This one is an HO/OO version in resin from the modelmakers Modellbau Luft
Direct link to the crane HERE .
A video of a treadwheel crane being used for real at the Guédelon Castle construction site. This one is an advanced version that turns so the load can be moved from side to side and not just up and down. Fredericus -Rex has recently brought out a medieval crane similar to the one at Guédelon which can be seen HERE
A couple more bits of my construction....a second (or is it third?) prison wagon....