more hot wires

The 15V power supply didn't work out, apparently due to some kind of current limiting circuit, so I cracked apart the 18V wall wart to find that a fuse had, in fact, blown. Deciding that a variable power supply was required, I built a simple one from a triac dimmer switch, the transformer from the busted 18V unit, and a fuse. This AC power supply works like a charm.

Subsequent experiments with steel wires revealed significant inadequacies. One problem was that flakes of some dark material (I assume an iron oxide) sputtered off, deteriorating the wires. Another problem was that the cool parts of the wire in contact with ice didn't heat back up enough to cut at a reasonable speed. Steel's relatively high temperature coefficient of resistance prevented the cold parts of the wire from producing very much heat. Fortunately, the nichrome wire performed better, and it didn't break unless I turned up the power supply higher than necessary.

With a little downward force provided by gravity, the nichrome cutter was able to slowly but easily slice through a 10 pound block of supermarket ice (about 6.5" thick). I didn't time it properly, but I think it took about a minute to penetrate the entire thickness of the ice block. A very small amount of refreezing took place in a couple spots, just enough to keep the slab from falling to the floor.

I was able to remove the slab cleanly with a whack from a rubber mallet. Hitting the ice with a mallet wouldn't be a good idea at very cold temperatures, but the refrozen bits could probably be broken safely with a stronger, cold wire. Maybe refreezing could be completely avoided by using a hotter or thicker hot wire or by passing something (teflon strip? cold wire? another hot wire?) directly behind the hot wire.

Gravity turned out to be a poor guide. If we were to use this technique for slab cutting, I guess we would need rails to guide the wire terminals.

Using the nichrome cutter, I carved a freehand trifle for Emily out of the small slab. Due to small inconsistencies in the perpendicularity of the cuts, I wasn't able to completely remove the carved piece from the slab without breaking something. For this kind of work, a stationary wire design would be better. I'll have to experiment with increased wire tension.

Hot wire cutting is clearly a valuable ice carving technique. While certainly not supplanting the chainsaw or die grinder, the hot wire is able to make precise cuts not possible with the more traditional tools. Although my first design was a hand-held tool for freehand cutting, I think that a stationary, vertical wire would be more useful for detail work. I also think that a slab cutter employing a long wire could be practical.

I'm still concerned about:

• electrical safety: longer wires require higher voltage
• cutting speed: it is very slow, although slab cutting doesn't need to be fast
• refreezing: after cutting the supermarket block, I'm feeling more confident about this one
• wire breakage: I'd like to try thicker nichrome and possibly other materials
• ice cracking: we'll have to test this at cold temperatures

music box

The model Lars sent arrived on Monday, and it is fantastic. He proposes to build a working music box out of ice for the Single Block Classic at Ice Art 2007. The model is finely constructed and works flawlessly. A ratchet prevents the crank from being turned the wrong way. The crank turns a cylinder by way of two gears. A pin on the cylinder lifts and drops a hammer that strikes the bottom edge of a vertical chime.

The model only plays one note, but it will be simple to add a small number of additional chimes. We'll make solid, rectangular ice chimes as, like Lars, I have no desire to make giant, hollow cylinders out of ice.

One question remains: What tune shall it play?

this is a drill and you will be receiving candy

Today at work, one of our hospitals performed a surprise anthrax exposure drill. I saw a flier entitled "this is a drill and you will be receiving candy" that explained the event. Two thousand bags of candy were distributed in lieu of antibiotics. While I personally feel that anthrax is one of the less likely agents of destruction that could affect our facility, it is certainly good for hospitals to prepare for all sorts of health disasters, and the use of candy was a great way to encourage participation.

ovation awards

Congratulations to my big brother, David O, for winning the Ovation Award for Sound Design for his work on Ubu Roi. He was also nominated for his Music Direction of The Wild Party.

blog blog

I've decided to try blogging about more than just mechanical ice sculpture. Does anyone care? Probably not. But, hey, blogging is more fun than watching television. Anyway, if you want to just read about the ice stuff, click on ice in the Topics sidebar.

documentaries

We enjoyed taking part in Sandra Skibsted's documentary production at Ice Art 2006. The last I heard, Sandra was shopping screeners around to various broadcasters in the UK and was in the process of hiring an editor. Hopefully we'll get to see it before long, although I wouldn't be at all surprised if Lars and I end up on the cutting room floor.

