Excavator quick couplers come in many variations with different locking mechanism designs and features. They range from the most basic mechanical designs to sophisticated multi pin-grabber models that automate the attachment process and allow quick changes on the fly.
“When you can change attachments on the fly, your excavator can get much more work done on the jobsite,” Cameron Noble, Norco Attachments, points out. It converts your excavator into a tool carrier. “With a quick coupler, you can grab the right tool and be more efficient in your operation.”
However, it’s important to understand how a quick coupler impacts overall machine performance. It can change the intended geometry of the excavator attachment, especially if the center-to-center pin dimension is significantly different than that of the OEM design.
Tip radius and breakout force
In almost every case, a quick coupler adds length to the stick. “It will move your bucket or attachment out farther,” says Ron Peters, product manager, CEAttachments. This will impact the tip radius of the bucket. “Depending upon the size of the machine, it will move it out anywhere from 3 to 6 in.”
Any time you lengthen tip radius, you lose breakout force. The trade-off is you gain flexibility. “You have to make a sacrifice when you install a quick coupler,” Noble admits. “It is a sacrifice for the efficiency of being able to change attachments. The reduced breakout force or increased tip radius is minimal compared to the big picture of what you can accomplish.”
According to Jamie Adams, JRB sales and product manager, Paladin Construction Group, “Increasing the stick length and tip radius of a given bucket will generally reduce breakout force by approximately 3% to 5%. To address this, some excavator end users and/or distributors have intentionally configured excavators with shorter sticks when installing couplers to limit the loss in breakout force.”
A coupler’s design can help to minimize losses, as well. “You have vertical and horizontal offsets,” says Noble. “A lot of the geometry we put in with the horizontal offset helps to reverse the effect of the vertical offset. So that helps you gain back that breakout force.”
Bucket design is also a factor. “Bucket selection will have an impact on the assembled tip radius,” says Adams. This tip radius change can be minimized when using a dedicated coupler and bucket design.
The load-sensing hydraulic systems of the new excavators can further compensate for any reduction in breakout force. “You really couldn’t tell from the seat unless you absolutely had the machine maxxed out,” says Noble. “Then, there probably would be a noticeable difference vs. the bucket being pinned to the stick.”
Most contractors tend to accept a loss in breakout force due to the advantages quick couplers provide. “They do not measure productivity as mere payload and cycle time, but more in terms of maximizing equipment utilization and the ability to do more with less equipment,” says Adams.
“Many times, contractors measure machine and coupler value in terms of lower costs for units of work done,” he continues. “For example, if the contractor is laying pipe, his concern is how many total feet of pipe he laid that day because he did multiple jobs with one machine, instead of how much dirt did he pick up with one bucket.”
Some couplers are better suited for digging applications. “For digging applications, a machine’s digging characteristics are equally influenced by configuration, material conditions/types and operator techniques,” Adams explains. “Couplers that feature minimal offset tend to be productive in high digging applications. For heavy material, a closer tip radius will dig better.”
In general, it’s best to keep the stick length as close to the OEM design as possible. “We have engineered our specific design to be the lowest possible profile to reduce that tip radius,” says Noble. “Anytime you can reduce the tip radius, it is a good idea to keep it as low as possible.”