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Rix Air Compressor and Sourdough Bread


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I acquired this Rix 3 x 3.5 compressor while ago. The previous owner had managed to break it free, but it turned hard and would not make air and he was tired of tripping over it. Figuring it couldn’t be that hard to make it work, and it’d look pretty cool belted to an engine, I bought it. Finally after better than a year of walking around it, I found some time to mess with it, and as I thought the discharge valve was stuck. Admittedly, I haven’t been in deep in too many compressors, and I struggled to sort out the discharge valve.
At first it seemed obvious, under all of the rust that covered the cylinder head, there was probably a disc valve in the pocket under the valve spring. I filled the pocket with penetrating oil after a quick wire brushing and let it sit a few days. When I returned to the project, I was disappointed to see that while the excess penetrating oil around the head had soaked in, the level of the oil in the center where I thought the valve was had not moved. I broke out a pencil brush and chucked into the drill, hoping to dislodge enough rust to at least see what I was up against. With a shot of brake cleaner and a quick wipe down I could see that all of the loose rust had been removed, but still the valve wasn’t visible. Not wanting to break anything, it was decided the cylinder had to come off, and maybe the valve could be dislodged by pushing it out. The four cylinder retaining screws were removed and soon I was staring into the top of the mostly rust free cylinder, and still no sign of a discharge valve. Really, it can’t be this difficult, right? It seems simple enough, air enters the cylinder and it’s pushed out under pressure. The low placement of the intake screens is a dead giveaway to a ported intake design, but where in the hell does the air go after being compressed? Looking up the cylinder wall, I can see that the machined surface of the bore goes all of the way to the top, up to the cylinder so obviously the head comes off…or at least it wasn’t there when the cylinder walls were honed. My best guess at this point was that the cylinder head was threaded onto the cylinder like the glow plug on a Cox model airplane engine. A couple of taps with a punch on the raised ribs radiating outward from the center pocket moved the head, seemingly confirming my theory. Finally, maybe some progress! Alternating between shots of Zep Twister penetrating oil and light taps on the ribs the head was turning, soon I was able to have spun it a full revolution, but it wasn’t visibly unscrewing. After dousing the outer edge of the head with more Twister, I continued “unscrewing” the head. It wasn’t too long before the penetrating oil had broken enough of the rust down to the point where the head could be turned by hand, but it still appeared that it was not unscrewing. Using the wood handle of hammer, I gave the head a nudge outward from inside the cylinder; it darned near fell out and the mystery was solved. What a cool design, a ported 360 degree intake, very similar to an old two stroke Jimmy, and the cylinder head doubling as the discharge valve!
Motivated by my progress to find out more about this intriguing piece of Iron, I started my web search. Quickly it was easy to see that the company, in some form or another, was still around but little other info was there. With nothing to lose, I penned a short email to the “contact us” link on the company web site asking for a little info, if they had any. Soon, I had a response from Eric, a warranty rep with Rix asking me for some further detail and a couple of specific pics to better able to ID what I had. Like me, he was thinking the compressor was of 1920s vintage, but thought he could do better if I could get him the dimensions of the bore and stroke. The next day, I received an email back which included more detail than I ever could have imagined. This was the only 3” x 3.5” pump built that remained on the West Coast during a two year period. The other few that were built were shipped out of state to Wisconsin and Texas. It was sold to the Larraburu Brothers Bakery in San Francisco on November 10, 1926, although it was “built from parts” sometime in 1925. Eric also commented that it was odd that the compressor was sold “off the shelf”, as Rix was building every unit to order at that time.
Long before hippies and crap all over the streets and sidewalks, San Francisco was known for sourdough bread, and Larraburu Brothers was famous for theirs. Opened in 1896 and located at 365 3rd avenue, the Larraburu Brothers Bakery lasted until 1976. What could an old air compressor have to do with the production of sourdough bread? A quick message to a Larraburu family member/historian on Facebook and I and I had my answer; it was probably used to service the fleet of delivery trucks that were used to deliver the bread. Okay, well that’s not as sexy as the compressor somehow playing a part in baking sourdough bread, but then again I guess greasy compressed air wouldn’t do anything good to the taste of it either.