How To Determine Your Forklift Capacity When Adding New Attachments

Jan 27, 2020
forklift carton clamp

Finding the right attachment for your forklift can be confusing. Use this simple formula to determine whether an attachment is appropriate for your lift truck.

If you’re in the market for forklift attachments, finding the right attachment for your capacity requirements can be a little bit confusing.  Your starting point should always be the lift truck’s rating at load center as stated on the data plate. This rating simply tells you the maximum safe weight your truck can lift with a centered load.

As you shift a load from the center point, your capacity reduces accordingly. For example, a 5,000-lb. capacity forklift may be capable of lifting that weight on 48-inch forks with a 24-inch load center.  However, if you were to extend the load to 60 inches with a 30 inch load center, your capacity may drop to 4,000 lbs. 

In other words, the further you move a load’s center, the more your capacity diminishes.  Many forklift attachments change the load center, reducing your truck’s capacity. 

Load Moment

The capacity for a forklift attachment can be calculated using something called the Maximum Load Moment, which is simply a formula that accounts for weight distribution based on center load distance and the resulting changes in capacity.  From a safety perspective, it’s essential to account for any change in load center, as pushing the center out too far can flip a truck. 

You can calculate a Load Moment by multiplying a load’s weight by its center distance from the fulcrum. In the case of a counterbalance sit-down truck, the fulcrum is the axle of the front wheels, which is the pivot point between the load and the weight of the lift truck. Simply stated, the Load Moment measures the overturning force applied to the front of the forklift. 

You can determine the Maximum Load Moment for any forklift by multiplying the weight rating by the center load distance state on the data plate.  In the example we used above, it would be a 5,000 lb capacity multiplied by a 24 inch load center (5,000 x 24), which gives you a Maximum Load Moment of 120,000 inch pounds.

Factoring Load Center Modifications

When you add an attachment that shifts the load center, you need to factor in that change.  You can do that by dividing the new load center by the Maximum Load Moment. 

Continuing the example from above, we went from 48 inch forks to 60 inch forks, which pushed the load center out from 24 inches to 30 inches.  To calculate the capacity with these longer forks, you can take the Maximum Load Moment of 120,000 inch pounds as calculated above and divide it by the new load center of 30 inches, giving you a new load capacity of 4,000 lbs.  

The formula is simple:

(Truck Capacity x Load Center) / (New Load Center) = Revised Capacity

Load Positioning

Of course, all of these calculations assume that you are handling uniform products with perfectly centered loads.  This is frequently not the case.  Many products are not uniformly shaped and pallet weights are not always evenly distributed. 

If you’re considering a forklift attachment that will change the load center, you must also consider the size and shape of the materials you will be loading.  If they are not uniform, be aware that extensions will reduce your load capacity by even more than your calculations projected.

Overloading a forklift is a serious safety risk that can result in injury or death.  It can also impact your business through product damage, property damage, OSHA actions and more. 

Talk To An Expert

If you have any questions about forklift extensions or other attachments, get in touch with a material handling expert at Raymond West  today.