Notes Page

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With a 12 ounce CO2 tank, you can get approximately 1400 shifts. This is with a 3/4" cylinder shifting a Honda F1 using a 2.5 inch shifter arm. The nitrogen tanks have a built in regulator that drops their pressure down to 700-900psi so that they will work with CO2 based equipment. Both tanks have a 13/16” (.820 major diam, 14 threads per inch) straight thread fitting that incorporates an oring.  This is a standard for paintball equipment in the US.

The inline paintball regulators will feed off of either liquid or gaseous CO2; there is no preference, so syphon tubes in the vehicle CO2 tanks are not necessary. The tank you use to refill your tanks needs a syphon tube, unless of course you don't mind holding the fill tank upside down when filling your small tanks.  Filling a tank with gaseous CO2 won't get you far.

 The paintball regulators I carry are very light, but not very precise. They don't need to be very precise, if they stay +/- 5 psi they will shift a race car just fine. Our system pressure was usually set at 110 psi.  They also should be used with at least one direct acting 3 way solenoid in the system or a pressure relief valve. The 3 way valve acts as a relief valve in that its valve poppet will raise off of its seat momentarily and vent pressure that exceeds its capacity.  While this valve is venting the rest of the system functions normally.  Even the venting solenoid will function normally if it is actuated. When actuated, the solenoid will take the slightly raised and venting poppet and pull it all the way to its actuated state which closes of the exhaust vent and pressurized the the shift cylinder. This need for a system pressure relief is incase the regulator valve momentarily sticks and over pressurizes the system, this is not that uncommon an occurrence with a simple valve like these, but in the 5 years we have used the regulators and solenoids at Cal Poly it has never been a problem that effected the operation of the system. I've had one school use the regulator without some kind of relief and they damaged some parts. Our shifters always used 2 direct acting 3 way solenoids, one for upshift and one for downshift.

Your shift system should incorporate an expansion chamber. This extra volume does several things, it lowers CO2 consumption by raising its temperature and it minimizes over pressure spikes.  In the past we have used a chassis tube for this, if planned ahead, it can really clean up the plumbing, especially if you are doing a pneumatic clutch

I actually prefer nitrogen tanks for race car shifting systems now because they are easier to fill and have a pressure gage that tells you how much gas is left in the tank. But, for FSAE they are going to weigh more because of the larger size and thicker walls required by the higher pressure they have to store the compressed gas at to get any worthwhile capacity. The CO2 is in a liquid state at a lower pressure with a thinner wall tank. The only way to check its contents is to weigh the tank because the gas pressure in the tank with the liquid CO2 is a function of temperature not how much is in the tank. If light weight is your priority, CO2 is lighter and works just fine. You just have to have multiple tanks and a digital scale handy to figure out how much is in a tank. If an extra 2 pounds doesn't scare you, the nitrogen is more convenient because it has a pressure gage that indicates how much is in it. It is also easier to fill, it has a little quick release fitting on the side that you can just hook a fill line up to.

At most race venues some one will have a high pressure nitrogen tank for filling tires or servicing shocks. For personal use, a scuba tank is a good idea, and adapters are available. A 20 ounce CO2 tank on a FSAE car is serious overkill.

Over filling a tank will cause it to pop the burst disk and scare the crap out of anybody standing near by. This is because filling past the rated capacity leaves less gas space in the tank. The less gas space left in the tank, the higher the internal pressure rise will be as the tank warms up after filling and also when sitting in the sun. We had a under our stewards lounge chair, it was neat to have snow at the Silverdome in May but he was a little jittery for a while. Using a scale will help avoid this, but even tanks filled to the correct level may discharge if left in the sun, especially the black tanks. These burst discs can easily be replaced once ruptured and are available at paintball gun stores

For any teams looking at a CO2 system, I'd purchase a fill station, see link.  We used one not quite so nice for several years, our kit didn't have the flexible hose and 2 extra valves. With this system you fill it while watching the digital scale to stop the CO2 when it gets to the right weight.

Digital scales for paintball CO2 tanks come in two varieties, a platform scale (a good buy) and a hanging scale. A hanging scale (example) is what most paint ball venues use as they fill tanks, I prefer a platform scale so that I can check any bottle in my inventory and don't have to find some where to hang it or somebody to hold it still. You should label each tank with its empty weight. These regulators require lubrication, each time a tank is screwed into the regulator, a drop of oil should be placed in the pin valve on the
tank.  The tank threads also should get some oil, these tanks can be a real bear to screw off sometimes.