Tuesday, February 11, 2014

More Lifter progress

The work on the dome lifters continues!

Let's break it down by periscope lifter and life form scanner lifter to make it easier to follow.

Periscope Lifter

The toughest part of the supporting structure was making a part that goes from the Servo Hub to the base of the periscope (the periscope riser cap).

At first I printed this piece...

And while that allowed for pieces to fit together nice, I needed to change it by adding a hole to the middle and side to allow the periscope electronics to pass thru.

The next big challenge was how everything is assembled, which required a re-think on the periscope risers, which go from the periscope housing into the base.  

As the periscope was originally designed, the risers bolt into from the top and bottom with 10-24 thread machine screws.  

However, for the rotation and lifter mechanism, the base has a thrust bearing under the riser cap.  For that bearing to perform correctly, the surface needs to be flat.  I also can not access the bottom of the periscope once the shaft is screwed onto the servo.  In short, to help you follow along, as you assemble the structure, you are working your way from the bottom up.  Once a part is covered, you can't access it.

That meant the holes in the riser cap, which allowed a 10-24 thread machine screw to pass thru would need to be filled in (welded) then drilled and tapped again.  Since the risers are thin, the option to go to the larger sized machine screw was out.  My buddy Fred welded in the holes and used his CNC machine to VERY delicately smooth out the surface.  The holes were then drilled and the holes tapped to accept a 10-32 thread.  The riser cap area this all goes into isn't extremely thick...maybe 1/8th of an inch.  I decided to switch to the 10-32 thread since it offered more threads.  With so little material for the machine screw to thread into, I wanted as many threads as possible to hold the periscope securely.

The risers then had to be bored out so the flat head screw would pass thru.  This also means all the periscope electronics had to be displaced to access the holes at the bottom of the periscope.  Very delicate work!

A 3 inch screw was a tad short, so I used a 4 inch ones.  

I marked off the very top threads with a Sharpie so I could cut the screws to size.  Remember, we want this side to be flush, nothing can stick out beyond the hole or it will interfere with the thrust bearing.

After trimming.

After the wiring was passed thru the hole, then into the hub adapter, the wiring was all set.  Then it was time to loosen the periscope risers so the assembly could be bolted to the servo shaft.  (Remember we assemble from the bottom up)

The last steps were to screw the periscope housing and risers to the base, then stuff the electronics back inside.  

I had my servo tester handy to make sure the alignment was correct...or in short, that the neutral position on the servo matched the direction the periscope faced.  It has to go back to the neutral spot so it can fit in and out of the dome opening!

Life Form Scanner Lifter

The Life Form Scanner (LFS) has a few challenges of its own.

The three pieces that make up the structure have different opening diameters.  Initially I had a 10-32 threaded rod going from the base to the top, with the scanner dish mount threaded to allow that to screw in.

However based on how the LFS looks in the movie, a threaded rod wouldn't look right, so a solid one should go in its place.

I decided to go with what works and improvise a little.  I would thread the top piece to allow for the 10-32 threaded screw, but cut off the head.  I used a screw long enough so that it would go half way into the base piece, and the remaining portion would use a 3/16th piece of steel rod.  Since the bottom piece doesn't fit tight around the 10-32 screw, I drilled and tapped a 6-32 hole that went into the middle....and used a 6-32 set screw to lock down the connection.

Like the periscope, the big concern is that the gadgets are both aligned and centered.  If the LFS wiggles or doesn't stay put, when the LFS is lifted out of the dome, or brought back down, it could collide with the sides of the dome opening.  

The next step will be to get some solid strand white wire, like 22 gauge, coil it, attach a small female crimp on connector and a attach it to the lighting.  Then, routing the wiring through the base and out.

With both gadgets securely attached to lifters, here's how they look in action