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Air Compressors

M

Mudstud

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My 6 hp 150 PSI 30 gal oilless Craftsman compressor has bit the dust. Had it about 9 years. All of these new compressors with about a 30 gallon tank these day only have like 1.6 HP- FTF? I all ready gave this 6 HP a run for it's money. I sure don't want to go down in performance. Is there some new fangled technology that allows a much smaller HP motor to perform to that of the older 6 HP motors?
 
Most oilless compressors list some kind of "peak" HP # whose only purpose is to sell compressors. What you care about is CFM. An oil-lubed, belt driven compressor with a replaceable motor is a much more durable design and your ears will thank you.
 
honestly, I'd do whatever it takes to keep the old one running. Is it just a motor, if so, that's totally worth replacing.


Pretty sure it's obvious, but if you replace it, don't go oil-less.
 
K85 Octane said:
honestly, I'd do whatever it takes to keep the old one running. Is it just a motor, if so, that's totally worth replacing.


Pretty sure it's obvious, but if you replace it, don't go oil-less.
Click to expand...
Speaking of oiless, did you get that one you had working right? It's funny right after you started that thread, mine did the same thing (stupid little silicone seal) fixed that and a new squirl cage and all is loud and working good as can be expected.
 
K85 Octane said:
honestly, I'd do whatever it takes to keep the old one running. Is it just a motor, if so, that's totally worth replacing.


Pretty sure it's obvious, but if you replace it, don't go oil-less.
Click to expand...

That's part of the problem, really. Many of the oilless units have the pump and motor integrated together. Some failures in there junk the whole assembly and the replacement can be >1/2 the cost of the whole compressor. I wore the ring out on my old Husky doing body work and replaced the piston/con rod assembly and the valves. That's about all you you can replace on some of these. I got like 6 more months and then the cast motor/pump frame cracked in half.

IMO, a 10-year-old "real" compressor is better than a showroom oil-less. The reason they put those big plastic covers on the oil-less compressors is so you can't see how small the motor and pump are. They are tiny, revved to 1,000,000 to get some CFM. For the same power and same airflow, an 8" diameter motor and giant (twin) cylinder case are going to dissipate the heat WAY better than a 3" diameter motor sandwiched together with a 2" piston moving 1000MPH.

I always post this analogy - you can get 100hp from a Yugo engine at 8000rpm or a BBC at 600rpm. Which one will last longer (and make less noise)?
 
Mudstud said:
My 6 hp 150 PSI 30 gal oilless Craftsman compressor has bit the dust. Had it about 9 years. All of these new compressors with about a 30 gallon tank these day only have like 1.6 HP- FTF? I all ready gave this 6 HP a run for it's money. I sure don't want to go down in performance. Is there some new fangled technology that allows a much smaller HP motor to perform to that of the older 6 HP motors?
Click to expand...
A real 1HP motor typically draws almost 16A from a single phase 110VAC supply. This means that if your compressor plugs into a 15A socket, it can't even make 1 real, running, average HP. For 110V, you'll want a dedicated 20A socket, which still can't even always get you 1.5HP. So a real 6HP compressor would need a dedicated 30A 220V circuit. It would be dual-stage, and at the "rule-of-thumb" 5CFM/HP for dual-stage, you should get 30CFM@100psi. That's truly a nice compressor.

You can believe the HP ratings on motor nameplates, so when those are blank, missing or covered up, don't believe the compressor-maker rated HP. They evaluate the absolute peak based on power plus inertia at one peak point in the cycle, not the true average running HP. CFM is typically pretty close and that's what you care about anyway.
 
livid4dirt said:
Speaking of oiless, did you get that one you had working right?
Click to expand...

It's thumping (like a cricket) away. The air filter quieted it down and the AN fittings with hose is pretty fail proof. I only use it with carpentry tools. My Husky and CP twin cylinder oil compressors are my little work horses.
 
So it'd be great to find a compressor and pump and just put it on my 30 gal tank.

My concern, I guess was won't a smaller HP rated compressor run all the time to keep the tank full? This 6 HP compressor ran enough trying to keep up. I don't want one that will run continuously and never shut off. Is there a decent 110 VAC compressor you'd recommend? I can't go 220.

Thanks, Dan
 
Don't worry about "6HP". It was a lie. Look at the CFM rating of that unit and find something rated as good or better.

Your plan is actually the same thing I did. I found a twin piston roll-around on Craigslist (old, but built in Wisconsin), cut the whole mounting plate off and grafted that motor and pump on top of my old upright tank. You can also run two tanks together if you want for more capacity.

If you're running air hogs like a DA sander or even die grinder, you won't find a 110V unit that can run them 100% duty. I don't know what to recommend, other than getting a 20A receptacle dedicated to it and finding the most CFM you can get on 20A/110V. Some motors can be wired for either voltage.
 
Thanks man. Appreciate the insight. Lets get a class action against Craftsman for lieing about HP. lol
 
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