Osgood
Western Thunderer
It looks like on these cranes the grab top block is permanently attached to the jib by chains, with the main hoist rope running to the lower transom.
So the crane is worked like this:
With bucket top block held by chains and keeping the hoist rope drum 'free' (i.e. no load), the open bucket is lowered onto the ash by lowering the jib rope (i.e. the jib lowers the bucket to the ash pile).
The main hoist rope is then pulled in which lifts the lower transom up, thereby closing the bucket.
At this point, either:
1) further hoisting of the main rope simply lifts the bucket up on those short chains until it hits the jib, and the jib gets pulled up by the bucket via the hoist rope, or
2) once the bucket is closed the operator pulls in both main hoist rope and jib rope at the same time, thereby raising the bucket but keeping the mount chains slack (once they go tight the bucket starts to open). The load must be taken by the hoist rope to keep bucket closed.
As the hoist rope is let out the jib and bucket fall until the jib rope goes tight, then the bucket falls on the chains, and once the chains are tight further lowering of the hoist rope lowers the transom and the bucket opens.
Or if the jib rope is tight with slack chains, lowering the hoist rope immediately lowers the transom and bucket opens.
Or raising the jib but not hoist rope will take the bucket load off the hoist rope, thereby opening the bucket.
A bit crude but simple!
So the crane is worked like this:
With bucket top block held by chains and keeping the hoist rope drum 'free' (i.e. no load), the open bucket is lowered onto the ash by lowering the jib rope (i.e. the jib lowers the bucket to the ash pile).
The main hoist rope is then pulled in which lifts the lower transom up, thereby closing the bucket.
At this point, either:
1) further hoisting of the main rope simply lifts the bucket up on those short chains until it hits the jib, and the jib gets pulled up by the bucket via the hoist rope, or
2) once the bucket is closed the operator pulls in both main hoist rope and jib rope at the same time, thereby raising the bucket but keeping the mount chains slack (once they go tight the bucket starts to open). The load must be taken by the hoist rope to keep bucket closed.
As the hoist rope is let out the jib and bucket fall until the jib rope goes tight, then the bucket falls on the chains, and once the chains are tight further lowering of the hoist rope lowers the transom and the bucket opens.
Or if the jib rope is tight with slack chains, lowering the hoist rope immediately lowers the transom and bucket opens.
Or raising the jib but not hoist rope will take the bucket load off the hoist rope, thereby opening the bucket.
A bit crude but simple!
Last edited:
I had a feeling it would something simple. I think there are a few variations on the brackets that hold the jib to the bucket via chains (hence my Mark II additons) but I've got a pretty good idea now how to finish it all. Inevitably there will be some compromises! 
