compressed gasses

[terc04]

Hi all. I am looking for some advise/expertise in the area of compressed gasses. Namely, those used in paintball and your shifting systems. I
have two basic questions. Is there any way to be able to run a CO2 tank and regulator on it's side (laid down)? If not, what happens to your
valves, regulator, etc? The second question is, what about using N2 or HPA? My fear of these is that since they are not a liquid they will lose
a finite pressure for each shift and cause us to have to adjust our regulator after so many hours of usage. I am just looking for some info
from those with more experience than anyone here.
Thanks in advance,

Tim
Mizzou Racing

[terc04]

Hi all. I am looking for some advise/expertise in the area of compressed gasses. Namely, those used in paintball and your shifting systems. I
have two basic questions. Is there any way to be able to run a CO2 tank and regulator on it's side (laid down)? If not, what happens to your
valves, regulator, etc? The second question is, what about using N2 or HPA? My fear of these is that since they are not a liquid they will lose
a finite pressure for each shift and cause us to have to adjust our regulator after so many hours of usage. I am just looking for some info
from those with more experience than anyone here.
Thanks in advance,

Tim
Mizzou Racing

[Duke of URL]

My opionion:

Don't use fluid power unless you absolutely have to.
That includes hydraulics and pneumatics.

Try to find an electromechanical solution first.

Check out the Solenoid shifter forum.

[sticks]

Frankly, I would worry significantly about the drop in pressure of the HPA or N2 in comparison to C02, as they will both drop in roughly the same degree. With the advent of truly high pressure tanks though (4500psi and greater), I think the advantage in terms of consistent air pressure and endurance has to go to HPA. However, the the actuating pressures for something like a gear shift, the operating pressure should always be sufficient. The only exception in regard to competition might be the endurance event. In oder to be relatively secure in not sucking liquid C)2 from the tank while lying horizontally, an anti-siphon tube inside the tank and attached to the valve would be recommended. While not foolproof, it would significantly lessen the odds. I would have to agree that the use of liquid is theoretically less ideal then electromechanical, but with the specs I've seen on most electronic actuators, I would be slightly swayed toward liquids as well. Mechanically I am a big fan of the butterfly shifting design, but thats a bio/mechanical solution, so probably useless to your design plans.

[Charlie]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Duke of URL:
My opionion:

Don't use fluid power unless you absolutely have to.
That includes hydraulics and pneumatics.
<HR></BLOCKQUOTE>

So, what is your reasoning for this opinion? I don't think you will sway anyone by simply your opinion, but if there are good reasons to stay away from this technology lets hear them.

-Charlie Ping
Auburn University FSAE 1999-present

[Richard Lewis]

Personally I'd take a hydraulic clutch over a cable one anyday...

-------------------------
UVIC Formula SAE Team
http://members.shaw.ca/drax77/UVICFSAEcar.jpg
http://fsae.uvic.ca

[Brent Howard]

I am not on the shifter design team for calgary, but my understanding of the reasoning agains the pnumatic system is that the loss of pressure per shift is fairly high and the wall thickness of the container to hold enough gas at a high enough pressure would be fairly high....resulting in a heavy syatem. In drag racing i was told that they fill teh chassis with compressed air, howerver, they are only doing one short run, not long laps. The reason behind not using hydralic systems is that the weight again is higher than an electromechanical system. Also, you have the potential for leaks. With and electromechanical system the weight is light, and also easy to make a paddle. Think of how hard it is to press the brake pedal with your hand and think of doing something simaler everytime you need to shift. With an electricl stsem all you have to do is change the circut.

Brent

www.ucalgary.ca/fsae (http://www.ucalgary.ca/fsae)

[Richard Lewis]

I totally disagree about the weight of shifting system being a drawback for electro-pneumatic. I've not heard of anyone with an elecro-mechanical system that found push-pull solonoids of a reasonable weight. You're looking at (don't quote me) in the area of 8lbs just for the solonoid if I remember correctly.

I believe our electro-pneumatic system as implemented last year weighed less than 8lbs, including bottle, fittings, lines, solonoids, cylinder, etc.

I'm sure a fully mechanical system can be made for less weight. My question is, do you really want to take one hand off the wheel? /infopop/emoticons/icon_smile.gif

-------------------------
UVIC Formula SAE Team
http://members.shaw.ca/drax77/UVICFSAEcar.jpg
http://fsae.uvic.ca

[terc04]

Here is what I have come up with.

