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Help me choose an air compressor for sandblasting and shop.


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#61 DH1 OFFLINE  

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Posted February 09, 2011 - 09:46 PM

I remember back when I worked at the landscaper they bought a brand new air compressor for the shop and it came set at 175 max (cutout) we cut it down to 100 on, 120 off. At the time all we had for regulator was 140, max. The biggest air tool we had was a 1" impact. Best thing about the new compressor is we got new larger dia. air lines, even the 1/2 impact worked better with the new lines.

#62 tractormike OFFLINE  

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Posted February 09, 2011 - 10:02 PM

George, Here is a place to check on compressor parts and info, they have been in business for a long time and all they do is compressors. Marcuse and son, website is marcusecompressor.com. Good luck.

#63 WQDL753 OFFLINE  

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Posted February 10, 2011 - 03:36 AM

You could use a greese gun to push up the pressure, I know you can get over 1000 psi out of one, I've used them to remove press fit dowells and stuff before.

When you start doing the plumping don't skimp on pipe dia. I won't go into detail now on do's and don't do's, but take a look at the last page of the manual I uploaded for my paint gun... I don't know how to link to it but it's in misc. / binks 2001. You can get a good idea about it from that, and sandblasting is just as oil and water sensitive as painting. Oh, and don't forget the duty cycle rating for your tools.................

#64 NUTNDUN OFFLINE  

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Posted February 10, 2011 - 06:26 AM

I think an oil and water separator is a must with any air compressor. A secondary water filter isn't a bad idea either. More then likely we will end up powering the compressor with a gas engine but we still haven't decided for sure on that. No matter what we power it with we are going to put it outside in a covered area. I would like to run a 1" line in to the garage and split it off to various locations in the garage. I might put one outside too for the pot blaster. I need to get some fittings to perform the hydro pressure test. I am going to go out and get some measurements tonight for the fittings I need and will try and get them tomorrow.

#65 olcowhand ONLINE  

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Posted February 10, 2011 - 09:41 AM

If it were me, I'd definitely go electric. Even if you just ran a 5hp motor at the minimum recommended speed, you'd likely have plenty of air, & double what most of us have available. A 5hp heavy frame GE motor pulls just 22 amps max. On our milker vacuum pump, under load, they each just pull 17 to 18 amps. These are not the lightweight cheesy motors either. They weigh over 100lbs, & cast iron.

This is a rep pic, not my own.
Posted Image

Edited by olcowhand, February 10, 2011 - 09:46 AM.


#66 NUTNDUN OFFLINE  

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Posted February 10, 2011 - 10:01 AM

I would honestly rather go electric. I know we have the engine(s) to power it but that would also meant constant run when I other then sandblasting we wouldn't be using enough air to justify constant run. If I plan on running a max psi of 145 I think a 5hp motor would do fine also. It would also save almost $200 for a new motor. I will have to get a new switch as the one that is on there now I am sure is for 175psi. Which is no big deal and they are not that expensive. I am anxious to get this thing going but it will probably be a couple weeks till it is running.

With the weather supposed to warm up a little this weekend I am going to try and get the pressure testing done on the tank and then get some funds together to get a motor.

#67 caseguy OFFLINE  

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Posted February 10, 2011 - 05:03 PM

I would honestly rather go electric. I know we have the engine(s) to power it but that would also meant constant run when I other then sandblasting we wouldn't be using enough air to justify constant run. If I plan on running a max psi of 145 I think a 5hp motor would do fine also. It would also save almost $200 for a new motor. I will have to get a new switch as the one that is on there now I am sure is for 175psi. Which is no big deal and they are not that expensive. I am anxious to get this thing going but it will probably be a couple weeks till it is running. With the weather supposed to warm up a little this weekend I am going to try and get the pressure testing done on the tank and then get some funds together to get a motor.


You might try a local motor shop too George. They may have some refurbished motors that will be just as good as new for probably 1/2 the cost. Just a suggestion. Can't wait to hear of your results!

#68 mikebramel OFFLINE  

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Posted February 10, 2011 - 06:47 PM

A new Baldor or Leeson is about $450-500, refurb might be the way to go

#69 NUTNDUN OFFLINE  

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Posted February 10, 2011 - 07:59 PM

I will have to see what I can find for local motor shops. I wouldn't mind finding a used or refurbed motor.

#70 Elecman OFFLINE  

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Posted February 13, 2011 - 01:03 AM

Guys, I am new, and I think it is important that you all read this if you want to build your own compressor so you will not be disappointed because of a common misconception that I blame Tesla Roadster company for their infamous torque curve (which is a rev-torque curve btw). I know my electric motors pretty well and I just wanted to say it is not correct to say that the 3-phase and single phase AC induction motors is 100% torque at all times. In actuality, AC induction motors have low starting torque unless it is capacitor-start, capacitor run for single phase or a specially designed 3-phase motor like the design C or D which produce their max torque at stall.

