Help Me Choose An Air Compressor

[Father Of Giants]

I want to do a leak down test soon and I'm beginning to hear suspension creaking so I will be acquiring air tools soon.

Again, the playing field is Craigslist, here are the contenders.





Another one, but this one is modern.


https://norfolk.craigslist.org/tls/6192059827.html


Probably my 1st choice


https://fredericksburg.craigslist.org/tls/6184971484.html

What do you guys think?

[barry12345]

The older craftsman if still in good shape is to me a much better compressor. The newer one puts out just half as much air and could even be a diaphragm type. The newer 3.5 horse rating is also a joke compare to the older motor.

[Father Of Giants]

Originally Posted by barry12345

The older craftsman if still in good shape is to me a much better compressor. The newer one puts out just half as much air and could even be a diaphragm type. The newer 3.5 horse rating is also a joke compare to the older motor.

Interesting. Well I don't mind unplugging the oven if need be. It looks like a beast.

[ah-kay]

Leak down test uses very little air and under 20psi to do the test. Pick a small and modern one unless you are a professional mechanic. That is my experience, everyone has different preferences.

[Father Of Giants]

Originally Posted by ah-kay

Leak down test uses very little air and under 20psi to do the test. Pick a small and modern one unless you are a professional mechanic. That is my experience, everyone has different preferences.

What about suspension work?

[ah-kay]

Originally Posted by Father Of Giants

What about suspension work?

The only time you need a big air compressor is doing paint spraying, professional garage, tire shops or you think you are a professional that you cannot do without one. All suspension work can be done by hand or a 3 gallons compressor. At the end of the day, it is your money and decision.

[barry12345]

Many points of view and understandable. There has been a generation that has known and lived with these limited smaller air compressors. I guess it is just a case of what you want to do both presently and in the future.


As for a test on a used compressor. The most important one is the time to fill the empty tank from empty. If it is rated at say nine cubic feed per minute output. It should fill the 20 gallon tank in just a little more than two minutes till shut down.

[HuskyMan]

Compressors must be drained after each use or rust can set up.

From the link below:

"This is an old sears belt drive V twin air compressor that was never drained properly. When air compressors run humidity in the air they compress condenses in the tank. The resulting water sits in the bottom of the tank until it is drained. When not drained regularly the tank will rust from the inside out, when the tank is weakened enough it will often fail catastrophically."

"Tanks have a maximum lifespan too. They still rot even with frequent draining. These compressors were built to replace in under 10 years. My personal shop compressor is built using a locomotive air supply tank ASME certified to 380PSI. The problem with that tank is, it's WAY too heavy for portability. So they make these thin steel tanks for portability thus the maximum life span. If a person really wants years out of a thin tank, they'll have the inside of the tank coated before the first use. Warranty void = yes. Life span increase = also yes. Pumps are another matter, few are built like they once were."

WATCH THE ENTIRE VIDEO - HE OPENS UP THE TANK SURGICALLY RUST RUST RUST RUST!!!! YIKES!!!!

https://www.youtube.com/watch?v=vdYimN5yOZc

[lorainfurniture]

The $99 pancake compressor from Home Depot has served me well. Noisy little turd but pretty good otherwise

[Neilert]

I'd buy the amrox, as you wanted 110v power. My advice would be to buy a compressor that allows you to change the oil. My experience is that they run much quieter.

[Mxfrank]

I've R&R'd both the front and rear suspension on my 190 with nothing more than an electric impact gun and hand tools, no need for air. Even the impact gun was a luxury. Leakdown test is another story, but a tiny compressor should be sufficient for that.

For 220, you would need a pair of adjacent slots on your panel, as the 220V feed is two phase. You can have an electrician wire a 220v socket, and it would probably cost three times the price of the compressor. While it's not hard to DIY, you can run afoul of local building codes (not to mention electrocute yourself). As for using your oven socket, maybe, if the plugs match. But how long is the cord on the compressor? If it doesn't reach, a two phase extension cord is not a cheap item.

[97 SL320]

Originally Posted by Mxfrank

For 220, you would need a pair of adjacent slots on your panel, as the 220V feed is two phase.

The two phase part of the above post isn't accurate. House power in the US is "split phase " though it is generally called "single phase".

The easiest way to visualize 1, 2 or 3 phase power, think of a 1 , 2 or 3 cylinder engine.

With obsolete two phase power, the second phase sine wave is offset by 90 * ( quarter of a wave ) . The circuit was generally fed with 4 wires and motors had 2 separate windings to consume the power. https://en.wikipedia.org/wiki/Two-phase_electric_power

With single " split " phase house power, sine waves are 180 * offset ( half of a wave ) . These systems have 3 wires but only use 2 depending on if 110 or 220 voltage is needed. No matter the voltage, everything remains consuming single phase. Motors have one winding that is used for run. ( There is sometimes a start winding that drops out after the motor is turning but that is beyond the conversation here. )

https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwiXzuCKivjUAhXGyj4KHanNCPwQjBwIBA&url=http%3A%2F%2Fwww.globalspec.com%2FImageRepository%2FLearnMore%2F20122%2F240120SinglePhaseWavefor mTransparente0e210f2a73b4e2aa95274447e1b5892.gif&psig=AFQjCNHtmjLOfLLyT6KVjHAbdiLmzvDx9g&ust=1499547921437169

With single phase house power, one can get 110 by selecting a hot and a neutral. To get the other "phase " of 110 you select the other hot and same neutral. To get 220 you select both hots.

Three phase power is used for generation and distribution to your neighborhood. It is also used directly by industry. With 3 phase power, the sine waves are offset by 120* ( third of a wave ). This is very efficient because the power transmission is smoother and motors less expensive / more reliable. Motors have 3 windings.