An old car of ours (1997 vintage) has an electromechanical shifter. Total system weight is 4.97 lb. The system worked well, but was hard on the F2's shift forks. Some creative EE thinking fixed the problem.

Our current cars (1998 - 2002) use a mechanical lever and either a push-pull cable or a system of rods and bellcranks. Most weigh in at under 2 lbs. Only a few of our drivers understand how to shift properly so we see a lot of missed shifts and bent or broken shifters.

Now for the new car. We have selected a tank, solenoid valves, cylinder, lines and fittings that has managed to keep the total weight at 2.62 lbs. We will also be able to integrate nicely with our ECU to give us a few handy features that will remain secret for the time being. The entire system is also well hidden on the car. Reliability is the only question still unanswered.

[Charlie]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by terc04:
Now for the new car. We have selected a tank, solenoid valves, cylinder, lines and fittings that has managed to keep the total weight at 2.62 lbs.

Reliability is the only question still unanswered.<HR></BLOCKQUOTE>

Hmmm... I'd say longevity is another question. Does that weight include the weight of the gas? And if so, how did you decide how much you'd need for the endurance event?

-Charlie Ping
Auburn University FSAE 1999-present

[terc04]

That weight is without gas. So add another few tenths.
In last years endurance I shifted 6 times, total. Three times up for third, and three times down for first. Our powerband and gearing was spot on for the course last year. There was only a couple of places that may have benefited from a little more torque, but I didn't feel as smooth when I tried second there. Afterwards I heard that my times were on par with the best of the day. If we do end up shifting more that can be counted on one hand then I also believe we will be covered. Conservation of volume, ideal gas law and a few safety factors lead me to this conclusion. We should have plenty of testing time to prove it as well.

Tim

[Charlie]

Compared to what we do, that sounds absolutely insane! We shifted more times than that in one lap.

The bottle is the heaviest part. If you've got a way to shift that seldom and still be competitive, hats off to you. I don't see how though. /infopop/emoticons/icon_confused.gif

How did you do in autocross? How many times did you shift there?

-Charlie Ping
Auburn University FSAE 1999-present

[MN]

Hi I have some question,Can I buy CO2 or Nitrogen in detroit?

[BeaverGuy]

I have a question about the cylinders used. It states that they have to be of proprietary design, does anyone else see that as having to be designed by the team?

[Charlie]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by BeaverGuy:
I have a question about the cylinders used. It states that they have to be of proprietary design, does anyone else see that as having to be designed by the team? <HR></BLOCKQUOTE>

Never heard that rule before. Can you reference where you got that from?

As far as getting C02 in Detroit, well its not exactly the middle of nowhere. I doubt you'll have any problems finding just about anything. We always have plenty with us as well.

[Matt Gignac]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by BeaverGuy:
I have a question about the cylinders used. It states that they have to be of proprietary design, does anyone else see that as having to be designed by the team? <HR></BLOCKQUOTE>

I'm pretty sure what this statement means is that the tank must be made especially for compressed gasses (i.e. not something you rig up on your own)

[BeaverGuy]

Rule 3.7.4
(b) The gas cylinder/tank must be of proprietary manufacture, designed and
built for the pressure being used, certified by an accredited testing
laboratory in the country of its origin, and labeled or stamped appropriately.

[NovaCat2005]

The gas cylinder/tank must be of proprietary manufacture...
I didn't know exactly how the rules were using the word proprietary so I looked it up on Webster (http://www.eonline.com/On/Holly/Shows/LewisE/), and I think I found how they use the word.
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Main Entry: 2proprietary
Function: adjective
Etymology: Late Latin proprietarius, from Latin proprietas
3: privately owned and managed and run as a profit-making organization
http://www.m-w.com <HR></BLOCKQUOTE>
Pressure vessels can be very dangerous, and can be deadly if not made properly. This is why they need to be certified then stamped or labeled. They should be hydrostatically tested every few years to recertify for use. I think we've all heard stories of welding tanks falling over, the nozzle breaks off, and then proceeds to fly through a cement wall. That's because compressed air tanks store a tremendous amount of energy (http://www.pbworld.com/pbenergy/caes.htm). There are many companies that make very lightweight composite wrapped pressure vessels for HPA Carltech (http://www.carltech.com/new-composite/new_othercomp.html)

Hopefully I've answered the question. http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Travis Garrison]

Just some advice from a paintballer...those composite wrapped tanks tend to cost $$ and weigh quite a bit. The CO2 tanks tend to be lighter for the shot count, I mean shift count http://fsae.com/groupee_common/emoticons/icon_smile.gif

The main reasons paintballers use HPA instead of CO2 would be cold weather (say below the 50F range) performance and consistency under rapid firing...liquid CO2 is not a solenoid valve's best friend which would be the down side for CO2, but if you are shifting rapidly enough to freeze a CO2 tank I think you'll want to abandon the project or go electric as you'd be going through quite a bit of gas during the endurance...

