In Vulcan Onshore Tip 65, the safe use of sheave type cylinder heads is discussed. A view of the different types of sheave/sheave head/sheave pin/retaining pins from that tip are shown at the right. In the a more recent post, a more detailed diagram of a sheave head is shown below.
Some Vulcan users feel they don’t need the sheave and its assist in lifting the hammer, so they take the sheave out, put the sheave pin and its retaining pins in, and run a cable around the sheave pin and lift the hammer.
Unfortunately this can create another problem. Vulcan Tip 65 advises the following:
Always pull the hammer straight up, not at an angle to its central vertical axis. Pulling the hammer at an angle could pull the sheave pin through the head, disconnecting the hammer and sheave wheel causing both to fall.
If the sheave is in place and the load on the sheave cables is angled with the centreline of the hammer, a good deal of the side load (but not all) will transmit from the sheave directly to the sheave head. If there is no sheave, all of the side load will transmit to one of the retaining pins, which runs the risk of shearing the pin and having the sheave pin coming out and the hammer falling down.
The latter condition is obviously the more serious one. The simplest way to solve this problem is to use a bar or suspension type head, which eliminates the pin altogether. The options available for Vulcan hammers are shown below.
The Sand Drain Type is explained here. The Suspension Type is more suited for hammers using stub leaders, as explained here. But either the bar or suspension type eliminates the sheave pin and its retainers. It also makes for a shorter hammer by 1′ or more, reducing headroom. Both of these types are available from Vulcan Foundation Equipment.