Details are important! Please read the following information for a better understanding of the load chart numbers.
- STANDARD vs PREMIUM ARMS: All flex arms are made with two wires – a hardened round wire for the spring, and a triangular wire wound into the spring for holding the spring in position when the arm is flexed. Our standard arms meet the majority of our customer needs, made with steel springs and steel triangular wire. Moffatt also offers premium flex arms (steel springs and brass triangular wire) to create flex arms that are totally silent since the brass wire prevents all potential noise. Quiet operation is a common expectation for medical arms and other high-end products. These charts offer recommended loads for both types of arms.
- RECOMMENDED LOADS: The loads in these charts are conservative maximum recommended loads. We capped them at 4.0 pounds (1814g) maximum and 0.2 pounds (91g) minimum because this is the load range we see for most successful applications with our basic arms. But if you need to exceed the loads or lengths recommended in the charts be sure to contact us! Moffatt can use internal stiffeners and dual arm constructions to stretch the possibilities. These are used for engineered arms only – tell us your goals and ask about these options for your design! Remember, the recommended loads are just good starting points and factors like vibration or shock loading can affect the final selection. It’s best to build prototypes and test them in your own application to make sure you have the right arm selected before beginning production of a new product.
- ASSUMPTIONS ABOUT CENTER OF GRAVITY AND FERRULE WEIGHT: The center of gravity (COG) of a product mounted on a flexible arm is usually located beyond the end of the arm. Our recommended loads are based on a typical two inch distance to the COG. If your COG distance is greater, these recommended loads should be adjusted lower accordingly. For example, use the next row down in the chart if your COG distance is 5 inches instead of 2 inches. Also, a typical 0.1 lb (45g) ferrule weight is also assumed. Adjust recommended loads for heavier end ferrules.
- ARM OD: The arm OD in these charts is for the bare flexible arm before a covering is added. Typical vinyl or polyolefin coverings add about .060” (for large arms) to about .030” (for small arms) to the OD.
- LOADS FOR ARMS WITH A HORIZONTAL BASE END: As explained in the learning center, we highly recommend the base of the arm be as vertical as possible to get the spring of the flexarm involved. The horizontal base recommended loads are much lower for that reason. Since some applications can’t have the base exactly vertical (maybe 45 degrees), you can also use the two charts to estimate the difference in maximum recommended loads if the base position is somewhere between vertical and horizontal.
- AVAILABLE FITTING OPTIONS: Moffatt stocks a large range of threaded fittings, couplers and die cast mounts for our flex arms, but not every fitting is available for every arm size. A chart of these options is coming soon, but for now just ask about available options once you select a certain flex arm size for your design.