Some 600 graves have been dug in the Luveve and West Park Cemeteries, in Bulawayo, Zimbabwe, using 428E Caterpillar Tractor Loader Backhoes (TLBs) fitted with Vesconite self-lubricating wear-resistant polymer bushings on the boom pivot pin.
This is according to Replants Africa’s Doug Bawden, who rents earthmoving and capital equipment to various companies, including to the Bulawayo City Council. The 428Es are good for grave digging as they don’t require a truck to transport them between sites. They have a variable displacement hydraulic pump that makes the machine more fuel efficient, and quicker when digging compared to a lot of other TLBs that use a gear type pump. However, grave digging is not easy and the equipment can take a beating depending on the soil type.
Bawden explains that, in sandy-clay soil, there is an approximately 400-500mm-thick crust, which can be difficult to get through. This can result in the entire back of the machine lifting off the ground when trying to penetrate this layer of baked dry ground.
“In this instance the Vesconite bushes are taking the full force of lifting the machine off the ground,” says Bawden.
Where mild-steel-backed bronze or brass bushings had been used on the boom pivot pin, located where the boom connects onto the machine through the swing frame, “they ooze out like grease”, he notes.
“By some unexplainable miracle, the Vesconite does not,” adds Bawden.
“I am still trying to understand how a plastic can take a load that large and not displace when steel does,” he says.
Bawden machined the bushings that have been fitted to the two TLBs that are used for grave digging.
The polymer bushings measured approximately 65mm (internal diameter) x 75mm (external diameter) x 260mm (length).