The majority AC induction motors produce their max torque at what is know as "breakdown torque" that when exceeded will cause the motor's output torque to decrease. Here is what I mean:

405ecm08fig2.jpg

The correct way to read this curve is as a LOAD CURVE. That means it is not correct to say "if I run the motor at this RPM I get this torque figure". NO! This is what the torque curve looks like when the motor is started from a dead stop until it reaches full load with a fixed voltage and frequency supply common to our power outlets or industrial 3-phase electrical systems. The torque curve is also true in reverse. So if we allow the motor to get to full load operating speed and then apply a load beyond full load, the motor will increase its torque until the breakdown point is exceeded by the load which results in the motor decelerating to a stall if the load is the type that remains constant, even as the rpm decreases.

With air compressors the main issue will be the starting torque of the motor as the breakdown figure is more than enough to meet demands as the compressor gets to the full point (more load is applied near the end before shut off). I recommend that the compressor have an off load valve for easy start if you do not have the right kind of AC induction motor design. Now if this was a DC motor powered air-compressor then you have no worries. Or if you wish to invest some money into a sensor-less vector variable frequency drive, you can make 3-phase AC induction motors (for designs A and B which have low starting torque) have the starting torque performance of DC motors. For single phase stick with capacitor-start, capacitor-run motors.


I hope this helps.




EDIT: I figured that to be as helpful as I can, I will post the motors that are best suited for compressors for all of you to take out the guess work.


KEY: LRT=Lock rotor torque, BDT= Breakdown torque, FLT= Full load torque, FLHP= Full load horsepower. All torque data is in Ft*lbs


Leeson single phase AC induction:

131616BDT=19; LRT=19.2; FLT=7.5; FLHP=5 @ 3501 RPM
132044 BDT=30; LRT=26; FLT=11.17; FLHP=7.5 @ 3515 RPM
131537 BDT=37.7; LRT=41.1; FLT=17; FLHP=5 @ 1756 RPM
131538 BDT=35.3; LRT=46.5; FLT=15; FLHP=5 @ 1758 RPM
140120BDT=61.2; LRT=88.5; FLT=22.5; FLHP=7.5 @ 1754 RPM
140581 BDT=69.5; LRT=90.2; FLT=30; FLHP=10 @ 1751 RPM
131543 BDT=35.5; LRT=43.5; FLT=15; FLHP=5 @ 1753 RPM
140707 BDT=62; LRT=85.5; FLT=22.5; FLHP=7.5 @ 1755 RPM

DC motors for portable homemade air compressors for automobiles:

D&D Motor systems - MO-ES-80A 0.85 FLHP @ 750 RPM for 60 Minutes at 95 Amps @ 12 volts DC.
Leeson 108322 1 FLHP @ 1878 RPM cont. duty @ 83.2 Amps @ 12 volts DC.


This is just a partial list that does not have 3-phase motors listed or other motor manufacturers except for DC motors. Nor does it list current or voltage ratings. All that data is available from Leeson.com by simply typing in the model number I have boldfaced into the "product quick search" box on their site.



Prices for the motors are available from electricmotorwarehouse.com or Northerntool.com.

Edited by Elecman, February 13, 2011 - 02:35 AM.
Decided to list some motors to help those get started.

  • NUTNDUN, mikebramel, mjodrey and 4 others have said thanks

#71 mjodrey OFFLINE  

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Posted February 13, 2011 - 05:30 AM

Elecman,:welcometogttalk:Glad to have you with s.

That is a very useful post.

#72 NUTNDUN OFFLINE  

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Posted February 13, 2011 - 09:02 AM

Guys, I am new, and I think it is important that you all read this if you want to build your own compressor so you will not be disappointed because of a common misconception that I blame Tesla Roadster company for their infamous torque curve (which is a rev-torque curve btw). I know my electric motors pretty well and I just wanted to say it is not correct to say that the 3-phase and single phase AC induction motors is 100% torque at all times. In actuality, AC induction motors have low starting torque unless it is capacitor-start, capacitor run for single phase or a specially designed 3-phase motor like the design C or D which produce their max torque at stall.

The majority AC induction motors produce their max torque at what is know as "breakdown torque" that when exceeded will cause the motor's output torque to decrease. Here is what I mean:

[ATTACH=CONFIG]10382[/ATTACH]

The correct way to read this curve is as a LOAD CURVE. That means it is not correct to say "if I run the motor at this RPM I get this torque figure". NO! This is what the torque curve looks like when the motor is started from a dead stop until it reaches full load with a fixed voltage and frequency supply common to our power outlets or industrial 3-phase electrical systems. The torque curve is also true in reverse. So if we allow the motor to get to full load operating speed and then apply a load beyond full load, the motor will increase its torque until the breakdown point is exceeded by the load which results in the motor decelerating to a stall if the load is the type that remains constant, even as the rpm decreases.

