The Ice King's Crown

My friends and I are big Adventure Time fans so I decided to make a prop from the show IRL. I made this back in February as a belated Christmas gift for my crazy Asian friend who bites people. Sorry I was in a rush to make this one so I don't have any in-progress photos.

Ice King (a.k.a. Simon Petrikov)

It's my take on the Ice King's crown. For the "gold" part, I first tried gluing plastic paint buckets together, but they were too thin. I ended up covering the outside of one bucket in Bondo and then cutting in the peaks with a jeweler's saw. For the jewels, I cut a positive mold for each one out of a scrap of cutting board, then pressed them into clay to make a negative mold. Then I mixed up some casting resin and red dye and cast the jewels. They were epoxied onto the crown before I locked them in with Bondo bezels.

If I were to do it again, I would use a more acute conic shape and make the peaks taller. I might also use fiberglass-reinforced Bondo and try a different gold paint. If I'm real adventurous I'll cast the thing out of scrap aluminum.

I've got some RepRap projects and another prop build in mind so stay tuned.

The Biggest Selling Point at the 2013 Washington Auto Show

Me and some foreign kid went to the 2013 Washington Auto Show in D.C. a few weeks back. Honestly, there wasn't anything spectacular...until we opened up the hood on the new Scion FR-S! There it was, sitting right on top of the engine: the oil filter!

Photo: Samin Emini

If you've ever changed the oil in a car, you'll appreciate the gift that Subaru has given FR-S owners. Oil filters are greasy, elusive, and tend to tighten themselves to a torque that no human can defeat. And on almost any other modern car, the oil filter is on the bottom of the engine mounted at an inexplicable angle with a skid panel or other parts obscuring its access. When you do finally manage to get it off, the residual oil sitting above the filter drains out all over your hands. The FR-S does you a huge favor by having the oil filter right there, right in front of you for easy access. Additionally, since it's on top, most of the residual oil will drain from it when the oil pan is drained. That way you don't get oil all over the garage floor. The only other time I've seen an oil filter this accessible was on an industrial diesel generator like this one:

On top of all that, they went with the classic form factor instead of Toyota's new plastic shell shit. I was pissed when I had to change the oil on a new Camry and discovered the new filters they're using. Instead of a metal, single piece filter, they chose a plastic shell with plastic threads that requires a special filter insert, and two different o-rings. It's okay to damage a metal oil filter because it's a consumable part, but if you break a plastic shell filter, you're dead in the water. Oh and it costs more. Who's bright idea was this?
Anyway the FR-S has other neat features such as rear seats that are extremely comfortable if you have no legs or head.

Also on display were some of the military's unmanned equipment, including some awesome shit from Boston Dynamics. Seriously if you haven't seen these before, take a look. They're nuts. First up was the RHex Rough-Terrain Robot:

The RHex just looks ridiculous when it's going full speed. I love it.
Next is another one of my favorites, the Sand Flea. That black rubber bumper is actually the foot of a piston that launches the robot over walls and up flights of stairs. It's one of those "Why didn't I think of that?" designs.

They also had a couple standard ROV platforms and a remote-operated mine-clearing skid-steer loader. Wow that's a lot of hyphens.

And last we have a deployable solar power station. I would love to design stuff like this for a living.

Santa's New Sleigh

How To: Classic Toy Car

Instructions in white.

Commentary in blue.

This project was inspired by MAKE Magazine's Fast Toy Wood Car article. Make's car uses layers of laser-cut plywood to form the body of their car. I liked the idea but wanted something more durable, something that would last generations of abuse, or at least a few hand-me-downs. My solution is to shape the car from a single block of wood.

Price: ~$20/car, cheaper if making multiple cars
Difficulty: Pinewood Derby
Time: 30-60 minutes/car, depending on tools used

Step 1: Tools/Materials
Tools:
-band saw/jig saw/coping saw
-miter saw/hand saw

In Pursuit of Human Flight

Last Friday, I drove up to Maryland to see UMD's Gamera II human-powered quadrotor. They are currently pursuing the Sikorsky Prize, established in 1980. Here's the team testing a new control system:

During this test, Gamera II flew for approximately 65 seconds, unofficially tying the endurance record that the team previously set. This flight time, plus the ability to remain within a specific boundary, satisfies two requirements of the Sikorsky Prize. Because the rotors are so close to the ground, the helicopter is benefiting from a cushioning effect of the air between the rotor blades and the ground. This effect will diminish exponentially when the team attempts sustained flight at the required 3 meters.

