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Help me choose an air compressor for sandblasting and shop.


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#121 NUTNDUN OFFLINE  

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Posted February 23, 2011 - 03:58 PM

I am guessing this one here would work too other then having to run 240v to the pressure switch: MtrStarter, w/Relay, 240V, 32A, Switch - Magnetic Motor Starters - Starters and Contactors - Electrical : Grainger Industrial Supply

Just in case they are out of stock of the other one.

#122 NUTNDUN OFFLINE  

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Posted February 23, 2011 - 05:41 PM

Well I just ordered the starter that railman linked to. Total with tax and shipping was around $106 which still isn't bad considering the prices of a lot of the other ones I have been seeing. Thanks for the link Railman.

#123 olcowhand ONLINE  

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Posted February 23, 2011 - 06:11 PM

Now for a motor and you'll be in business!

#124 NUTNDUN OFFLINE  

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Posted February 23, 2011 - 06:15 PM

Now for a motor and you'll be in business!


I know the one I want which is a 7.5hp Baldor motor but I am waiting for an echeck payment to clear before I have the funds to purchase it :D

#125 olcowhand ONLINE  

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Posted February 23, 2011 - 06:17 PM

That is a great motor George, and at a $100 discount at least.

#126 NUTNDUN OFFLINE  

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Posted February 23, 2011 - 06:22 PM

He has two left in stock so hopefully he doesn't sell out or if he does hopefully he has some more.

I was also looking at Polar Air/Eaton's website and they sell their pumps separately. I figure worse case scenario if I find out this pump doesn't perform up to snuff the one Eaton pump would be perfect and it is $364 and I would still be just under $1300 for the whole rig. But I have a pretty good feeling this pump is still in great shape and will perform above my expectations.

#127 NUTNDUN OFFLINE  

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Posted February 23, 2011 - 07:57 PM

I just did the buy it now on the 7.5hp Baldor motor which was this one: NEW BALDOR 7.5HP ELECTRIC MOTOR AIR COMPRESSOR L1510T - eBay (item 390284253894 end time Feb-23-11 16:26:19 PST)

I went to Baldors site and downloaded the drawing for it because for a minute I was about to nuts because I thought the 215T frame was the perfect fit but the 2f measurement which is the front to back hole measurement is an 1 1/2" too long so I wanted to check and make sure the mounting plate had the hole at 5 1/2" inches also which it does.

Now the thing that concerns me is on the drawing list it shows starting current being 184 amps. I hope that isn't the case as it will trip the main breaker every time it starts. I will attach the drawing to this post.

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#128 RailmanB110 OFFLINE  

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Posted February 23, 2011 - 09:06 PM

George,
I'm glad you bought that starter. It should work fine with the motor you bought. I might even pick one up, just to have a spare. It's a nice pakage.

The amp rating you looked at is the max startup amps. It only lasts for a few miliseconds, & drops off rapidly. I ran a 25hp 3600rpm 3ph screw compressor for a while, & the motor was rated at 60 amps. The amps at startup ( from test reading) was something like 600, but the breakers, & fuses are made to deal with the momentary draw. It shouldn't be a problem.

Now all you need is a presure switch (with unloader?), & to select a pulley to match your pump cfm displacement. If you know the bore & stroke, you could probably make a pretty good guess as to the pump rpm your new Baldor 7.5 motor would pull.

I'm guessing your pump pulley belt goove is 5/8" wide at the wide edge. If you go to a BX belt, you'll only need to run 2 belts. My 5hp two stage, runs a 6 1/2" motor pulley, & the pump is 16". It uses only one 5/8" belt, & after 10 years of daily use, it's never even been readjusted. The trick is the large diameter drive pulley you can use with the low rpm motor. Definately use a tapered hub pulley setup on the motor. They offer several advantages, & run very true. Go to Burdens Surplus suply for belts, & pulley. They are good quality, & the prices are tought to beat.
Joe
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#129 Elecman OFFLINE  

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Posted February 24, 2011 - 02:33 AM


The amp rating you looked at is the max startup amps. It only lasts for a few miliseconds, & drops off rapidly. I ran a 25hp 3600rpm 3ph screw compressor for a while, & the motor was rated at 60 amps. The amps at startup ( from test reading) was something like 600, but the breakers, & fuses are made to deal with the momentary draw. It shouldn't be a problem.


Beat me to it.



NUTNDUN or I guess George if that is your name,

Baldor is definitely a good buy. I would say better than even Lesson, but they are very expensive. You got lucky though on the price!! The LRT of 53 Ft*Lbs is more than enough to start up a compressor. Keep us posted on this project.
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#130 WQDL753 OFFLINE  

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Posted February 24, 2011 - 04:28 AM

For your confidence benifit George,
I'll :ditto: all that's been said.
Your common slow or delay fuses/breakers wil handle some crazy spikes. (this is so the compreser in your ice box can work, and why your delicate electronics need extra protection, on a circuit that won't burn your house down if something goes wrong)
Baldor/reliance moters are built like tanks... enugh said.
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#131 NUTNDUN OFFLINE  

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Posted February 24, 2011 - 06:09 AM

Thanks for the input guys. Puts confidence back in my decision for buying the motor. I got worried at first when I checked the mounting hole dimensions on the nema chart but then confirmed it did have the mounting holes at 5 1/2". I figured worse case scenario I could have drilled the second set of holes myself.

I am hoping the parts lady at Ingersoll pulls through for me with some specs on the pump today. If I have to I can always pop off the head and measure the bore and stroke.

#132 NUTNDUN OFFLINE  

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Posted February 24, 2011 - 06:36 AM

While I am thinking about it, 6awg wire should be sufficient right? The compressor is going to be about 30' away from the breaker box. Also if the motor is 32 amp at full load, I remember hearing or reading something that the breaker should be 3 times the amp rating so would a 60 amp breaker be correct?

#133 NUTNDUN OFFLINE  

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Posted February 24, 2011 - 06:44 AM

Now all you need is a presure switch (with unloader?), & to select a pulley to match your pump cfm displacement. If you know the bore & stroke, you could probably make a pretty good guess as to the pump rpm your new Baldor 7.5 motor would pull.


I am not sure if I need an unloader, the compressor pump has a centrifugal unloader and I also have the adjustable unloader to put back on it.

#134 olcowhand ONLINE  

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Posted February 24, 2011 - 09:41 AM

While I am thinking about it, 6awg wire should be sufficient right? The compressor is going to be about 30' away from the breaker box. Also if the motor is 32 amp at full load, I remember hearing or reading something that the breaker should be 3 times the amp rating so would a 60 amp breaker be correct?


6awg will do fine. 60amp breaker should work fine also. That's what we've run on our 7.5 in the milk parlor for years.
Baldor are superb motors...one of the best in fact. You should be fine with the unloader system you already have.

#135 NUTNDUN OFFLINE  

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Posted February 24, 2011 - 04:15 PM

Alright guys. I got a call back from the Ingersoll service center. While they can't get me any parts because of the age of the compressor. She was able to find out the bore and stroke. She said it is a 5" bore, and the strokes are 3 1/4" and 3 1/2". I don't know which one is which though. I am guessing the first stage would have the longest stroke.

Hopefully this info helps as I don't know how to figure it out. I guess I could if I get the formula and get the volume of air per stroke and multiply by rpm.




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