Originally Posted by Mxfrank

You can have an electrician wire a 220v socket, and it would probably cost three times the price of the compressor. While it's not hard to DIY, you can run afoul of local building codes (not to mention electrocute yourself).

As for using your oven socket, maybe, if the plugs match. But how long is the cord on the compressor? If it doesn't reach, a two phase extension cord is not a cheap item.

I don't know the current rate , but don't see an electrician charging more than a few hundred $ to install a 220 system if the wire / outlet can be fastened to the wall. For a short run materials would be sub $ 50 and take an hour.

Installing a 220 V outlet differs only slightly from a 110 v outlet. The actual wire is the same, the breaker needs to be a 2 pole ( we are using both hots ) and the third terminal is a safety ground not a part to pickup 110 V. If the device like a clothes dryer needs 110 to run the motor and 220 to run the heater, 4 wires must be used ( 2 hots , one neutral and a safety ground )

At higher voltages, a smaller wire diameter can be used Vs running the same load at a lower voltage. A three hp single phase motor running at 220 V will consume 13 amps , A 14 wire gauge extension will work though the thicker 12 gauge is better. ( for house wiring, 14 G is good to 15 amps and 12 G to 20 )

The oven socket will be rated for 50 amps so the plug won't work directly. You could make a jumper cord to a 220 V 15 A socket but in theory the cord should have it's own breaker. Breakers are rated for expected load and wire size. If a compressor that consumes 13 A locks up and the load goes higher, the breaker won't trip the the compressor will become a heater element.

[Father Of Giants]

Originally Posted by 97 SL320

The two phase part of the above post isn't accurate. House power in the US is "split phase " though it is generally called "single phase".

The easiest way to visualize 1, 2 or 3 phase power, think of a 1 , 2 or 3 cylinder engine.

With obsolete two phase power, the second phase sine wave is offset by 90 * ( quarter of a wave ) . The circuit was generally fed with 4 wires and motors had 2 separate windings to consume the power. https://en.wikipedia.org/wiki/Two-phase_electric_power

With single " split " phase house power, sine waves are 180 * offset ( half of a wave ) . These systems have 3 wires but only use 2 depending on if 110 or 220 voltage is needed. No matter the voltage, everything remains consuming single phase. Motors have one winding that is used for run. ( There is sometimes a start winding that drops out after the motor is turning but that is beyond the conversation here. )

https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwiXzuCKivjUAhXGyj4KHanNCPwQjBwIBA&url=http%3A%2F%2Fwww.globalspec.com%2FImageRepository%2FLearnMore%2F20122%2F240120SinglePhaseWavefor mTransparente0e210f2a73b4e2aa95274447e1b5892.gif&psig=AFQjCNHtmjLOfLLyT6KVjHAbdiLmzvDx9g&ust=1499547921437169

With single phase house power, one can get 110 by selecting a hot and a neutral. To get the other "phase " of 110 you select the other hot and same neutral. To get 220 you select both hots.

Three phase power is used for generation and distribution to your neighborhood. It is also used directly by industry. With 3 phase power, the sine waves are offset by 120* ( third of a wave ). This is very efficient because the power transmission is smoother and motors less expensive / more reliable. Motors have 3 windings.



I don't know the current rate , but don't see an electrician charging more than a few hundred $ to install a 220 system if the wire / outlet can be fastened to the wall. For a short run materials would be sub $ 50 and take an hour.

Installing a 220 V outlet differs only slightly from a 110 v outlet. The actual wire is the same, the breaker needs to be a 2 pole ( we are using both hots ) and the third terminal is a safety ground not a part to pickup 110 V. If the device like a clothes dryer needs 110 to run the motor and 220 to run the heater, 4 wires must be used ( 2 hots , one neutral and a safety ground )

At higher voltages, a smaller wire diameter can be used Vs running the same load at a lower voltage. A three hp single phase motor running at 220 V will consume 13 amps , A 14 wire gauge extension will work though the thicker 12 gauge is better. ( for house wiring, 14 G is good to 15 amps and 12 G to 20 )

The oven socket will be rated for 50 amps so the plug won't work directly. You could make a jumper cord to a 220 V 15 A socket but in theory the cord should have it's own breaker. Breakers are rated for expected load and wire size. If a compressor that consumes 13 A locks up and the load goes higher, the breaker won't trip the the compressor will become a heater element.

So essentially the 220v compressor will work, but will need a special extension cord correct?

Also, can I just buy the cord or do I literally have to build it from scratch?

[Mxfrank]

Originally Posted by Father Of Giants

So essentially the 220v compressor will work, but will need a special extension cord correct?

Also, can I just buy the cord or do I literally have to build it from scratch?

There are several different 220 outlets, depending on the current rating and whether or not it's a locking plug. Assuming the socket on the compressor is the same as your oven plug, you can probably find an extension at an electric supply house. Otherwise, you'd need a custom cord:

StayOnline.com Custom Power Cords (NEMA, IEC-320 or IEC-309) - Cable Assembly & Pricing

Either way, the extension cord will cost more than the used compressor.

[Father Of Giants]

Originally Posted by Mxfrank

There are several different 220 outlets, depending on the current rating and whether or not it's a locking plug. Assuming the socket on the compressor is the same as your oven plug, you can probably find an extension at an electric supply house. Otherwise, you'd need a custom cord:

StayOnline.com Custom Power Cords (NEMA, IEC-320 or IEC-309) - Cable Assembly & Pricing

Either way, the extension cord will cost more than the used compressor.

Yeah, i'll pass on the 220v compressors then.

Looks like i'll get the weird V twin compressor then.