Piecing together a 7.5HP 2-stage compressor

I have a Quincy QT54 and it so far has served me well enough. Im painting 1 project, and maybe another down the road, I am by no means an expert when it comes to painting or compressors. But the way I see it, you would be better off buying something that is new, has a warranty, and is a complete ready to run package, vs putting your own together on an unknown tank. If the QT54 isnt going to be big enough then step up to an 80 gal, it has alot of the features that were talked on above, and its only another 800 over what you were going to spend on a pump and motor. If you get a new compressor you should be able to sell one of your single stages and recoup some of the money as well.
 
theres a reason most compressors are mounted outside in a cage . anything above 5 hp needs to go into a safe space. and no one needs 175 lbs in a tank . period.
 
I think safety concerns are important to discuss in a positive fashion, so that DIYers can be informed about possible issues in case they go ahead with their own modifications against advice. I'll list a few things here that I know and practice, but I'm not an expert, so I'd encourage others to help me add to it:

  • Make sure that every tank has a functional pressure release valve, and test it regularly. (Pros, a test procedure goes here. I just pull the ring once in a while to make sure it's free)
  • Drain your compressor every time you are finished using it. Keep an eye on what comes out. If it's rusty, you may need to stop using that tank! Tanks are not that expensive, so using a sound one should not be too costly. (Pros, tank inspection procedures go here, bore scopes are getting more common, so looking inside is an option)
  • If you connect two tanks that each have pumps, there should be no shut-off valve in the connection between tanks. This ensures that either pressure switch can stop the operation of a pump, and that either release valve can react to an over-pressure situation.
  • As DATEC explained earlier, wiring two pumps can get complicated, and delay switches are often necessary to prevent voltage from sagging due to excessive start-up loads. Also I have heard of pressure switches being wired improperly, this combined with the inadvertent closing of a tank shut-off can produce catastrophic results!
  • It's best to locate compressors in an enclosure when possible, not only does this make them safer, it cuts noise dramatically. Knocking together a 2x4 and plywood enclosure should be no problem for the average DIYer.

I'm sure I missed a lot of things. My list is only safety related, not maintenance or air quality. I'd love to add to the list.
 
I've used tanks before with rusted bottoms. Not proud of it it but I have. They don't blow up, just severly pitted parts start leaking at the pits. I'm more concerned with a severed air line flying around than a rusty tank.

One nice feature of the Quincy QR pumps is no need for a check valve where the pump dumps into the tank. The valves are built heavy enough they don't leak. This means multiple pumps can be hooked up without each having large check valves. I had a check vavle fail on my Eaton along with everything else.

Wiring for my setup was easy because each pump has it's own breaker and it's own pressure switch.

Shine is right about air pressure. No need for that kind of pressure. Mine are set to 140 and regulated to 100psi at the tank. Which is around 90psi by the time it reaches my air hoses.

Here is a picture of my second work on progress. Since this photo was taken the air dryer is consolidated onto the unit. It's PTO driven from the tractor. 370 pump and a 350 pump. Variable speed with the speed of the tractor. Makes a lot of air for blasting. In the past all my blasting problems were water related. These dryers stop that.
 

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I've used tanks before with rusted bottoms. Not proud of it it but I have. They don't blow up, just severly pitted parts start leaking at the pits. I'm more concerned with a severed air line flying around than a rusty tank.

One nice feature of the Quincy QR pumps is no need for a check valve where the pump dumps into the tank. The valves are built heavy enough they don't leak. This means multiple pumps can be hooked up without each having large check valves. I had a check vavle fail on my Eaton along with everything else.

Wiring for my setup was easy because each pump has it's own breaker and it's own pressure switch.

Shine is right about air pressure. No need for that kind of pressure. Mine are set to 140 and regulated to 100psi at the tank. Which is around 90psi by the time it reaches my air hoses.

Here is a picture of my second work on progress. Since this photo was taken the air dryer is consolidated onto the unit. It's PTO driven from the tractor. 370 pump and a 350 pump. Variable speed with the speed of the tractor. Makes a lot of air for blasting. In the past all my blasting problems were water related. These dryers stop that.
Damn, that is a cool setup.

