building own air compressor: need advice on compressor pump


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Old 09-27-08, 09:31 PM
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Question building own air compressor: need advice on compressor pump

ok, im in the beginning stages of building an air compressor.
i have found two pumps that i think are ok.
here are links to them.

http://chicago.craigslist.org/sox/tls/856114761.html
and
http://chicago.craigslist.org/nch/tls/856019707.html

now, i know the 2nd link has the best cfm rating, but is it a quality compressor pump???

both links are oiled compressors, and the 1st link i have little to no info on the pump. the guy selling the 1st link pump said he put $50 into the rebuild of the pump and will sell it to me for $50- a great deal. but the other one is only $75.

here is the email the 1st link guy sent me:

There are numbers 265-103 on the bottom of the compressor. I listed this on craigslist before with the 33 gallon tank and pressure switch. Anyway but it came off 5hp 33 gallon 220v compressor. The tank and swich were scraped last week, so i have no idea on model numbers.


http://cgi.ebay.com/Craftsman-Profes...d=p3286.c0.m14


That is what it looked like. I believe all the compressor motors were the same.



SO PLEASE tell me anything and everything good or bad about these two, and which one you would choose.
Thanks alot for the help.

Jackson
 

Last edited by Jackson1; 09-27-08 at 09:44 PM. Reason: Icon Change
  #2  
Old 09-27-08, 10:37 PM
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Welcome to our forums Jackson,

I would say that the V style compressor would be better considering it looks like it could be possibly new.
I have the identical one waiting to go on one of my compressor units.
I believe I paid $69.00 for it brand new.

Before you start on this project you should be aware that if you build this compressor properly I can guarantee you will not be doing it to save any money.
Believe me, I speak from experience.

Compressor units have come down a lot lately and a new one with a head like you show would be less than $500.00 with a one year warranty to boot!

Click image:

Image courtesy of harborfreight.com
 
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Old 09-28-08, 07:29 AM
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Hi GregH, Thanks for the quik reply!
So do you think the ratings on the v-style compressor are legitamate or are they some odd spec that tricks me into thinking its good?

can i really expect 13.5 cfm@90psi?

also, is this compressor a good way to start off my build or is it cheap and it will wear out quik?

the v-style sounds too good to be true, am i missing something?

other name brand compressors like ingersoll rand can cost 500 just for a PUMP like this one.

thanks, Jackson
 
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Old 09-28-08, 08:39 AM
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If the compressor is capable of an actual 13.5 cfm you need to know it would take at least 5 true hp which is not the hp ratings you commonly see on consumer compressors.

If you are going to try for 13.5 cfm that 5 hp industrial motor would likely draw around 20 amps on a 220 volt circuit.

The most you can get out of a 15 amp 120 volt circuit is around 6 cfm @ 90 psi.

I would say that if you powered the V style pump at 6 cfm @ 90 psi and an actual 2 hp motor you might be able to use it on a regular circuit and may get reasonable life out of the pump.

I'll likely power mine up to around 8 cfm with a 3 hp industrial motor.

If you buy that v style compressor you would need to have the manufacturers specs before doing so as you would not have a clue as to what rpm and hp you would need.
If you don't have this info you would need a clamp on ammeter which you should have any way for a project like this and several motor pulleys to dial in the right rpm.
I do not have this info for my pump but I have a wide selection of pulleys on hand as well as an ammeter to set it up.

Again, building a reliable compressor is more than just hooking up a motor to a pump.
Add the cost of a clamp on ammeter to whatever you will spend.
 
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Old 09-28-08, 09:23 AM
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Part of my bussines what I do as electrician I do hook up alot of air compressor and here a quick run down so you can able dail in with good performace on the unit.

For the 1800 RPM motors you will need anywhere from 2˝ to 3 to 1 pully ratio.

Make sure you double check the compressor head some will state the max safe rpm you can run. { Most will useally are 1200 RPM or less depending on the set up }

If hard to start you should check the unloader valve to make sure they are working and you can downsize the motor pully one size down to overcome the hard starting.

For the 3600 RPM motor you will need to get 5 or 6 to 1 ratio

To check the current drawing when the compressor start on zero tank pressure it will read about 75% of motor amprage and it will rise when the pressure in the tank go up and just before the cutoff { pressure switch kick it out } it should be right below of the max motor amparage rating.

For the ampmeter I used anlong { not the digtial meter } the reason why I used that because I can able tell if it is running right when you read the " ripple " or bounce on the ampmeter if you have even pulse then you got it right but uneven then you have issue with something along the way.

once the compressor kick out draw the air down to the point where the it will kick in { start up } it should able start up without any issue but if wont start or buzz like heck you need to check the unloader valve or other related issues

some of the compressor the pressure switch do have unloader valve right on the switch.

For all the readers there is two critical item you have to remember is the safety valve and the drain valve.,

The drain valve have to be open up end of your day or useage to keep the amout of water or other stuff build up espcally true in cold weather you need to do it more often and also on hot humid day you want do that daily if used everyday.

Merci,Marc
 
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Old 09-28-08, 11:39 AM
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Hey guys thanks for all of the help.
I know how to hook it all up and put it together, and all the electrical stuff, but...

I really just need someone to tell me if i should get either of these two pumps:

http://chicago.craigslist.org/sox/tls/856114761.html
and
http://chicago.craigslist.org/nch/tls/856019707.html


or are these just junk? here is a link to the v-style compressors page.

http://www.harborfreight.com/cpi/cta...emnumber=93786

please suggest which one to get or tell me if they are just junk, and i should get a name brand.

thanks, Jackson
 
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Old 09-28-08, 12:39 PM
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I do a fair bit of work servicing all types of air compressors and know what a quality air compressor is.

I will say that the higher the quality (cost) the higher the duty cycle and life will be.
The manufacturer of these compressors will not tell you what the estimated number of hours service they will give so you have to decide how much you will use it.

If you are doing basic hobby work running the thing an average of 10 - 15 hours a month then any of the import units will last a long time.
But, if you are running the compressor almost daily then these units will not stand up.

Advising you on the options you have given us I would say the used V type would be better then the straight block 2 cylinder.
The guy says it is rebuilt but what exactly does that mean.

If it were me, considering the cost and amount of work to build this thing the new one from Harbor Freight would be a no brainer.

As I said, I have this V style pump waiting to be mounted and I am expecting it to last a long time.
 
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Old 09-28-08, 04:34 PM
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Normally the cast iron V type pump useally last longer than inline units { this is true with larger unit or two stage }

As what Greg was saying I will say about the same thing and also keep in your mind what the tank pressure you going ?? if you are under 120 PSIG you can use either single or two stage compressor { 140 PSIG is borderline for single stage }

But if used everyday myself I rather use hevey duty two stage unit i know it cost more over single unit but it will last much longer compared to light duty alum compressor unit.

Merci,Marc
 
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Old 09-28-08, 06:57 PM
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i will go with these last two posts, if you are going to be useing this compressor a lot, buy a good cast two stage compressor. if you are just a hobby user go with the v compressor and good luck.

life begins when the kids leave home and the dog dies
 
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Old 09-29-08, 06:31 AM
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I'll second the guys before me. If you are going to go through the trouble and expense of putting together your own comp., it does not make any sense to put a cheap pump on it. Buy a old cast iron, pressure lubricated, two-stage american made pump and rebuild it. You'll get a lot more use out of it, like 30 years maybe.
 
 

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