Air Compressor Oil

[hazmat]

<font color=blue>My mind would not wrap around the idea that a 3hp CAPO could put out 6.2cfm at 125psi when a 5hp Campbell could only put out 5.2 at 90 psi. Someone was either in-violation of newtonian physics or stretching the truth about the ability of their machine.</font color=blue>

Actually, both may be stretching the truth. The 5HP is a maximum developed horsepower under lab conditions, just before it stalls, feeding the motor as many amps as it will take before it blows up.

The 3HP also violates physics when plugged in at your shop.

115V * 20AMPS = 2300 Watts * .746 HP/1000 Watts = 1.7HP available on 115Volts. Ever notice how most table saws with a big honking motor are "only" 1.5HP. This is what they actually produce in the shop.

The difference is what kind of power they develop in your shop. the CAPO may very well make 1.7HP, while the cambell might only do 1HP. Looks like the CAPO has an induction motor vs. one of the universal motors. The induction motors tend to develop more usable HP. Also the CAPO compressor could be more efficient in transfering the power.

 

[neilw]

hazmat

You've gone and done it. Taught me something about electricity.

Additionally, your peeked my interest in just how much amperage does that compressor pull at start up and during operation? What is the difference between an induction motor and a universal motor and which do I have. And what about when various oils do they really make your compressor more efficient?

I've dug out a multi meter with one of those induction amp measuring devises. On the next cold wet day I plan on constructing an extension cord where I can get at the hot, neutral and ground wires individually.

Yes for you industrial safety coordinators I will be careful!

After all just like Justin Wilson I wear a belt and suspenders just to be safe.

 

[JerryT]

I am in the market for a 110-115 v air compressor on a limited budget ($300) I have looked at all the compressor threads. My use is probably about 1-2 hours per month max. I have it down to 2 choices.
Sears - oiless 30 gal. 8.6/6.4 CFM at 40/90 PSI max. PSI 150
Price $299.00 with a few tools.
Ranger - oil 13 Gal. 2.5 HP 8.8 CFM @ 90 PSI (no spec at 40)
Price $260.00.(with shipping).
With the Sears deal you are supposedly getting $139 woth of tools. My dilemma is that because of these discussions I would prefer OIL but the bigger TANK and higher pressure, my low use, plus the free goodies with the Sears makes it rather attractive. Any comments would be appreciated.

 

[JohnMiller3]

Go with the Sears unit... lots of value and a big outfit to back the unit for a year...

My first unit from Sears was a nightmare from Haiti... even with Sears extended warranty (they freely gave but it still didn't help)... but I can't say they didn't try... /w3tcompact/icons/smile.gif

 

[MikePA]

Jerry, might want to check out for this <A target="_blank" HREF=http://greenvalleycompressor.com/miva_apps/Merchant2/merchant.mv?Screen=PROD&Store_Code=PT&Product_Code=CP3AC&Category_Code=Capo>compressor. At $270 plus shipping it might end up costing a little more than you wanted to spend, but it looks like a lot more compressor.

 

[Bird]

Jerry, most of the folks I know in the business figure an oil lubricated compressor will last approximately 10 times as long as the oilless ones. Now I generally recommend oil lubricated, cast iron instead of aluminum, etc., but for the amount of use you mentioned, that oilless Sears compressor will last you a long time. Another nice thing about the Sears compressors is that the manual includes a parts list and exploded views, so if you do wear something out, you can completely rebuild one in less than an hour.

 

[Rubintropfen]

<blockquote><font size=1>In reply to:</font><hr>

And what about when various oils do they really make your compressor more efficient?

<hr></blockquote>



I don't know about wear, or efficiency at shop temperatures, but I once rented an oil-filled compressor for use in an unheated barn in January. It was pretty cold (5 or 10 degrees F?). Wouldn't run without popping the breaker until I warmed it up in the garage and wheeled it down to the barn already running. When I turned it in and told them what happened they told me it had 30 weight oil in it, not the compressor oil.

 

[neilw]

Jerryt

The Green Valley compressor mentioned above is the one I bought 11/11/02. A very solid unit that I have described above.

I bought a 3/4 HP oiless Sears compressor that did me good for 8 years of airing up car tires, balls and air mattresses. But very light farm use put it in its grave in just under a year.

 

[ScottAR]

I have somthing similar to the Sears unit, I think mine's 25 gallon. It works ok, for air wrenches and airing up things. I'm saving for an upright two stage compressor. The sears will still be ok for nail guns and when I need somthing portable for as long as it lasts.
The sears I have is very loud, and forget about running any sanders/grinders or painting guns. I'd get the oil if for nothing else than noise factor. Most oil compressors I've been around aren't much louder than the average dishwasher or clothes dryer. just my opinion, take it for what you paid.

 

[hazmat]

Neil,

Sorry I didn't get back to you sooner. Check out this link. It explains better than I can.

<A target="_blank" HREF=http://www.popularwoodworking.com/features/fea.asp?id=1090>popular woodworking electric motors 101</A>