I was looking around, and only saw one old JCB excavator with a weird sliding boom that stuck out the back quite a ways. This idea is interesting since a VA boom excavator could get away with a piece like this and change the dynamic of the machine to be even more versatile. I feel it would be even easier to grade with as you can cover more area, and you could reach out further and maintain your dipper strength. The attatchment companies sell telescoping dipper arms and call them "booms". I'm not sure where that confusion comes from..... Anyways. Thoughts?
Good day These were a feature of a number of machines as I recall the JCB had an hydraulic locking device others used a variation of pins the fasten to two parts. Most machines ended up with the boom in one position and many were welded to form one piece, the concept created a heavier component that was more subject to cracks and ware. May be there are applications that could benefit but as a general idea there appears to be little demand. Kind regards Uffex