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Forrest Addy
04-29-2003, 01:26 PM
Air compressor alert, Attention shoppers

Look before you leap while shopping at Lowe's:

They''re offering a Campbell Hausfeld 7.5 peak HP, 60 Gallon 140 Max PSI High Flow, Oil Lube Air, Air Compressor - Item #: 20849, Model: DP4615. 230 V. 17.3 Amps, 13 .4 CFM for $599.00.

This is an impressive looking compressor featuring a V twin design with monstrous looking cylinders and a finned tube connecting them.

It's a fake. It looks like a two stage compressor but its not. There are two 3/4 IPS air intakes one on each cylinder. The finned tube that looks like an intercooler is only a crossover. It's intended to look like a two stage compressor but instead is only a single stage. It's prominently placarded for 100% duty cycle.

This is probably a stout durable compressor but it lacks the two features that are required for the 30% extra delivery two stage operation give you: the LP (larger) cylinder that pumps into the HP (smaller) and the inter stage cooler that permits the HP stage to take a cooler gulp of air. Both cylinders in this compressor are the same size and they both pump directly into the tank. It's a single stage and so less efficient than a comparable two stage.

The advertising makes much of "7,000 hours of extended life". Might be. It's a husky looking machine.

The compressor is equipped with an ODP induction motor rated 230 Volts @ 17.4 Amps. This is a bit less than 4 HP if NEMA ratings can be safely interpolated. The compressor is rated for 7.5 HP peak. This rating is attainable in practice and in a compressor furnished with a pressure switch is unavailable to the user.

The next compressor down Lowe's food chain is:

Campbell Hausfeld 7.0 peak HP, 60 Gallon 135 Max PSI CAST IRON Oil Lube Air Compressor Item #: 18499 Model: VT6329 230 V 25 Amps 11.1 CFM for $399

This is a two cylinder side by side compressor. Electrically and mechanically it's 17% smaller in specification compared to the V twin but at 4/7 the price it's a far better buy. And there's no fakery about it except for the phony "7 HP" rating.

ibewgypsie
04-29-2003, 02:30 PM
Got one of the second models you mentioned.. it works fine, but only puts out 1.5 times what the 2 hp portable I used to use. Much better tho my wallet is not.

Anyone ever made a gas compressor out of a V6, I saw one once it used two cylnders for a air pump and the other 4 to drive it. The guy was sand blasting a building front. The motor was running about 50 percent throttle. No air tank.

lynnl
04-29-2003, 04:49 PM
What does that max CFM rating indicate? Is that the max it will provide running continuously, ie. you consume pressure from the tank as fast as it can be replaced? (In which case the compressor would never cycle off.) ...or something else?

I have a Campbell H. 6Hp that's rated at about 9 or 10 or 11, and one of those Ingrsl Rand orbital sanders (the cheaper, red import kind) will just about keep it running continuously, tho it's air appetite was supposed to be much less.

How many people drain the tank at the end of the day? That's what my owner's manual suggests!

Next question: are replacement tanks readily available?

ibewgypsie
04-29-2003, 05:51 PM
Orbital sanders are real air hungry.. almost like a "vane type motor". Mine runs continuous with my orbital. Like I said.. my 6hp is not 1.5 times the 2 horsepower I used to have.

Rotate
04-29-2003, 07:54 PM
Thank Forrest for demystifying the compressor products. Compressor manufacturers along with router and shopvac manufacturers should stop using these nonsense HP figures to describe their products. I don't really care what the peak horse power of the motor is, just before it stalls. Put a big fly wheel and you'll get even more peak horse power. As always, buyers be aware.

Albert

wierdscience
04-29-2003, 11:48 PM
The hp ratings are intended to reflect the motors max output in the instant before it incenerates http://bbs.homeshopmachinist.net//biggrin.gifAdd Sears to your list they do the same thing.Ibew,I currently own a Linsey 80cfm pump thats made from a Dodge 360 engine,they used their own valves and head on one bank for the compressor(4run and4pump)I like it,sucker is cheap to fix and it will push a pretty good size blast pot,for some reason they come up at auction a lot and they go cheap,I guess because they fall in between homeshop units and big commercial ones,I got mine from a local junk dealer for $250.00 he said he couldn't make it run and had even bought a new dist.for it,I got it home and all that was wrong was he had the firing order off on all four cylinders,hot battery and some fresh gas and it litt up and ran good,I need to do some valve work on the compressor cause it woun'tbuild enough pressure to trip the idle speed contol but I think that it will be minor.I also saw a guy that had a unit he built out of two VW flat fours turned back to back.One was a 1900cc for the pump and the other was a 2300cc for the motor,he ditched the factory heads and made his own intake and exhuast headers as well as popett valves,last I heard from him he had it running good.

