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Old 09-16-2007, 08:24 PM
oldred oldred is offline
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Originally Posted by blsnelling
Why would we believe the number on one IR and not on another? I thought they were touted to be a reliable company with a long history? Has anyone bought this single-stage IR to disprove its claims? Would anyone have links to someone with experience with this compressor?

You mention that the 2-stage IR would be quieter than the single-stage. They both have the same motor. However the motor pulley is larger on the 2-stage causing it to run 1375 RPM instead of teh 100 RPM the single-stage runs. So the 2-stage is running fast and compressing higher pressure. Wouldn't that make the 2-stage louder and hotter?

Another thing. It makes sense to me that the single-stage can put out more CFM than the 2-stage. If you look at the cylinders on the pump, you will see that the cylinders on the single-stage are both the size of the larger cylinder on the 2-stage. It would only stand to reason that it would compress more. If you take one of those cylinders and make it smaller, as on the 2-stage, you're now making greater pressure but at a lower volume. Does that make sense?

Buy what you like but the advice I gave you is based on nearly thirty years of selling and servicing compressors and air systems. As far as the two stage vs single stage a good two stage design will out-perform a comparably powered single stage because it is a more efficient design. It will run cooler for the same reason and also because it will dissipate some of the heat during the second stage of compression. Comparing the piston sizes is meaningless because they operate on a different principle, the two stage partially compresses the total volume of air with the large cylinder then transfers it to the smaller piston where it is then compressed even further to higher pressure before being discharged into the tank. The single stage simply compresses the air directly into the tank with each piston operating independently of each other as far as compression is concerned, kind of like two single piston pumps working together on one tank and motor. As far as the truth about CFM ratings again believe what you like but that single stage is aimed at the small home type shop and the two stage is more of a commercial unit so the sales tactics are different for two differer markets. I have tested the flow on quite a few compressors in the last 30 or so years with a bunch of them being in the 3-5 HP range with single stage pumps and I can assure you I have never seen a single stage with only five HP put out anywhere near that much CFM. With any given amount of HP you can you can get high flow and low pressure or low flow with high pressure but you can not have both, not with a single stage anyway. It is just like having a car with one gear, you could have high acceleration but no top end or you can have a high top end and no pulling power. On a single stage compressor a compromise must be made and about 13-14 CFM@ 90 PSI is about all 5 HP is capable of with a piston design and that IR is a simple piston design. If you want to believe those numbers they list for that single stage then it is your money so buy it but I would bet that a good Eaton single stage with 5 HP would produce as much or more, probably more, (they have a better V pump design) and it will be rated somewhat less. Again it is your money but that CFM number is a sucker trap even though the compressor is very well built and will last a long time, it has so much else good going for it that it is a shame they had to be so reckless with the truth about performance.
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