# Cheap Air Compressors - the how & why



## precisionworks (Dec 5, 2013)

These are my experiences over the past 10 years with a couple of generic Big Box Store compressors. If your need for air is small they'll probably last a long time. If not plan on a rebuild of the pump or motor as needed. YMMV.

Both compressors are the Campbell Hausfeld Husky & they've painted these red, blue & now black. 60 gallon vertical tank, 3hp at 240 volts, 10.3 scfm @ 90 psi. Pump is single stage, two cylinder, cast iron, splash lubrication. Home Depot now sells these for $489 (Model #C601H). 

These aren't the worst unit available nor are they the best, more like middle of the road. Both mine were purchased in 2003 & at that time the C-H pump was made in the USA (& that's cast in bold letters on the pump) & the motor was a USA Marathon. I've read that the current pumps are cast in India, cannot verify that, but at least they aren't from China.

Which brings up an interesting point ... both electric motors bearings and both pump bearings are Chinese. If you purchase a C-H either new or used the China bearings should be replaced with something of known quality.

The motor is 3450 rpm & that means high pump speed and a fair amount of noise. C-H rates the pump for 3000 hours of intermittent use so it can last a long time if your need for air is low. 

Even with regular (4X per year) oil changes, synthetic oil & an extra large intake filter the pump will need rebuilding at some time. Mine go about five years before they begin to clatter & that noise indicates wear between the crankshaft & the rod as well as wear between the piston pin & the rod. Today's cost for 2 connecting rods, 2 piston pins, 1 oil seal & 4 piston retaining rings is $83.54. A pair of 6204 open ball bearings (Timken made in USA) runs about $20. Roughly $100 to get it back in the game if the cylinders & rings are OK. 

IMO one of the issues with cheap compressors is that the pressure switch is used as a motor starter. Might as well replace that at the same time as a pump rebuild, about $25. 

Better compressors use a slower speed 1725 rpm motor, the pump turns slower & more quietly, a magnetic starter is used for motor control, non-Chinese ball bearings are (sometimes) installed, etc. The C-H Husky isn't a bad unit especially if you can catch a sale price. Buying used is hit or miss as the prior owner may or may not have changed the oil & air filter as needed & that means rebuilding a lot sooner.


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## KC2IXE (Dec 5, 2013)

It's funny, Dad built our compressor, oh so many years ago, and it probably has the one of the strangest setups you've ever seen. He brought home a LARGE 2 cylinder pump, and a 5 gallon tank. We rebuilt the pump (I think it is sized for 10-15 HP, it is a BIG pump). The joke? we have it attached to a 3/4 HP 1750 RPM motor with the smallest pulley you can buy to keep the motor draw down for plug into a 15 amp 110 circuit. When running, I think the pump is running circa 90 rpm - SLOW, but man, it's been running for 40 years that way (very intermittent duty. I figure I'll die before it needs to be rebuilt


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## AnAppleSnail (Dec 5, 2013)

That sounds like an ideal way to build the pump - Large, slow pump with a good drivetrain to a small, quiet motor running near its rated power.


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## precisionworks (Dec 5, 2013)

I considered purchasing an 80 gallon 2-stage 5hp compressor & selling the C-H. I-R's run around $2k as does Quincy & other top name units. I did find one low cost machine made in Brazil by Schulz. Their Model 580VV20X-1 sells for $1250 delivered & the pump design is a Xerox copy of the I-R Type 30 (both are rated for 100% duty cycle). Low speed motor & pump, mag starter, etc. Might as well copy something good.


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## Lyndon (Dec 9, 2013)

Do the pistons on these compressors wear out and need rings or anything like that?

About two years ago I bought an old compressor at a garage sale at a nearby farm. It's not a diaphragm pump: has a piston driven with a large reduction belt driven by a beefy looking motor and a 10 gallon (I think) tank. Paid $20 and more than got my money's worth (they even loaded it for me so I wouldn't get my work clothes dirty). 

I recently noticed that the tank is now leaking badly. It's always made a weird chuffing noise and taken a while to build up pressure, but now it can barely maintain 20 psi. I used to think it was a worn piston/cylinder but now I think it was a small leak in the tank that has grown larger and I'm wondering if it's worth it to pick up a new tank from Tractor Supply or is there likely to be so much wear elsewhere that I'm better off just buying a whole new compressor. This thing is well made: I don't recall seeing any Mfr name on it, but it looks too well built to have been a cheap import.

