Air tank pressure

[Fahad Muhammad]

We are a first year team and using electro-pneumatic gear shifting. The system conist of smc actuators powered by smc solenoid. Air is supplied through 9oz paintball tank.The problem that we are facing is that on a single shot airpressure is dropping drastically, about 4psi per shot, however the tank is initially charged upto 110 psi, we have checked for any leakages in the fittings all are properly sealed.What could be the reason for such sudden pressure drop? note that we are using compressed air in co2 paintball tank. Any suggestions would be higly appreciable
Cheers!

[Carrington]

you do realize that when air leaves the tank to move the actuators, it doesn't find it own way back into the tank?

[Fahad Muhammad]

No there is no feedback, the air doesnt gets back in to the tank

[Whis]

Um...

You're doing it wrong. Most co2 tanks use liquid co2, meaning that the vapor pressure inside the tank is fairly high. I am not going to tell you the pressures that most co2 tanks are typically filled to, because A) because I'm afraid you'll hurt yourself and B) they are filled by weight.

A simple google search was all it took to figure out the pressure...

Go find a certification class on how to properly fill tanks. And use a compressed air tank, please, not co2.

[Demon Of Speed]

Pressure regulator

[Kirk Feldkamp]

Originally posted by Whis:
Um...

You're doing it wrong. Most co2 tanks use liquid co2, meaning that the vapor pressure inside the tank is fairly high. I am not going to tell you the pressures that most co2 tanks are typically filled to, because A) because I'm afraid you'll hurt yourself and B) they are filled by weight.

A simple google search was all it took to figure out the pressure...

Go find a certification class on how to properly fill tanks. And use a compressed air tank, please, not co2.

I agree with the sentiment to get certified how to properly fill and maintain the tanks, but I don't see a huge problem with using CO2. There are a number of FSAE teams that have used it quite effectively for years without any issues. That said, I think it's an unnecessary complication for a first year team to spend any time developing a system like this. Clearly there are going to be more important things to worry about than a fancy shifter system. Driver training... vehicle troubleshooting and development... actually finishing your car in time... the list goes on and on.

[Chapo]

A standard paintball tank should be good for up to 3000psi, our carbon one is good for 4500, Couple that with a pressure regulator/stabliliser and you can have a constant 110 psi source that will run up to a thousand shots.

regards,

[CameronBeaton]

Originally posted by Kirk Feldkamp:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Whis:
Um...

You're doing it wrong. Most co2 tanks use liquid co2, meaning that the vapor pressure inside the tank is fairly high. I am not going to tell you the pressures that most co2 tanks are typically filled to, because A) because I'm afraid you'll hurt yourself and B) they are filled by weight.

A simple google search was all it took to figure out the pressure...

Go find a certification class on how to properly fill tanks. And use a compressed air tank, please, not co2.

I agree with the sentiment to get certified how to properly fill and maintain the tanks, but I don't see a huge problem with using CO2. There are a number of FSAE teams that have used it quite effectively for years without any issues. That said, I think it's an unnecessary complication for a first year team to spend any time developing a system like this. Clearly there are going to be more important things to worry about than a fancy shifter system. Driver training... vehicle troubleshooting and development... actually finishing your car in time... the list goes on and on. </div></BLOCKQUOTE>

I´m no expert on paddle shift system, but I do know a far bit on the pros and con of CO2 vs. air as I work and a paintball place and at some point or anoughter we used both.

My gut instinct would be to go with compressed air as, for reason I con´t remember, the CO2 becomes very unreliable if left out in the sun on a hot day and caused the guns to missfire.

Also on a cold day CO2 their a bitch to fill as it leaves your hands numb (possibly not a big issue if you just have to fill one though)

[Carrington]

One of the main downsides of CO2 is it will vent when heated, which can happen from sun or engine heat, so usable capacity will be less than you think. The upside is more options for compact bottles.

For compressed air, you should be using a nitrogen bottle and regulator. You will most likely need 2 regulators, (high and low pressure) since combination regulators are hard to find, and reliability is spotty.

Be sure to read the rules for requirements related to regulators, shielding, and bottle placement.

For an inexperienced team, simple is better. Not sure electro-pneumatic systems are for everyone, and a system thrown together without much thought, probably won't produce the expected results.

We have also found out the hard way that high-pressure air isn't readily available in many areas.

[kcapitano]

The reason you are seeing a pressure drop is because the air being used during the shift cant be replaced fast enough by your tank (this may seem obvious to some but no one had said it yet). In previous years I have used an expansion chamber upstream of the regulator. The expansion chamber holds an extra volume of air in your system so that when you shift you lose a smaller percentage of your air supply, therefore reducing the pressure loss in the system. You can make the chamber any size you like, but I would suggest make it big enough for two or three shifts.

As for air vs CO2 my team has been using CO2 for the past three years, and haven't had too many problems. As a safety measure most CO2 tanks will have a burst disk, which bursts when the pressure climbs too high. If the burst disk goes you will lose all the CO2 in your tank; this is a common site at paintball events on a hot summer day. That being said my team puts our CO2 tank next to front sprocket and have never blown a burst disk.

Most paintballers would tell you to run air, but this is a very different application. When CO2 is used on a paintball marker it is very easy for some of the liquid CO2 to get sucked into the marker, which can freeze the markers internals (and your hands). Mounting your CO2 cylinder upright and using an expansion chamber can prevent this problem.

In north america I prefer to run CO2 due to availability and cost, but you can run whichever you like. As long as you take some precautions with CO2 it can be just as good as air.

[Owen Thomas]

It seems to have been mentioned collectively, but to sum it up the reason you're losing so much pressure is because you need a return line. With a regulator on your tank you can manually set how much pressure is released each time you actuate, and they usually come with a spot for a return line.
Our team is using a similar system, 12Oz paintball CO2 canister with a pressure regulator going to a pneumatic ram. We did have a blowoff on a hot day, but aside from that, very reliable. I'm assuming since you called it a paintball tank, you got it from a paintball store or somewhere that vends paintball equipment. Go to them to get it filled and you don't need to worry about it (but still store it properly/carefully).
TL;DR - Get a regulator.

[Drew Price]

Originally posted by Carrington:
One of the main downsides of CO2 is it will vent when heated, which can happen from sun of engine heat, so usable capacity will be less than you think.


What?