Monday, April 25, 2011

More work on the gripper arm

Over the weekend I continued to make some progress on the arm assembly.

One thing that bothered me was how close to an inch of space was wasted trying to make a 1/4 20 thread fit into a 10-24 thread actuator.  A coupler was required but I wanted to find something better.

By accident, I think I did!

I found a 10-24 thread grommet that had potential.  I just had to add some holes for a 4-40 screw to pass thru.

 The grommet is too small to reach the existing mounting holes, so I used a small, square-shaped piece of aluminum that would.  Then it was creating two countersunk holes for the mounting to the claw, then two threaded holes for the grommet to be secured to.  (No room for a lock nut where those screws go in)

As you can see, with the old coupler and mounting piece in the foreground.  In an area that already has tight clearances, this helps a lot.

The next obstacle is the attachment of the linear actuator to the servo.
Ideally, you want the servo horn to be screwed into the servo.  However, with the attachment pictured below, that's hard to do...

The L16 Linear Actuator includes mounting hardware, a U-shaped bracket and 10-32 threaded screws and lock nuts.  I drilled a hole large enough for the bolt to go through the servo horn.

 Now I can just use electrical tape on the bottom part for now and then the arm slides onto the servo fine.  However, anticipating Murphy's Law, I would like to find something better.  For now it will suffice.

And here is where I am at now, R2's arm assembly moves out, extends and the claw can open and close.  However, the next step in this challenge is to have it going straight out, in relation to where R2 is pointed.

I was going to work on this some tonight but decided to address the issue with the door not opening all the way properly.  This requires removing the GOOP adhesive since it dried crooked (clamp slipped off).  As a result, the door is perfect at the bottom but as you go up, the hinge is falling into the body.  I have some toluene solvent, which will dissolve the GOOP adhesive.

The one good thing about all this time in the basement has been my dedicated assistant, "Mokey".  Anytime I get up, he steals my chair.  When I am staring out in space, trying to find a solution to something, he's rubbing around my legs, desiring some of that attention.  Gotta love a great wingman!