• if high shock loads are anticipated, mount the cylinder to take full advantage of its elasticity, and don't forget: the fluid lines are along for the ride, hold fixed-mounted cylinders in place by keying or pinning at one end only
• use separate keys to take shear loads: at the head end if major shock loads are in thrust, at the cap end if they are in tension
• locating pins may be used instead of shear keys to help take shear loads and insure cylinder alignment. Avoid pinning across corners - this can cause severe warpage when a cylinder is subjected to operating temperature and pressure. Such warpage also is imposed on fluid connectors at cylinder ports, and
• pivoted mounts should have the same type of pivot as the cylinder body and the head end. Pivot axes should be parallel, never crossed.
Many fluid power cylinders incorporate cushions to absorb the energy of moving masses at the end of a stroke, including the masses of the piston and rod, the load being moved, and the fluid medium operating the cylinder. When the cushion operates, the additional thrust is imposed on the cylinder assembly and it will change length. What about the fluid conductors?
Consider protecting exposed rods from abrasion and corrosion that could destroy the rod surface and, in turn, the rod seal. In especially dirty environments, protect the rod with a cover such as a rod boot or bellows.
Cylinders undergoing pressure and temperature changes elongate and contract. In addition, flexing and rocking makes the mounting head sway under load. The type of mount to specify depends on the application, but the effect of pressure and temperature changes must be provided for or the cylinder will leak. Consider these factors:
• Cylinders with non-centerline-type mountings tend to change length and sway under load and temperature change. Any rigid tubing connected to a cylinder cap port will be subject to that resulting force and motion. If a cylinder is rigidly plumbed, the question is not whether it will leak, but when.
• Cylinders with non-centerline mountings often require stronger machine members to resist bending, so consider the rigidity of the machine frame. For example, where one end of a cylinder must be overhung, an additional supporting member should be provided.
• In most cases, a layout of the rod-end path will determine the best type of pivot mounting.
* Fixed, non-centerline mounted cylinders with short strokes add another strength problem because mounting bolts will be subjected to increased tension in combination with shear forces.
• Do the major applied forces result in cylinder rod thrust or tension? Cap-end flange mounts are best for thrust loading; rod-end flange mounts are best if the rod is in tension.
• If misalignment occurs between the cylinder and its load, the mounting style may have to be altered to accommodate the skewing movement. A simple, pivoted centerline mounting, such as a clevis and trunnion, compensates for single-plane misalignment. If multiple-plane misalignment is encountered, the cylinder should have self-aligning ball joints on the cap and rod ends of a clevis-mounted cylinder - and fluid-line connections should be able to accept the movement.