Tuesday, December 30, 2014

Day 104 and 105 - Recasting the plungers and making cowl 2.0

I got my Polytek A70 rubber in the mail, and set to work on recasting the plunger.  This stuff is so much different than the A30!  It's still a two-parts-in-equal-measure substance, but the pour time is only five minutes (as opposed to 30), and the demolding time is only an hour (instead of 18 hours)!

Once the first one had been released from the mold, I turned around and made five more that day.  I've got six plungers in all, and a whole lot more of the stuff left!  I'm debating on using it all, and that would net me about—at rough guess—18 plungers or so, since
I've only gone through about a third of the two bottles.

(I've since discovered that two of them have one small air bubble each in the cup portion, but they're hardly noticeable, and I will probably just cover them with a few permanent marker penstrokes.)

In the meantime, the A30 plunger has all but fallen completely apart.  Poor thing.

Then I set to work on my second attempt at the dome cowl.  I had again pre-cut my fiberglass pieces for the first layer (to make sure all the angles were shape to mitigate air bubbles), and then planned on using surfacing veil for the second layer, and thicker ripped-up chop mat for the third and potential fourth layer.

I got out the dome cowl mold and washed it.  Having neglected to add the name tag indentation on my first attempt with the cowl, I corrected that this time.  I took an old plastic convention entry badge (PAX, for those who are curious), cut two 7.5cm x 3cm rectangles out of it, and cementing them together with carpet adhesive, clamped for a nice amount of time.  Then, I sprayed a lesser-grade adhesive (the one I used for the rubber dome inserts) onto one side, let that get tacky, and clamped it onto the cowl mold for about an hour.

I coated the mold with a sponged-on layer of PVA (left to dry), and then a few passes of silicone release agent spray.  No wax this time.  My leftover can of gel-coat had set in its tin since the time I had last cast a cowl, so I needed to go get another one, grumble, mutter.

With the fresh tin in hand, I stirred it all up so that it wasn't all settled and separated.  Then I poured myself five ounces or so in a separate pot, added the catalyst, and stirred, stirred, stirred.  I sponged all that on (with about an ounce left over), and let it sit for two hours with the heater on in the garage.

Once it was mostly dry, I placed the pre-cut pieces into position and mixed up about four ounces of resin.  Once those pieces were in place, I added a layer of surfacing veil glass over the top, ensuring that I had taken care of any visible air bubbles.  I took about an hour break, and then tackled the next layers of chop mat, mixing up six more ounces of resin for that.

All in all, I think this one will turn out much better than the first.  I'm still going to need to do a lot of repair work on it to smooth it all out due to the rough, ripply texture of the mold, but hey, that's what Bondo and sandpaper are for.

I'll get this Dalek done if it kills me!  (Or rather, unless it kills me!)

Monday, December 15, 2014

Day 101 through 103: Floppy plunger time!

This will hopefully be an informative yet amusing post.  So, where did we leave off?  Oh yes, I had made a plunger master mold out of ABS plastic and PVC pipe.  Let's show the kiddies what I did with it!

I was very inspired by chrisosborne's post about making a two-part silicone mold for the plunger, but I didn't want to build a mold box out of acrylic sheets.  I looked around on the web for alternatives, and after perusing a few YouTube videos on the subject, I decided to build one out of Lego bricks.

Keeping this mold exactly centered was very important to me, as I wanted the final rubber plunger to have a uniform wall thickness (the thinnest part of the plunger only being 1/8" thick).  The main advantage of having a Lego mold box, according to my thinking, was that all the Lego studs would keep everything very much in center.  I used a forstner bit to drill a hole in one of my sacrificial Lego bricks (*gasp!*) to center the PVC portion of the plunger.

For the bottom of the mold box, I made an extra reservoir space with a grilled floor.  This would force the cured bottom mold to be perfectly in place and not move around, again ensuring the centering of the final piece.

To keep the plunger master mold in place, and to prevent silicone from seeping into the inner cup, I filled the plunger bowl with plasticine putty.  When I placed the master mold back into the mold box and centered it, it stayed put.

(Not pictured is the event known as the "cup overfloweth", where I lost about $75 worth of leaked silicone when I tried to mold the bottom part first without making sure things were sealed.  Lego like to come apart when weight is placed on them.  Who knew?)

Next up was to mix up a batch of the silicone (I used something called a Squirrel mixer, which caused me no end of amusement, ah, the visuals) and whipped up a bunch of blue goop in no time.  It has a nice 30-minute pour time, too.  I placed the mold box on the floor, and from about three feet up, I poured the silicone in a very thin bead to reduce air bubbles.  After a few long minutes, I was done and the mold was filled.  Now I just had to let it set for 24 hours.

A day later, I checked on the mold and the silicone was nice and firm.  I took the bottom part off and cleaned out all the putty, wiping off any remaining smudges of it with paper towels and a microfiber cloth.  I placed the bottom of the mold box back on, prepare more liquid silicone, and fill in the bottom part of the mold.  And then wait another 24 hours.

When the other half of the mold was ready, I removed the whole lego enclosure and looked at my handiwork.  I had two wonderful halves of the plunger mold, complete with alignment keys and perfectly centered.  The man at TAP Plastics told me that nothing sticks to silicone like more silicone, so I used some release wax and an oil-based agent (called Pam cooking spray) on the mold interior.  I was thrilled to mix up a batch of black rubber and get to work!

