Saturday, August 27, 2011

My CPU Arm Project

I've been collecting more parts and now have everything I need to try and get this CPU arm working. I bought a Fergelli L-16 actuator which is the medium length model with a 100 MM stroke.
First I unscrewed the end plug.
Next I bought an 8MM metric stud with a 1.25p and cut it to length so the CPU arm would screw on it. 
I tapped the CPU tip to 8 MM and then cut the stud to the correct size and tried a few tests with 12 volt power and everything seems to work perfectly.
The tube came with this plastic plug. So I filed it down until the L-16 would fit inside of it.
I cut that mount off the rear because I need to recover that space. You gotta be careful not to cut off the wires.
With everything installed and the rear plug installed. I still need about 1/4 of space to get the plug to fit inside. So its off to the bandsaw.
I screwed in a 1/4 -20 rod and pushed it to cut off what I'll use later as a shim. DO NOT try something like this by hand. Trust me you'll need your fingers to operate a droid.
I'm almost a straight cut, but a little crooked. I filed down a square hole in the left over 1/4 inch piece of round aluminum.
That shim then goes over the actuator and holds the rear end of it centered and then the rear aluminum plug fits. So its time to test it out!
The tip came out as it has during all the tests and snapped off and fell into the cat's water dish:(
I was so close and ready to install it and the L-16 you've failed me. So its time to take the L-16 apart and see if I can fix it.
Here is the inside of the L-16. It has a screw drive that has a high pitch. One you can't fabricate parts for with a metric tape and dye set. The motor and everything works just fine. What happened is a piece of plastic broke off from the square limit switch.
This is a closeup of what I believe is the limit switch. There used to be a small tube of plastic that threaded to in the inner part to this screw shaft and its outer part was 8mm. So it was very thin and the weakest link in the system. Somehow I need to fabricate this square part seen and its tube part out of aluminum. Otherwise this L-16 is of no use.
So the moral of the story is don't follow in my footsteps if you were considering this route. After about 8 tries the L-16 failed and rendered itself to the junk pile. Now I'm not sure how to proceed. If I can find a tap set to duplicate this pitch I might just JB weld a small tube over this square piece. I'll try a few things before this hits the junk pile.
One day I will get this to work and save people from getting crushed in the trash compactor.