First Air Compressor?

[Longhunter7]

Gentlemen,

I am in need of an air compressor for the shop, and I need some advice!

I am looking at a Sears Craftsman, 6 hp, 33 gallon, 150 psi, single cylinder, and oil free.

It is available in an upright or horizontal version. Is there any advantage to either style, or is it just a matter of footprint, (floorspace)?

Is 150 psi enough for most jobs?

Is this an overpriced piece of junk or is it a decent air compressor?

Thanks for any advice!

[salemlampworks]

Hello
I have been in the autobody biz for 30 years.There is no substitute for CFM.If you are going to use it for sand blasting(pressure blaster),and painting complete cars and trucks.I suggest nothing less than a 220 volt,5HP,2stage piston,60 gal tank.This will get you about 11.5cfm@90psi. Anything less and you will run out of air ,and have to wait for it to build back up.The diaphragm ones sears sells are good my dad has one, fast recovery but noisy.They are cheaper than piston but every time you need air ,you'll say to yourself I should have gotten the 2 stage.
For what its worth.

[pieter]

I will say I held out until I could buy me a big compressor.
6.5 hp, 80 gallon @ 175 psi. granted I had to wire in 220v, had to find a specialized place that had regulators that would go over 175psi and some other things like that...

But I will say it was worth it. I got my compressor at Sams Club and i think it was about $800. I do run out of air at times. I have sandblasted plenty with a pressure pot @ 90 psi. I can go for about 20 minutes when about half the sand is gone. Then i fill up and by the time I fill up, the compressor finally kicks off. I've run it for 8+ hours like this on many different ocassions and haven't had a problem.

I'd say, hold out till you can afford it. a 33 gallon is probably portable or a stationary unti. I guess it all depends on where you are going to use it and how much room you have.

Pieter

[Gordon Maney]

It is very exciting moving toward pieces of equipment that are so widely useful in automotive repair activities. The compressor, the acetylene torch, the mig or stick welder, the major lifting device. I smile as I consider how exciting this must be for you, getting to choose.

You don’t mention if you want portability, you don’t mention if you may move again someday, and we of course know that all things become compromise of some sort.

When I went to purchase my first major compressor, I had the good fortune of getting to talk to a salesmen. I say that somewhat tongue-in-cheek, as typically salesmen lie to you. This guy was unique in that he did not try to sell me a particular compressor. His idea was that he was responsible to tell you about compressors. His company sold all major brands new and also a vast array of used equipment. He did not care what you bought, and it seemed he did not care even if you bought from them.

His first remark was to say that horsepower ratings are not meaningful. People talk about their 5hp compressor, for example.

You need to look at the CFM rating and the pressure at which that rating is expressed. He said there are lots of compressors that yield high CFM ratings, but at high pressures and at very high speeds. He said that what you want is a compressor that can produce all the air you want at an easy, slow speed.

I ended up buying a rebuilt compressor, a DeVilbiss, that produced just over 19 CFM at 110 psi. It loafs when it runs.

So, I am not telling you what to buy. You may see this compressor as a stepping stone toward a larger one someday. Or, you may consider looking around carefully for a used one that is larger. Most of this decision comes from you and your situation. It is exciting in any case.

I remember many years ago when I brought home a first compressor, how fun it was realizing that I could fill a tire and operate a blow gun for cleaning purposes. And the sounds of the quick disconnects....

[JimmieD]

I just bought a Sears 919.184191 compressor. It was on the Sears yearend clearance for about $450 at about 20% off. Max developed: 7 h.p., max running 3.2 h.p., max 150 psi, 12.4 cfm @ 40 psig, 10.2 @ 90 psig. with 60 gallon reservoir. I'm expecting it to be just enough to run tools or a paint pot or plasma cutter, and maybe some media blasting.

Was going to buy the next lower rated unit but salesman showed me how much more I was getting for about 50 to 75 bucks, so.....and also a major point: the larger unit had a MUCH stronger warranty, with the ability to cheaply extend for a little more $.

I decided I wasn't going to get a lot of chances, so buy the best I could in each category of tools while viewing the overall budget. Because the compressor is the heart of several other tools or systems it seemed best to buy the better unit and as good as I could afford, now.

Bottom line: I suggest you buy the best you can afford from a quality company with a sound reputation and a good warranty policy.

[MoparNorm]

All good answers,

...buy the largest CFM, compressor that you can afford. If you do it right, it will be the last one that you buy. I think what you are hearing is that it is better to buy one expensive compressor than to be forced to buy an expensive compressor...AFTER buying a cheap compressor.
MN

[JimmieD]

Exactly! And remember, it is potentially the very heart of a huge tool system. Cheapo air guns and tools work fine for part time hobby use, but the compressor is an investment that will be used for years to come, long after tools are worn out.

[Longhunter7]

Air Compressor?

Gentlemen,

Thank all of you that took the time to respond! I was way off in my choice of compressors!

Doing it right the first time, is what I am all about!

The information provided, will help when I find the right one, thanks!

[MoparNorm]

Just so you know....

Quality doesn't always mean expensive. e-bay, and other sources can score you a nice find.


I got this little baby here for "free" by trading some work for a manufacturing company. 8hp, 25 CFM, 3 phase, 180 gallon tank.

