{"id":2627,"date":"2009-01-26T17:31:07","date_gmt":"2009-01-26T22:31:07","guid":{"rendered":"http:\/\/toolsofrenewal.com\/?p=2627"},"modified":"2009-01-26T17:31:07","modified_gmt":"2009-01-26T22:31:07","slug":"my-degree-may-have-to-be-rescinded","status":"publish","type":"post","link":"https:\/\/toolsofrenewal.com\/?p=2627","title":{"rendered":"My Degree May Have to be Rescinded"},"content":{"rendered":"

Compressor Confusion<\/em><\/p>\n

Figure this out for me. I’m elaborating on an earlier post.<\/p>\n

The classic air dryer for cheap metalworkers is the Maxhootue\/Harbor Freight job. Same compressor, different sellers. “Maxhootue” is an Ebay user who sells them. They are rated up to about 21 CFM @ 140 psi. I keep my compressor’s pressure switch set at 175, and I never raise the output pressure above 125, although I suppose there is no reason why it couldn’t pump more than 21 CFM at the lower pressure. It’s probably at 90, now that I think about it.<\/p>\n

I don’t really know how much it blows. It does 17.4 at 175. Presumably, the pressure and volume relationships are linear and so on (Ideal Gas Law), so you would think it would go up to maybe 25 CFM at 125 psi, with nothing connected. I am too lazy to use “calc.”<\/p>\n

These things are made in China, but everyone, without exception, seems to like them.<\/p>\n

Right now–do not ask me why–Grainger is selling a bigger drying machine for the same price as the Ebay job. It’s a Speedaire. Probably also made in China, but somewhat more reputable, and there is a local dealer I can raise hell with if it craps out. The Speedaire will do 40 CFM at 175 psi.<\/p>\n

The odd thing about these machines is that they seem to work better at higher volume rates. It’s as if the big thing limiting the capacity is the compressor, not the dryer. Jack up the psi, and you get more CFM, and the dew point remains the same. <\/p>\n

Okay, wait. If that’s how it works, then either compressor is fine for my needs. The figures must describe the unit’s ability to pass air, not its cooling ability. That would explain why more pressure gives more dry air, with no penalty for shoving more molecules through the system.<\/p>\n

Now my head hurts. What if my compressor blows LESS air at 125? If it works the same way as the dryer, that’s what you’d expect.<\/p>\n

Maybe I need to put bigger fittings and a bigger hose on this thing. Curtis recommends 3\/4″ pipe for 20 cfm.<\/p>\n

The Curtis materials say this thing blows over 16 cfm pretty much regardless of pressure, so I guess the 125 psi figure (assuming I’m not choking the machine) is about 16. How can that be? You would think it would suck matter in at the same rate, all the time, so it should also blow it out at the same rate, so you would think lower psi would equal more CFM. BUT APPARENTLY NOT.<\/p>\n

Hmm…if they’re measuring at the inlet into the tank, it would make sense. No, it wouldn’t. Geez.<\/p>\n

I am going to go dig out my diploma and confirm that I really have a degree in physics. Maybe I imagined it. I can’t believe I’m confused by this crap.<\/p>\n

Anyway, I’m wondering if there is any point in getting the Grainger machine. The cost is the same, and it will be murderously effective even if I upgrade to a bigger compressor some day, and it probably has a warranty that actually functions. And resale should be high. On the down side, it weighs twice as much and is about the size of a 15,000 btu unit air conditioner. The Ebay thing appears to be roughly the size of a PC tower case.<\/p>\n","protected":false},"excerpt":{"rendered":"

Compressor Confusion Figure this out for me. I’m elaborating on an earlier post. The classic air dryer for cheap metalworkers is the Maxhootue\/Harbor Freight job. Same compressor, different sellers. “Maxhootue” is an Ebay user who sells them. They are rated up to about 21 CFM @ 140 psi. I keep my compressor’s pressure switch set […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[13],"tags":[],"class_list":["post-2627","post","type-post","status-publish","format-standard","hentry","category-tools"],"_links":{"self":[{"href":"https:\/\/toolsofrenewal.com\/index.php?rest_route=\/wp\/v2\/posts\/2627","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/toolsofrenewal.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/toolsofrenewal.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/toolsofrenewal.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/toolsofrenewal.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=2627"}],"version-history":[{"count":0,"href":"https:\/\/toolsofrenewal.com\/index.php?rest_route=\/wp\/v2\/posts\/2627\/revisions"}],"wp:attachment":[{"href":"https:\/\/toolsofrenewal.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=2627"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/toolsofrenewal.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=2627"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/toolsofrenewal.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=2627"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}