Skid steer loaders are categorized into three sizes: Small frame, medium frame and large frame. Each size has a specific rated operating capacity, or ROC.
Small Frame
A small frame produces under 50 horsepower and can lift a maximum of 1,750 pounds. Small frame models have an operational capacity up to 1,750 pounds and are ideal for tight spaces. A small frame skid steer can operate in tight spaces and drive through narrow paths. They're the most common, and can normally be found on landscaping projects. Small-frame skid steers work great for interior demolition and underground construction. Their compact size lets them move between buildings and squeeze through tight spaces. They have convenient front and rear tie-downs that make transportation simple.
Medium Frame
A medium frame produces 50-70 horsepower and can lift anywhere from 1,750 to 2,200 pounds. Medium-size loaders, as the name would suggest, offer a middle ground between compact and powerful. They're stronger than small-sized skid steers, but not quite as powerful as larger models. Medium-frame skid steers hit the sweet spot between power and maneuverability. These machines handle loads between 1,750 to 2,200 pounds. Their balanced design makes them perfect for construction tasks and material handling jobs of all types. Medium frame track loaders are often used on road work, since they offer standard construction power while still being small enough to drive over asphalt or concrete.
Large Frame
Large frames produce over 70 horsepower and can lift anything over 2,200 pounds. Large-frame skid steers deliver the most power for tough jobs. These powerful machines can lift over 2,200 pounds. The large loaders are the most suitable for extensive work within grading, drilling and extensive demolition work. While storing and maintaining them might be more difficult than some small models, they are large enough to move around sites without needing to be transported by a semi-truck.
Common Applications
With a comprehensive understanding of these components, we can now see how skid steers are deployed across various industries.
Skid steers are one of, if not the most common, pieces of heavy equipment. Seen on almost every job site, skid steer loaders are the workhorse of the construction industry. This is primarily because of their range of sizes, the versatility of attachments, and overall performance capabilities. They're everywhere—from highways and farms to construction sites and even backyards.
Construction
The versatility and usability of a skid steer makes them ideal for construction work. Moves dirt, gravel, and debris, or levels ground with a bucket or grader. Skid steers can use dozer blade attachments to clear and move material between points, but with concrete mixer, concrete crusher and roller attachments, their roadwork utility diversifies. Their compact design makes them perfect for interior demolition work. They easily fit between houses and pass through gates.
Landscaping
Digs holes, hauls mulch, or clears brush with attachments like augers or mowers. Many landscapers utilize skid steers for loading and hauling vegetation for planting around the site. They can also help with trench digging and stump grinding with the right attachments. Attachments like the tree spade, trench-digger, stump grinder and wood chipper make it an ideal tool for landscaping work. Small skid steers also do minimal damage to any modified terrain thanks to their light weight.
Agriculture
Handles feeding livestock, moving hay bales, or clearing manure with forks or buckets. Farms rely on a variety of heavy-duty equipment for crop growing and harvesting. A skid steer is a common accessory on the farm due to many of the functions noted. Brush hogs/cutters clear unwanted shrubbery with ease, auger attachments can make holes for fences or trees, with bale squeeze and bale spear attachments great for managing hay bales.
Snow Removal
Clears snow from driveways or parking lots using plows or brooms. Skid steers can help remove snow from roads and parking lots in fast order when outfitted with the right attachment. Snow blower, snow pusher, snow blade, and V-snow blade attachments are specifically purposed to remove obstructive snow from roads and areas.
Demolition
Breaks up concrete or removes small structures with hydraulic breakers. They're also ideal for gathering debris for removal. Skid steers can be outfitted with rippers, trenchers, tillers, and wheel saws that make excavation much more convenient.
Material Handling
Need to carry heavy equipment from one location to the next? Skid steers are ideal for loading and moving materials around a site. You can even use a pallet fork attachment to reduce the need for a forklift. While most people associate skid steers doing work outdoors, they also have a place in the industrial warehouse - particularly when it comes to material handling.
