A while back (few months ago) I took a chance on an eBay listing that, being the only bidder, I somehow managed to win.
This was a fairly large (3/4" bore) oscillator that had some rather unique features that attracted my attention.
First off, it was heavily logoed, with cast in, machined in, and decaled on identification markings.
The next sort of unusual feature noted was that it had no piston rod, but rather the lower skirt of the piston was cross bored to accept the crank pin directly, such that the lower cylinder wall had to be slotted to allow clearance.
Oh yeah, and the piston itself was some form of plastic rod stock. Perhaps Delrin, or possibly Nylon, or maybe even Teflon ..... or something else entirely?!?!
One other thing noted is that it seems to be a bit less than fully finished as the back side of the ports have not been tapped for any sort of fitting that could provide steam to the port face. Of course, it is possible that it is not steam capable and is only intended to run on air, such that the back side of the port holes are left untapped with the intent of just pushing the nose of an air gun up against them to facilitate operation, which I have done.
Depending on the type of plastic the piston is made from, expansion coefficients may well prevent it from ever running on steam.
The frame and cylinder appear to be a fairly rough sand casting with barely readable logos cast in, which was then machined to produce the necessary finished surfaces and bores, and also to mill in a logo on a curved surface.
Cutting to the chase, this was obviously a "school" project from a university engineering/manufacturing class, perhaps to give the students a hands-on experience with some different production methods such as casting and machining of parts from different materials.
In any case ...... here ya go:
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It should be made clear that Cal Poly and SLO represents the University of California at San Luis Obispo, beautifully located along the Southern California coast. Cal Poly being a reference to the schools original founding as the California Polytechnical college, which was designed to provide technical training to its students instead of simply just academics.
I really like that this comes from Cal Poly...a school dedicated to training young engineers for real world hands on careers.
Chunky fellow, rather unusual .