November 2016 No. 71 Vol. 11
Features
Five Factors To Consider Before Selecting A Crawler Or Wheel Excavator
At first glance, it may seem like the only noticeable difference between crawler and wheel excavators is their undercarriage. But if you look more closely, you will notice each machine has its own features and benefits that need to be considered before purchasing.
Ground conditions, for example, play a large part in dictating whether a crawler or wheel excavator will be used. However, there are other factors such as stability, mobility and attachment versatility, as well as maintenance considerations, to contemplate before purchasing or renting a crawler or wheel excavator.
Assess ground conditions
Before selecting a crawler or wheel excavator, it is important to first consider the scope of work. Will the machine primarily be working in dirt excavating, grading and site development applications, or on finished concrete or asphalt in highway/street development applications?
Crawler excavators perform exceptionally well when working in applications such as excavating, grading and site development. For these applications, they can be fitted with attachments, including a grapple for land clearing, a bucket to dig foundation footings or trenches for underground utilities, a clamp for site prep projects, or a plate compactor to finish trenches. Some crawler excavators are designed with reduced-tail-swing configurations to work in limited-space commercial or residential areas, or at new road and bridge construction projects.
Wheel excavators are manufactured with rubber tires, making them a popular choice when working on improved surfaces such as finished concrete or asphalt, where the excavators can drive on the surface with minimal ground disturbance. Among the applications where wheel excavators work well are ditch-cleaning projects and underground utility installations.
Determine stability needs
Machine stability is important on any job site, especially in heavy-duty digging and lifting applications. According to Shane Reardon, Doosan crawler excavator product specialist, a crawler excavator “can maintain great contact with the ground due to its tracked undercarriage, creating a stable machine.”
Wheel excavators, on the other hand, depend on their tires, a dozer blade and outriggers for their stability in digging and lifting applications.
“Wheel excavators can be equipped with a front dozer blade with outriggers in the rear or outriggers on either end of the machine,” said Brian Bereika, Doosan wheel excavator product specialist. “The dozer blade can be used to replace a secondary machine when leveling or backfilling material, or stabilizing the machine during digging applications. In addition, the blade’s large dozer bottom and parallel design minimize ground pressure.”
Outriggers can be individually controlled to level the machine on slopes, Bereika adds.
As far as digging performance goes, both crawler and wheel excavators perform similarly. However, when the outriggers are down, Bereika says wheel excavators can have just as much stability as crawler models. “This allows wheel excavator operators to not lose as much lifting capacity when working over the side as with a crawler excavator,” he said.
Randy Miller, vice president of Iowa Erosion Control, oversees the company’s use of wheel excavators with hydraulic breakers and buckets. The company specializes in concrete and asphalt repairs. “We configure our Doosan wheel excavators with four outriggers for additional stability when breaking up or removing concrete,” Miller explained.
Anticipate transportation costs
Moving an excavator from job site to job site may be the norm for many contractors, depending on their type of application. If you anticipate that your excavator will require frequent transport, you will need to determine whether a trailer should be upsized or downsized to match the machine, or if there are more expensive travel permits required for heavier crawler excavators. It is also important to determine whether you have the proper hauling truck in your fleet.
“If you’re moving a crawler excavator around to various construction sites, it will need to be matched to an appropriate-size trailer and be permitted to meet the area’s hauling regulations, which vary widely by state,” Reardon said. “However, if you are working primarily in mining or quarry applications, the excavator will likely be delivered to the worksite and will live its entire working life in one location.”
You may decide to select a wheel excavator, instead of a crawler, if you are frequently transporting an excavator in areas that can be accessed by road. “Wheel excavators could lower your transportation costs and provide more flexibility around a paved jobsite,” Bereika said. “These machines are designed to provide an alternative when you need to travel quickly between tasks. Because the excavators are equipped with wheels, there is less need to trailer and move it when traveling short distances.”
