For Manchester Day 2015, it was proposed to build a large Meccano model in Albert Square. The first suggestion was a Tower Crane (the main sponsors being a Civil Engineering concern) but in the event, Chris. Shute's Rotating Aeroplane model was chosen. The tower was to be about 10 feet tall and the boom radius about 6 feet. Although a Hammerhead crane can be balanced, this is difficult if the tower is slender. A bearing which would not pull apart was needed. This is my trial design. I used a similar bearing, using Märklin ball bearings for the Tornborg City Crane in the Atkinson at Southport.