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Sat May 06, 2006 5:18 am

Dusty1 wrote: I've got a couple biggies, old three phase dual stage Ingersoll-Rands, good stuff and stupid-expensive!

If you're not sandblasting you don't need that much air, don't let the guys who do this all day every day scare ya!

For around $400 buy a 5 horsepower 30 gallon single stage portable, that's about the biggest compressor you can run on 117 volt single phase power. I really like a good portable to run off a generator at the track plus on more than one occaison I've done "house calls" with it when the customer had the body off the chassis over their place or something.

It will run most paint guns but not all without a lot of recycling. Single stage is noisy so you won't be able to use it after hours unless you are out in the country, and it sure won't run many sanding tools very well. My 3.5 dual stage 25 g won't run a rachet worth a dang. Maybe the extra 5 g will help there, but I expect you will be disappointed. That said I did not have room for a big one so I accepted that, but went for the quieter operation of a dual stage. That way I can do some stuff off hours if I want. It's all a big trade-off. For years I used a tiny non-tank straight compressor and did quite a few excellent paint jobs on bikes, motorcycles and such. Never did a car with it and it certainly was not HPLV at that time, but it worked.

Sat May 06, 2006 5:56 am

basic 5hp it is a starting point...
portability is a good thing sometimes.. likie i said in a earlier post im planning to buy a small compressor to have in my vw bus & run on an inverter only want to use a few smaller tools.
small single stage compressors are noisy & depending on what tools you plan to use may have a hard time running or keeping up with air consumption...
i used to have a portable 4hp 12 gallon tank hated it from the day i bought it.. i gave it to my former boss at harley shop the week his shop compressor went out till he got it fixed... he has cussed it for close to 7 years but it is only used on occasion & used as a portable
this 1 had ill say an unusual feature.. when i built up pressure to 125 it would cut off but it had an air bleed to bleed air offf. after it dropped to 100 it would cycle back on so it would constantly cycle & that was disabled by me first day i got it.. & we adjusted pressure up on it to 140psi using a good gauge not relying on cheap compressor 1 for a little more oomph breaking bolts loose 1 7/16" bolts now days he uses a makita 3/4" electric impact
i have owned close to 8 compressors & have used tooo many to think about think hard about your useage.. & if under powered you might be sitting waiting for compressor to catch up & play that game with compressor all day & that is no fun......
right now my main portable is too big to really be portable.. it is a 33 gallon 6hp 220 volt & i have a 50 foot extension cord & use dryer & range plugs to use it. it is a craftsman & it would get a person by pretty well other than da sanding & it keeps up pretty good with my good da the cheap ones it has a hard time with
220 volt is a better home owner model it will cost less to run & is generally quiter
120 volt will do as homeowner but usually dont keep up as well & work harder & are more noisy.. but if you need portability they are the way to go i hate loading & unloading my 33 gallon compressor but once loaded i have a nice air supply with less work on compressor

Now ill ask anyone have opinion on a 2 to 4 hp portable to leave on vehicle at all times?
basically it will run airbrush, detail gun, impact, air ratchet, die grinder, drill & a few other misc.. & i dont want to lug my big 1 all the time & dont want to loose the floor space either
Randy

Sat May 13, 2006 4:34 pm

Look for as much VOLUME of air at 90psi as you can afford. high hp wont help if the volume of air is not there. 40-60 gal tank would work fine

Tue Jun 27, 2006 11:53 pm

A good compressor is like a good wife, it puts out a lot and doesn't yell much. A small, cheap compressor is like a bad wife, it huffs and puffs, screams a lot, doesn't put out much and will probably cost you money down the road.

I'd recommend an IR 7.5 Hp, 80 Gal. Well worth the marriage.

I had an old auto body guy tell me, never buy cheap tools, because you'll have to buy them again and again. You might was well save up and get the best and only buy it once (probably good advice for a marriage too).

Thu Sep 21, 2006 12:09 pm

I've read most of this thread. I am working on a shoe-string budget and looking to purchase a compresser also. I have one locally that someone is selling:

"5.5 hp 22 gallon tank - $175.00 - Campbell Hausfeld air compressor, approximately 2 years old. Over $300 new. Maintenance free, oil-less pump. Can be stored/used either horizontal or vertical. Runs great, just too big for my needs. Looking to downgrade. "

SCFM @ 40 PSI: 6.6
SCFM @ 90 PSI: 5.8
Cube: 17.33
120/240V Amps: 7.5/15
Weight: 172
Voltage: 120/240
Maximum PSI: 135

Would this allow me to run a sander and paint gun?

