![]() You've bottomed out the angle at the "skate block" pulley to zero degrees and you're holding a third of the load. The skate block set up just became a z-rig that you're lowering with. Now (bear with me here as I continue with my example) climb the tower with the lowering mechanism still on your harness and run the exactly same rigged operation from atop the tower. Considering ideal mechanical advantage (not practical), you're doubling the load up there. If you walk with the lowering mechanism toward the wall/tower until the skate block pulley becomes unloaded per a 180 degree angle in the rope, it's very easy to see then what you're doing to the anchor holding the redirect pulley atop the operation. They go different ways on the graph, intersecting at 120. What's going on? Consider the relationship between anchor angles and directional angles. The angle in the rope at the skate block pulley is getting flatter, but the skid force resistance required of your feet is far less. Notice that if you, say, put the lowering mechanism (rack, I'D, etc.) to your harness instead of to a fixed anchor and you stood way out from the wall so as to offset the package as it comes down, you're going to be resisting skid force with your feet. It's just that the "directional pulley" here and the skate block pulley are one and the same. The angle at the skate block pulley is creating a "directional angle" in the rope. I think you're actually thinking "anchor angles". I'm going to have to pick up two dynos and grab some numbers. Granted there's remedeys for this such as choosing or building a anchor point on the ground that's closer to the structure your victim is being lowered from or extending the distance of the chest pully or "guide pully" by means of prusick cord. The angle the victim creats between the two anchors is close to 120 degrees. I'm not concerened about the initial forces applied during the pulling force to clear the victim of the tower I was more curious about the forces on the topside directional pulley and the bottom side directional pulley when the load is about midspan. If we are talking about two different things feel free to delete my post One other note.As with any other time you tension a rope, you only tension as much as needed to get the job done. You would need to know the load, the angle (distance of the anchor from the base) and then it would be dependant on how much tension was actually needed. There are too many variables to tell you what the forces would be. If an MA is used again it should be used sparingly. First, if a handpull is used to tension, the pullers will feel the reactive forces and will not be able to overload the system. To be honest, I wouldn't be overly concerned with the forces in this application. This should amount to very little tension in the system. The term skate block is generally used in tower applications in that environment tension would only be applied to clear the tower and the fence. ![]() The only purpose of tensioning the guiding line is to clear the obstacle. ![]() With that being said, we recommend that tension be applied with personnel only (2 people with no MA), or with a minimal MA with minimal personnel (I wouldn't use more than a 3:1 with 1 or 2 people). The guiding line system aka: skate block, is a low-tension technique. We decided it best for the training community and from an applicaiton stand-point to seperate the two. When we were outlining topics for my book we wrestled with application of low- and high-tension systems. If you are talking about a sloped tesnioned line than a completely different response will be required I assume by "skate block" you mean a low-tension guiding type line.
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