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Let’s take it apart

The Latest from The Skunk Works


I’ve recently found myself in need of an air compressor larger than the one I currently use. After a bit of poking around on my favorite marketplace (eBay), I ran across a manufacturer of compressors within easy driving distance (Dayton, OH). I had a 5HP engine sitting around and decided to put together a compressor.

The compressor I picked is a 3 cylinder 2 stage from Eaton Compressor rated at 16SCFM@175 psi and 18CFM@100 psi and should run with a 5HP motor. Since the whole point of this exercise is to get a compressor suitable for sandblasting at a price that won’t break the bank, this fits the bill nicely. As a bonus, this particular compressor has concentric ring valves and head unloaders.

The story is that ring valves are better than the reed valves that most smaller compressors use. The head unloaders are handy because they can force the valves open when not compressing, allowing air flow to cool the compressor. Since I’m powering this with an always-running gasoline engine, the head unloaders are a good feature. Yet another nice feature is the ability to service the valves without pulling the entire head off of the piston. I hope I don’t have to use that one.

Motor and compressor sorted, I needed a frame on which to mount everything. Fortunately, I had a source of free steel. After digging through the steel pile, I came back with some C6x10.5 and C3x5 material. I started by getting a general idea of what size I needed the frame to be.

I tried to leave plenty of room between compressor and engine not only to make assembly and service easier but because I plan on putting spring loaded idler in between engine and compressor.

It wound up being about 16″ wide and 34″ long. I was initially planning to miter the ends of the steel and turn the flanges inside to build the frame. After a little thought, I decided instead to still bevel the corners on the long sides with the flanges out allowing square cuts on the short sides with the flanges in. This makes the joints at the corners easier as well as the joints inside the frame.

I made the cuts with an oxy-acetylene cutting torch using a short piece of steel channel as a straightedge. After making the cuts, I had to do a substantial amount of grinding to smooth up the cuts and get them to exactly the lengths I wanted. In the photo above, you can see that I’ve turned the flanges out on the long sides and in on the narrow ones.

To get the top flat, I clamped the frame rails to pieces of channel. I used a square to make sure the ends of the rails matched on at least one end. I then fit in the ends and welded everything up.

I completely welded the outsides of the joints at the corners and ground them smooth. I also made short welds inside the corners. This was my first good shot at SMAW welding and I wound up doing a substantial amount of grinding, rewelding and more grinding.

The engine will sit on two C3x5 pieces welded between the long C6 rails. Since these are smaller and thinner members, I cut them with a cutting wheel on the grinder.

The compressor itself will sit on two long C3x5 members supported by the frame on one end and share the engine mount on the other.

More to follow.

posted under BuildIt, Equipment

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