Thanks!

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Thu Oct 12, 2006 11:17 am

Well, having to sh!t or get off the pot, I purchased a Craftsman 6hp/2hp-running - 33 gallon compressor. I also received a bonus air tool kit with ratchet wrench, impact wrench and an air hammer....all for $315

I know the tools are not the best but it gives a jump on what I need. Swap Meet on Saturday....looking an orbital sander!

Sun Oct 29, 2006 5:59 am

Went to the swap meet last weekend and ran into someone who rebuilds these for a living...he told me that the one I purchased was not going to be enough....that I'd "burn it up" using a DA.

He advised one that was not "oil free" and one that was not 110v. He said there is no way that a 110v could generate the power needed to do what I wanted it to do.

Unfortunately, he didn't have any used or rebuilt at the moment. :cry:

Sat Nov 04, 2006 2:59 pm

I bought a Ingersoll-Rand 3 h.p. 7.9 h.p. peak 60 gallon Idustrial commercial compressor from Tractor Supply. 4 yrs ago I have painted numerous cars and parts plus ran da's, plasma cutter, and all my air tools to build 2 verts and love it I am always working on something in that garage I mean 6 days a week it os running.Other than normal maintaince it has been troble free!! Total cost was less than 700.00 I think It was really around 600.00 not sure now. But it rolls with everthing but my da when I am sanding nonstop. This should fit a budget and I think it is perfect 2 stage is nice but could be over kill for home shop. Hope this helps some

Wed Nov 15, 2006 4:53 pm

My dad bought a """"""""5 hp 80 gallon BIG ONE"""""""

Fri Nov 17, 2006 6:45 pm

The home Depot one for $450 if its the 60 gal one and the smallest 220volt, it works well. get a pressure regulator for it and set to 90 psi for most stuff down to 8o psi for die grinder/cutoff wheel, all the way up for impact gun and stubborn bolts. It keeps up faily well for me and it is rated for continuous duty.

Bill

Thu Jan 25, 2007 7:42 pm

What is the difference in the different "phase" compressors? My dad has some Craftsman ~20gal, no idea what kind of HP or phase, but its loud as all get out. Almost uncomfortable to be in the garage while its on, and certainly can't shout over it while its on.

Are the higher # phase ones quieter?

Wed Feb 14, 2007 12:38 pm

I have two

one is a 50 ltr tank 2hp giveing about 7cfm

and one 150 ltr tank 3 ph motor giveing a wopping 15cfm and can sand all day long .. this was a Ebay bargain.. good make to..

with compressors you have to go for as big as you can get... it's the CFM you need.. 15 is perfect DIY.. heck it;s nr pro stuff..

Thu Feb 22, 2007 10:57 am

Here's an article on compressors I wrote for the VVWCA Newletter a few years back. I was going to reply in this thread, but I realized that I had already summarized my thoughts in this article back in 2003. Hope someone finds it useful.

BTW, I've had the Quincy for 4 years now and LOVE it. Never lacking for air and I do a lot of blasting...

----------------------------------------
Compressor Science

As I mentioned in the "MIG Miracle" article a couple months ago, there are two "big ticket" items in any well outfitted shop. Those being a welder and a compressor. My compressor (and the air tools used with it) share a category in my life with such things as an icemaker in the freezer, cable modem/DSL and a flat top stove in the kitchen. That category is things that didn't always have, wonder how I ever got by without them and will never go without again. Things that make life so much easier.

But compressors, and more importantly their specifications, are often misunderstood. So I'll attempt to clarify a bit here. How big of a compressor do I need? How many horsepower? How big of a tank? These are all common questions.

Compressor outputs are rated in cubic feet per minute (CFM) at a given pressure in pounds per square inch (PSI). To understand the relative function and effect of the compressor components, think of a compressor as a water pump and a big barrel. The horsepower spec more or less determines how much water the pump can move, let's say in gallons per minute (analogous to CFM). The barrel determines how much water the thing can "store up". That is your tank. Now lets say your pump is rated at 10 gallons per minute, and you have a 100 gallon tank. It will take your pump 10 minutes to fill the barrel (actually this calculation has little relevance to the compressor example, as the water isn't actually being compressed and the pump output rate isn't affected by the amount of water in the barrel). The pump shuts off when the barrel is full. If the water is used, and the barrel begins to empty, the pump will start up again. Compressors have on/off thresholds in their switching circuits, lets say in our water pump example the pump shuts off at 100 gallons but comes on again at 95 gallons.

