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Vintage Ingersol-Rand 3-R-36 Radial Air Compressor
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Yup. This is an Ingersol-Rand 3-R-36 "Spot Air" Radial Air Compressor.
Ingersol-Rand built these awesome radial engine air compressors in the 1940s and 50s. The six cylinder radial engine uses three of the cylinders for power and the other three to compress air!
The majority of these units were sold to the railroads and used by crews for track repair. They weigh in around 250lbs and were rolled around using a wheelbarrow-like attachment that I do not have. (I have mounted casters to the base to make it easier to move around the shop).
The three cylinders that make the power have a 3.125″ bore with a 2.5″ stroke and the “compressor” cylinders have a smaller 3″ bore with the same 2.5″ stroke. The carbureted engine has one crank pin, a master rod, five articulating rods, and three cams. Spark is provided by a magneto.
It can develop 80psi of working pressure and makes around 36cfm of air.
These compressors are straight piped with no mufflers, so it is loud, and it sounds like a smallish version of an old "round engine" airplane, especially when you goose the throttle.
This engine is in remarkable shape for it's age and runs good. It can be a little tough to start with the pull rope, so I've made an adapter that you can put into a drill to turn the engine over and start it almost effortlessly. The factory maintenance plate is still present and readable, and the fuel strainer has a new fuel bowl.
These compressors were not designed with a holding tank. The two coils of pipe or tubing you can see at the bottom of the unit are basically a pressure manifold. There is a blow off valve that actuates once 80psi is reached in the manifold moments after the compressor is started. In reading stories, the men on the railroad would stand at the ready with their equipment, and as soon as the compressor was fired up, their tools jumped to life. Without building air in a holding tank meant immediate action for the tools.
The engine is air-cooled and has a crankshaft-driven fan that spins inside the shroud at the base of the unit.
This vintage compressor is a rarity, and the only one I've ever seen in person. It is quite the conversation piece, and is so cool to actually run. With the exception of the low-boy wheelbarrow cart to move it, it is all there and runs very well. It would be a great addition to someone's collection, a candidate for restoration, or a tool for actual work (I used it to run mechanic's impact wrenches in the field).
I am trying to downsize the amount of equipment in my shop, and have reluctantly decided to part with this very unique piece.
Completely restored these go for upwards of $4k. This fine example can be yours for $1500/obo