Don
 
The OP said in his post about water removal that he has a 6.5 hp compressor. Those things were available from multiple sources and sold at the height of compressor hp overrating. They all pull right at 15 amps on a 240V circuit. That's 3 hp all day long.

I've got a little 3hp Sears compressor I bought in the late 70's before lying about hp and cfm on homeowner compressors became the common practice. It pulls 15 amps and its rated at about 9 - 9.5 cfm at 90 or 100 psi. Those are legitimate numbers, and most likely reflect the something real close to the actual output of the OP's compressor.

If you look at the current 5hp high speed compressors with legitimate ratings, most all of them will put out about 15 - 16 cfm and they draw 23-25 amps on 240V. Just like my old Sears job, the motor will draw about 5 amps per legitimate hp, and will put out right around 3 cfm per legitimate hp. A low speed 5hp will typically put out right around 17.5 cfm because its pumps more efficiently than the high speed ones. Ain't no magic construction techniques or marketing lies that will make any noticeable difference in these numbers, regardless of manufacturer.

We've got several portable compressors. Biggest one is 1600 cfm, driven by a 475 hp diesel. Do the math, and that works out to about 3.4 cfm per hp. Once again, no magic involved, and the cfm per hp is near identical to that of a good low speed 5 hp compressor.

The point of all this being the OP thinks he needs a 7.5 hp rig because he thinks he's got a 6.5 now. In reality, if he upgraded to a legitimate 5hp rig, he'd have close to 70% more air than he's got now, even if he bought a high speed unit. And close to double what he's got now if he went to a 5hp low speed unit.

IMO, the most important sentence in this entire thread is Shine's statement that no one needs to be pumping to 175psi for the work discussed here. Absolutely true. All it does is pump more heat into the air and wear the compressor at a much faster rate. At my shop where I make a living, we've got a 10hp that's inside the building. I picked up a 5hp Sanborn high speed rig about 15 yrs ago in near new condition for $300 to have as a back up. I put it outside, and ended up using it as the primary because I can't hear it run when its outside and I'm working in the shop. Its got one of those Italian made pumps a lot of these types of compressors have. I set the pressures down from the original 150 and 175 to 110 and 135. The difference in the temperature of the pump when operating continuously for a while is easily 30 to 40 degrees cooler than it was when set for 175 cutout. After about 12 years of near daily use, it uses no oil and still runs like a champ. No doubt in my mind it would be dead and buried by now if it had spent its life pumping to 175 on every cycle.
 
Just painted this Quincy 325 in SPI Black Epoxy. There are a few real good rebuild videos and solid available parts manual for these old Quincy pumps.

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Thats a pretty good home depot compressor.

I went the DIY route with the Quincy 325. For roughly $600, I'll have a totally rebuilt Quincy 325 (2-stage), a 5 hp motor, pilot valve and a 40 gal horizontal tank. Thats probably 15-20CFM. Got lucky on some parts, the Quincy pump was $26. I've had to wait around for good deals on a few parts too. Almost done and started it off/on mid September.

I'm going to put a little bit more money into it and make it a badA** mobile compressor with trailer wheels, filter, dryer, air hookups, retractible hose, and small drawer. I think I can do this for under $1k total in a 5ft tall, 5 ft long compact package. Much cheaper route if you consider your labor near $0...
 
Has anyone ever done this? Brand new compressors (tank, motor, and pump) fully assembled seem to cost $2k-$3k online. Those are the Quincy prices on eBay anyway. I have a 60gal tank and single stage compressor set up already. Would it be wise of me to buy a 7.5HP motor for $500 ( https://www.ebay.com/itm/271956786548 ) and a cast iron 2-stage compressor for $600 ( https://www.ebay.com/itm/391668039922 ) and just mount them on the tank I already have? In some previous posts you guys said my compressor wasn't big enough. This route would only cost me $1100. I realize I may have some more money in the retro fit, but it shouldn't go over $200. This route could save me $700-$1500 I figure