Now lets say that you have a "tool" that uses 5 gallons per minute, and you attach it to a spigot on the bottom of the barrel, and the barrel is full. Once you start using it, the water level in the barrel falls and the pump starts again when it reaches 95 gallons. You keep on using your tool, but since the water now going into the barrel is going in at 10 gal/min, and the water going out (what your tool is using) is at 5 gal/min, the pump easily refills the barrel and shuts off when it is full, all the while you use your tool. The barrel drains again to 95 gallons, and the cycle repeats.

If your tool uses exactly 10 gal/min, the pump will kick in when the water level falls to 95 gallons, but since the input and output are equal, the pump will run continuously while the tool is being used and the water level will not fall or rise.

But if a tool is connected that uses 20 gal/min, the water level will fall, the pump will kick in, but since the tool is using water from the barrel twice as fast as the pump can return it, the water level will continue to fall in spite of the pump running, and eventually the tool will run out of water to use.

So now you see the relationship between pump CFM and tool use CFM. Does that mean that you can't use any tool that has a higher air demand than the pump on your compressor? No. The point is that you can actually use the high demand tool for a short period of time, and/or intermittently. A compressor with a sufficiently large tank, can easily operate a tool that requires more air (CFM) than the pump can supply, if the tool is used only intermittently. But for continuous use tools, an adequate CFM rating is required, and a large tank really can't make up for any shortcomings.

As it turns out, most of the tools I use are intermittent use tools. Impact wrenches, grinders, air chisels, all are tools that I seldom run for more than 20-30 seconds at a time. So there is no problem running a big air-hog tool on a smaller compressor as long as it is used for short periods. Run it for longer periods and the pump will kick on and never be able to "keep up".

What about continuous-use tools, or air tools that are run for prolonged periods of time? Two come to mind that I use often: spray guns and abrasive media blasters. If you are going to use these, it is important that you have a compressor whose output is above that of the tool. I have been doing more and more media blasting at home and my poor old Sears Craftsman 3.5 hp compressor just can't keep up. If I keep my finger on the trigger and let the pump run, the system pressure eventually falls away to an unusable level and I have to take a break and let the compressor catch up (and my wife hates the sound of that thing running constantly!). Incidentally, the flatbed truck mounted compressor that the shop that stripped my '57 Beetle uses runs at only 25PSI at the nozzle, but a whopping 300CFM of volume!

As for paint sprayers, there is some good news. In recent years, high volume, low pressure (HVLP) guns have become very popular. These propel the paint from the gun with more air volume, but at a lower pressure. The result is less overspray, more efficient use of paint, and to the liking of the EPA, less volatile organic compounds (VOCs) released into he atmosphere. Initially, these guns which used only 10-30 PSI or so, needed 10-15 CFM of air, still well beyond the range of the small, 120volt "home" compressor. But recently, new guns have come out that will operate on low pressure and reasonable volumes of air. While you do suffer a small loss of paint transfer, you do get the same benefits of the "pro" HVLP guns. Some times downsizing a paint tip will help too. In any case, check the consumption specs of your gun against any compressor you intend to connect it to. Spray guns are continuous air demand devices, your rated CFM will need to be able to keep up.

One other thing worth mentioning. Small "detail" guns for painting small parts have minimal air requirements. If you plan on painting but don't do whole cars, you can still get by with a modest air compressor.

So what size compressor are we talking about for "average", non-continuous tool use? Well, let's look beyond spray painting and media blasting, as a compressor is a tool that will be used for many other things and is a good investment (tell your spouse that). Most "do it yourselfer" type intermittent use air tools like impact wrenches and air chisels will use around 4 CFM at 90PSI. A 4 CFM compressor may be as small as 1.5 hp. But you wouldn't want to buy a compressor with the bare minimum you expect to need. My recommendation is that a minimum sized compressor for home use should be 6-7CFM at 90 PSI. This would be a 2-4 hp unit (when comparing CFM ratings, always make sure you are comparing specs at the same PSI value. 90PSI CFM ratings are good ones to compare). If you intend to do media blasting or large scale painting, you will need as larger compressor.

Now having just gone through weeks of spec reviewing and comparisons, and eventually ordering a new 2 stage 240 volt 480lb compressor for my own use, let me make some other relevant points about compressors. The first is noise. My current Sears compressor is bolted to a chain supported shelf, high on a wall in my garage. It is a 120 volt direct drive unit and it is LOUD. The buzz resonates through the garage and seems to vibrate whole house. Not ideal, but it has served my needs for the last 9+ years and driven my wife nuts more than once. You will find that most consumer, low-end compressors are direct drive. This means that the electric motor shaft is connected directly to the pump, and spins the pump at motor speed, usually 1800 or 3600 rpm. And direct drive compressors are LOUD (did I say that already?).

