Entry tags:

acrylic, halloween, howto, steampunk

Steampunk Cane, Part 2
Or, how to craft a keyed flux channel for your aetheric jumpship.
(This is part two of a how-to series. Start at Part 1 or continue to Part 3!)

The Tube 'Glass'

Now that the base is done, the circuit works, and the rails are ready for soldering, set it all aside. Everything is for naught if it doesn't fit in the tube!

This video convinced me that this project was possible, and without his techniques, I never would have been able to make the tube. You may have seen it before - it's a nice, relaxing video of a gentleman who makes vacuum tubes by hand. It's really inspiring stuff; almost everything in his shop appears to be hand-made. I really recommend grabbing a cup of coffee or tea and giving it a watch, if you haven't seen it.

Flaring the Base

As a disclaimer, I should mention that while I did some cursory research, I'm not positive that everything I did here is completely safe. Look up safety information for handling and forming acrylic before continuing!

I bought 1 1/4" OD (1" ID) extruded clear acrylic tubing from McMaster-Carr. As an aside, I really recommend them for this sort of work. They're not always the cheapest, but their selection is huge, their selection tools are top notch, and you can almost always get a minuscule quantity of whatever you need.

Cut the tube a little more than twice as long as it needs to be. I don't have his nifty jig for spreading the base out, but I made due with my distant memory of the glass blowers at Hale Farm and Village. I have a heat gun for stripping paint, and knowing I had this project in mind, I got the good version with lots of different temperature settings. I've heard you only need 300°F to shape acrylic, but that's with putting it in the oven for a couple hours over a form. I need most of this to be unheated, and it's out in the open air, so I used 450+ on the heat gun. The base only needs reshaping, so a lower setting is probably better.

I just heated the end of the pipe, rolling it in my hands as I went to try to even out the heat. For the shaping, I used the rounded, outside edge of a pair of adjustable pliers. Remove the tube from the heat and roll it with one hand while putting the pliers inside the tube and gently flaring the end. Take it slowly and heat it multiple times, always working it until the plastic hardens up and doesn't want to be shaped any more. If you stop shaping too soon, it will tend to pull back towards its original shape (the same will happen when you heat it again, so don't be surprised by that). After you get a nice flare, heat it up one more time and gently press the flared end into a clean, flat surface. Rotate it around while eyeing it (or using a level, I suppose) to get the flare as close as you can to perpendicular to the tube. If the flare is crooked, it will never sit right in the union, so take as much time as you need here. Of course, it won't be perfect, and IMO that just adds to the 'hand blown' look of the bulb.

Once you have a suitable flare, sand it down to fit in the union. Be careful to keep the outside of the flare concentric with the unheated portion of the tube. There's probably a better way to do this, but I just used a coarse sanding wheel with my drill press set to its lowest RPM. Take quick bites out of the acrylic, and don't hold it against the wheel too long, or it will heat up and go liquid, gumming up your sandpaper. I checked both fit and concentricity using the union.

Rounding the Dome

I did this part much later, but in retrospect, it would probably be best to do it right now. When I made the bulb, I was not yet certain how long the rails would need to be. This put me in the awkward situation of setting aside the acrylic work for days to work on the circuit, then having to reheat the tube and work the end. Better to do it now.

This is where the vacuum tube video really helped. On my first tries on test pieces, I did it all wrong, and it just wasn't coming out well at all. I was about to give up, when I remembered the method he used—gave it a shot, and it worked perfectly the first time. Kick the temperature up a bit on the heat gun. We don't need to just deform the plastic now, we need it really ductile. Be careful, though - at ~650°F you can start to boil the plastic, which leaves little bubbles embedded in your tube as it cools. I got a few, but it doesn't look too bad. If I were to do this again, I'd attempt to do it at the same lower temperature that I did the shaping, but since I'd put off forming the dome, I was low on time and didn't want to mess up my half-finished tube in an experiment.

Slowly rotate the center of the tube in the heat. Get a feel for how far away each of your hands is from the heat gun, because it's easy to lose track of where you are and drift off center. As you rotate with your hands, occasionally lightly pull the ends from each other. You want to heat the center to plasticity, drawing the middle thin, until the two ends pull apart. Be careful and increase you rotation as the center starts to come apart - the thinner plastic will heat more readily, and this is when your bubbles form. The new ends will be ragged and brittle where it is thinnest.

Allow the plastic to cool completely. Acrylic is insulating, so this may take a while. Grab a file and carefully file the ends down to make a flat. It doesn't have to be perfect, but you're just trying to eliminate the bits of plastic that basically break apart at a touch. Be careful, but don't fret if you get some little cracks at the top. You're about to melt the ends again, anyway.

Return the rough end of the tube to heat. Heat the very tip, slowly working your way towards the bulk of the tube. The thinner plastic will pull in on itself, making more of a domed shape. Unlike the glass in the video, I couldn't get it to pull all the way in, so I helped it along. After the plastic stops changing shape readily, and to avoid bubbling again, I pulled the tube from the heat and just rolled it by hand on the clean workbench. Ideally, I would've had some sort of dishing form, but the flat table works if you're careful. The dome doesn't have to be a perfect hemisphere—what you're looking for is to close up the hole at the top, primarily, without pushing too much material into the rest of the tube.

To finish up the look of a glass bulb, cut a clean end in solid 1/8" acrylic rod. Heat the end of the rod until it melts and starts to deform a bit under its own weight. Don't be so worried about bubbles here, because you're going to deform it. Carefully, warm the dome of the bulb while you do this, too, but it doesn't need to be so warm that it will shape easily. Touch the melted end of the rod to the dome, push in to give it a good contact, then pull it away, giving a little twist. The end will pull out and give a nice little 'tail.'