I'm not a shop. I'm doing 1 car. I may do another one in the future, but this is a rare occurance and only a hobby. I am a farmer though, and my compressor does fall behind with the regular use of air tools. It may be time for an upgrade anyway.
I ha
Has anyone ever done this? Brand new compressors (tank, motor, and pump) fully assembled seem to cost $2k-$3k online. Those are the Quincy prices on eBay anyway. I have a 60gal tank and single stage compressor set up already. Would it be wise of me to buy a 7.5HP motor for $500 ( https://www.ebay.com/itm/271956786548 ) and a cast iron 2-stage compressor for $600 ( https://www.ebay.com/itm/391668039922 ) and just mount them on the tank I already have? In some previous posts you guys said my compressor wasn't big enough. This route would only cost me $1100. I realize I may have some more money in the retro fit, but it shouldn't go over $200. This route could save me $700-$1500 I figure

I'm not a shop. I'm doing 1 car. I may do another one in the future, but this is a rare occurance and only a hobby. I am a farmer though, and my compressor does fall behind with the regular use of air tools. It may be time for an upgrade anyway.
 
I actually just did this with a quincy tank that had a failed pump. I purchased a 5-7.5 hp kellog pump online for 550 dollars and a 300 baldor real 5hp 1740 rpm motor and Starter on ebay and 2 new belts all for less than 1000 dollars and i couldnt be happier. This compressor smokes my 7.5 hp 80 gallon ir t30 in my front booth and its on a 60 gallon tank. Was easy as pie.
 

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That might be the Kellogg name applied to a chink pump but it isn't like the original. I had a 335 pump I rebuilt years ago, ran it for 5+ years and sold it to a buddy. Kelloggs are great pumps. This looks the same but the castings have an import flair to them. It's about as American as a Saylor beall clone pump is.
 
I have 4 compressors-2 Belaire, an ingersol rand T30 from the early 90's, and I agree that a Saylor beall is one of the best pumps ever made, however any splash lube compressor is going to have a finite life span-American or otherwise. In a bodyshop environment that Saylor beal is going to wear out just like all the rest and its going to cost you big time to repair or replace-that 705 fully packaged costs over 3000 dollars and the Kellogg American 1800 dollars if you buy it loaded just like my Belaire 418. The Chinese are making better CNC stuff than 10 years ago as evidenced by the warranties. This pump is good, as good as the 335 used to be? time will tell. It runs slow and fills quick -you wouldnt believe how fast and is quiet. My guess is this pump will run as long as that Michigan made pump. I used to be an american only snob too, until Miller stuck it in my butt over a very expensive repair that shoulda been covered under warranty on a Millermatic machine. I fixed it myself and never looked back. I use off shore welders and plasmas like my Northern tool plasma 375 that carries a 3 year warranty and out cuts Miller and Lincoln any day both in speed and depth of cut all at 1/3 the cost. My money gets spent on the best value weighted by cost benefit every time.
 
...I actually had an after thought - before i bit on that so called clone 335 pump-i called and spoke with The new Texas based manufacturer about the pump-they bought not just the rights to build these pumps but Kelloggs whole operation machines and all. This pump has KELLOGG cast into the iron, not something Tong Yang usually does with a cheap knock off. If it falls apart after a few years what have i lost? I can always buy a real 705.
 
I'm sure they probably are a decent pump. My 335 never had Kellogg casted into, just a data tag riveted on. I'm just saying that isn't the same Kellogg as what they used to be. It's the american way of revamping a classic name with heritage and building them cheaper than the co. that went out of business. The price is competitive now kinda like a Quincy reed valve setup. I'd rather have the Kellogg design than the cheaper Quincy.

Probably fine but after my Eaton fiasco I'd never purchase another foreign compressor pump. I'll rebuild a 60 year old Quincy QR and have twice the pump as any of these clones.
 
I hear you. The tank this is built from was a Quincy-it lasted 0 days. Bought it new from northern and after plumbing it, it blew oil from the breather. Quincy sent another one, i installed it and it was worse. They finally gave up and Northern refunded my money and Quincy in an effort to compensate me-abandoned this compressor-get this- they said it was more money in shipping than they had into building it. I bought this pump to fix it. Funny thing is when we tore the old/new pump apart we found it was full off metal and not castings or ring material, but sabotage near as we could tell. It was like someone had poured odd scrap metal chunks into the pump while building it. i imagine it has something to do with ABAC closing plants and consolidating companies that have employees who are losing their very old jobs. My buddy who is a master engine builder examined the pump and rings and says he could fix with some honing-maybe ill fix it and have a spare-but the moral to this story is non of them are worth a shit any more.
 
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