With air compressors the main issue will be the starting torque of the motor as the breakdown figure is more than enough to meet demands as the compressor gets to the full point (more load is applied near the end before shut off). I recommend that the compressor have an off load valve for easy start if you do not have the right kind of AC induction motor design. Now if this was a DC motor powered air-compressor then you have no worries. Or if you wish to invest some money into a sensor-less vector variable frequency drive, you can make 3-phase AC induction motors (for designs A and B which have low starting torque) have the starting torque performance of DC motors. For single phase stick with capacitor-start, capacitor-run motors.


I hope this helps.




EDIT: I figured that to be as helpful as I can, I will post the motors that are best suited for compressors for all of you to take out the guess work.


KEY: LRT=Lock rotor torque, BDT= Breakdown torque, FLT= Full load torque, FLHP= Full load horsepower. All torque data is in Ft*lbs


Leeson single phase AC induction:

131616BDT=19; LRT=19.2; FLT=7.5; FLHP=5 @ 3501 RPM
132044 BDT=30; LRT=26; FLT=11.17; FLHP=7.5 @ 3515 RPM
131537 BDT=37.7; LRT=41.1; FLT=17; FLHP=5 @ 1756 RPM
131538 BDT=35.3; LRT=46.5; FLT=15; FLHP=5 @ 1758 RPM
140120BDT=61.2; LRT=88.5; FLT=22.5; FLHP=7.5 @ 1754 RPM
140581 BDT=69.5; LRT=90.2; FLT=30; FLHP=10 @ 1751 RPM
131543 BDT=35.5; LRT=43.5; FLT=15; FLHP=5 @ 1753 RPM
140707 BDT=62; LRT=85.5; FLT=22.5; FLHP=7.5 @ 1755 RPM

DC motors for portable homemade air compressors for automobiles:

D&D Motor systems - MO-ES-80A 0.85 FLHP @ 750 RPM for 60 Minutes at 95 Amps @ 12 volts DC.
Leeson 108322 1 FLHP @ 1878 RPM cont. duty @ 83.2 Amps @ 12 volts DC.


This is just a partial list that does not have 3-phase motors listed or other motor manufacturers except for DC motors. Nor does it list current or voltage ratings. All that data is available from Leeson.com by simply typing in the model number I have boldfaced into the "product quick search" box on their site.



Prices for the motors are available from electricmotorwarehouse.com or Northerntool.com.


Welcome to GTtalk. That is some good info. The Leesson motors were the ones I was looking at on Northern Tool. I will check and make sure the one I was looking at will work. With that being said the compressor pump does have a centrifugal unloader on it so that should help with the start up torque. I just gotta figure out if a 5hp will do what I need it to do since I only plan on running the compressor at 145psi max. I know it should make for easy work for the compressor pump but I gotta make sure the motor I get will get the job done.

#73 NUTNDUN OFFLINE  

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Posted February 13, 2011 - 09:11 AM

Well I do have some good news. The tank hydro pressure tested good up to 250 psi which is a 1.7 safety factor if we are running 145psi max.

I ended up have most of the fittings needed to plug what needed to be plugged to do the test. We did need to get a 3/4" NPT cap and also a 1/2" ball valve which I can use at a later time when we actually install the compressor. My intentions were to fill the tank up and keep the pressure washer turned off while pulling the starter rope to bring the pressure up. Problem was I didn't have a check valve to keep the pressure in.

So we ended up have to fire the pressure washer up and using the ball valve to slowly let pressure in and it worked great. We didn't have fine control of it but I was able to open it a little and close it quick to only allow 2 - 4 psi at a time.

After we were done with the pressure test we rolled the tank down the driveway so I could pressure wash it and the same with the compressor pump. While we were at the hardware store we got some almond colored paint for the tank and some satin black for the compressor pump :D

I am going to try and get some time today to clean up the tank and compressor some more and prep for paint. It is supposed to be warm by the end of the week and I will get some painting done then.

Here are some pics, dad snapped a couple while I was washing and I didn't know LOL

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#74 NUTNDUN OFFLINE  

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Posted February 13, 2011 - 09:14 AM

I forgot to add that while pressure washing the tank, I knew there was a bolt or two under the mounting plate that were left there and never dug out. Well I ended up finding about 8 bolts and the two plates that were plasma cut out to allow for easier access to the nuts.

#75 NUTNDUN OFFLINE  

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Posted February 14, 2011 - 08:01 AM

I got some time yesterday to strip the piping off of the compressor pump and remove the manifold from the tank and grind the weld smooth where it was mounted. I also got both the pump and tank wiped down with Naptha and got it all painted. The pump is finished, the tank still needs about two more coats of paint but I ran out, only got two cans thinking it would be enough. I painted the tank almond gloss and the pump is satin black. I will get some picks when the last couple coats are done drying and we get the pump put back in place. I will get olcowhand to make me up some Ingersoll Rand stickers to put on it then :D




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