# Pressure regulator efficiency question

I heard that pressure regulators are not very efficient. Is this inefficiency sufficient enough to warrant using, say, 3 pistons on full air rather than 4 pistons on pressure regulators in places like catapults?

And also, are pressure regulators effective when the solenoids are kept in the “on” position for an extended (7-10 seconds) amount of time?

I believe that the pressure regulator has a very small loss / decrease of air when used. The pressure regulator will drop the pressure from say 100 to say 70 psi, effectively increasing the time to extend and decreasing the max force. at 100 psi, the force is .12 * 100 = 12 inlb of force. at 70 psi, this would be .12 * 70 = 8.4 inlb of force.
See the inventors guide insert
This also increases the time to extend the piston.

I would use only 2 cylinders with full pressure, mounted at ~~90 degrees to the thing you want to push.

This should not matter much, as there is little leakage. see http://en.wikipedia.org/wiki/Pressure_regulator for a fairly good explanation.

Does having a pressure regulator actually save any air, or does it just give you a constant force every actuation of the cylinders? Since the vex regulator is a relieving pressure regulator, doesn’t it just vent off the excess pressure, not actually saving any air?

The pressure regulator saves air yes, basicly you are saving air because the pressure regulator does not vent off air, it only restricts the air flow from the air tank to a certain PSI. Now the lower the pressure, the less air because less air has been forced into a certain volume hence a lower PSI.

If you don’t need the full power you would use a pressure regulator, because it saves you air. There is no deficiency to a pressure regulator. In addition to saving air, it gives you a constant force every actuation of the cylinders as well.

A real life application would be scuba diving gear. The air tank may hold up to 2000 PSI, but you won’t be able to breathe that, so a pressure regulator is used to only feed the air at a lower pressure, thus also allowing 2000 PSI in a tiny tank to last a long time.

So if you have 3 tanks for you launcher, do you want a regulator? I want good force, but I still want 12+ over the bar shots.

I’m fairly certain the pressure regulator does vent some air to the atmosphere, it’s a relieving pressure regulator and they by definition relieve excess pressure to atmosphere. What I’m not sure of is if it wastes less air than would be wasted by using full pressure for every stroke.

Anyway, I’m going to go do an empirical test with my robot’s launcher with and without a regulator. If it saves a lot of air, I’ll probably use it, but if not, I’d rather have my first launch have 100 psi to launch a ball in front of the enemy cylinder in autonomous.

With 3 tanks, you should be fine either way, my friend’s launcher (1497A) got 17 full field shots with 2.

3 tanks means still 12 pounds of force. 2tanks is still 12 pounds of force. This is because there is not an increase in psi, only capacity of air, meaning you will get more actuations. The choice of whether to use a pressure regulator, or not is not based on the number of tanks you have. It is based on the efficiency of your launcher the following is an example.

If your catapult launches 12 inches farther than needed (to make a full field shot) at 12 pounds of force per piston(100 PSI) then you are using more air than needed because you are technically over shooting. Now if you were to use a regulator which does not waste any air through venting, you would drop the PSI of the air going to the pistons from 100 to say 80. This means that you save 1/8 of your air(this may not be accurate because the air capacity is not linear to the PSI but you are saving air for sure). In turn you should be able to shoot 1/8 times more full field shots. That means you can make 9 shots instead of the normal 8. Note that this only works if you have a very efficient catapult to begin with, one that shoots farther than needed(some people have this and is very possible because there have even been 1 piston full field catapults).

In the end what I am saying is: A regulator is handy for getting more full field shots. However, if you have say 2 or 3 air tanks, you most likely wont be shooting more than 8 times a match, that is full field.

No, less pressure but the same volume of air is used each time. The regulator will allow you to maintain a constant (lower) pressure for more shots. lets say you loose 10psi with each shot, with no regulator the first shot would be at 100psi, the next at 90, then 80 etc. With the regulator set to 70psi, the first shot would be at 70 as well as the next three, at that point the pressure in the reservoir would be lower than 70 and the regulator would not help anymore.

Yes that is true, the regulator only helps up to a certain pressure, but after that the regulator doesn’t do anything anymore. But what I’m trying to say is up until that pressure you do end up saving air. So it’s save some air v.s. save no air at all.

Okay, so if I have 3 tanks, keeping the regulator on will help get more launches until it reaches a certain PSI. Right now, the regulator is tightened all the way.

Well if you want more than how many launches you are getting, which I think is a lot with you having 3 tanks, just slowly unscrew the pressure regulator until you barely make the shot.

Also note that after you drop below the restricted air pressure of the regulator, you wont be able to make a full field shot anymore anyhow so a regulator saves a lot of air.

Oh. So, when the pressure is at or above the limit of the regulator, we can make full field shots (say the limit is at 70psi). So from 70psi-100psi, I can make full field shots, but when the pressure drops below the limit (<70psi) then I won’t be able to make full field shots.

Am I correct?

Yes, if the catapult can make a full shot at 70 it’ll keep making shots until the pressure drops bellow 70.

No, Check out this Diagram.

I wouldn’t say that it wastes anything, it dousnt wast, just uses.

3 tanks with a regulator set at 70 psi should be able to get full field shots for a long while. Elastics to counter gravity will also help, but only to counter the weight of the metal or one ball too.

This is true, but only if you can do it with the lower psi in the first place.

Well I just found out that relieving means air is vented to atmosphere only if downstream pressure becomes higher than tank pressure, so no useful air is wasted. Thanks 7793r and Inspector Gadget