Howdy from sunny/snowy Reno Nevada! I decided it might be a good time to document my build, and this seemed like the right place to do it. I'm a long time fan of the HAMB, and hopefully this build is HAMB-worthy. This build started after I received an amazing Christmas gift from one of my employees (Drew), a miniature toy steam engine: I've loved steam powered machinery since I was little, but this was the first time I'd had something steam powered to play with. I was hooked. This damn tin toy triggered a months-long, multi-thousand dollar build. Knowing that I lack the machining skills to make my own steam engine from plans, on Christmas Day I started browsing the internet for a suitable steam engine to power a small car. I thought it would be easy to source one, but after a couple hours of not finding anything I realized that most guys who are into steam aren't really into the whole internet thing. I'm not saying they are all old, but based on most of the websites I encountered, they all still have dialup. Ebay came to the rescue after setting a few automated searches for a week or so. I found a promising engine in Washington state, built by a gentleman with many years of steam experience. After sending some cash, the engine arrived via Fastenal freight about a week later: The design is from a marine-style steam engine from the early 1900's. Twin piston, dual action (steam pushes up and down on the pistons). 3" bore, 3" stroke. Depending on the boiler the engine has a theoretical potential of 7-10 hp. Doesn't sound like much, but steam is amazing when it comes to torque. Based on the bore, stroke and some 1800's steam power math, this engine should develop about 300 lbs/ft of torque at 1 rpm. Here's the engine running on about 60psi of compressed air: Next up was boiler design. I had a few design goals that led me to build an "Olfelt" style boiler: Safety (I didn't want to make a bomb), packaging, ease of fabrication, cost, weight and aesthetics. I ruled out "fire tube" boilers, like the ones in old steam trains mostly due to safety concerns. With a fire tube boiler, you are heating a large amount of water by passing your flame through tubes submerged in the pressure vessel. These work great, until you run low on water. If the fire tubes are not submerged they become extremely hot and eventually melt. Usually the engineer notices the low water level, panics because he's about to melt the boiler, so he adds more water. The water contacts the exposed hot steel, flash boils and blows the whole thing up. Blowing up is not attractive to me, so I went with a water tube boiler instead. Technically it's a hybrid of water tube and fire tube. My design heats a relatively small amount of water (about 2 gallons total) by passing water through copper tubes exposed to the flame. This has a few advantages over the fire tube design, namely if I run low on water one of many brazed copper fittings will fail individually, reducing the chance of catastrophic explosion. Also, if there is a failure I'm releasing the stored energy of a few cups of water vs. 20-30 gallons. Boiler fabrication started with a couple 3,200 psi rated nitrogen cylinders. Here is one of them after bead blasting the paint off and prepping for fittings: Milling ports for the steel nipples that will connect the copper coils to the steam drum: Many, many drilling, cutting and chamfering operations later: My attempt at "TIG on MIG" welding in an attempt to remove any porosity: I made the copper coils using a 3" piece of exhaust tubing clamped into my shop vice. I used 3/8" refrigeration tubing since it's very ductile and easy to work with. I considered filling the tubes with sand or salt and sealing them before bending to reduce kinks, but after a couple test coils I was satisfied with the results. Here's the partially assembled boiler system, minus the copper. I joined the steam drums (steel nitrogen bottles) with a couple pipes to keep the water level balanced between the two. I used a high-temp silver braze to join the copper tubes to the steel nipples. Brazing copper to steel is a huge pain in the ass. The copper melts only a couple hundred degrees above the melting point of the brazing rod, so you have to be on your game. I also learned that the more copper you add, the more heat you need. The conductive qualities of copper are pretty impressive. If I heated the steel nipple, the copper coils would suck all the heat out the assembly and redistribute. I ended up preheating the whole thing with a rosebud oxy torch to get everything to work. One side done, one to go: Finally got all the copper coils brazed in place. Now it's time to pressure test and see how good my welds/brazes are: My desired operating pressure is about 150psi, so I hydro tested to a little more than 300psi. I wasn't paying attention at one point and saw 400psi but everything survived. I found a few small pinholes in a couple joints so I re-brazed and called it done. No major issues! During the boiler design/fabrication process I was also looking for a good chassis donor. I considered building a chassis from scratch, but I always like to have a title in hand when heading to the DMV. It's a lot easier than doing a constructed vehicle title or whatever. Plus, I figured that whatever I found for a donor would add to the character and theme of the car. After a couple weeks I found a perfect candidate (a 1928 Model A, no body) for sale in northern California. Poor Drew went over the pass to pick it up for me (a 3 hour drive) and ended up in a huge snowstorm. The return drive was about 12 hours...whoops. Once off the trailer and in her new home I started putting parts in proximity to each other to get a sense for the packaging: Since I'm concerned about the potential lack of horsepower in the build I am trying to keep weight to a minimum. To set a baseline we put the 1928 Model A chassis on my Longacre race scales: 1,310 lbs overall. Not too bad, but not great either. I'll be removing the Model A engine, but the weight of the steam engine, boiler, water tank etc. could add up. We'll see how heavy she ends up.