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Which air compressor?

Posted: Fri Apr 24, 2009 12:40 pm
by qwerty
Im thinking of making a cloud bbmg but im not sure what compressor to by i dont want to spend over £55 but i also want it to have some power.

Posted: Fri Apr 24, 2009 2:17 pm
by psycix
A good compressor costs some money.

Unless:
-You buy it via ebay or something like that
-You rip it out of a fridge (though you will need a reservoir and some patience for that. Low-ish flow, very high pressures)

Posted: Fri Apr 24, 2009 2:32 pm
by POLAND_SPUD
@ psycix
Low-ish flow
you can add a big tank or build several fridge compressors to overcome this problem... I've already build a tank and I am going to add new compressors in the near future

now I just start the fridge and go for a smoke and coffee... when I get back the tank is at 300 psi and I let it run to add more air... I don't know about you but reloading and setting/inspecting targets takes quite a lot of time for me so I never run out of air...

in fact 2 or 3 compressors would provide more air than I need... I am not sure if it would be enough for a BBMG but with a big enough tank and several compressors it should be ok...

the beauty of firdge compressors is that they are quite simple, expendable and you can moddify you 'filling station' as you wish...

so you can start with a very basic setup consisting of just a compressor and gauge - and then add a pressure switch, tank, more compressors or a fan for cooling the whole system

ok..... enough advertising fridge compressors..... (in this thread I mean) :wink:

Posted: Sat Apr 25, 2009 4:52 pm
by psycix
I have a big tank: my tnak!
Fire extinguisher. 30 bar reservoir, about 10 L

Multiple fridge compressors? That will draw a LOT of power. Dont start them at the same time.

Posted: Sat Apr 25, 2009 4:59 pm
by twizi
go to a goodwill store and and buy a mini fridge and rip out the pump

Posted: Sat Apr 25, 2009 9:31 pm
by POLAND_SPUD
@twizi not all mini fridges have fridge compressors - I think that Mr Crowley had one but it turned out it has something else

@psycix
most of them are 90W... of course they use more power when starting up

Posted: Sun Apr 26, 2009 3:00 pm
by psycix
90W?! I thought they drew way more.
When starting up, the lights in the room dim a bit, so I expected a 1kW+ during startup and at least a few hundred watts in normal operation.

Posted: Sun Apr 26, 2009 4:03 pm
by POLAND_SPUD
the first one was 90W as well as the one I use now... AFAIK most of them are close to 90 - 100W... usually their wattege is clearly indicated on the case

I seriously doubt it's 1 KW on startup...
the lights in the room dim a bit
there must be somehting wrong with wiring in your house

I don't experience such problems even when starting up a lawn mower (1500W)

Posted: Sun Apr 26, 2009 5:11 pm
by daberno123
The lights dim in my basement when I start my A/C compressor...

Posted: Sun Apr 26, 2009 6:31 pm
by POLAND_SPUD
lol it's just an electric motor - nothing more

ok I admit... I can hear that it is starting up if I am listening to the radio or watching TV but it's the same effect I get with any appliance with brush motors

Posted: Sun Apr 26, 2009 6:41 pm
by daberno123
I think it depends on what switch it has. My dehumidifier compressor is on a "turn" switch where power is applied gradually but the A/C compressor is on a light switch. The dehumidifier compressor starts without dimming the lights when power is gradually applied but if the switch is turned to full power and then plugged in the lights are dimmed. Doesn't seem to be a big deal really. :D

Posted: Sun Apr 26, 2009 10:54 pm
by jmccalip
I have a Kill-A-Watt electricity meter. I will test the fridge for start up watts, and run time watts if ya'll want.

Posted: Sun Apr 26, 2009 11:23 pm
by starman
Fridge compressors are amazingly efficient at the job they do. They just don't move the volume of air that standard air compressors move...focusing more on higher pressure of a much smaller volume.

I saw a label on a new fridge the other day that it claims to operate on the same power as a 75 watt light bulb.

Posted: Sun Apr 26, 2009 11:27 pm
by Technician1002
jmccalip wrote:I have a Kill-A-Watt electricity meter. I will test the fridge for start up watts, and run time watts if ya'll want.
The Kill-A-Watt meter is a nice tool. In AC power, Watts does not equal Volts times Amps like it does in DC except for a purely resistive load.

In AC Volts times Amps equals Volt Amperes. VA times the Power Factor equals Wattage. Power Factor can be either leading or lagging depending on if an inductor or capacitor has the biggest contribution.

I know.. Whoosh for most spudders. The fridge can draw a lot of Amps on start that will dim the lights in some houses, but it's not all Watts.
I saw a label on a new fridge the other day that it claims to operate on the same power as a 75 watt light bulb.
True. Don't be suprised when the label on the motor indicates a VA rating that is higher than the Wattage listed. This is normal. The motor is inductive and has a Power Factor of less than 1. The Amps if marked may be well above 1 amp.

On some (misleading advertising) the average power is near 75 Watts. The power while running may be quite a bit higher. Read the fine print. Does it run at 75 Watts or uses an average power of 75 Watts. :?:

Posted: Mon Apr 27, 2009 4:44 pm
by covey12
im not sure if the have ace hardware where you live, but they sell compressors for 100$ USD, im not sure what currency