Quote:
Originally Posted by Al Skierkiewicz
Just so we can be clear on the response for us non-pneumatic guys. The response is that the end caps alone cannot take the forces encountered with a cylinder moving at 80 in/sec. Users that design this speed of movement will require external stops that limit the piston from contacting the end caps in operation. Did I read that right?
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Al,
There are 2 parts to that answer.
The first is that the seals are capable of 80 ips as long as they are not in constant use. This is a good thing considering most of the applications here in FIRST.
The second is the end cap, which is much more troublesome. Most cylinder endcaps are pressed in (usually with a 1 ton press) and then double cinched (or crimped) to retain the endcap. During normal operations (with restricted air flow) the cylinder should not be able to create enough inertial momentum to cause severe problems. However, in many of our assisted acceleration systems (spring assist, locked cylinders, etc) with large inertial masses causes the impact against the endcap to become greater than the manufacturers expectations. This is his reasoning for requiring not bottoming out on the end cap (our cylinders themselves are not generally capable of those speeds on their own). It would be my suggestion that
ANY cylinder that is acceleration assisted or has a large inertial load (1 LB or higher) should be required to have a hard stop before bottoming out on the cylinder end cap (<S1> ruling).
Should a cylinder end cap fail, it will most likely be shot with considerable force. The mass of an endcap of a 1 1/2" cylinder is probably about 1/2 the mass of the soccer ball, so it could be shot further than the machines kicking distance.
Hope this helps.