Hmmm. I think I just talked myself into stopping at Tractor Supply on the way home ;-)


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## precisionworks (Dec 9, 2013)

Lyndon said:


> Do the pistons on these compressors wear out and need rings or anything like that?


The pistons serve only to support the sealing rings & yes the rings will eventually wear out and the cylinders will eventually wear larger. So far (2 rebuilds in 10 years) the bores mic good & the rings show no measurable wear ... which is incredible. 



> I recently noticed that the tank is now leaking badly. It's always made a *weird chuffing noise* and taken a while to build up pressure, but now it can barely maintain 20 psi.


That sounds like a bad valve plate (most use reed valves). If you can determine who made the pump you may be able to find a valve plate. The noise comes from air blowing back through the bad reed valve & into the cylinder. That also causes one cylinder to run really hot.


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## smokinbasser (Dec 9, 2013)

Campbell -Hausfield air compressors has a reconditioned Air compressor store in Blue Ash Ohio just north of Cincinnatti and they are a great buy since they are actually in better shape than new ones because they replace all worn components and are a better choice than new since they go through a more complete inspection than even the new one are.


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## precisionworks (Dec 15, 2013)

The parts package arrived from C-H so I took the crankshaft to my auto machine shop for a clean & polish - the best $10 that can be spent during a rebuild. The reason is that the big end of the connecting rod in low cost pumps uses no type of bearing - it's bored & honed to exactly fit the crankshaft journal with the correct clearance so journal smoothness is important. Right below the big end is a "dipper" that works like a paddle to sling oil all around the inside of the crankcase:







Dippers are sometimes called slingers because of the way they sling the oil. If you pull the oil filler cap & shine a light down into the crankcase while the pump is running you'll see the violent splashing/slinging action as the crank rotates over 1000 rpm ... since each connecting rod has a dipper that's 2000 splashes per minute in a 2-cylinder pump.

Better pumps don't allow the soft aluminum rod to directly contact the much harder cast iron crank, instead they insert a brass sleeve bearing to minimize wear & extend time between rebuilds:






They also use needle roller bearings at the small end of the rod that rotates around the piston pin & they use tapered roller bearings to support the crankshaft instead of ball bearings. 

Of my three compressors one is a Quincy QTS-3. It is noticeably quieter than either of the two C-H units, partly because it runs a larger flywheel & that makes the pump turn 862 rpm. Rebuilding is easier as it uses two-piece connecting rods that allow loading the crankshaft into the crankcase through the bearing plate opening. Overall the Quincy is at least twice the compressor as either C-H & it costs twice as much. The current model is less desirable than the older model as it uses a cast aluminum crankcase versus the cast iron crankcase on older units. 

Some companies offer both splash lubricated & pressure lubricated pumps. The big advantage to a pressure lubed pump is twofold - constant pressurized oil flow to all bearings PLUS micron level oil filtration, just like an automotive engine. Pump life runs about 15% longer because of those two factors. Cost is about 20% higher for the PL models.

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Some tear down & assembly notes if you decide to do this ...

Keep each piston in the same bore it came out of. This is especially important if you aren't replacing the piston rings. 

Use an assembly lubricant on both rod ends to minimize startup wear. There must be 50 different brands & any of them are better than plain compressor oil - they are usually honey thickness or paste & stay where you put the goo. 

Glue in both the front & the rear crankshaft bearings. Loctite 641 is what I use as the bearings will need to come out of the housings again in the future. Degrease the contact surfaces, coat, press into place & let cure for 24 hours. 

Synthetic oils are preferred by most pump manufacturers & each has their own brand. I use Valvoline Synthetic 20W-50 racing oil & it seems to work well. Any high quality oil should be fine if you change it on a regular basis. 

Keeping the air filter clean extends piston ring & cylinder life. My pumps have aftermarket Solgerg filter/sliencers that do a good job on both filtration & noise reduction. Even though my pumps only flow 12 SCFM the filters are rated 35 SCFM. Filter area is huge compared to stock filters. 

Low cost pumps have no bearings at either end of the rod & there is immediate wear on the aluminum rod ends - this is visible as a metallic glitter in the crankcase oil. Oil needs to be changed pretty quickly after a rebuild (or when a new pump is first put into service) - the procedure I use (which is the procedure Quincy recommends) is to open the tank drain, blow the tank down to 0 psi, then run the pump for one hour. Because the pump is running under no compression load the rods are gently worn in to mate with the crank & piston pin. After one hour the power is disconnected & all oil is drained from the crankcase. Refill with fresh oil & the pump is GTG until the next scheduled service.


