Terex Franna recently announced it has designed, engineered and manufactured a new 25-tonne capacity spreader bar. Matthew Edwards is a design engineer at Terex Australia and led the development. He provides the background to the launch of the new product.
The development started around the end of 2020 when a customer asked for clarification around the setup requirements of Franna’s existing 15-tonne spreader bar that has been offered for many years.
“I was looking into the enquiry when I noticed in the formulas that form part of the design calculations, it looked like we could make a much more efficient design. We realised there was an opportunity to improve on the design of the existing spreader bar and some quick calculations said it might be possible, so we went ahead and started the detailed design process for a larger capacity spreader bar,” said Edwards.
A critical parameter for the design was to keep the spreader the same size so it would fit onto the existing Franna models.
“The starting point was the existing Franna spreader bar mounts and then optimise the design to make a higher capacity bar that could still use these mounts. Then we just went back and said: ‘How efficient can we make that size spreader bar.’ Through a range of design improvements and calculations, it turned out we could take the existing approximate size and increase the capacity to 25 tonnes through clever engineering principles.
“The engineered part of the design comes from the fact that we’ve shifted all of the load onto the neutral axis of the bar or the centerline of the bar. The 15 tonne bar that we’ve offered for a long time has two lifting points, one above and one below the neutral axis which introduce bending into the spreader bar itself. For the 25 tonne bar we have shifted the connection point directly onto the neutral axis, i.e. straight onto the centerline of the bar, which takes out the introduced bending, makeing it purely a compressive load, which significantly increases the capacity.
“The lack of introduced bending allows riggers and lift planners a greater variety of rigging options. This 25 tonne bar is capable of multiple sling angles to work with, each with a unique working load limit based on the configuration of the rigging setup. This variety of sling angles allows lifting to be completed within external conditions, such as limited head height, without compromising on the lifts safety.”
The new bar fits in the same mounts as the 15t bar it’s approximately the same length, and it is only 10kg heavier than the existing Franna 15t bar. The initial feedback Franna received when it was presented to customers has been very positive.
“They were concerned about manual handling, and the weight of a larger capacity spreader bar. But it’s still easy enough to rig with one person. It’s very similar to how you’d use the standard 15t bar, but obviously you are getting a much larger capacity,” said Edwards.
The target market for the new bar is the MAC25 models up to the AT40 models. When the AT40 went to market, customers were asking for a larger capacity bar.
The new spreader bar is going to be offered as an option for existing customers and new customers on the MAC25 and AT40 models. If existing customers have a crane already in the field, they can order it through Terex’s spare parts department, or if a customer is ordering a new crane, they can order it as an option.
“To our knowledge, this is the first time there’s been a ‘small-scale’ pick and carry spreader bar, in the market with a 25t capacity range. Plus is it is designed by Franna for Frannas. It is a completely Australian designed, engineered, and manufactured product, made with Australian steel,” said Edwards.
He goes on to explain the testing process of the spreader bar.
“We manufactured a prototype which we designed and tested to AS4991 to learn as much as we could. We found a few small things in the design that we could improve on and so we went back and tweaked a few things. We then built a second prototype, which exceeded the requirements, and when we destructively tested it, let’s just say it damaged the rigging gear before it damaged the bar,” said Edwards.