Help Mechanical grab and release

[2526]

I need a way to grab a piece of metal and still be able to hold and let go of it quickly under a great amount of force without breaking and while still staying legal. I do not mean holding on to the rack.

Huge thanks in advance...

[Matt H.]

It is difficult to be helpful with so little information to go on. Is the object you're grabbing any specific shape? How many lbs of force should the grabber provide?

[Jon Stratis]

Without knowing more details, i would say pneumatics is the way to go. A claw powered by pneumatics can squeeze pretty tightly, and then opened again by reversing your action.

[2526]

I dont want it to squeeze it only hold it in its grasp so if it pulled something it would not let go until i wanted it to. and it is grabing a square pipe larger than a 1 x 1 in. and it is not known how many pounds yet because without this piece it is an incomplete design that would take along time.

[Jon Stratis]

Lets take this one part at a time...

Originally Posted by 2526

I dont want it to squeeze it only hold it in its grasp so if it pulled something it would not let go until i wanted it to.

Your options for doing that are to either squeeze the target, creating a large amount of friction that needs to be overcome before it will be pulled away, or to completely enclose it in such a way that it can't get out until you release.

For example, pick up a full pop can and hold it with only two fingers, one on each side. squeezing it, you can hold it this way. If you loosen your grip, however, the pop can will slide out. Now wrap your hand completely around the pop can and cradle it. You don't have to squeeze at all, but it won't be falling out.

and it is grabing a square pipe larger than a 1 x 1 in. and it is not known how many pounds yet because without this piece it is an incomplete design that would take along time.

Sadly, the amount of force needed really does matter in this situation. imagine securing a 50lb weight to the ceiling. Sure, you could set it up with zipties... but those will break and fall. Or you could use a strong, stainless steel hook, properly anchored into the rafters and you'll be perfectly fine.

My best advice is to start by looking at what you're grabbing on to. Are there restrictions (like other robot parts) that might get in the way? Try to grab onto it and hold it yourself (safely, of course!) - whats the best way to accomplish that? Can you design some king of hook or piston or lock that will do the same thing? Is there something existing already (like a gate latch) that can accomplish the same goal? Do you need to release it completely, or simply allow a certain predictable, predefined motion at certain times - in other words, is there another way to do it that doesn't involve grabbing and releasing?

Check around chief delphi here for links to kicker videos. Teams have come up with some great ways to hold a kicker arm back under high force that you may be inspired by.

[Matt H.]

Depending on you design and machining capabilities you could also consider putting a hole in the pipe and inserting/retracting a pin using a pneumatic cylinder. The un-lubricated coefficient of friction between steel and aluminum is .45 so the piston pulling out the pin would need to have roughly 1/2 the loading on the bar (or less if you oiled the parts).

[DonRotolo]

Look in a boating catalog for a quick-release-under-load clip; then have your design such that a smaller bar (think "U-Bolt") extends from the 'bigger than 1x1' bar, and that is what you grab.

[elmer_fud]

I was thinking a quick release could work well.