In general, pump RPM is directly related to noise level. A belt driven pump turns slower than a direct drive one (just look at the relative size of the pulleys). Low pump speeds are in the 800-900 range. Moderate speeds seem to be 900-1100 or so and high speeds (for belt driven pumps) above that. So most often, a belt driven compressor will be less noisy. If noise is a concern, you may want to look for a belt driven unit. However, most all "low end" compressors I see these days are direct drive.

The last point is about that intangible line between the small/medium compressor and the "big boys" that can deliver the air needed to do large scale spraying and media blasting without breaking a sweat. The line seems to be delineated by the voltage of the unit (120 vs. 240 volt) the motor horsepower (3.5 is about as high as you can go on 120 volts) and the pump (single vs. 2 stage). Don't be fooled by the big "8 HP! (peak)" sticker on the side of the compressors at Home Depot (or wherever). You should refer to the data plate on the actual motor for the "real" HP rating. And what is a 2 stage pump? A 2 stage pump has 2 cylinders and uses one to pump air to around 100PSI, and then transfers that air to the other cylinder to run it up to 175 PSI, typically. Most 2 stage units will go to 175 PSI. And don't mistake a "2 cylinder" compressor for a 2 stage one necessarily. Many compressors have 2 cylinders (or more) and yet are still only one stage (one pressurization stage) units.

All of that being said, if you need more than about 8CFM at 90PSI, you should seriously consider a 240 volt 2 stage compressor. Yes, it is a quantum leap in cost, with the smallest of that class stickered at around $800. But even with just a (true) 5hp 240 volt, 2 stage unit, you'll get air volumes of 15-17 CFM at 90PSI with comparatively low noise.

Brands? Be aware that Cambell Hausfield makes a lot of homeowner compressors. They make the big red ones that say "Husky" on them that Home Depot sells, and I have been told that they make them for Coleman and Sears as well. CH is a decent brand but cannot be compared to Ingersoll-Rand or Quincy. IR and Quincy are well established compressor manufacturers that make all kinds of industrial compressors. But as you would expect, the high end units carry high end price tags.

Lastly, here's one more "fine point" for you to look at when comparing specs. When a pumps CFM output specs "fall off" between PSI ratings, this is an indication of how hard the pump is working and how close it is to its limits. For example, if one compressor runs 8.5CFM at 40PSI, and 5.5 at 90PSI, its pump is much harder worked than one that does 8.5CFM at 40 and 7.6 at 90. This is one way to see just how over, or under-designed a compressor is. A harder worked compressor is more likely to suffer wear failures than one that is not, all other things being equal.

Had enough? The quick summary is unless you are going to do large scale spraying and/or media blasting, a 120 volt, 2-3 hp, 5-7CFM @ 90PSI compressor will do the trick. You can get one for as little as $250 and it would probably be a Cambell Hausfield unit. Quincy and Ingersoll-Rand are better, but you will pay more. Also, seriously consider trying to find a belt driven model. They will be harder to find (in the smaller units) and maybe more expensive, but you ears and your family will appreciate it. If you want a "big boy", you'll have to go to a 240 volt unit. While you don't have to go 2 stage, to me it seems crazy not to. You get more max air, more CFM and a more lightly loaded pump that will last longer in most cases.

So what did I buy? I bought a 240 volt Quincy compressor, 2 stage, 4 cylinder (2 low pressure, 2 high pressure) belt driven, 5hp that will do 15.4 CFM at 135 PSI, and 15.2 CFM at 175 PSI. I am hopeful that it is quieter than the direct drive that I have now (it will sit on the garage floor on rubber pads, not bolted to the house!) but it almost has to be. I should be able to do all the media blasting and painting I want with that one. All I have to do now is wait to hear the flatbed truck backing up the driveway to deliver this 480lb "tool"…..

Sun Mar 04, 2007 8:27 pm

I bought the craftsman 33 gallon, 2 hp for around 300 bucks. Sears has d=good sales. I works fine but you can only use a DA sander for about 10 or 15 minutes before you have to stop and wait for the tank to build back up, which takes 3 minutes or so. The unit is the biggest I could find that operates on 110 volts but it is oilless and it is LOUD. lOUD LOUD LOUD LOUD

Its fine for me

T Capps

Mon Mar 05, 2007 7:25 pm

25-30 gallon compressors are all I ever needed.

