Guide to electric air compressors for home shops

Not a bad article, if you don't mind the tone of the Very Authoritative Home-moaner.

But as far as size goes, buying small-ish isn't necessarily a bad thing, as compressors are simply additive. Three small compressors should be exactly equivalent to one big one, with a few advantages:

1. You now have inherent staging, with all of its advantages: reduced electrical surge/"demand"; greater economy at low demand. Would proly need better pressure regulators in each unit, tho, as those in small units are usually not the best.
2. Likely quieter. Doubling the number of sources of the same noise only adds 3 db, vs. perhaps a much greater decibel increase of a larger unit. ie, two trumpets each at the same db is not as loud as one trumpet played more forcefully.
3. Smaller = portable, if nec.
4. May be easier to fit numerous smaller compressors in nooks and crannies.

1. Repair is easier, due to redundancy -- you won't be totally out of air. And Quincy's are nice, but I could proly buy a whole new small HD/c.h. for the price of one Q repair.

2. One can be set up for special apps, like painting, etc.

Proly some other advantages, as well.

HD/campbell hausefeld has a very nice upright 30 gal compressor, dual voltage motor, belt driven cast iron compressor w/oil, sight glass, wheels, VERY quiet. I would buy multiples of these in a minute.

Also, in many cases, larger resevoir volume is all that is needed, not a bigger compressor. I have numerous small makeup tanks for about 70 gals, works great with one small compressor. Would work even for air tools, depending on how much you use them vs. your total gallons.

Air compressors have losses . V belts are a waste , not necessary .

I just bought 6 HarborFright 40400 DIRECT drive ( 8 gallon tank) for

$100 each .

I can series them , output of one could enter the crankcase of the next

stage then directed to the head intake valves .....IF the seals would hold ..

But 1 stage is efficient if PSI is below about 60 ( 4:1 ratio ) ...

At 110 PSI , its a big loss to have only one stage .

Auto a/c is over 10:1 on a hot day and condenser is not gulping 50 MPH

air .

Or i could parallel 4 , staggering the start up by 5 seconds .

This is more efficient than a $600 , 5 H.P. , 12 CFM belt drive ,

I could also put a 6004 2-RS ball bearing on crankshaft ..

I needed these for the H.F. 4 amp PLASMA cutter .

at half the price ( $700 ) of competition , i bought 2 . I also

bought 50 Zirconium/halfnium electrodes ( abt $250 ).

I can reshape the copper cups , easily .

This 40 amp Plasma uses a 4 transistor "H" bridge ... BAD idea ,

but as i said , i got a low price on the cutter ..

Modern circuitry uses only 1 or 2 transistors a single primary winding ,

driving it in one direction , NOT a half bridge , just a simple one sided

forward converter . This way transistors saturate the core , then hit it again

saturate the core etc etc . This is enhernetly safer than the complicated

current mode chips driving alternate NPN's . But i could always take out

the extra transistors , save them for a rainy day , use only 2 for even higher

output . 2 NPN IGBT's inparallel will drive MORE , than the lossy H bridge .

Plasma uses a mcu AT91xxxx . waste of mcu ....

Torch electrode is negative . copper cup with .8 mm hole is POSITVE , but

has a huge choke of 2.2 mil henries . Theres no capacitors

in the circuit , so the pulsating D.C. is limted by the choke and is called

Pilot arc ( aka starting arc ).

The zirconium electrode is pulled away from copper cup as soon

as circuit measures current in the ground cable .

Small cables used here cause plasma uses 90 vdc at

low amps ( 10 amps can cut 1/8" steel )

pull torch away from work , and pilot arc starts again .

NO MOVING PARTs , nothing to wear out ,

except chrome plated tiny electrodes at $6 each .

Lincoln electric inc' said they cut 1/2" plate

and got 450 feet of cut with each electrode .

Plasma cuts fast narrow and encredibly clean.

I bought 3 H.F. Stick/T.I.G. inverter welders ( red box ),

i call it "e-welder" . Buzz boxes can't limit the current , set at

100 amps

they go to 200 amps til you can pull it free !

But e-welder can "fold back current " instantly . And it will go out , if

you pull the electrode away , even to an 1/4" !

Buzz box just increases the voltage !

All my friends are raving about it . im doin diagrams on it .

It will power a Wire Feed . It needs circuit mods to hold D.C Voltage constant .

It does not use mcu's , only a current mode controller and an

IGBT half bridge , . dumb ! MJE13007's cost $0.12 each and are lower

loss when enough are paralled to the same amps as the IGBT's ...

Insulated Gate Bipolar Transistor is much higher loss , much higher cost ,

passing 20 amps , IGBT have about 2.5 to 3.5 volts of LOSS , MJE13007's in parallel can do 0.5 vdc !

paralleld Schottkies can use current sensing to shut them down on

over heat . It has a tiny 60hz transformer to power CONTROL ckt .

Ill replace it w/ 80 to 260 VAC switcher , then add big

Caps and Diodes to MOD it to run on 110vac . Now its 220vac ONLY .

They use a current mode controller chip and 4 surface mnt NPN's to drive

yet another transformer to drive the IGBT gates ! waste of circuitry !

Even if transformer doesnt have a winding to drive the bases , you can add

a tiny toroid in output , as all C.F. flourescents have ,..

ALL cost effective IBMPC power supplies saturate the transformer , to

save a chip . But output has a chip that sends back a signal to control the

MJE13007 , ussualy just to shut it dn prematurely , then allow it to self start

into the next cycle ...

One MJE13007 and a tiny transformer makes 450 watts ! That was my plan til HF

inverter showed up . I bought 20 PC power supplies from MCM and started

figuring how to parallel them to weld with .

Inverters can run 100% duty cycle with low cost MODs .

Plasma cut be MODed to do 40 amps at 100% duty cycle .

e-welder can do 130 amps at 100% .

The Ferrite transformer is the limit .

It stops working at a very low "Curie" temperature .

simply force a little air over it ! e-welder has fan far away ..

I also got 6 HF 13HP gas engines , i will MOD to Atkison cycle ,

since the CAM allready has centrifugal advance ...

I got 2 , 13hp , 5500 WATT gas GenSets .. they use brushes in alternator .

Ill be busy for months modifying this stuff !

BTW WiFi will be your new cell phone . The world will link up WiFi

and a new GUI method of communication . No voice , nor text , you will

have 8 buttons that send ICONs and Thumbnails and European traffic warnings

that will be understood by all humans , no need to translate ...

The B.W. is very wide . You can vu a Hollywood movie on WiFi , and with a dish

you can link at over 80 miles . The world will simply store and forward in

a cooperative way .. Also the new pocket PC is a GP2X game box , w/

80 GB HDD .. some one hooked a WiFi to GP2X .

Much easier to do in Linux ,, than in WXP op systems

snipped-for-privacy@yahoo.com from Guadalajara MX ..

***Snipped unreadable post***

It may be easier to do in linux. Too bad it turns out unreadable text.

Hi, Which compressor would last longer? Belt driven or direct driven)lubed or oil less)? de VE6CGX

in general an industrial belt drive compressor will run 24X7 for years, I'd expect an HF compressor in similar duty to be suffering in a month or less. My quincy, bought used, is at least 35 years old.