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Another way to get 400 psi

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Another way to get 400 psi

Unread postAuthor: boyntonstu » Thu Jul 02, 2009 12:08 pm

Another way to get 400 psi

Almost any 12 V 200 psi tire inflator can be purchased for under $20.

Some can do 250 an a few claim 300.

O.K. We have 200 psi and we need to double it.

Let’s say that our chamber has a 4 cu in volume.

We have to compress 8 cu in into 4 cu inches to get 400 psi.

We need a piston whose face area is .5 sq inches.

A 0.8” diameter is almost .5 sq in.

If we apply 200 psi against a 0.5 sq in surface, we double the pressure to 400 psi.

All we need is a 4 cu in cylinder whose ID is 0.8”.

We apply the 200 psi from the pump against a free floating piston and push it to the bottom and out into the chamber.

Presto! 400 psi. Inexpensive, compact, light, portable and pretty fast!

BoyntonStu
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Unread postAuthor: twizi » Thu Jul 02, 2009 12:20 pm

i have truck air i have gone to 320psi its possible
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Unread postAuthor: boyntonstu » Thu Jul 02, 2009 12:25 pm

twizi wrote:i have truck air i have gone to 320psi its possible




Is you compressor 320 PSI?
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Unread postAuthor: Hotwired » Thu Jul 02, 2009 12:44 pm

The duty cycles on those little compressors are very poor. Run them for too long without a break and the magic smoke escapes.

http://www.spudfiles.com/spud_wiki/index.php/Compressor

Also:

If we apply 200 psi against a 0.5 sq in surface, we double the pressure to 400 psi.


I think you meant 200lb of force as opposed to 200psi.
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Re: Another way to get 400 psi

Unread postAuthor: Technician1002 » Thu Jul 02, 2009 12:58 pm

boyntonstu wrote:Another way to get 400 psi

Almost any 12 V 200 psi tire inflator can be purchased for under $20.

Some can do 250 an a few claim 300.

O.K. We have 200 psi and we need to double it.

Let’s say that our chamber has a 4 cu in volume.

We have to compress 8 cu in into 4 cu inches to get 400 psi.

We need a piston whose face area is .5 sq inches.

A 0.8” diameter is almost .5 sq in.

If we apply 200 psi against a 0.5 sq in surface, we double the pressure to 400 psi.

All we need is a 4 cu in cylinder whose ID is 0.8”.

We apply the 200 psi from the pump against a free floating piston and push it to the bottom and out into the chamber.

Presto! 400 psi. Inexpensive, compact, light, portable and pretty fast!

BoyntonStu


That works if you count all the dead spaces. :D Don't expect to get all 4 cu in out the valve into the chamber. :(
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Re: Another way to get 400 psi

Unread postAuthor: velocity3x » Thu Jul 02, 2009 1:22 pm

[quote="boyntonstu"]Another way to get 400 psi

Almost any 12 V 200 psi tire inflator can be purchased for under $20./quote]

If you'd consider carrying along extra equipment such as a compressor and battery (you may also need a solar panel to maintain the battery). why not go to a welding supply and rent or buy a bottle of gas. It's less to carry, more reliable and with 2,000+ psi at your command you'll fill the chamber in an instant.
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Unread postAuthor: POLAND_SPUD » Thu Jul 02, 2009 1:36 pm

well I know I say it all the time but you can build a fridge compressor for less than 20$ if you already have the compressor itself (from a junkyard or any other source)... and it's something that ofers good performance and lasts

I had a tire compressor for a few weeks and I've been using fridge compressors for the past few years and I got to tell you that there is no comparison between the two
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Unread postAuthor: boyntonstu » Thu Jul 02, 2009 1:54 pm

POLAND_SPUD wrote:well I know I say it all the time but you can build a fridge compressor for less than 20$ if you already have the compressor itself (from a junkyard or any other source)... and it's something that ofers good performance and lasts

I had a tire compressor for a few weeks and I've been using fridge compressors for the past few years and I got to tell you that there is no comparison between the two


You are probably right.

