theoldwizard1
Well-known member
But it is a good excuse to buy a "potable" unit to "add on" to you existing compressor !
Please explain air compressors
- Thread starter Gus68
- Start date
Too_Many_Tools
Banned
Sears used to sell a TWO STAGE OILLESS 60 gallon compressor..so yes folks they do exist.
sberry
Banned
@sbery looking good. I think the biggest trouble with a lot of box store compressors are that one is rated at 20cfm@90 psi then the next one is 15cfm @120 psi. Which one is better I don't know. Oil is better than oilless. Cast steel is better than cast alum. Bigger tank is bigger reserve. For more continues use you need more cfm. A good one can run pretty steady all day for many years. Our local garage put a Devibliss in in 1978 it runs for 3 mechanics, tire changers and car hoist. Never did a dam thing to it. If you really need lots of air you have to go to a screw comp
larger tank/quicker recovery/better name like an ingersal rand. go on the website an go off your power rating in your garage. possibly upgrade to more power in your garage, and have an electrician install it. A commercial compressor will last a lifetime if you maintain it.
Fixnair
Well-known member
Hate to disappoint you sasky but rotary screws are not as efficient as recips are. A commercial recip will produce about 4.5 SCFM per horsepower. A screw about 4.
It's too bad the big box stores ruined this industry about 20 years ago with their advertising BS. Believe it or not there were standards set forth by the industry so everyone would rate their machines the same. They used the term SCFM, which meant Standard Cubic Feet per minute. An SCF is one cubic foot of air @ 68* and @ 14.7 PSIA. There were minor differences in the temperature used but they didn't mean much until you got up in the 100 horsepower range. Now everyone has a different scale and the user in nothing but confused. Too bad!
It's too bad the big box stores ruined this industry about 20 years ago with their advertising BS. Believe it or not there were standards set forth by the industry so everyone would rate their machines the same. They used the term SCFM, which meant Standard Cubic Feet per minute. An SCF is one cubic foot of air @ 68* and @ 14.7 PSIA. There were minor differences in the temperature used but they didn't mean much until you got up in the 100 horsepower range. Now everyone has a different scale and the user in nothing but confused. Too bad!
sberry
Banned
I agree and the tool ratings do not help. I am going to ramble a minute here and this is just generalization and some of the way I do it, for more exact ask finair but to second what he says,,, the number is 4.5 but unless there is a reason to be exact I use 4 just the same as I do on electric circuit, while it may be true that 120W is an amp I use 100 when generalizing design requirements.
Machine philosophy 101,, when you start this you tend to be captn overkill, I always had the best, 3x etc, as I get older I manage for the load a little better and from huge amoungs of experience and real general observation between expectation and reality have become an expert in estimation if there is such a thing.
Last real math I used was to calculate a bill and had to get a calc out just to do a simple number I had forgot. I cant anyway, most of it is over my head, many of these things are too difficult but if someone points to the comp and says, will that work to paint a truck,,,,,????? Then I am on it. I can tell you ,, not mathmatically,, well kind of in an estimate way that you can do body work and paint from 12 cfm if you are right on it, thrifty, concious to some extent with only a little wait a single guy can manage.
2 is a different demand and 3 can run under 30, over is better, this excludes continious blasting which is a specialized demand.
60A electric will support 2 men in a garage,,, 3/4 water line and an inch is a jump way bigger than it appears. We talk about pipe, 3/4 main for 10 ft to a reg which ends up with a 3/8 hose and take and open it up with a blow gun and see how fast it drains these little dinky comps.
Like the farm dealer down the road,,, has 7.5 or 10 hp for shop air I need to be above that 12 threshold for the additional activity from multiple users, I am around 30% load depand in some sense, I dont upsize every code by 3 or 4 but 1 and I can meet the demand.
