Hack the claw -- custom claw modifications

Modeled after the Main Lobster, Maryland Blue Crab, and Bayou Crayfish, upgraded by 100’s of hours of robotics expertise by IFI engineers, the VEX Claw is a thing beauty of where design form meets function, the requirements from outside the box become possible inside the box. Plastic melds with metal and the claw is formed.

Shipped to you in container that any 2 carat diamond ring would be pleased to travel in.

You open the box and while you bask in the inital glow you reach for the … and convert it to …

Tell us how you’ve changed the claw (for good or for evil)

After an accidental breakage, we now pull the pins from the front of the support arms and use black cable ties to hold it to the primary arm. This allows the arm to open much farther. While the arm support is a little less and the face grips don’t stay parallel, the overall grip of cubes, tennis balls and hockey pucks is much better.

I remove the spring that tries to keep it closed, and I use a servo to drive it.

Eventually, I hope to insert an FSR under the finger pad and use that as input to a PID loop so I can maintain a constant closure pressure.

Only used for good though, never evil (well, just the once…).

  • Dean

I have ended up with four of the claws (got 2, then got 2 vexplorers cheap on woot).

On one of my first ones, I removed the spring. It was good. I also use a servo instead of a motor, I love that it holds its position. I wish my servo would go a little further past its bounds, because it could open up just a little more.

I also removed one of the plates and flipped it over, so the little side tabs are pointed away from each other instead of in the same direction.

One thing I would really like to do (but am scared to try) is to bend the metal wrist tabs up 90 degrees so they are easier to mount to a gear for rotation (also makes it a little shorter). But I’m afraid it would break and also that I can’t make a clean, straight bend.

All of these are quite tame… I just don’t want to ruin one of these things. I’d love a 2nd style of slotted plates, perhaps one designed for a claw that closes with a bigger gap. Instead of going from touching to ~3" gap, how about one that goes from ~1" gap to ~4" (or something like that).

I mounted the Vexplorer arm on a 3" Lazy Susan so that it could rotate 0:360 degrees on the Vexplorer platform and added a heavy duty geared DC motor to elevate the arm, giving it added agility. It is now able to fetch small objects from almost any angle around the house and bring them back to me using the wireless video.

I extended the length of each of the “links” (the driving link attached to the 36t gear, and the idler link).

The longer these links are, the wider the claw can open, without changing the overall claw geometry.

What did you use for your new links?

That is a great idea, I too am curious what you used. I could see a few lego parts filling the role, but I’m not sure they are quite strong enough. Maybe something custom fabricated, like a few square pieces of metal with holes drilled in them?

I used the links from a 2nd claw with minor mods. This worked pretty well.