Operating Weight and Specifications
Beyond understanding applications, knowing the technical specifications helps in making informed equipment decisions.
These pieces of machinery have a load capacity from 800 pounds to over two tons. Even so, they're light and move around easily. Their operating weight (less than four tons) makes it safe to use inside buildings. Weights range from the smallest skid machine at approximately 2,806 kg (6,180 lb.) to the largest models weighing around 4,660 kg (10,264 lb.).
When you're looking at skid loaders, these are the specs that matter most:
Operating Capacity – How much weight the machine can lift without tipping over. Small loaders handle around 760 lbs, while the biggest models lift 3,400 lbs.
Horsepower (hp) – More hp means more powerful digging and lifting. Modern skid loaders run between 23.5 and 105 hp, with most ranging from 48.5 to 88 kW (65 to 118 hp).
Lift Height – Measures from the ground to the bucket hinge pin when the loader arms are fully raised. More lift height makes loading trucks or stacking materials easier. Height to bucket hinge pin on skid-steers spans from approximately 94.5 to 132 inches.
Speed – They move at a speed of approximately 10 km/h.
Safety Features and Operation
Understanding how to operate skid steers safely is just as important as knowing their capabilities.
They have multiple locking systems to prevent accidents, so security is one of its main features. All skid steer loaders have a locking system via rocker switches near the console, which have to be activated and deactivated to put the machine in motion. They allow for high visibility, which is an advantage for safely and efficiently performing any construction work.
Before allowing anyone, including adults, to operate a skid steer, they should be assessed on their ability to safely operate the machine and trained in its safe operation. Per OSHA, skid steer loader operation can only be done by competent persons. It is recommended that employers follow the training guidelines outlined in safety standards.
Safety is the top priority when operating any machinery. Skid steer loader operators need to receive professional training to understand the equipment's operational procedures and safety precautions. Before operation, operators should check that all functions are working correctly and ensure that all safety devices are operational.
Operators should ensure that any helpers or bystanders are clear of the machine before starting it. Organize work projects away from ground personnel and always be aware of people working around the machine. Always travel with the bucket or load low to the ground.
Maintenance Requirements
Proper maintenance extends equipment life and ensures optimal performance. Regular maintenance and servicing are crucial for ensuring the equipment's long-term stable operation. This includes checking hydraulic fluid levels, replacing worn parts, and cleaning the equipment. Manufacturers usually provide detailed maintenance manuals to guide users in performing daily upkeep.
Routine maintenance involves checking and servicing key components like the engine, hydraulic system, and tires or tracks:
Hydraulic System: Regularly check the fluid levels and inspect for leaks. If any leaks are detected, repair them immediately to avoid further damage.
Engine Maintenance: Clean the engine and air filters regularly, and ensure the engine oil is changed as recommended by the manufacturer.
Tires/Tracks: Inspect the tread wear on tires or tracks, and replace them when necessary. Properly inflated tires improve efficiency, while tracks should be checked for wear and tear.
They have low maintenance costs, as well as high durability. Wheels generally require less maintenance than tracks. If the job is going to be muddy and messy by nature, choosing a tracked skid steer will help keep efficiency and productivity up, though it is important to clean the undercarriage of a tracked machine, especially in the winter, as it can affect the performance.
Why Choose a Skid Steer Loader?
The ability to swap attachments quickly—what a skid steer does best—saves time and reduces the need for multiple machines. Its compact size makes it a popular machine in smaller and medium-sized work projects and locations. Since the medium-frame skid steer is lighter than traditional demolition equipment, you can equip it with tires or tracks and drive over asphalt or concrete without damaging the surface.
One of the things that makes this piece of equipment so useful in construction is its versatility. This comes largely from the different compact equipment attachments that can expand a skid steer's functionality. Skid steers are workhorses across multiple industries, thanks to their adaptable attachments.
Note: When operating a skid steer loader, always consult your manufacturer's manual for specific operating procedures, maintenance schedules, and safety guidelines. Proper training and certification are essential for safe operation.