The last reason to think twice about HPA would be that its not the easiest thing to get your hands on...where as CO2 can be had at any welding shop.

In regards to the original question, laying down a CO2 tank will require an anti siphon tube if you want to keep the liquid out...typically a bent piece of copper tubing that screws into the back side of the valve and points towards the top of the tank when its in its expected position...downside is that if you rotate your tank you now have a siphon valve http://fsae.com/groupee_common/emoticons/icon_smile.gif

On the HPA loosing pressure, you are absolutely correct. Which is why paintballers tend to double regulate HPA systems...either way (CO2 or HPA) will give consistent pressures when setup properly, but HPA will tend to weigh more, and cost more.


-Travis Garrison
UW FSAE

[NovaCat2005]

Something for the Electrical and Computer Engineers to play with:
Good shot to shot consistency is important for paintball too. (http://www.actionvillage.com/is-bin/INTERSHOP.enfinity/eCS/Store/en/-/USD/DisplayProductInformation-Start;sid=7UjN9Cqb8nvNnWstcqoNXCBSSAh4KIU0nD0=?Pro ductID=20qsFAY7uJkAAAD3CmKlA_2t#)

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>but HPA will tend to weigh more <HR></BLOCKQUOTE>

Is this really true? My 20oz bottle is a handful when it is full. I thought those carbon fiber bottles were feather light!

[Cement Legs]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by NovaCat2005:
I think we've all heard stories of welding tanks falling over, the nozzle breaks off, and then proceeds to fly through a cement wall. <HR></BLOCKQUOTE>

Ummmm.... we chain them to a wall..... http://fsae.com/groupee_common/emoticons/icon_razz.gif

[Cement Legs]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Travis:
The last reason to think twice about HPA would be that its not the easiest thing to get your hands on...where as CO2 can be had at any welding shop.
UW FSAE <HR></BLOCKQUOTE>

I agree fully but I think it was Charlie who reminded us that the competition is in Detroit. May sound a little sarcastic, but using air would be a problem on the Moon not at FSAE. Heck you could probably get moonshine there if you were aloud to run on alcohol http://fsae.com/groupee_common/emoticons/icon_wink.gif.

Cheers

[NovaCat2005]

For anybody that likes graphs, I know i do http://fsae.com/groupee_common/emoticons/icon_smile.gif, there is a nice graph of co2 Pressure vs % Fill and Temperature on this site.

co2 Properties (http://www.warpig.com/paintball/technical/gasses/co2dynamics.shtml)

Also I found the weights of empty HPA composite tanks here. (http://www.scicomposites.com/paintball_cylinders.html)

The weight of 1 cu inch of liquid CO2 is 1.140 oz.

The weight of 1 cu inch of Air @ 4500psi is 0.210 oz.

Emperial Units, OH YEAH!http://fsae.com/groupee_common/emoticons/icon_cool.gif

[Travis Garrison]

was going to say that I wasn't sure of exact tank weights...but its right above me http://fsae.com/groupee_common/emoticons/icon_smile.gif



-Travis Garrison

[Travis Garrison]

OK, little bit of google research and I get ~3.0 to 3.5lbs for 4.5k psi 88ci tanks with a regulator

and ~3.25 lbs for a full 20oz CO2 tank...

You'll need a regulator for both unless you go with some of the fancier HPA tanks that come setup for low pressure (~120 psi - 250 psi range is typicall)

So I guess its a toss up...of course if you can't get 4500psi N2 in your area you might need something more along the lines of a 114ci tank....

I guess I'm used to the older 3k psi glass wrapped tanks...sorry about that...