The helicopter transfers the pilot's pedal power by unspooling cable from pulleys, mounted on the shafts of each of the four rotors. Flight time is limited by the pilot's stamina and the amount of cable stored in each pulley.

The rotors are constructed of carbon fiber, balsa, and foam, and are covered in a plastic film.

All in all, it was a cool experience. I've never seen so much carbon fiber in my life! I look forward to seeing the team win the Prize.

IT'S ALIVE! (again): New Hotend Test

Last night I got the RepRap Huxley put back together and fired it up and now it's putting out perfect prints! My new hotend works without a hitch, I just had to tweak a few temperature values for the non-standard resistor. Here's the first test print:

In the above picture, you can see the new hotend block that I made. I'm a little uneasy about the exposed wiring; I'd like to make an enclosure for the whole hotend out of PTFE.

Also, I learned that at printing temperatures (200-300°C+), the adhesive on foil tape begins to boil and bubble out as a black liquid. It also puts out some nice white smoke that I probably shouldn't have been breathing in. 

I then attempted to print a lens mount that I had modeled months ago. The first part came out perfect:

It actually fit on my camera with minimal cleanup (I had to scrape off the tiny bumps on the bottom edge). If anyone knows what settings I can adjust in Skeinforge to get rid of those, your input would be greatly appreciated.

Anyway, so then I started printing the second part and promptly ran out of plastic, at 85% completion. What color should I get next?

Resurrecting the RepRap

It's been months since my beloved RepRap Huxley broke down (thermistor issues, what a surprise) and I haven't gotten around to fixing it until now. Turns out that somehow, while it was turned off for a matter of weeks, the hotend thermistor insulation managed to burn up and fry the thermistor. This is probably the third or fourth one to go out. I've known since I built the Huxley that the tiny thermistors and their hair-thin leads would be an issue, that coupled with the fact that I never got any PTFE heatshrink. This is a serious design flaw of the machine; if the thermistor, held in place by friction,  falls out of its hole in the hotend, it will register a temperature reading that is much lower than the hotend's actual tempurature. The software, trying to restore the hotend to the right temperature,  will then increase the current through the heating element until it burns through the insulation, causes a short, and sparks a fire (this has happened before).

So I decided it was time for a redesign. I ordered five thermistors from Digikey, this time opting for the larger through-hole type, in hopes that these would be more durable. My solution was to make a new block for the hotend. I already had a LOT of 6061 aluminum from my paintball marker builds and it was just a matter of hacking and filing it down to size. A milling machine would be a dream at this point.

I elected to change the placement of the hotend parts. I moved the thermistor to the opposite side of the heating element and removed material from the block so that only the bead of the thermistor would be inside the hole. This way, I wouldn't even need to insulate the leads. I decided to call it a night when we got to the point of tapping the hole for the nozzle; there was no way we would have metric taps. I would go to Lowes the next day and get the right size tap. Then my dad pulled out  a single stray tap from the drill bit drawer. It was metric. And it was the correct size! What are the chances of that? So I tapped the block and began reassembling the hotend when, to my terror, the brass nozzle snapped off. I then had to cut a slot through the block and the nozzle just to get the nozzle out.

This is my biggest issue with the RepRap project. Nearly every part must be special ordered, and from overseas most of the time. One piece can set your project back by a week, and shipping almost always costs more than the part.



Another week is gone and I just got my new nozzles (I bought two, just to be safe) in the mail from England. I put the hotend back together and here's what it looks like:

There's still the problem of fitting the resistors into the holes. It's pretty much trial and error by wrapping them in different lengths of Kapton and foil tape. It's an improvement, though. At least the thermistor won't be able to fall completely out of the hotend assembly as in the original design. Ideally, I would lock the resistors into place with set screws.

Tonight I will put everything back together and see if I can get a decent print.


Life update: Got an A on a Calculus 3 exam. Achievement unlocked.