Not so with next year's film! My friend, Dan Gottesman, has decided to create a documentary about Lars's and my adventures in mechanical ice sculpture and our quest to build a working ice clock. He is teaming up with Brian Kallies, video producer, and Tamara Kubacki, folklorist, for the endeavor. They hope to make the trip to Fairbanks for Ice Art 2007 and 2008. Crazy.

Dan, Brian, and I played together in a fun band, Flocos, in Chicago several years ago. It's been a long while since Flocos fizzled, but we still can't bear to take down the web site.

error analysis: drill bits

The spade bits I made for the 2006 event just didn't hold up. The steel blades rotated out of position and bent, and the nuts and bolts broke, bent, or simply came unscrewed. They worked briefly but couldn't withstand sustained use. I should have:

• used thicker steel,
• ground the cutting edge symmetrically, and
• welded instead of using nuts and bolts.

Lars says he'll try to do just that and make us a nice set of giant spade bits for the 2007 event. With a 3/8" shaft, I think they'll hold up well and will hopefully last for many years.

Another option would be to use commercially available forstner bits, but a set of very large ones would be quite expensive. We prefer to make whatever we can and save our money for the things (giant chainsaws!) that are hard to make.

masquerade

Lars took a break from building a "walk off" runway at Belfair for the upcoming Zoolander-themed masquerade. We talked on the phone for the first time in months and compared notes in preparation for Ice Art 2007. He is sending a model of his design, and it should arrive tomorrow.

hot wire ice cutting

The high E string on my little guitar was sacrificed Wednesday night for my first attempt at hot wire ice cutting. The strings needed changing anyway as they have miraculously survived more than 2.5 years of frequent travel without a case. With an old cell phone charger (5.7V, 800mA) as a power source, the wire warmed up enough (maybe 150°F) to easily cut through foam peanuts, but it did nothing to a block of ice.

More electrons were required, so I dug around until I found a bigger power supply (18V, 1111mA) from an old DSL modem. With that much juice, the wire became red hot in less than a second! I gently cut through the corner of a 10 pound ice block and noticed that the wire went dark where it came in contact with the ice. After penetrating about an inch, the wire broke. It seems that it became extremely fragile at the edge of the ice where there was a high temperature differential. After it broke, I noticed that the ice had re-frozen behind the wire, leaving the wire trapped within the ice.

Encouraged, I glanced around for some sturdier wire and decided to try some 1/16" picture hanging wire. This turned out to be a poor choice as I stupidly failed to measure the wire's resistance prior to hooking up the power supply. It didn't heat up at all, and the power supply completely stopped working. Oops. I then discovered that the wire had no measurable resistance, so I had probably blown a non-serviceable fuse in the power supply by creating a short circuit.

At the office the next day, I happened upon Noel throwing out a 15V 1.2A power supply with a damaged DC cable. Perfect! I also picked up some nichrome wire and a couple sizes of steel wire at a hobby store. Hopefully I'll be able to come up with an effective but less fragile combination of power and wire.

error analysis: blogging

I think I did a fair job as a first time blogger capturing the events of the week, but I certainly could have done better. I didn't blog or even photograph a whole bunch of things that I could have:

• chainsaw modifications
• ice chime experiments
• Sandra, Patty, and Annie's documentary production
• competitors and their tools and techniques
• fans who visited us repeatedly
• the lathe in action
• the gear tooth cutter in action
• the sub-zero natural ice lubricant showdown
• Wednesday night's pizza box design session at Belfair
• observations on day one of the multi-block

My process for posting photographs was way too slow. I had to take the camera back to Belfair (we were only there for a short time each night), transfer the images to my laptop, select good ones, edit them with the GIMP, copy them to a flash drive, take the flash drive to Ice Park, and upload them to the blog at a convenient time at the warming hut. All of this activity created about an eighteen hour delay. I should have used ImageMagick or some such thing instead of the GIMP; since 90% of the image edits were just resizing and occasional rotation, batch processing from the command line would have saved time. The greatest benefit would have come from being able to upload photos directly from the camera to the blog on the warming hut computers, but my need to edit the images prevented me from doing so. (Also, I never tested connecting my camera to a warming hut PC; it might require special software or a separate CompactFlash interface.) I could probably download Windows binaries of ImageMagick or maybe even use a Linux LiveCD. Another option might be to use Flickr or a similar service.

it's been too long

Yikes! It's been over seven months since my last post. I guess we've been up to other things, but the return of cold weather is making us think of ice once again. Lars tells me he has a working model of a possible design for Ice Art 2007. I can't wait to see it!