I modified the Lego box a bit by only using a few rows of bricks around where the two mold pieces meet, to prevent leakage.  In the center of each side, I built pillars all the way to the top of the mold to lay a jig, which would be used to suspend and center a bolt within the plunger stem.  This would then screw in the plunger to its arm bushing.  I destroyed another sacrificial lego by drilling a centered 1/4" hole for the bolt.  I then mixed up some of the two-part rubber and added the black pigment to it (note that it says "shore A-30" on the bottles, this will be important).  This mixed very thinly, so I needed to slap a bit of the plasticine clay onto the Lego to prevent leakage.

After about 18 hours or so, it was time to demold the plunger.  I was very excited!  The bottom mold popped off easily enough, and before too long I managed to get the top part off, too!  And then I held my plunger to the light, and it ... started ... to ... droop.  And there were weird and bumps on its surface.  The drooping, I later found, was due to the shore number (remember A-30?).  A-30 is softer than a pencil eraser (which is A-40).  A-70 is about the strength of a car tire.  A-85 is a wheel on an inline skate.  TAP Plastics doesn't carry anything beyond A-30, since they're selling mold-making materials.

So, again, I referred to chrisosborne's post, and saw that he ordered A-70 rubber, which I promptly went online and ordered, too, from the very same store!  It hasn't come in yet, but when it does, you'll be the first to know how it goes!  (Well, after me, obviously.)

As far as the pits and blemishes, I can only assume that the TAP Plastics guy was wrong about the vegetable oil.  I think it reacted to the liquid rubber and made things kinda weird, chemically.  The plunger is still a bit tacky (bits of rubber fall off when a finger rubs it) even after several days, now.  ChristmasDalek expressed a potential interest in it, but I'm not sure its ability to survive in our harsh world.

Thursday, December 4, 2014

Day 100 - Eyestalk pivot and plunder plug assembly

Although I've been working on Rainier since July of 2013, this marks day 100 of active work on him!  So, I wanted to post something iconic: the completed eyestalk and the plunger!

My previous attempt at making the eyestalk pivot wasn't too successful, as I had neglected to make sure that the circular pieces of MDF and HDF were all lined up perfectly when I glued them together.  I found, after sanding them, that there was a slight angular tilt instead of a perfect cylindrical piece.  Because of this unevenness (and the fact that it was already cut in a circular shape), it was very difficult to drill a shallow hole where the eyestalk tube would be inset.

I mulled over in my mind how else I wanted to approach this.  What I decided to do was to take larger rectangular pieces of MDF and HDF—cut to the same size and squared on the table saw—and glue those together as before.  Once the glue had set, I marked off the square I wanted to work with, found center, and drilled the shallow where the eyestalk rod would be inset.  I also took the opportunity to drill the centered 3/8" hole for the lamp rod to pass through.  Then I took the 4" circular saw blade to it, and cut out the circle.

To solve the issue of how the lamp rod and axle rod would meet, I decided I would use my leftover 1" aluminum tubing for the axle.  Using the same 1" forstner bit, I drilled a hole all the way through the center of the pivot on its side, then test-fitted the tubing.  When I get ready to fit the lamp rod, I will simply use the eyestalk pivot itself as a jig to drill the 3/8" holes through the aluminum tube.

The outside diameter of the saw is 4", which means that the resulting piece is shy of that by about an 1/8".  Using some of the 4" Plastruct ABS tube I bought for the eyeball, I measured and sliced off a section and clamped it on with a two-part epoxy glue.  Once that had set, I carefully drilled (starting small and working my way up with larger and larger bits) the eyestalk tube hole.

A nice advantage of having the ABS plastic on the outside was that I could now adhere the pivot strips.  I took a tip from Jon Place's build diary and used zip ties.  I couldn't find ones that were flat; the only ones I could find had a texture on them, but I actually quite like it.  It compliments the more industrial look of the NSD-type daleks in my opinion.  One problem with the plastic these ties were made from, however: it basically ignores my acrylic cement.  So, what I used instead was simple super glue.  To space the strips evenly, I used a blade from my jigsaw.  Afterward, just for kicks, I ran a bead of acrylic cement along each space, let that set for a bit, and then took an X-acto knife to trim off the excess.

I carefully trimmed the zip ties along the inset hole and test-fitted the eyestalk tubing.  It was a very nice fit, so I assembled the eyestalk with the new pivot, and am very pleased with the result.  It is now set aside for eventual sanding and painting, not to mention the electronics.

Moving onto the plunger, I followed lochsloy's method of measuring out and cutting the inner and outer Plastruct cup parts.  For removing these sections, I used my Dremel tool for the major work and some 80-grit sandpaper for fine-tuning.  I switched to finer and finer grits to polish it off.

The part of the plunger that had me confused the most was the outer flare.  In lochsloy's diary, he leaves the part as-is, only sawing away the hole for attaching it to the plunger.  In screenshots and prop photos that I've seen, the outer flare seems to be trimmed quite a bit.  My decision was to leave it as-is, and when I cast the eventual rubber plungers, either trim it down with an X-acto knife or just leave it alone.  What I did have to do, however, was cut back the four outer ribs by about an 1/8" so that I could attach the flared rim to the outer bottom part of the middle plunger cup.

Attaching everything together was done by using the same acrylic cement I used for assembling the light cages.  I didn't need to use melted ABS glue as I did for the eyeball, since this is intended to just be a plug for an eventual silicon mold.  I also took some two-part epoxy glue and attached a measured length of 3/4" PVC pipe for the stem.  This will then fit in nicely with my 1" tubing I will be making the "hard" back section of the plunger out of.

And there we have it!  Next up: making the silicon mold of the plunger!