Sunday, September 28, 2014

Day 95 - The light cages and the eye

I spent a productive day working on the light cages and the eye piece.  Back in February of this year (2014), my plastic parts from Plastruct were delivered to me.  Prior to that, in November of 2013, I had a local maker shop laser-cut the parts for the light cages.  Assembling these was another task I was afraid to tackle, mainly because of the cost of the ABS plastic, and the cost of the laser-cut acrylic.  In addition, I had no back-up pieces in case I screwed up.  I hadn't ordered any glue from Plastruct, either, so I didn't have a means of gluing them together.

I had, however, obtained acrylic cement from TAP Plastics, and so I started there, with the light cages.  First, I drew a square, with the sides being the same as the diameter of the bottom part of the light cage.  I drew diagonals to find the location where the light cage struts were to be cemented, and lightly scored the acrylic with my box cutter blade.

Afterward, it was essentially a breeze to cement everything together.  The cement applicator has a needle nose, and, while holding the strut to be glued in place with one hand, I gently dragged the needle along the base.  The capillary action of the cement allowed it to draw itself directly under the piece.  After holding it in place for several seconds, a secure bond had formed.  I repeated this for all the remaining pieces, and eventually, I had to lovely (unpainted) light cages assembled!  In 24 to 48 hours, the molecular bond of the welded pieces will reach maximum strength.

(Of course, I would prefer to have aluminum light cages, but so far it's been prohibitively expensive for me to do that.  Maybe someday!)

Next up: Cutting up the stepped cone for Rainier's eye.  I took the smaller of the long tubes and sat it in the cone to find where I was going to cut it.  I marked out the spot and made a test cut one step higher for practice.  It wasn't too difficult of a job; I mainly just gently scraped the razor along the "L" of the step, over and over again until it was free.  Then I repeated that on the marked line once I was confident.

The resulting piece needed to be cut into two sections.  I again marked the places that needed to be cut, and soon I had both pieces ready to assemble.

I also needed to get the tubular sections of the eye piece cut to length per the plans, so I used my miter saw to do that on both the small tube and slightly larger one.  The miter saw wasn't my first choice for this, but I didn't have a miter box for a handheld saw.  Very carefully, I cut until I couldn't lower the saw further, then rotated the tube, continued the cut, and soon the job was done.  Some light sanding using 120-grit paper, and I had the pieces I needed.

Now, how was I going to glue all of this together?  I went to the web and googled what the proper bonding agent for ABS plastic was.  I ran across several videos where people demonstrated making their own glue using acetone and scrap pieces of ABS.  Eureka! I thought, and decided to give it a try.  Heck, it made sense to me—use ABS as a means to weld other ABS together.

First, I chopped up the scrap rings from the cone I had cut, and threw them in a jar.  I added a small amount of acetone to it, screwed on the lid, and let it sit for about an hour.  When I came back to check on it, it was all pretty much melted.  I gave it a good stir with a stick, and was very satisfied with the consistency.

After flipping over the two front eye pieces and placing them in their final position, I took a cotton swab, dipped it into the goo, and ran it along the edge of the seam.  I made sure a good amount of the slurry covered the piece.  Then I let that sit for about 30 minutes or so.  I was very pleased.  It was still slightly malleable, but, like the acrylic cement, it should be nice a solid once the acetone has completely evaporated.  I then added my glue to the edge of the smaller tube, and pressed the eye front onto it.  I repeated this for the larger tube edge, and squeezed the back eye hemisphere onto that.

Now they're both curing, so I'm going to give them all the time they need to dry.  Later, I might add another layer to the front piece and to the interior joins of both the tubes, just to make sure everything is nice and secure.

Thursday, September 25, 2014

Day 94 - Gunbox interior assemblies

Again, following the path AdamSt paved, I have been working on a job that I've put off until now—the gunbox interior assemblies which keep the gun and plunger arm in position within the shoulder section.  Since nothing is currently holding the globes in place (except gravity), the approach is to "sandwich" them in using MDF plates, bolts, springs, and wing nuts.  The front of the gunbox (the exposed part on the shoulder section) can't be marred with the bolt holes, so similarly-shaped internal plates need to be made and installed.

I couldn't find my protractor, so I went back into my own build diary to see if I had logged the front angle of the gunboxes, and I thankfully had done that.  It has a 20° angle, so I set my table saw blade accordingly and cut four pieces of 1/2" MDF to match, two per gunbox.  One of these will be attached via wood screws onto the interior of the gunbox as the middle part of the "sandwich", and the other will be the back.

Now, I should have made these assemblies at the same time as the gunboxes themselves, because getting the exact measurements of the interior was a bit tricky since they're now part of the shoulder section proper.  As such, I cut the plates with a larger initial width, then trimmed them until they fit in each gunbox.  I then took a pencil and ran it along the edge of the gunbox holes, tracing a rough circle onto the two "middle" plates.  This was so that I knew the approximate location for where to drill with my 4" hole saw.  I traced an accurate 4" circle on top of that and drew a square around it to find the center.  Then I cut holes in both the left and right plates.

