www.youtube.com/watch?v=WC2B-Y1JrwU

This is certainly not an over-engineered machine. Rather, it is designed to be just enough — finding a careful balance between cost and functionality — and that is what makes this such an elegant solution. The design of the MakerBot is very clever, primarily using laser-cut plywood that bolts together. The X and Y sliding suspension parts are ground rods and plastic bushings, which is a little loose and may be a source for some inaccuracy… we’ll see when I get it fired up.

The best part about the MakerBot is its open-source nature and the community of hackers that are constantly tinkering with it. I can already see room for improvement, and I plan to get busy on it too. For starters, I moved the Plastruder PCB off to the side of the assembly so I can see the mechanism working.

Also, I cracked several of the acrylic Plastruder parts by tightening down too much on the screws. I might have chosen polycarbonate instead ($$) for strength reasons, but I understand the cost trade-off.

I can’t wait to start making stuff… this is an awesome little machine!

What’s cooler than transformers? A Cupcake CNC transformer with a Bre head? This is a fully articulated assembly that transforms from a Cupcake CNC to a Bre-bot.
I started with a snap-together design (see the attached concept sketches) but migrated to a bolt-together kit or various reasons. The final design allows for fine adjustment of the joint tension so the transformer can stand in any position but still be movable, positionable, transformable!

Buildable in two Cupcake CNC builds (see screenshots), this transformer is assembled with commonly available 6-32 (3/4″ long) flat head machine screws and corresponding lock nuts. NOTE: may be substituted with M3.5 x 20 screws and nuts. 15 sets of screws and nuts are required.

Download the .stl files at Thingiverse.

UPDATE: Thanks a bunch to Frank for printing one!

UPDATE: Here’s another print:

I made the boards the same way as before, except that I tin-plated the finished boards with Tinnit to protect the copper from tarnishing and to improve the solderability.

For this batch of boards I decided to finally try my hand at reflow soldering, using the skillet method described by the Sparkfun guys. I bought an inexpensive skillet at Target, an infrared thermometer at Lowes, and some no-clean solder paste. The solder paste came in a syringe package but didn’t come with any needles, so I squeezed a little paste onto a paper towel and carefully dabbed it onto the PCBs with a toothpick. Using a pair of tweezers I placed each LED into position and pressed it into the paste, which held the component fairly well.

Before trying any soldering I looked up the reflow profiles for both the solder paste and the LEDs, and experimented with the skillet to see what settings would yield the target temperatures. I may one day build an Arduino temperature control for the skillet to more precisely control the profile, but I think these reflow characteristics are pretty flexible and for now it’s working just fine.

I put the PCBs into the middle of the skillet (I got wildly different temperature readings from different spots on the skillet) and turned it up to “LOW”, watching the temperature with the thermometer. As the temperature leveled off at around 165°C the boards began to smoke and I turned it up to “MED”. Within a minute or so the solder liquified and flowed nicely, in some cases shifting the LED into perfect alignment with the solder pads (apparently a result of the solder’s surface tension).

I made breakout boards of several different LEDs: “warm white“, “ANSI 2700K white” (an even warmer white), “amber“, and red, green and blue. After the skillet reflowing I hand-soldered on a couple of header pins for the breadboard.

This breadboard setup allows me to swap out different combinations of LEDs to evaluate the color of the light (here I have six 2700K Rebels installed). For this mock-up I used a 24VDC desktop power supply powering a BuckPuck LED driver, switched with a momentary pushbutton. I’m getting closer to the color temperature I want, but right now these are all on (full power) or all off. The next step will be PWM control over individual LEDs or groups of two or more to start precisely dialing in the settings.

It turns out that making seltzer at home is very easy, and once you have the basic equipment the cost-per-bottle is extremely low. Here’s how I set it up:

The tank and regulator kit are from Micromatic. The rest is just a handful of fittings from McMaster-Carr, screwed into a hole drilled into a seltzer bottle cap. Here’s the parts list:

* you may need to turn this in for a full tank, although some places will fill your tank while you wait
** I bought a good one, you can get these cheaper
*** unfortunately you sometimes have to buy 10 packs (or more) from McMaster. You can get individual hose clamps from your local hardware store.

Here’s how it goes together:

I drilled a hole in the cap (#10) that was just big enough for the threaded end of the coupling socket (#8) and assembled them together with the nut (#9). I used teflon tape in between parts 6 and 7. I also use my CO2 bottle for a keg when necessary, so I got a second set of part 6 and 8 and attached it to the hose coming from the keg tap. This way I can connect and disconnect from one system to the other.

One thing I learned, and this is VERY IMPORTANT: Apparently there is a chemical reaction between the CO2 dissolved in water and copper (or copper alloys like brass) that creates a toxic substance that will make you sick. Never use brass or other copper-based fittings with seltzer! All of these fittings (or at least the ones that will be in contact with the seltzer for any length of time) are either zinc-plated steel or stainless.

