Oxfordshire Woodland Group

The Weald & Downland Open Air Museum, Singleton, West Sussex erected and refurbished a timber derrick crane in the museum's wood yard in 2006.

All of the timber parts were renewed using relatively young halved Douglas Fir which though strong does not have the same durability as European Larch. Douglas Fir has knot whorls that potentially can cause localised weakness whereas larch arranges its branches in a helix pattern thereby reducing the possibility of localised weakness.

By 2015 following a detailed inspection of the crane it was found that the foot of one of the crane jib posts had rotted out within its metal cannister and so the crane was quickly dismantled to prevent any collapse of same.

There is an interesting contrast between the two post bottoms in as much that one of these appears still to be in good condition. Given the rust patterns that exists on one of the cannisters it might be the case that the crane was not completely level resulting in rainwater running across the jib post bottoms and in one case then running betwen the post bottom and cannister and in the other to the open side of the cannister.

Ken Hume