hvlp

[Jay Pique]

Thanks, Mike. It's good to see you doing the right thing.

JP

[nailshooter41]

ljaques wrote:

[ljaques]

On 12 Feb 2006 21:44:01 -0800, with neither quill nor qualm, [e-mail] quickly quoth:

[eclipsme]

[brianlanning]

Judging from how long my PC pancake takes to fill from empty, you'll be waiting a long time. I'd say it's maybe two or three minutes to fill the existing tank. Depending on how big the extra tank is, it could take 15 minutes or more to fill, affecting the life of the pump. And I bet it would discharge in a matter of seconds. There's not even enough air in my compressor to take a wheel off a car with an impact wrench. It runs after every 2-3 lugs.

I think you'd be better off with a turbine system.

brian

[B a r r y]

I tee'd my 6 gallon PC compressor with a Milton quick connect between the pressure switch and regulator. One or two 11 gallon auxillary tanks can now be plugged in. The compressor is still used most of the time as designed with absolutely zero fuss.

Do they take a long time to fill initially? Yes! One key is to only use them when you need them and to store them full. I also keep the compressor full all the time. This gives you an initial charge of cool, condensed air. When all 28 gallons are charged, I can spray for a surprising amount of time with a touch-up gun before the compressor kicks in for a refill. By that time, I often need to move, reposition the hose, etc...

By inserting the tanks before the regulator, they all get charged to 135 PSI, then the air line pressure gets set to 40-50 PSI. I'll usually use another in-line regulator right at the tool for fine adjustments. If you leave the 11 gallon tanks charged, they're always ready to shoot a bunch of brads, finish nails or fill tires away from the compressor. The extra was a great use of $20.

Will this wear out the compressor faster? Of course! Can I spray a whole kitchen or entertainment center without waiting? Nope! Will this replace an 80 gallon unit or turbine? Definitely not. But all in all, the setup is surprisingly useful. I already owned the tanks (off-road tire air), so all I needed was less than $10 of hardware to build it.

[ljaques]

On Thu, 16 Feb 2006 06:50:50 -0500, with neither quill nor qualm, eclipsme quickly quoth:

Correct.

Yes, even a little 12v car tire compressor (if it didn't melt first) could pump enough air into a large tank to spray a set of cabinets.

You need X cubic feet of air at Y PSI for the gun. How you produce it doesn't matter.

[nailshooter41]

eclipseme wrote:

[eclipsme]

Thanks for the reply.

So the question becomes, how long will the tank last before needing to recharge?

Seems like a straight forward math question, but I don't have the critical information.

If we take a 10 gallon tank, pressurized to 120psi, then regulated to

40psi, how long can you draw 6cfm out of it before dropping below 40 psi? How many cubic feet of air is in 10 gallons at 120psi? How much at 40psi? 60?

BTW - Are these tanks safe at 120psi?

Thanks, Harvey

[Mike Marlow]

Ugh! That one would make my head hurt.

Yes - most of them are rated around 125psi.

[Art Greenberg]

To compute this, you need to know the following:

10 gallons (US) is about 1.55 cubic feet 120 psi is about 8.2 atm (14.7 psi = 1 atm) 40 psi is about 2.7 atm

I'll assume no temperature effects for simplicity (in reality, temperature changes will occur, and those changes will affect the actual amount of air available).

I also assume the discharge rate of 6 cfm is at 1 atm (probably fair).

You start with 1.55 cu. ft. * 8.2 atm = 12.7 cu. ft. of air in the tank. You end with 1.55 cu. ft. * 2.7 atm = 4.2 cu. ft. of air in the tank. So you have taken 12.7 - 4.2 = 8.6 cu. ft. out of the tank. At a rate of 6 cfm, that would take about 1.4 minutes, or 1 min 25 sec.

[eclipsme]

Wow. Nicely done!

I agreed to buy a 7 year old Sears 2hp, 20 gal, 220v, cast iron oiled with oil separator, used lightly, for $150.00, rather than mess with above, esp. for 1 1/2 minutes of air!

Sound good?

Harvey

[nailshooter41]

Just check the cfms generated at the pressure you want to run your selected gun. That compressor is probably a good machine that will last a long time, but it may not generate what you need to run a larger gun.

If you have your gun, check its requirements against the cfms generated by the Sears compressor. If your gun requirements are where some of the larger ones are (10-14 cfms at 50 - 70 lbs), you will be able to run your gun but you will have limited spray time as above.

The cast iron part sounds good; so does the 20 gallon tank. It is probably a CH compressor sold by them as their "Black Max" line. One of my buddies had one for a long time, and he used it all the time as his shop compressor and he liked it a lot.

Of course, YMMV.

Robert