Compressor Refurbishment – Part 2

Time to tear down the compressor itself. Of course, I waited until I got stuck to find some directions, so this may not be the most sensible order of things, but here we go.IMG_2337.JPG

I started by draining the oil and removing the oil filter. This unit conveniently has a length of pipe that takes the drain plug over the edge of the tank deck. I’m not sure if that’s present on all units, but certainly handy (and an easy install if it’s missing).

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Wow that oil looks gross. Clearly has both water and rust in it. The open bottle on the bottom of the picture is underneath the oil drain, I should have pulled a bin out and put it under the filter location, but I didn’t realize how much oil had been forced up into the hydraulic unloader when I ran it.

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Pulled off the crankcase cover — look at that seal. These are all paper seals, and they are tough. You can also see the crankshaft and connecting rods chilling in there. From here I took a winding detour that included pulling off the hydraulic unloader, unbolting the head, rebolting the head back on, putting the hydraulic loader back on, then using this guy’s trick to get the last connecting rod bolt out.IMG_2523.JPG

Everything is out now, except the crankshaft. You can kind of see the bend it in here. While it was still installed, I decided to measure how bent it is. Pulled out my Noga indicator base (possibly the greatest invention since sliced bread) and popped a cheap Fowler indicator into it, resulting in around 125 thousandths of runout — in other words, 1/8″!

There are a few options at this point:

  1. Buy a new crankshaft. I haven’t asked Quincy or one of their distributors for a quote yet, but some quick trips to my favorite sites for this project (and most of my projects, honestly) — Practical Machinist and Garage Journal — suggest it’ll run $800+. Thta’s more than I’m willing to spend, considering some patience would probably turn up a 325 with a good crankshaft to drop into this for less.
  2. Try to bend it back with my hydraulic press. This seems like a bad plan, as it’s a cast iron part (note the texture of the unmachined surfaces). It will probably crack. That also means I can’t…
  3. Weld a new shaft on. I could braze one on, but I don’t have brazing equipment or any experience brazing. This is a fairly tight tolerance application, so I’d rather not try something new this time.
  4. Turn the end of the shaft down so it’s straight, then make a spacer to fit the pulley back on.

I’m going to start by trying number 4, which means checking whether this thing will even fit on my tiny 10″x33″ lathe, and then figuring out how to get it mounted for turning.

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