Joel
04-29-2003, 11:51 PM
lynnl,
SCFM is standard cubic feet per minute, and it the amount of air that the compressor can sustain in use. CFM may be used by a dishonest mfg. to make their compressors sound bigger than they are. The CFM output of a compressor head is greater than the SCFM rating in actual use. Use SCFM for comparisons.
Peak horsepower ratings must be a bad joke.
Duty cycle is huge if you are running a DA sander or other high consumption device. If you plan on doing any quantity of sanding, you need a 2 stage, or at least a 100% duty cycle. Use a dryer also.

I drain my compressor frequently, especially after heavy use. I put a ball valve and a 90 degree fitting on the bottom of the tank, leading into a plastic bowl. This makes it VERY easy to drain. Takes maybe 2 seconds. The water in the bowl has evaporated before the next drain.
Replacement tanks are readily available, but always seem to cost close to a new compressor.

CCWKen
04-30-2003, 12:52 AM
One more thing Joel. The ratings are based on design and NOT actual output. In more cases than not, a compressor is outputing 10-20% less than it's rating. I have a 5hp 80gal 17scfm @ 175psi compressor that stays pretty busy with a DA sander also.
One note here: I just picked up a HF Pro DA sander (#1677) that is much quieter and uses less air than my IR sanders. (I think it was on sale for $27). And the pad was flat! Good deal, I'll see how it holds up in the long run. After four solid days of sanding, it's still tight and going strong.
I don't drain my tank every day. I have a cooler and a water trap. I just purge the trap daily. Every time I've check the tank drain, It's been dry.

Thrud
05-01-2003, 03:33 AM
Forrest
That is why I roll my own - quality control. I agree with the motor assement - they are rather wishfull ratings at best.

lynnl
05-01-2003, 09:49 AM
The ratings on the small I/C 4cycle engines have been equally inflated over the years. Today's walk-behind lawnmowers almost all claim at least 5, and more commonly 6hp. But they don't seem nearly as powerful as the old 2 and 3hp Clintons and early Briggs & Strattons did 30 or 40 years ago. BTW, what ever happened to Clinton? Did they fold or get bought out? I never really noticed when they disappeared? Anyone else remember them?

JCHannum
05-01-2003, 10:01 AM
Who'd buy anything with a name like Clinton?

Hellbender
05-01-2003, 10:27 AM
Anyone have experience w/ the automatic drain valves?

I put one (a cheap HF $10 one)on my stationary compressor about a year ago and it seems to work great (but I better go check, I may have 1/2 tank of water http://bbs.homeshopmachinist.net//biggrin.gif).
HB

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NRA Lifetime Member

[This message has been edited by Hellbender (edited 05-01-2003).]

Forrest Addy
05-01-2003, 01:25 PM
A Clinton power mower might mow the lawn OK but don't leave it in the dark with an under-aged hedge trimmer.

Might leave a spot on the gas tank.

lynnl
05-01-2003, 02:10 PM
The one we had was missing the gas tank cap.
But we just stuck a cigar in, and that seemed to work fine.

Cass
05-01-2003, 11:04 PM
It is educational to price a really good industrial air compressor like a Quincy 5 hp or bigger and look at the spec's on a good one. 100 percent duty cycle, pressure lube, spin on oil filter, pumps up to 200 psi with no sweat and will go to 550psi if you want to and have a pressure tank rated that high. Sounds like a Harley with a good muffler, never quits, 5 hp 3 ph. motor draws 20 amps at start. Five horsepower compressor costs around $3500 with an 80 gal. vertical tank. Makes you wonder what a similar sounding compressor at Home Depot is at a price of $800.

Crazy Ed
05-04-2003, 05:22 PM
I had a 1 3/4 hp lawn mower in the 50's and early 60's that would work circles around those today. I agree, hp's are way over inflated today. I think it was a lawton?? motor??

Used a blade that had two farm tractor hay mower blades bolted to the ends...we put a piece of flat belting across the back as a 'safety' shield...