It has been awhile since I have looked at bucket trucks. On most makes it was a big No, NO, to lift objects with the upper boom, some makes it was OK to use the lower boom. Some of the newer models have a small material handling boom mounted on the upper boom, I have no idea how much they can handle.
Personally, I would not lift anything with the upper boom of a knuckle other than the weight of a man and the tools needed to do the task. Many tree guys here rig limbs and wood to the upper booms of their rigs, not safe IMO, puts to much strain on the upper boom section and the knuckle joint.
One outfit we have around here broke the upper boom in half doing this stunt, the operator was hurt bad but was able to recover.
Lifting with the lower boom doesn't give you much options to move and position a load, your limited to only lift up and the radius of the boom for swinging the load to position it on another truck or trailor. I would find a different way too load logs if you have to do it alot, sounds like you were in kind of a jam with the concrete in the log thing.
This is the reason why I chose an Elliott boom over the knuckle type boom, just so we could lift big heavy wood to load onto a smaller one ton dump truck. Elliott booms are basically light cranes with a self leveling cage on the end, most units will have the heel winches, cable at the back of the boom and a sheave under the the basket. A special lift plate with a ring is also welded to the bottom of the extension boom. The crane feature is nice for getting stuff out of back yards, or removing storm damaged trees from roofs of houses or trees with tight LZ's.
Larry