The travel speed can be adjusted by selecting between three transmission speeds for increased productivity on a variety of job sites. For instance, operators strictly transporting the wheel excavator can select the high travel speed, which can reach up to 23 mph. However, if your operators are working on rough terrain or cleaning out ditches, they may choose to use the creep mode, which has a maximum speed of 2.5 mph.
In some cases, your operators may be working on job sites where space is limited and will need to maneuver around several other machines. “Wheel excavators are compact enough that they can efficiently work in one lane of traffic without closing down an entire section of highway or damaging existing infrastructure,” Bereika added. “In addition, some wheel excavators have a two-piece variable angle boom that bends in the middle, giving your operators improved visibility to both sides of the machine and additional flexibility when digging.”
Miller echoes Bereika’s comments about working on highways with wheel excavators.
“Wheel excavators are critical in our line of work, especially since we are constantly working on finished concrete and asphalt,” Miller said. “These wheel machines give needed flexibility and power to easily complete maintenance and repair projects.
Consider attachment versatility
One of the greatest advantages of excavators is the ability to pair them with the right set of attachments to diversify the services that you can offer and be more self-contained on the job site. Investing in a quality attachment connection system – such as a quick coupler – makes it convenient to change attachments. You can easily swap a ditching bucket for a grading-style bucket for grading applications, or change buckets to match trench width requirements to avoid over-digging or under-digging.
Other common attachments for crawler and wheel excavators include a hydraulic breaker for demolishing existing structures and concrete or asphalt; a grapple for land clearing; a trenching bucket to dig foundation footings or excavate for underground utilities; or a plate compactor to finish trenches. If daily projects require the consistent use of two-way auxiliary hydraulic flow attachments like a hydraulic clamp, otherwise known as a thumb, it is important to make sure your machine can be fitted with the proper hydraulics to meet your needs.
If selected appropriately, the right attachment can help diversify your service offerings. In the initial stages of evaluating the attachments that can meet your project needs and help you expand your services, you should focus on tools that will provide the best return for the shortest time frame at the least possible cost.
Inspect components
A crawler excavator’s undercarriage consists of many moving components and wear items that need to be maintained for the machine to function properly. According to Reardon, it is important to routinely complete a full undercarriage inspection for excessive or uneven wear, as well as to look for damaged or missing components.
“If the machine is being used in harsh applications or other challenging conditions, the undercarriage may need to be inspected more frequently,” Reardon added.
The following crawler excavator components should be inspected on a routine basis:
- Drive motor
- Drive sprocket
- Idler
- Rollers
- Track guards, if equipped
- Track bolts
- Track links
- Track shoe
- Pins and bushings
- Track tension
In addition, check the tracks to see if any components look out of place. If so, this could indicate a loose track pad or possibly a broken track pin. Rollers, idlers and drives should also be inspected for oil leakage. Oil leaks could indicate a failed seal, which could lead to a major failure in the rollers, idler or drive motor.
There are minimal wear items in a wheel excavator undercarriage to promote uptime protection for the owner and operator. According to Bereika, wheel excavator operators should follow preventive maintenance schedules, including visually inspecting tire pressure, wear and damage on a regular basis. These are detailed in the owner’s Operation & Maintenance Manual.
“A visual inspection will show if the tire has tread punctures or sidewall damage because of road hazards,” Bereika said. “Also, look for rocks wedged in between dual tires, which can cause tire failure. Steel spacer rings are sometimes added to prevent rocks from entering in between tires, but it is still important to visually check the tires before use. Following preventive maintenance schedules can save you significant money by reducing downtime, which then improves productivity and profitability.”
Ground conditions are an important factor in choosing a crawler or wheel excavator. However, it is also necessary to consider the need for stability, mobility or attachment versatility, as well as maintenance considerations, before selecting a crawler or wheel excavator. With the many models available today, you can tailor a machine to best suit your needs, and fit it with a variety of attachments to increase uptime protection and, in turn, increase your productivity.
FOR MORE INFO:
Doosan Equipment, (877) 613-7970, www.DoosanEquipment.com
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