Mon Mar 26, 2007 5:56 pm

Well I won't use the good wife concept but it templing.
I have the Craftmans professional I believe Jwvert referenced earlier. It's an oiled two stage much quieter than the single stage compressors. Its works with standard 120 and 220 volts, 25 gal tank 6.8 scfm @ 90 psi. The cost is 400.00 dollars new. Its a good compressor with die grinders and cut-off tools but with a capacity of only 25 gals you would be better off getting a electric sander. Sanders need huge air capacity, for a compressor to cover the sanders without having periods were it runs out of air you would have to spend huge bucks.
This compressor is great for the weekend shop guy who wants to use their compressor regularly, use many air tools, wants the ability to use 120 standard house voltage, and do not want to piss-off the neightors with major sound.

Wed Apr 18, 2007 7:24 pm

Darksoul wrote: Well I won't use the good wife concept but it templing.
I have the Craftmans professional I believe Jwvert referenced earlier. It's an oiled two stage much quieter than the single stage compressors. Its works with standard 120 and 220 volts, 25 gal tank 6.8 scfm @ 90 psi. The cost is 400.00 dollars new. Its a good compressor with die grinders and cut-off tools but with a capacity of only 25 gals you would be better off getting a electric sander. Sanders need huge air capacity, for a compressor to cover the sanders without having periods were it runs out of air you would have to spend huge bucks.
This compressor is great for the weekend shop guy who wants to use their compressor regularly, use many air tools, wants the ability to use 120 standard house voltage, and do not want to piss-off the neightors with major sound.

How does it work with something like this?
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=47603

Also, what product model did you get?

Mahalos

Thu May 10, 2007 7:14 pm

There are some great ideas here. If you don't expect to have 220 volts and all the money at once. You might get a 110 volt unit with about a 20 gal tank. This is a starter unit and will do lots of work, if you give it time. Next, buy another one, insert a T fitting between the two and let them share the load. Finally, get a third one, let it help as mentioned above. With the 3 you should be pushing about 9 hosses compressing air into a 60 gallon capacity! Balls to the wall cfm for one man. As with any compressed air supply, you must have the ability to ensure that no wet or oily air comes out of your air tool, especially paint guns. Compressed air tanks have water, use the drain as per manufacturer specs. Among the best filters for the bux/pounds are those that a roll of toilet paper fits within. Like all toilet paper, fresh works best.

Mon May 28, 2007 5:59 pm

I got one of those 5-6HP, 40gal compressors from Menards for about $360. It runs the sandblaster okay, but can't run a air rachet worth a damn.. I thought at that price it would have worked out better.

Still a good compressor though. Better than the $30 one it replaced.. perfectly fine for the powder coating I do with them.

Wed Jul 18, 2007 6:49 am

This is what I have "Heard" from many guys over time and the one message I get seems to be the same with all of them ...

Take it as you read it. This may not be the answer but it seemed to make sense to me ....

"Tank size is most important"

Since it is hard to justify myself to buy some monster 7.5 HP 18.x CFM compressor head running 3 phase 240V, the amount of avilable standing air is also an important consideration. I just don't do that much compresor work.

For example, Sandblasting. The one guy I talked to stated that my new dual piston 15.8 cfm head hooked up to a 110v motor would work best tied to a huge tank like 100gal or so. He also suggested if I wanted to do a "Commando" version, an old propane tank of about 110 gal or so would be great to provide a really good steady quantity of air for about 15 mins or so at 155psi at the tank side. For a D/A sander, I suspect the same air needs or so. Of course, if you want to work longer than 15 mins at a time and the back doesn't get sore, etc, a bigger motor and head would cut down on recovery time.

My problem with my 5HP 12.8 CFM / 25 gal compressor was that I was always losing the battle and waiting for recovery. My air rachet guns were basically useless because as soon as I pressed the trigger, the air flow pressure to the gun was less than desireable. Apparently, more standing air will help resolve that I hear. We'll see...

Right now, I picked up a compressor tank that is 50 gals at a garage sale with pressure reg, 1.5 HP motor and gauges ( head was seized ) for 20 bucks ! I'll put the new head on it ( from Princess auto @ 149 bucks ) and hopefully that will help a bit. next stage would be up upgrade the tank for more standing air and see what happens.... I am a little leary of using an old propane tank safely as I don't want a 100gal bomb sitting beside my head while I work :( Call me crazy but ..... :)

Just my 2 cents, take it for what it's worth :) ..... This is an Interesting post !