# What the HECK is LAM or LAF mean? - Crane Rental Podcast Episode 6 - 4K

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In the crane rental industry and heavy rigging industry we use what are called slings to attach a load to the crane hook. These slings can consist of synthetic materials, braided steel and other materials. The manufacturer of the sling rates the slings in a few standard situations and are as follows: vertical, choke and basket. The manufacture will rate the slings based on these three lifting situations. But the capacities of the slings are only rated for these three situations when the load is perpendicular to the sling. Meaning the sling angle in relation to the load is 90 degrees, or another way to look at it is the load is directly below the hook. You can clearly see this in the drawing above. This is an example of the load being directly below the slings. The angle between the load and the sling is 90 degrees. This is how the manufacture would rate the slings. Let’s say that the load here weighs 10,000 lbs. In the example above the load that each sling experiences is 5,000 lbs. In theory/on paper you could use 5,000 lb. slings for this lift and be “okay.” But in reality you would want to use slings that were rated higher than 5,000 lbs. This adds more play room, perhaps the load weighs more than when it was manufactured [i.e. build of material on the load could increase weight]. This is merely one example. Okay, so we have now established the basics of slings and how the manufactures rates slings capacities. What happens though when we introduce a lower angle to this scenario, i.e. the angle between the load and the slings decreases and goes below 90 degrees?

When you start to lower the angle between the load and the sling, math and geometry is introduced into the equation. Your slings are no longer experiencing 5,000 lbs. like they would if the angle was 90 degrees. In the example above, now we see that our slings are at a 60-degree angle in relation to the load that we are hoisting. The force that the slings are experiencing have increased since the slings are no longer at 90 degrees in relation to the load. Here is where the math and geometry comes into play. To find out how much force the slings are experiencing we will need to use the Pythagorean Theorem. The Pythagorean Theorem basically states the once you have a triangle that has at least one 90-degree angle then we can take the square of two sides of the triangle to find the length of the third or missing length of a triangle. The theorem can be visually shown as; A2 + B2 = C2. The 2 here indicates that we will need to square that number. In the above example, we have a right angle that exists from the center of the load to where the slings meet. In episode 6 of our crane rental podcast we go over this example visually. But to keep everything congruent we will be using the same information. In the above picture we have labeled all of the information required to get B squared, which is the hook height. It is worth noting again that you only need to know two out of three sides to get your LAM or LAF factor. In this case we know the lengths of the slings we are using and we know the length of the beam, which is where we derive A from. From here it is a simple math equation to find B, which is our unknown. If the equation is A2 + B2 = C2, then we will need to modify the equation to fit what know values we have. What the heck is LAM or LAF? Well they are crane rental industry terms that mean load angle multipliers [LAM] or load angle factors [LAF]. Okay, so now you know what the words technically mean, but what do they practically mean in the crane rental industry?

In the crane rental industry and heavy rigging industry we use what are called slings to attach a load to the crane hook. These slings can consist of synthetic materials, braided steel and other materials. The manufacturer of the sling rates the slings in a few standard situations and are as follows: vertical, choke and basket. The manufacture will rate the slings based on these three lifting situations. But the capacities of the slings are only rated for these three situations when the load is perpendicular to the sling. Meaning the sling angle in relation to the load is 90 degrees, or another way to look at it is the load is directly below the hook. You can clearly see this in the drawing above. This is an example of the load being directly below the slings. The angle between the load and the sling is 90 degrees. This is how the manufacture would rate the slings. Let’s say that the load here weighs 10,000 lbs. In the example above the load that each sling experiences is 5,000 lbs. In theory/on paper you could use 5,000 lb. slings for this lift and be “okay.” But in reality you would want to use slings that were rated higher than 5,000 lbs. This adds more play room, perhaps the load weighs more than when it was manufactured [i.e. build of material on the load could increase weight]. This is merely one example. Okay, so we have now established the basics of slings and how the manufactures rates slings capacities. What happens though when we introduce a lower angle to this scenario, i.e. the angle between the load and the slings decreases and goes below 90 degrees?

When you start to lower the angle between the load and the sling, math and geometry is introduced into the equation. Your slings are no longer experiencing 5,000 lbs. like they would if the angle was 90 degrees. In the example above, now we see that our slings are at a 60-degree angle in relation to the load that we are hoisting. The force that the slings are experiencing have increased since the slings are no longer at 90 degrees in relation to the load. Here is where the math and geometry comes into play. To find out how much force the slings are experiencing we will need to use the Pythagorean Theorem. The Pythagorean Theorem basically states the once you have a triangle that has at least one 90-degree angle then we can take the square of two sides of the triangle to find the length of the third or missing length of a triangle. The theorem can be visually shown as; A2 + B2 = C2. The 2 here indicates that we will need to square that number. In the above example, we have a right angle that exists from the center of the load to where the slings meet. In episode 6 of our crane rental podcast we go over this example visually. But to keep everything congruent we will be using the same information. In the above picture we have labeled all of the information required to get B squared, which is the hook height. It is worth noting again that you only need to know two out of three sides to get your LAM or LAF factor. In this case we know the lengths of the slings we are using and we know the length of the beam, which is where we derive A from. From here it is a simple math equation to find B, which is our unknown. If the equation is A2 + B2 = C2, then we will need to modify the equation to fit what know values we have. 