Determining the hydraulic cylinder to use is influenced by many factors, not just the application it’s being applied to. Working load, geometry of motion, stroke length, duty cycle, and mounting needs, are all considerations that should be taken into account by your hydraulic cylinder supplier. Purpose Built hydraulic cylinders, such as those offered by Aggressive Hydraulics, ensure the optimum strength and performance for your application.
The most important piece of information in determining what size and style of hydraulic cylinder to use is the working load. Working load helps to determine the required operating pressure needed. A great example is if you want to lift 5000lbs vertically, you’ll need at least 5000lbs of operating force to lift the load. However, if you want to push 5000lbs horizontally, you can utilize less force to move the weight, because you only need to overcome the resistance of the objects friction sliding over a surface. A hydraulic cylinder that has been Purpose Built will take this into account as part of the initial design phase.
Once you’ve determined the force required for your hydraulic cylinder to exert, the next step is to calculate the bore size required of the cylinder. Engineers use a formula that calculates the bore size needed to achieve the force. The force produced by the hydraulic cylinder is calculated by multiplying the hydraulic pressure by the area of the internal piston surface.
Geometry of motion
After the working load has been determined, the geometry of the hydraulic cylinder’s motion needs to be considered. For a machine like a fork lift, the load is being raised and lowered vertically. This makes the calculation fairly straight forward, and much simpler to incorporate into a Purpose Built design. However, when the motion of the hydraulic cylinder is off center from vertical, or horizontal, and the lifting force shifts, the force required can change considerably. In some cases, the load on the end of the hydraulic cylinder rod can be 10x or more the actual working load. This may require the Purpose Built design to have a larger bore, larger rod, or both depending on distance of the stroke length.
Now that we know the working load, the hydraulic cylinder’s geometry of motion and the intended application, we can take into account the stroke length to determine the appropriate rod size. Standard off the shelf hydraulic cylinders may only come with one or two rod size options. A hydraulic cylinder that has been Purpose Built for an application will take these factors into account, compensating for all forces with a margin of error to prevent buckling of the hydraulic cylinder’s rod. As the rod size, and stroke length increase, so do the loads inside on the bearing surface, and the piston. Getting the right product for your fluid power application ensures an efficient, safe, and durable hydraulic cylinder you can rely on.
Finally, the duty cycle of a hydraulic cylinder should be taken into account. Calculating the static loads mentioned above is basic to a hydraulic cylinder’s development, but having a Purpose Built cylinder that can take into account the dynamic loads, inertia, and how many cycles it will run through daily, plays a large role in a hydraulic cylinder’s specifications. Understanding this will help to prevent fatigue to threaded and welded joints on the hydraulic cylinder. Aggressive Hydraulics engineers use finite element analysis to understand these forces and the role they will play on material selection and size. Additionally, industry and application specific safety interlocks must be factored into the overall design as well, based on these forces.
Selecting the right hydraulic cylinder for your application doesn’t have to be a daunting challenge. The engineers and technical sales staff at Aggressive Hydraulics have over 100 years of combined experience to get you exactly what you need for your application. Whether you need one, or one thousand hydraulic cylinders, give us a call at 866-406-4100 and we will work with you to get the right solution on your equipment!