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Posted: 11/11/2015

Interpreting the Specs to Find the Right Compact Excavator

A Bobcat E35 Compact Excavator at work.

When it comes to compact excavators, you’ll find that the majority of key specifications relate to the machine’s size, power or performance. Depending on the manufacturer, you’ll find a range of sizes, engine horsepower ratings, dig depths, dump heights and arm and bucket breakout forces. Here, we’ll break down a spec sheet to help you find the best compact excavator to fit your needs.

Size

In order to get the most out of your compact excavator, you have to make sure it can access your jobsites and then have the capability to do the work once it's there.

First, you’ll want to look at the dimensions of the compact excavator, meaning its width, height and weight. The size of machine you need should be determined by the application, environment and tasks you anticipate.

But height, width and weight are only part of the equation. Tail swing configuration is another feature to assess before committing to a machine. Zero tail swing and minimal tail swing allow more unrestricted rotation when working close to structures or against a wall. If you anticipate routine work where you or your operators must pass through narrow property lines or gates, a conventional tail swing may be a better fit.

Bobcat also offers a retractable undercarriage in select models when you need a machine that won’t sacrifice over-the-side lift capacity for accessibility through tight entryways like fence gates.

The weight of your machine is also important when it comes to transporting to and from jobsites. Double-check the weight limits of any vehicle you plan to use, and think about how you plan to haul your excavator before selecting a machine size.

Dig depth

This specification is defined by the maximum depth that the excavator is able to dig on flat, level ground. It is important to realize that an excavator is only capable of reaching its maximum dig depth for a small portion of the machine’s workgroup path. Therefore, you may want to select a machine that has 20 percent more dig depth than your routine requirements. By doing this, you will significantly minimize machine repositioning and enhance productivity.

Reach

An excavator’s reach is measured from its center rotational axis to the tip of the standard bucket tooth at ground level. This is an important specification, especially if you’ll be digging trenches, because greater reach means less repositioning and more productivity. If you want more reach and dig depth, you might want to consider excavator models with long-arm and extendable-arm options.

Dump height

The clearance that your compact excavator will need to dump the material from its bucket is called dump height. It’s an important selection, especially if your excavator will be frequently used for loading trucks. Dig depth, reach and dump height are all affected by the excavator’s arm options — standard arm, long arm or extendible arm.

Standard arm configurations come with every excavator model, giving you maximum breakout force and lifting ability with greater digging performance. However, if you need greater reach and dig depth, equip your excavator with a long-arm option. Extra reach, combined with higher dump height allows you to do more work without repositioning the machine and helps load trucks easier. The long-arm option includes additional counterweight to enhance your excavator’s lifting capabilities.

If you need even more reach, some manufacturers offer a clamp-ready extendable arm option for select compact excavators. It offers the best of both worlds: power and lifting performance, combined with the ability to extend the machine's dig depth and reach when you need it.

Engine horsepower

The reason you wouldn’t purchase a truck with the smallest-horsepower engine is the same reason you should demand more horsepower in a compact excavator. By having more engine horsepower, your excavator is able to generate more hydraulic horsepower when it counts — under tough digging conditions. When looking at horsepower specs, make sure you compare apples to apples, as some manufacturers publish net horsepower, while others publish gross horsepower. Also consider the availability of a turbocharged engine if working at higher altitudes, as they sustain usable horsepower better than a naturally aspirated engine.

Arm and bucket breakout forces

Two of the more commonly published and compared compact excavator specifications that you may be familiar with are arm breakout force and bucket breakout force.

Arm breakout force is the excavator’s ability to produce a “pulling force” using the arm hydraulic circuit. You might also have heard this referred to as arm, dipper and crowd force.

Bucket breakout force is the excavator’s ability to produce a “prying force” using the bucket hydraulic circuit.

It’s also important to note that published arm and bucket forces are theoretical (i.e., they are calculated by each individual manufacturer).

Cycle times and multi-functioning hydraulics

So what are cycle times? It’s the amount of time, measured in seconds, that a particular function takes to be cycled (i.e., boom up).

Remember, faster cycle times mean you’ll be getting the most productivity out of your compact excavator — whether you’re digging, trenching, grading or grappling. Some excavators provide multifunctioning hydraulics that enable you to use up to four functions at the same time (e.g., curl bucket, raise boom, extend arm and slew). You would typically use all of these functions when digging a hole or loading a truck.

As mentioned above, if your excavator has more engine horsepower, it’s going to provide more flow at higher pressures — which translates into faster cycle times under load.

Auxiliary hydraulics

Auxiliary hydraulics is a dedicated source of hydraulic oil intended to provide oil flow for specific attachments. An excavator’s auxiliary hydraulic flow rates and pressures are a key determinant of its attachment capacity and capability.

Rated lift capacity

Because excavators are frequently used for lifting objects on jobsites, you need to know the working limitations of the machine. The rated lift capacity often dictates what attachments are approved for the machine. It is important that an excavator’s rated lift capacity be adequate to handle the attachments you intend to use.

All Bobcat excavators are equipped with a rated lift capacity decal, illustrating three general lifting positions:
●    Boom over the blade, with the blade down
●    Boom over the blade, with the blade up
●    Boom over the side, with the blade up

In addition to these lifting positions, you should also be aware of the anticipated lift point radius and lift point height. The lift point radius is measured horizontally from the excavator’s center swivel point to the bucket pivot pin. The lift point height is measured vertically from ground level to the excavator’s bucket pivot pin.

Now that you’re armed with the knowledge to interpret a spec sheet, you’ll still want to do one very important thing before making the decision to buy — demo your top choices. The best way to choose from a long list of compact excavator options is to get in the operator’s seat. Operating a machine in common applications like loading trucks or trenching can help you get a feel for how it performs. This can help you make the final call on what machine is right for you.

Get started and browse our full line of compact excavators or contact your Bobcat dealer to request a demo.

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