I'm supprised that no one has mentioned the MAIN advantage to HPA systems: cheesey and possibly inapropriate graphics http://fsae.com/groupee_common/emoticons/icon_smile.gif

http://www.3a-paintball.com/category.asp?CategoryID=3

-Travis Garrison

[gug]

Adelaide's tank was on its side without a siphon tube. we brought a pressure release valve that sits downside of the regulator to get rid of any liquid flowing through the regulator, but i was planning to put it in if we had any troubles. we didnt have (that kind of) trouble, so it didnt go in.

of course, we also didnt get much testing time. maybe the problem would show itself if we tested more.

it probably also helped that our tanks were only 1/4 to 1/2 filled because they were overheating and blowing up. ive been searching for a picture of where our tank was positioned, but the rear verandah on our car keeps putting the tank in the shade and you cant see it. it was hidden away under the intake anyway, ontop of the gearbox (cbr600 f4 engine).

CO2 is easy to refill yourself. this is essential when the burst disc on your tank goes, covering the car in a spectacular cloud of steam while you are lining up to race. i refilled our tanks about 4 or 5 times over the competition ( because we were trying to keep them half full).

also im pretty sure that CO2 tanks are smaller than HPA tanks. this can help out alot when you have a tightly packaged car like ours. we couldnt have used anything bigger than a 12oz CO2 tank.

[winnie]

side cars (not all of them) have been running air shifters for quite a few years, a little tank and a little compressor. I don't know the hp loss but the system i saw weighed ~6.5kg. Sorry i can't remember the manufacturer......

[BrianD]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by MN:
Hi I have some question,Can I buy CO2 or Nitrogen in detroit? <HR></BLOCKQUOTE>

Yes. We have a couple suppliers that we get donations from. You can get a tank filled at any paintball store though. Check the yellow pages.

[RagingGrandpa]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by MN:
Hi I have some question,Can I buy CO2 or Nitrogen in detroit? <HR></BLOCKQUOTE>You can fill from any large CO2 or Nitro cylinder (I'm sure your U has some around, or you can rent from Airgas) but you'll need the adaptor from the tank to your bottle (ASA). The paintballers running HPA also use scuba bottles sometimes, and the paint shops sell adaptors for those bottles. There should be either a scuba shop or a paintball shop somewhere near you, so it's really not a problem.

[gug]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by RagingGrandpa:
You can fill from any large CO2 or Nitro cylinder (I'm sure your U has some around, or you can rent from Airgas) but you'll need the adaptor from the tank to your bottle (ASA). The paintballers running HPA also use scuba bottles sometimes, and the paint shops sell adaptors for those bottles. There should be either a scuba shop or a paintball shop somewhere near you, so it's really not a problem. <HR></BLOCKQUOTE>

if your going to refill the CO2 you need a liquid draw bottle. either that, or you can turn the bottle upside down http://fsae.com/groupee_common/emoticons/icon_smile.gif . i had no trouble hiring one, only AUD$30 for a month.

[MN]

Thanks BrianD,Raging Grandpa and gug!!
I will charenge AIR SHIFTER SYSTEM(UP and DOWN).

[Dave Cook]

I've been carrying some airshifter parts good for FSAE cars at www.paradigmmotorsports.com (http://www.paradigmmotorsports.com)

I can answer a few questions really quick, with a 12 ounce CO2 tank, you can get approximately 1400 shifts. The inline paintball regulators will feed off of either liquid or gas CO2. There is no preference, so syphon tubes are unneccesary. The paintball regulators are super light, but not precise. They don't need to be precise, if they stay +/- 5 psi they will shift just fine. They also should be used with direct acting solenoids incase the valve momentarily sticks and overpressurizes the system. With direct acting 3 way solenoids, (one for upshift and one for downshift) this extra pressure will just momentarily raise the valve poppet and relieve itself, not effecting the shift system operation at all.

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 higher pressure they have to store the compressed gas at to get any 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 funtion of temperature not how much is in the tank.

If weight is your priority, CO2 is lighter and works just fine. You just have to have multiple tanks and a digital scale.

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 and the scuba tank idea as a fill station is a good one.

For anyone looking at a CO2 sytem, I'd purchase this fill station from, http://www.3a-paintball.com/detail.asp?ProductID=58 We used one not quite so nice for several years, our 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.

A 20 ounce tank on a FSAE car is serious overkill.

Someone mentioned having tank discharged due to overfilling. 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 pressure rise will be as the tank warms up after filling and also when sitting in the sun. We had a blow off valve pop off next to our steward, it was neat to have snow 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 in the sun, especially the black tanks.

[MN]

Hi guys.
I have a idea Pressure of Air Tank is following 1.0MPa.But I have uneasiness.
So Is everyone following pressure in air tank??