Having gone through the exercise of looking at the pros and cons of purchasing a new excavator – it never ceases to amaze us how often that purchase decision can be compromised by a rough and ready decision on the attachments that go on that expensive new excavator.

All too often, the decision centres on a delivery date, preferred supplier arrangements and price. It is clear that very little consideration is given to the varying impacts on “ break out force” that different brands of attachment can have on the performance of the excavator.

We know this because we are hardly ever queried on this aspect of Calibre equipment. Yet, it is in this whole area of break out force efficiency that we concentrate much of our design and energy - because of the huge impact this aspect has on machine life, efficiency of operations, ease of use, fuel and maintenance costs and the speed in which the job gets done.

In simple terms, break out force is a measure (measured in kN- kilo newtons) of the structural stress on the excavator. More specifically, it is a measure of the amount of force that the working attachment can exert against the material you are trying to work with. It is affected by the size of the working attachment, the cylinder size, the hydraulic pressure applied, the geometry of the linkage that tilts the attachment and the overall length/ height of the attachment from the boom.

A machine with higher breakout force will perform generally better in a harder digging situation. However, too much breakout force will damage the machine - for instance, excessive increase in breakout force on a small excavator might blow hydraulic hoses, bend rams and break buckets /arm/boom to name a few.

In developing Calibre attachment designs for couplers, tilting devices, buckets and other working attachments - our models and simulations provide us with a keen insight on the magnitude of forces at play and stresses that are set up in the structural designs.

While various brands of attachments standing side by side might not appear to differ that much – when in operation there can be a considerable variance in performance.

This is particularly so where tilting devices are involved. When tilting devices are used, OEM rated break out specifications are compromised. A combination of “ bucket force “ and “ arm force” determines the optimum digging performance. In one recent test – where the OEM standard brochure spec rated “ bucket force “ at 143kn  - it dropped to 109kn with a third party ram tilt and the OEM Bucket combination attached. It got worse with a third party bucket – it went down to 95kn – a 34% decrease in bucket force. Using the Calibre Sure-Grip, Ram-Tilt and Wide Bucket combination, the bucket force was at 130kn – a 9% decrease.  While the “arm force” calculations has less impact, the tests reflected a 29% decrease with the third party bucket as opposed to 7% decrease with the Calibre combination and 25% decrease with the OEM bucket.

At the end of the day,  buying an excavator requires thorough research and demonstration - including choosing the attachments and attachment combinations. Buyers shouldn’t make any assumptions about brands until they have gotten hard facts on the attachment performance and preferably have some use time with them, so they can fully weigh their options before investing.

Experienced operators are quick to notice the difference in performance when working with the different combinations.  That is why Calibre put in place and promotes their Calibre Demo Program.


Graham. L Smolenski.

Calibre Contracting Equipment - Managing Director

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