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ltf is on the money. I have been a compressor mechanic for 6 years, so here's my two cents. Oilless--Avoid at all costs. You will be lucky to get two years out of one before the rod snaps or the valves pack it in. They aren't new space-age technology, they are a cheap piece of crap. I have seen rods as expensive as $90 a piece, you could hold it in the palm of one hand. If the bearings go in the gear drive, the compressor is toast, since it is usually integrated with the motor armature and cannot be disassembled. They are also extremely noisy. They usually break the discharge line in a couple of months due to vibration and the fact that they use cheap aluminum tubing because it is so easy to bend. They often use crappy check valves too. There is nothing to recommend them except low price, and that quickly disappears when they need a repair. Almost all the parts are special order, and good luck asking for any technical help from the teenager who sold it to you from the big box retailer. 5HP- Doubtful. Be very careful here. No 5hp motor can run on 110V. Period!! It is quite a pull for household 220v single phase as well. ltf is right about the 4cfm per hp rule. No one is going to beat it. And who cares what the air delivery is at 40psi? Check the HP on the motor, it will say something like SPL, ie, they don't want to tell you. A Quincy 325 is the best 5hp pump made. It is 265 lbs. Nothing 1/3 the size and 1/10 the weight is a 5hp pump. Good rule of thumb, 1hp is required per 10 cubic inches of first stage piston displacement, i.e. the piston pumping from atmosphere. Use the displacement of all pistons if it is a single stage pump. Aluminum pumps----Most are crap, except Champions, which are excellent, cool running, quiet, durable, high cfm pumps. Highly recommended. Single stage vs two stage.---- Single stage pump produce more air, two stage pumps more pressure. Another mechanic and I built two 5hp compressors on vertical 60 gal tanks and we had a race (we are very boring people :-) ). The pumps were Fu Sheng TA 80 (single stage) and a Fu Sheng HTA 80 (two stage). The single stage compressor hit 100 psi a full minute sooner than the two stage. No one needs 175 psi at home. Look at your tools, I bet they need 90 psi max. Single stage compressors are better for most users, lots of volume, not lots of pressure. IR makes a nice single stage vertical twin cast iron compressor on a vertical 60 gallon tank for under $1000. In my opinion, it is a better unit than the Type 30 V-twin that they are selling as a light duty 5hp. The new one turns just over 1000 rpm, the v-twin (which is really a 3hp pump sped up, a 234 I believe) turns 1400 rpm. I know which one I would buy. Grainger sells the Speedaire line, which use Campbell Hausfeld cast iron pumps, which last a long time. I have seen some CH, VT series pumps 30 years old in good condition. I like the v-4 unit they sell. Be dubious about the HP claims though. Belt drive---Best. Checking, changing and topping up the oil is a very small price to pay for having a quieter, longer-lasting compressor. Keep it level too, and don't neglect the air filter. Should be no chore for a bunch of guys in the tractor resurrection biz. DON"T USE ENGINE OIL! It is the best way I know to turn your compressor into a oil puking, glazed cylinder mess, not to mention totally carbon fouling the valves. Hope I have helped.
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