pressurizing cannon help

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pmruk
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Thu Sep 30, 2010 4:31 am

I joined the forum about a month or so ago and after having a good look around the forum thought it was time i had a go myself and the attached pic is the result, the problem i am having is i can only get it up to about 40 psi that is using a clark air compressor, what am i doing wrong ? would appreciate any help on this.

Moderator edit by MrCrowley: Topic title. Topic titles are there for you to describe the topic.
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jackssmirkingrevenge
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Thu Sep 30, 2010 4:52 am

What happens at 40 psi, does it start to leak or can't the compressor cope? If you block off the compressor pipe will it pressurise it any higher?

Very nice first effort by the way, given the copper construction you should consider buying a shock pump or adapting a fridge compressor in order to take it to 300 psi and beyond :)
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pmruk
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Thu Sep 30, 2010 5:32 am

jackssmirkingrevenge wrote:What happens at 40 psi, does it start to leak or can't the compressor cope? If you block off the compressor pipe will it pressurise it any higher?

Very nice first effort by the way, given the copper construction you should consider buying a shock pump or adapting a fridge compressor in order to take it to 300 psi and beyond :)

thanks for the reply, there is no leak and my compressor pumps no more than 40 psi the air transfer just stops, how do you mean block off the compressor pipe ?, this is my compressor I think it is good to 115 psi got a shock pump on the way to me but that might take a hell of a lot to pump to high pressure.

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MrCrowley
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Thu Sep 30, 2010 5:36 am

Don't mean to state the obvious but...is the regulator on the air compressor set to 40PSI?
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Thu Sep 30, 2010 5:38 am

Check the regulator knob (arrowed), tighten it clockwise and see if it makes a difference ;)

edit: damn you MrC :D
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hectmarr wrote:You have to make many weapons, because this field is long and short life
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pmruk
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Thu Sep 30, 2010 6:27 am

the regulator is at its highest setting and showing about 115 psi or so on the gauge, all new to me this and it has got me puzzled.
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Thu Sep 30, 2010 6:30 am

What about the filling attachment, maybe it has an in-built limiter for 40 psi?
hectmarr wrote:You have to make many weapons, because this field is long and short life
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pmruk
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Thu Sep 30, 2010 6:45 am

jackssmirkingrevenge wrote:What about the filling attachment, maybe it has an in-built limiter for 40 psi?

I am using a tyre inflator attachment but not sure if it has any kind of built in limiter will have to look into that one.
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Thu Sep 30, 2010 7:24 am

It would make sense, you don't fill up tires above 40 psi often. Look for a different attachment, maybe some quick disconnects or something.
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Crna Legija
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Thu Sep 30, 2010 8:56 am

you could put a male quick connect in the bottom of the blow gun and get rid of the tee, or leave it so you can still pump it with your shock pump
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pmruk
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Thu Sep 30, 2010 9:21 am

I have now gone straight through from the compressor to the valve on the cannon but still only pumps to 40 psi or so, i borrowed a shock pump from a friend and went from the 40 psi to about 100 psi but that was about 100 pumps or so.
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Big-E
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Thu Sep 30, 2010 11:28 am

How well maintained is your compressor? I have an old Sanborn compressor in my garage, used to be my brother's; It's been well maintained, and still runs like a champ; it delivers about 120 PSI consistently. mostly because my bro works in auto body, and takes good care of his equipment. I in turn do the same.

Here's some tips:

1: Change the oil, if the oil is old, the compressor may not deliver enough pressure due to a poor seal. may be a good time to check the intake filter as well.

2: check for wear. If your oil hasn't been changed in a long while, you may have worn rings on your piston, therefore a poor seal and low pressure. check your regulator for wear, as well as any popoff safety valves. the pressure switch may also be going bad in your compressor, causing the motor to switch off prematurely.

3: Check for leaks. Check all the plumbing for leaks, spray soapy water on all fittings and joints in the plumbing and check for air bubbles. if you find any, disassemble, apply teflon tape and reassemble.

4: Check the drain petcock on the tank. Look at the bottom of your compressor's tank, there should be a wingnut-shaped drain petcock. you are supposed to open this once a day to blow all the moisture and sediment from the tank, if not tightened enough, it will leak air. if you never purge your tank, accumulation of moisture and other crud will rust the tank out from the inside, and create pinhole leaks, which could also cause a loss of pressure.

Lastly, always have an extra pressure gauge handy, I've had them wear out on my compressors before, and they don't report the pressure correctly. always make sure your pressure gauge is working correctly by getting a second opinion.

PS, check your tire chuck (schraeder fill attachment) if it doesn't push in the valve stem completely, you will not be getting all that pressure into the chamber. I always use a schraeder chuck with a clip or screw on connection. I sometimes use a press-on chuck to quickly fill my pneumatics (the wand-type variety) and have never had a problem. there's definitely something limiting the pressure available, and if your reg says your putting out 115 PSI, then either your regulator went bad or there is something up with your air line or filler attachment.
Good luck man, hope you get it all sorted.
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Technician1002
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Thu Sep 30, 2010 1:54 pm

If the compressor is not at fault, either there is a restriction closing off flow when the cannon is up to pressure, or the gauge on the cannon is not indicating the correct pressure.

I have had the gasket in the fill adapter get grease in it which expands the rubber, which permits filling as air forces its way through, but when the differential is low such as the cannon rising in pressure the rubber closes back off. This is the most likely fault. Is the seal in the tire fill adapter replaceable? Is it swollen and soft?

How do you know the cannon is only at 40 PSI. Have you screwed the gauge into the compressor to test the gauge? In a rapid discharge situation of an air cannon, I have had gauges on the cannon go out of calibration.
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pmruk
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Thu Sep 30, 2010 3:19 pm

Technician1002 wrote:If the compressor is not at fault, either there is a restriction closing off flow when the cannon is up to pressure, or the gauge on the cannon is not indicating the correct pressure.

I have had the gasket in the fill adapter get grease in it which expands the rubber, which permits filling as air forces its way through, but when the differential is low such as the cannon rising in pressure the rubber closes back off. This is the most likely fault. Is the seal in the tire fill adapter replaceable? Is it swollen and soft?

How do you know the cannon is only at 40 PSI. Have you screwed the gauge into the compressor to test the gauge? In a rapid discharge situation of an air cannon, I have had gauges on the cannon go out of calibration.


there is no gauge on the cannon but when i pump it up with the compressor to 40 psi then connect a shock pump to the cannon the gauge on that show 40 psi i can then take it to 100 psi os so with the shock pump but take a while.

Big-E thanks for your advice I have had a good look at my compressor but all seems fine as far as i can tel.
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