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## precisionworks (Dec 16, 2013)

Here's 30 seconds of audio of the rebuilt C-H pump, first from 6' away and then backing up to 12' away. Quiet it is not but certainly less clatter than before the rebuild:

http://www.youtube.com/watch?feature...&v=TpZoOM40fIg

Then listen to the Quincy from the same distances:

https://www.youtube.com/watch?v=H06J3i7pyvM

You wouldn't want to try to sleep next to either one but the Quincy is certainly less annoying.


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## inetdog (Dec 16, 2013)

The edit link you accidentally posted for the Quincy will not work.

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## precisionworks (Dec 16, 2013)

Just got it corrected, thanks for the heads up.


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## wquiles (Dec 17, 2013)

precisionworks said:


> Here's 30 seconds of audio of the rebuilt C-H pump, first from 6' away and then backing up to 12' away. Quiet it is not but certainly less clatter than before the rebuild:
> 
> http://www.youtube.com/watch?feature...&v=TpZoOM40fIg
> 
> ...




That is pretty good. My Quincy seems to be running 1/2 as slow as yours, so it seems more quiet, but if you recall, my 5HP motor is being ran at 3HP (with a different pulley), and I am running it at less than max, so mine is hardly working hard at all


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## precisionworks (Dec 17, 2013)

My Quincy runs 862 rpm so yours is probably about half as fast. Be sure never to run below 450 rpm on a splash lubed pump as that's the minimum Quincy (& other manufacturers) recommend. Below that speed causes inadequate oiling as the dippers lack the speed required.

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## precisionworks (Dec 20, 2013)

First video with factory air filter: http://www.youtube.com/watch?v=qcRh4-LkQMs

Second with larger Solberg filter: http://www.youtube.com/watch?v=4DXo9E80pak

I can't tell a lot of diff in sound except maybe some of the higher pitch notes are attenuated.






Filter is huge compared to the stock filter (also a Solberg)






Filter is 1" MNPT at the rear & compressor head is 1/2" FNPT so reducer & nipple are required.


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## kuksul08 (Jan 2, 2014)

Thanks for the great info.

I have a small 4 gallon DeWalt compressor that is about 10 years old by now. Only ever changed the oil once, about a month ago. The sucker is so loud, and will leak from 120PSI to 80PSI in about an hour of sitting there. Currently looking into something bigger but most importantly, quieter.

Do you have yours plumbed in your shop with hard or soft lines?


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## precisionworks (Jan 3, 2014)

All three compressors connect into 1" black iron pipe. A 70' long main line runs the entire length of the shop & was installed by the prior owner. I've added on & added on & added on ...



> Currently looking into something bigger but most importantly, quieter.


That's gonna cost you :devil:

You can add a large Solberg filter/silencer for about $35 & it helps. Stay far away from the el cheapo Home Depot/Menards/Lowes units, they all use a 3450 rpm motor & turn the pump 1000 rpm. The crankshaft doesn't have balancing weights so they vibrate like a jack hammer.

Before I forgot about being broke I looked at everything from $1000 to $3000. IMO the best buy is the made in Brazil Schulz 5hp, 80 gallon, two stage, vertical tank. $1250 on eBay but the seller will knock off $50 if you contact him. 






It's usually listed on the web as 580VV20X-1 & it's a dead nuts copy of the Ingersoll 2475N5 that sells for $1900. Pump runs at 500 rpm on both the Schulz & the I-R, both have counter-weighted crankshafts, etc. Either one is as quiet as you'll find in the market, just a matter of deciding on the brand. Both have 2 year warranty.

FWIW Schulz manufactures the pumps that go on many name brand compressors.


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## subwoofer (Jan 3, 2014)

An interesting thread, thanks.

I have a Bostitch 24l oil-free 2.2hp compressor which was a replacement from the insurance company for a stolen similar unit. I use a tank full of air on average once a fortnight and have had it for around 8 years.

I've certainly noticed it becoming noisier and noisier especially over the last few times I've charged the tank. Now I'm thinking its days are numbered, as once noises like this start the degradation gets faster.

Looking at the rebuild costs you mention it will not be an economical repair so I'll probably have to get a new unit.


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## precisionworks (Jan 4, 2014)

The Bostitch site shows that as cast iron cylinder & oil lubricated and that is as nice as you can get in a small compressor. Looking online shows some parts available & rebuild cost about $50.


Barry Milton
Precision-Gunsmithing.com
iPhone5 voice recognition


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