As JimmieD mentioned, it is a system that you want to think about. On paper write down every air tool that you want to own. Get the manufacturers specs for those tools (all the CFM ratings) and add in a reserve cushion, plan on the potential of two tools operating at the same time, just as a mind exercise. Those figures will tell you how big to go and how small you can get by with.
With a small compressor you will be listening to it run almost constantly, not good for working around and not good for the compressor. With a large or correct size compressor the motor will actually be working less to keep up with the demand and running shorter because it can fill the tank faster.
Good Luck!
MN

[Longhunter7]

Plan "B"

MoparNorm,

As a mater of fact, I was considering looking at used compressors!

I have all Winter to plan this out and weigh all my options and requirements.

I really appreciate all the expertise and proffesional advice here on the Forum!

[JimmieD]

I suggest that if you are considering buying used that you do some research ahead of time on parts availability from different manufacturers. Ingersol Rand has built some very high quality units over the years, especally larger 2-stage units similar to what Norm shows in the pic.

I believe parts are fairly widely available due to their common use in industry, and they used to be the mainstay of service stations, back when such places had garages, pumped your gas, checked your oil, washed your windshield and checked your tires....!

Always good to check abandoned service stations and if you find one there chase down the property owner and put in a 'haul it off' bid.

[MoparNorm]

Part availability...

...is a remarkable thing since the advent of the internet. Some guy in Frostbite Falls with three parts on his shelf for a 1972 IR can now let everyone know about his business. Most manufacturers have manuals in PDF format and a list of parts available, with price sheets.
MN

[Gordon Maney]

The guy who educated me on air compressors said that every big building you pass has an air compressor in it, unless it has several compressors in it. The purpose being climate controls.

Just as I type this, I wonder if all of those controls are now electronic, acccomplished by PLC [programmable logic controller] or now PC's. The compressors may still be sitting there, however.

My compressor is a Devilbiss 432, as I recall. Not all parts are available for it, but most are.

From what I know, Quincy is the very best, using disc valves. One important aspect of quality of design is the type of valve used.

We will see if we get some disagreement here on which compressor is the best.....

[MoparNorm]

My Devilbiss....

...broke a reed, I located the part source on-line, but not the part, so I drove to the source listed, an little old timey place not far from me, owned by a little old timey man. There were new compressors, very old unsold compressors, and very old used compressors, parts bins galore and the smell of grease and oil everywhere. In short, my kind of place! The man apologized that he did not have my reed in stock, but he could order it from Illinois and have it here in a few days. I said OK, how much? I was thinking, $8-$12 for the part, shipping, etc, maybe $20-$25?
He said, $4.60. I'm wondering how you can talk to someone over the counter for 15 minutes, order and supply the part for $4.60??? He also called me every day until the part arrived. It will be a sad day when the BIG BOX stores replace the last American Mom and Pop Merchant.

As for Pneumatic controls every factory or large building with HVAC still has that type of system, especially the more modern computer controlled systems, they rely upon air to work the VAV (Variable Air Volume) control boxes and open and close the dampers. It is much more efficient than electric controls. You will find the electric controls on smaller buildings, but the huge office buildings and factories have air.

As for the best type? Anything big, heavy and American Made...= )
MN

[JimmieD]

As to parts availability I was more cautioning to stay away from a manufacturer that does not offer support. Day by day the old standby and trusted mfgrs. are turning to China sourcing so it's best to check parts availability AND origin of machine.

Reed design is not so important as reed materials and manufacturing technique. A low quality reed will fracture from metal fatigue or distort from heat/cold cycle and may not seal on the mating surface even when brand spanking new! A good quality reed valve can last for 30 to 40 years or more [think chainsaw].

A disc valve if of the rotary style, spinning to close and open ports, is very effective where close tolerances are used in the manufacture and where a quality bearing/bushing is used, and again, mating surface is fairly critical. Disc distortion can have an effect on performance but due to its spinning it is somewhat self-cooling and does not have the contact surface with cylinder head as found with reed valves.

There are still some old tulip valve units pounding away out there to this day and that design speaks for itself: l-o-n-g lasting! Not common.

The controls systems in large buildings have moved into areas of electronic monitoring and manipulations far beyond yeterday's simple air logic systems. Simple air logic is great, but limited without the related transducers and sensors to give a continuous real world feedback of system performance.

Todays large buildings, especially hotels and office buildings, have control sytems that would reduce the untrained to tears in a heart beat! Redundant PLC's programmed from a laptop computer, linked to a master control light board, linked to a color coded wiring system, linked to a fire control light board, linked to the building alarm system, linked to the fire suppression equipment, linked to Public Safety & Fire response units, and able to give an instantaneous readout of every single room individually, in addition to the secondary zone system readings, plus give readouts of the status and funtionality of each individual control! Yipes...and a big bucks occupation for those who have a bent for CONTROL/CONTROL/CONTROL.

Even the 'small' Davey & Kellog American rotary vane or screw type compressors have a complete PLC control system that is quite sophisticated, even being equipped in California with motion sensors to automatically shut down the whole system in the event of an earthquake! Rotary vane and screw types are unmatched for output volume but lack in actual efficiency, as bang for the buck on utilities useage. They're quite similar to the Paxton/McCulloch superchargers in design. Most common in manufacturing where you have assembly line processes using many dozens of air tools simultaneously or wherever a very high output volume is required.

Anybody remember the kits to turn a Volkswagen or other engine into a self-powered air compressor? 2 cylinders used to run self and 2 cylinders used to pump air, while maintaining engine reciprocating balance! Simple, cheap, effective and lasts for years and years.....not hard to fab up yourself either.