I have a few hi motor load, air comp, a little welding, some cooling at 30A but still have 400A, I can run my whole place on 100 if I was thrifty. Its rated 400 for other reasons, the price was right, I do not need to manage, I can add without upgrades, can turn on a 300 synch and not concern myself. But again,,, right price, the farm dealer solved his air issue by getting new 10 hp,,, I did it for a day of reman and old comp someone gave me and added a unit that really never runs, allows for short sandblast without additional air and a bit of pipe blow out etc,,, once in a great while it will come on if we sand long enough but its kind of rare. The clunker it is,,,, is fine, it runs 1 hour a year (if I hear it come on I know the score) and is a backup to allow for un interupted air should something go south with the main.
For a home shop one of those 60 gal things are really a minimum but adequate, could do everything to a car you needed to. For light shop I see one,, an Ir, probably from the farm store with 18cfm, maybe 20 on the side, nice unit. As I recall just legal for a 10 wire? Anyway that is farm size, a man would tire with a sander or be done before air demands became a real factor.
Machine philosophy 101,, when you start this you tend to be captn overkill, I always had the best, 3x etc, as I get older I manage for the load a little better and from huge amoungs of experience and real general observation between expectation and reality have become an expert in estimation if there is such a thing.
Last real math I used was to calculate a bill and had to get a calc out just to do a simple number I had forgot. I cant anyway, most of it is over my head, many of these things are too difficult but if someone points to the comp and says, will that work to paint a truck,,,,,????? Then I am on it. I can tell you ,, not mathmatically,, well kind of in an estimate way that you can do body work and paint from 12 cfm if you are right on it, thrifty, concious to some extent with only a little wait a single guy can manage.
2 is a different demand and 3 can run under 30, over is better, this excludes continious blasting which is a specialized demand.
60A electric will support 2 men in a garage,,, 3/4 water line and an inch is a jump way bigger than it appears. We talk about pipe, 3/4 main for 10 ft to a reg which ends up with a 3/8 hose and take and open it up with a blow gun and see how fast it drains these little dinky comps.
Like the farm dealer down the road,,, has 7.5 or 10 hp for shop air I need to be above that 12 threshold for the additional activity from multiple users, I am around 30% load depand in some sense, I dont upsize every code by 3 or 4 but 1 and I can meet the demand.
I have a few hi motor load, air comp, a little welding, some cooling at 30A but still have 400A, I can run my whole place on 100 if I was thrifty. Its rated 400 for other reasons, the price was right, I do not need to manage, I can add without upgrades, can turn on a 300 synch and not concern myself. But again,,, right price, the farm dealer solved his air issue by getting new 10 hp,,, I did it for a day of reman and old comp someone gave me and added a unit that really never runs, allows for short sandblast without additional air and a bit of pipe blow out etc,,, once in a great while it will come on if we sand long enough but its kind of rare. The clunker it is,,,, is fine, it runs 1 hour a year (if I hear it come on I know the score) and is a backup to allow for un interupted air should something go south with the main.
For a home shop one of those 60 gal things are really a minimum but adequate, could do everything to a car you needed to. For light shop I see one,, an Ir, probably from the farm store with 18cfm, maybe 20 on the side, nice unit. As I recall just legal for a 10 wire? Anyway that is farm size, a man would tire with a sander or be done before air demands became a real factor.
sberry
Banned
I will also say screws do not apply to this discussion in general. Marginal effeciency does not either.
The spikes in demand are rare as I was eludeing to,,, 12 barely keeps up, lags just a little but the additional comp with 16 barely runs,,, but,,, if the primary was 5.5 or 6 the second would be on all the time.
I got air threads confused, this goes with the discussion about the 30 vs the 60.
The spikes in demand are rare as I was eludeing to,,, 12 barely keeps up, lags just a little but the additional comp with 16 barely runs,,, but,,, if the primary was 5.5 or 6 the second would be on all the time.
I got air threads confused, this goes with the discussion about the 30 vs the 60.
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