| 摘要 |
An earth drilling machine includes a crown block assembly, a travelling block assembly and a drawworks. The drawworks includes a drum which rotates about a drum axis. The drum axis is oriented at right angles to a fast line plane defined by a fast line sheave included in the crown block assembly. In this way, the fleet angle between the drum and the fast line sheave is kept substantially equal to zero. Various sheave arrangements are described which combine proper selection of sheave pitch diameter, sheave axis angle, and sheave placement to ensure that the fleet angle of all of the sections of line extending between the crown block assembly and the travelling block assembly are reeved with a fleet angle exactly equal to zero. In this way line wear is reduced and the height, weight and windage of the mast are all minimized. |