The carbonating process is simple. Fill an empty bottle with the liquid of your choice and refrigerate it. Replace the cap with the special one you made and attach the quick-disconnect hose to it. Make sure the shutoff valve on the regulator is closed, then slowly open the main valve on the tank until the regulator shows pressure. Adjust the output pressure to about 45psi and open the shutoff valve, pressurizing the bottle. Now loosen the cap on the bottle just slightly while squeezing any air space out of the neck of the bottle, then tighten the cap. This will purge any air from the bottle and replace it with CO2. Now shake the bottle vigorously for about 20-30 seconds; this will help dissolve the CO2 into the liquid faster. Shut off the CO2 at the regulator and disconnect the hose from the quick-disconnect fitting. You can now remove the special cap (slowly, the contents are now carbonated!) and replace it with a regular cap.

So on the first day I made seltzer water. On the second day I carbonated apple juice, grape juice, and Gatorade, and ended the evening with a carbonated vodka martini (nice!). What else can I carbonate?

I designed the board in Illustrator and laid out several together on a page, then printed it onto a sheet of toner transfer paper (from Pulsar). I laminated it to a copper-clad board and ran it through again with a “white TRF foil” as an etch-resist layer, as the toner alone tends to be somewhat porous.

I then etched the boards with ferric chloride in a Tupperware dish floating in hot tap water in the bathroom sink, agitating the dish continuously.

After about 25 minutes in the etchant I rinsed the boards, drilled the holes, divided them up and removed the toner from the remaining copper with lacquer thinner and a scotch-brite pad. I soldered the LEDs onto the board, along with a female header to connect wires to. For testing purposes I connected two C batteries together and plugged them into the header.

Luxeon Rebels are designed to dissipate heat through a large “no connection” solder pad directly under the chip. There are specific guidelines for the design of the PCB to draw this heat away from the LED which include a multitude of plated vias to increase the copper surface area. I’m unable to create plated vias in my homemade boards, so my intent is to mount the board to an aluminum plate, using an aluminum machine screw to draw the heat through the hole in the middle of the board.

I learned some important lessons from this first attempt. The main problem is hand-soldering these tiny surface-mount LEDs to such a large copper field, which resulted in a sloppy, lumpy mess of solder. I also realized that I may need to experiment with other combinations of LEDs to get the color right. This first try produced a pleasant white light (and yes, red, green, and blue light does combine into white…I know the theory is fundamental but seeing it happen before your eyes is pretty exciting!) but compared to incandescents and even some of the warm CFLs in my house it still looks very cold.

A good first effort, with room for improvement…

CAD files:
smoker.stp
smoker.igs
wood_rack.stp
wood_rack.igs
charcoal_basket.stp
charcoal_basket.igs

And here’s an unmodified 55 gallon drum model (minus some of the details, like lid and caps, etc.) in case you want to create your own design:
55gallondrum.stp
55gallondrum.igs

Here’s the bill of materials:

I thought about doing an battery-powered electric conversion, but quickly found that the components alone would run me over $1000. I found a guy in Minnesota that did a cool corded electric snow blower conversion that could be quite inexpensive, but I would really want the portability of battery power.

So I gave up the ambitious plan and bought a replacement Tecumseh engine from  Small Engine Warehouse, which I recommend for this kind of thing. I couldn’t find a direct replacement for my machine on their web site but the guy I talked to on the phone gave me three different options. I was disappointed about the electric plan not working out so I upgraded to this 11hp beast:

It took two trips to the local lawnmower place — I couldn’t get the sheave off the old engine and then found the traction belt was worn out — but it bolted right on and fit perfectly, if a bit tighter than the old one. We still have some snow on the driveway so I took it for a little test spin. I was expecting to be launching snow onto the neighbor’s house with all that extra horsepower, but the snow is now icy and chunky so I wasn’t getting the distance I was hoping for. Next fresh snowfall I’ll see what this baby can do.

The Selleck Striker ready for action.

Lisa about to show it who’s boss.

Beer pong!

That’s a lot of facial hair.

There’s something special about creating useful objects. A smoker is a nice combination of supremely useful (preparing sustenance) and slightly frivolous (do you need a smoked pork butt to survive?). There are certainly faster and more efficient ways to cook food, but damn smoked meat is good.

I looked around at commercial smokers and custom hacks and talked to a few connoisseurs, and decided the Weber Smoky Mountain was a good design to start from. It’s simple and effective, and in the end it mostly convinced me that the design need not be complex.

Something appealed to me about using the iconic 55-gallon drum as a building block, so I went out and bought a couple from the local scrap yard. One of them even got immediate use as a beer barrel at Crushtoberfest!

A little sketching on different configurations, and I decided a ‘T’ shape would be simple, stable, and functional, and provide plenty of opportunity to practice the MIG on some thin sheet metal. I laid it out in CAD, which made it easy to generate the intersecting curve between the two barrels.

