A leading manufacturer of materials-handling machines has been using TWI to check its latest designs. TWI has offered its Industrial Members the facility of on-site strain measurement for over 30 years. Member R-B (Lincoln) plc has been one of the latest to use this service.
R-B is a well-known and long-established manufacturer of heavy earth-moving machinery and among its products is a range of long-reach excavators. Model VC30, the subject of the study reported here, is the largest in the range with a maximum reach of 30m. Even in this age of powerful computer aided design, R-B is well aware of the difficulty in predicting real in-service loads and stresses seen by its products.
Fifty-eight strain gauges were bonded to the machine at critical or highly-stressed locations at R-B's workshops in Lincoln. The machine was then transported to a local quarry where it was put through its paces digging in sand, gravel and clay. Static and dynamic strain data were recorded and back at TWI, areas of high and low stress were quickly identified, together with the machine operations that produced the stresses.
Furthermore, TWI performed a comprehensive fatigue analysis. Fatigue is one of the worst enemies of heavy earth-moving machinery and products like the VC30 usually have an arduous life, so the company places special emphasis on pre-production testing to iron out any potential problems. Experimental analysis minimises the risk of fatigue failure by allowing service fatigue data to be collected from a real machine - generally much more reliable than theoretically-produced data. Any areas identified as high risk can then be redesigned before production begins.
As well as providing a strain analysis service, TWI is always on call to help and advise in related areas such as general design, production methods and, of course, welding.
Similar exercises have been carried out for other TWI Member companies on numerous items of earth-moving and mechanical handling plant. For example loading shovels for Matbro and telescopic boom materials handlers for Sanderson (Forklifts) Ltd.