Not an exact science by any means!  I checked my work thus far by seeing if the globes would pass through the 4" hole untouched (the middle plate doesn't hold the globes in place, that's the back plate's job).  I also checked to see if the holes lines up with each other, and if the 20° angle was accurate for the slant.  The globe still poked out of the gunbox unobstructed.  Success!

Next, I lined up the back plate to the middle plate, and traced around the 4" hole that I just drilled.  I repeated my process for finding the center of the circle.  Now, since this back plate will be butted up against the other side of the globe, the hole needs to be smaller.  I switched from my 4" saw to my 3.5" one and cut those holes.  Like the front of the gunbox, it needed to have a 45° chamfer.  Switching to my hand router, I added that detail.

Now that I had all four holes drilled and lined up, I set to work creating a 20° jig for drilling the bolt holes.  These need to be parallel in relation to the top and bottom of the gunboxes.  Some quick work with scrap 2x4s (from when I mounted the wheels to the fender), the table saw, a hammer, and some nails, and I had a nice jig.

When I drilled the bolt holes, I made sure to clamp the middle and back plates together so that the holes were evenly lined up.  After a bit of time, I had them all drilled, and added bolts to test the alignment.  I was worried that the the tightness of the corners nearest the shoulder walls would be tricky to allow the addition of the eventual wing nut, so I tried to keep that in mind when deciding where I wanted to drill.  All these angles were making my head hurt!  I did a quick test to see if the wing nut had enough room to spin, and it indeed did.  Whew!

Since the middle plate is going to be attached to the back of the gunbox with wood screws, it needs to sit flush against it.  The bolt heads currently prevented that from happening, so a little countersinking was in order.  Switching to a forstner bit and using my jig, I added the proper countersink to each of the bolt holes.

I also switch to a small countersink bit and drilled (not at a 20° angle this time) the holes that the wood screws will use for attaching the middle plate to the interior of the gunbox (not pictured).

Now that everything was cut, trimmed, and drilled, I spritzed the pieces with my PVA wash (4 parts water, 1 part Titebond III) and waited for it to dry.  Since these pieces are going to be inside, they'll be exposed to water vapor from my breath, so I decided to seal them up before eventually painting and installing them.

Once dry, I re-added the bolts, springs, and wing nuts.  I haven't installed them inside the shoulders yet, as I want to prime and paint them (and the rest of the shoulder interior), which will come later.  Once painted, I'll attach a soft felt lining so that the globes don't get scraped when the gun or plunger arm are moved about.  Then they will be installed into the shoulder section.  Until then, they are resting comfortably in the same box where I keep my shoulder slats.

(As an aside, while I waited for the PVA wash to dry, I shopped for some proper exterior bolts to eventually attach to the fender, eye piece, dome cowl, dome lights, and gunbox details.  I was having a hard time converting the metric description of the bolts to what's available in the US, until I ran across acrodrome's post in the "2005 Design Dalek Appendages" forum.)

Sunday, September 21, 2014

Day 93 - Cutting bits for eyestalk and plunger arm

Wow, it's been a month since I last posted!  I feel neglectful!  Part of it is that I'm in a weird phase where I'm losing confidence in the build, and most of it has to do with the bloody dome cowl.

ChristmasDalek did as best as she could removing all the stuck-on linoleum remnants and other crud, but it's still a pretty nasty, crinkly mess inside.  So I just put it (and Rainier) out of my mind for awhile and sulked.

But, I'm trying to muscle my way through the funk.  I cleaned up the garage (which was one MAJOR thing that was keeping me from continuing), and that helped a lot.  The after shot should speak volumes.  No, I'm not a hoarder.  (At least I hope not!)

Now that my tools were back in reach with elbow room to spare, I set about on something else entirely (eschewing the cowl for now).  I decided it was high time to cut up all my aluminum tubing that I've had laying about.

First I set to work on the various pieces for the eyestalk, per the manual.  Now I need to get the eyestalk lenses cut to size and drilled.

Then I cut up the large plunger tube so that I had 20cm sticking out the back end for me to grab.  This matches what's currently the inner length of the gun tube, but I may trim both down if they prove too awkward for me to wield once I'm situated snugly inside.  From the front of the globe, 39.5cm of tube protrudes, per the manual.  For now, I also cut up the two smaller tubes to approximately the same lengths.  I'll be using 1" diameter acrylic hose as a means to extend the arm rather than longer lengths of tube, for safety's sake.

I can't remember if I mentioned it earlier in this diary or not, but the same friend who micro-lathed my gun bosses also carved me up some top hat bushings that I designed one day in Goggle Sketch-Up for my plunger arm tubes.  I've been keeping them in my freezer for months (thermodynamics and all that) and finally attached them to the cut up tubes.
On each of the inner tubes, I temporarily affixed masking tape 20cm from the top as a means to stop them from falling completely out of their respective housings.  Here's a shot of Rainier with his new arm fully extended!  Note the screw in the front bushing; a similar screw will be set within the eventual rubber-casted plungers that I'll be making.  Then, they can simply be screwed on to the arm!

That's all for now ... perhaps I'll try and fiberglass up the cowl soon after repairing some of the air pockets.  Or I may work on the eyestalk lenses ... we'll see!