Also, with a medium sized inverter you can run the fridge compressor from a car battery.


However, my homemade design is cheaper in the field.

What pressure does yours pump to?


Modified or stock?

Thanks,

BoyntonStu
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Unread postAuthor: POLAND_SPUD » Thu Jul 02, 2009 2:42 pm

fridge compressors reach 300 - 400 psi with no problems... it what makes them different from tire pumps, which have problems getting past 250 psi mark

fridge compressors can reach more than 600 psi.. in fact maggotman has reached 1000 psi but that wasn't the safest idea and it was defienatelly too much

mind you that, although these things are not designed to reach 400 psi or more, they can handle it quite good but going past 600 psi puts a lot of strain on the motor and parts (as it's several times more than what they normally pump when they are still a part of a fridge)

ohh and no there are not altered in any way... they are cut off from a thrown away fridge.. converting one into an air compressor takes about 0.5 hour
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Unread postAuthor: joepage2008x2 » Sat Jul 04, 2009 9:03 am

My mini car compressor used to go up and over 400psi until one day i was trying my homemade bb gun up to 400psi and the piston seal blew and could not be fixed.
In my opinion a fridge compressor is the way to go, there usually free and are built well. Im searching for one at the moment, going to attatch it to a gas cylinder,and hey presto - i'll have a 40L compressor that can go over 300psi and it will cost me nothing.
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Unread postAuthor: Technician1002 » Sat Jul 04, 2009 10:43 am

A common complaint is the cheap ones run on 12 volts and fridge compressors can't. A proper inverter will work, but due to the higher power draw, a lighter socket won't provide the power. A properly wired inverter is required.

The inverters are not expensive. Mine was under $60 at Costco. I can run a 1/3 HP compressor or fridge. I use a regular compressor for my low pressure cannons. The volume delivered is much higher than a fridge compressor which is low volume at higher pressure.

It takes several minutes to fill the large cannon. The small cannon shooting marshmallows or tennis balls is simply load and fire, no wait.

Small Harbor Freight compressor running on an inverter in my trunk filling my t shirt cannon. The inverter is above the compressor to the left of the light. The black inverter in the shade doesn't show well. The red power switch and green power light can be seen.
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A discussion thread including details of an inverter installation to run this stuff away from AC power is detailed in this thread;
http://www.spudfiles.com/forums/how-to-pump-up-a-large-cannon-in-the-field-t18124.html
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Unread postAuthor: POLAND_SPUD » Sat Jul 04, 2009 4:45 pm

fridge compressors are designed to last long... lol just realize that they have to run for several hours everyday for several years...
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Unread postAuthor: Technician1002 » Sat Jul 04, 2009 5:31 pm

POLAND_SPUD wrote:fridge compressors are designed to last long... lol just realize that they have to run for several hours everyday for several years...


They are not designed to handle dirt and moisture. Keep it in mind. Expect shorter life with air which has both. An intake air filter is recommended. For the small inlet size, a new gas line filter works great.
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Unread postAuthor: feathers » Tue Jul 07, 2009 1:47 pm

its kinda funny reading all these crazy complicated ways to get to 400 psi i work at a paintball feild so i can get 68 cu in of 4500 psi regulated down to 800 psi coming out of the tank wouldnt it make sense to buy some sort of paintball hpa or scuba tank get it filled once then regulate it down to what you need
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Unread postAuthor: jeepkahn » Tue Jul 07, 2009 2:29 pm

feathers wrote:its kinda funny reading all these crazy complicated ways to get to 400 psi i work at a paintball feild so i can get 68 cu in of 4500 psi regulated down to 800 psi coming out of the tank wouldnt it make sense to buy some sort of paintball hpa or scuba tank get it filled once then regulate it down to what you need


A lot of people on here do just that, I lease a 50lb co2 bottle for $50 a year, and 15 for refills, and have adapters to run paintball regs and filler hoses to fill the cannons... I'm setup so that I ca run unreged(850psi) or reg down to 600 or add a reg to reduce to 150 to 200....
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