I printed the curve at full scale and wrapped it onto the barrel, traced the curve, then cut the barrel with a jig saw. The first dry fit was amazingly close (way to go, CAD!) but there was still a lot of grinding here and there to accommodate the ribs in the barrels.

I measured and marked the door openings on the barrels and cut them out with the jig saw.

The next step was grinding the paint off. The last thing I wanted was burning paint fumes getting into the food, so every bit of paint needed to go. If I were to do this again I would find another way… sand blasting, chemicals, burning it off, etc… anything but taking it off little by little with an angle grinder. I’ll admit the Gator brand paint & rust remover discs I found at Lowes were very effective (if a bit pricey at 9 bucks a piece). But my shop is now coated with a thin layer of green paint dust, much of which ended up in my nose and likely my lungs.

On the first day of grinding I wore a respirator and glasses but nothing else. After washing my hair three times in a row to get the paint dust out I learned to don more protection. For the insides of the barrels I also used an LED headlamp.

As the barrels were made of surprisingly thin metal (20 gauge) the door openings needed to be reinforced with some angle and rolled sheet metal strips, which were plug welded from the outside and tacked from the inside.

The doors also needed reinforcement, in the form of sheet metal ribs tacked onto the undersides.

I welded small pads onto the barrels and doors for the stainless steel hinges. These pads were ground flat then drilled and tapped.

After grinding the rest of the paint off I welded the two barrels together. This was a challenge, since the metal was so thin and the fit was far from perfect. To prevent burn-through and warpage I used a “stitching” technique where you put a quick tack weld across the joint, wait a second or less and put another tack next to it, continuing like that for about an inch at a time. Apparently this puts less heat to the metal than a continuous bead, but the end result looks very similar. With a little practice I was even able to bridge relatively large gaps between the barrels with short, controlled beads that build on each other, kind of like ants crossing a stream.

I shopped around looking for off-the-shelf replacement grates that would work but none of them were big enough for this guy. So I bought about 80 feet of 1/4″ diameter 304 stainless rod (from onlinemetals.com) and cut it to length on the abrasive chop saw. I scored a piece of 1x pine on the table saw at the proper spacing to use as a jig, and clamped the rods down. The MIG would have been perfect for welding the grates, but I would have needed to buy stainless wire and a separate tank of tri-mix gas (65% argon, 33% helium and 2% CO2). The stainless itself was already pushing my budget, so I bought a handful of stainless welding rods and used the arc welder.

Next I drilled holes for the dampers– two sets of three holes at the top and two sets of four holes the bottom. The top ones were made like typical grill dampers with a round rotating plate. The bottom ones needed to be on a curved surface, so they slide along the surface rather than rotating.

In both cases the moving damper is retained by screws, so I drilled holes and tacked some steel nuts behind them.

I then drilled a series of holes to allow the smoke and heat into the top barrel. My step drill bit did an amazing job, but the cordless drill still went through two fully charged batteries getting the job done.

Next I tacked on some small support tabs for the grates and six small sections of square tube as feet.

After a thorough deburring, wire-brushing and degreasing with alcohol, I set about applying a high-temperature grill paint. There are several available but Rustoleum High Heat Brush On was a) available at Lowes and b) didn’t require curing at a high temperature like most of the products I found online. Unfortunately it only comes in black, which is actually slightly brownish. They recommend only applying one coat, which I agree with after trying to touch up a few spots after drying, resulting in some weird gloss differences. I then tried the spray can version of the same paint, but found it to be flat finish (vs. the brush-on which is satin). The lesson here is get it right with the first coat because you really can’t go back and hit it again.

While the paint was drying (24 hrs… it’s oil-based) I fabricated some handles out of a 1″ maple dowel. I don’t have a wood lathe but the metal lathe did the job. A few coats of Polycrylic and they’re ready to assemble.

The smoker can be used in one of two different ways– with charcoal in an expanded metal basket or with wood on a traditional fireplace grate. I suppose I could retrofit some gas burners or even electric heating elements, but that’s a project for another day.

And last, final assembly. I bought a 3″ smoker/grill thermometer online, and used some nickel-plated chain for the lid stays. I also fabricated a sheet metal “drip tray” to cover the holes under the food and deflect some of the heat.

I figured my brother-in-law Pete would make much better use of this than me, so we gave it to him for Christmas. Here he is opening it…

]]> http://jmillerid.com/wordpress/2009/12/55-gallon-drum-smoker/feed/ 58 http://jmillerid.com/wordpress/2009/10/crushtoberfest-promo-video/ http://jmillerid.com/wordpress/2009/10/crushtoberfest-promo-video/#comments Thu, 29 Oct 2009 15:46:46 +0000 joel http://jmillerid.com/wordpress/?p=158