pros and cons of dual regulators

[lamby]

Ok, I am not a "fluid dynamics" expert, so I am going to ask the people that might know.

Is there a benefit to running dual regulators for lets say a cocker (tank and main reg) as opposed to just running a single adjustable tank into the marker? I was thinking that if you eliminate the main reg from the gun and install a gas thru or a volumizer that you would have a faster recharge rate than having another reg that has to stablize to a fixed pressure after a shot. Plus you get the extra volume of air that is already regulated to what ever pressure you want.

Is there any logic behind this idea that I have, or is a minor issue in paintball. (I know in electronics, there is a disadvantage to dual regulators, but that is based on current draw as opposed to voltage) so in fluid dynamics I believe that pressure would act the same as voltage and flow rate would be the same as current.

Any insight would be helpful.

Any mechanical engineers out there with a specialty in fluid dynamics?

[RRfireblade]

It's not really a fluid dynamics issue.

The simple fact is a Regulator is just a pressure balancing act between the Air pressure in the tank and the spring/springs in the Reg.

Any Reg will have certain range of pressures that it can 'balance' within best.In a paintball world,we typically use(HPA)3000-5000psi and try to reg it down to 800 or 400 or what ever.That's quite a long and wide range and quite alot to ask of a single Reg.When,as in most markers,the operating pressure has a large effect over velocity,you really need to have a pretty precise final regulation for best overall consistancy.

IMO.

[lamby]

no, it IS a fluid dynamics issue.. that is why I need to see the formula. Becasue if what I think is correct. Dual regs will adversly affect flow while incresing the accuracy of pressure.

[Cristobal]

This is going to be a little light on equations, but maybe qualitatively helpful. (And if you've heard all this before then simply ignore )

The precision of any given regulator is based on a number of mechanical factors, and if I understand Palmer's previous posts on Deep Blue, one of the most important is the ratio of areas for the control surfaces. In mag terminology bigger the area of your downstream reg piston, compared to the area of your reg pin. IIRC, the Stab has something like a 70:1 ratio (which alone is better than most other regs) and the new fatty stab has close to a 92:1 ratio. The better the area ratio, the more accurate the regulation, and if you're dealing with LP where accuracy is particularly important, I can see how the Fatty could help.

The conventional wisdom behind running two regs is as follows: the output of any reg will vary slightly as the input pressure varies -- and the better your ratio, above, the less variation. You will get a more consistent supply from two regs than one, simply because the first will take most of any fluctuation in supply pressure out, and the small fluctuation coming out of the first reg will be smoothed over by the second reg which will see a much more stable input pressure. Hence, your output will fluctuate less for a given input fluctuation if you use two regs to get to your desired output pressure rather than just one. Palmer's site says that double regging gives you "appoximately 25% greater control and consistency".

This is one advantage that HPA has over CO2: the built-in reg on the bottle keeps a nearly consistent pressure output even as tank pressure drops. By the time the gas goes through the reg on your gun, you get rock solid pressure stability. Triple regging for paintball purposes is generally considered overkill as the improvement is usually too small to be important.

The problem, as you point out, with any reg is that there is an associated flow restriction and a certain amount of time it takes to recharge the downstream air to full pressure after a shot. The ability to recharge is affected by input pressure, which is why its suggested to keep at least 200 psi difference between the outputs of regs in series. Furthermore, regs perform better when there is a sizable difference between in an output pressures, and depending on the response of their springs they may work better for some pressure diffentials than others. I don't know the formulas to calcuation a regs response time given input and output pressures. However, if you look over in the official datat thread you'll see response curves for a number regs plotted graphically. My *guess* is that for regs separated by several hundred psi, you have a minimal drop in response time, and one which is probably worth the benefit in consistency.

Finally, I don't think that adding an extra volumizer would be a mixed benefit. True, the added volume means that after a single shot, the pressure drops less -- and I suppose if you took another shot soon after, you would feed a higher pressure into the valve than with a lower volume. But you still have to refill the air that you used on the shot, and it will take the reg just as long to do that with or without the volumizer. So the best solution is to improve your reg rather than add a volumizer. PMI (I think) has an interesting volumizer with a piston and spring inside it which is designed to shrink the volume as gas is drawn off during a shot -- hence keeping the pressure constant. Its an interesting idea in theory, but I have no idea how it works in practice.

[RRfireblade]

Originally posted by lamby
Becasue if what I think is correct. Dual regs will adversly affect flow while incresing the accuracy of pressure.

Well it IS obvious that dual regs will slow down the flow rate over a single Reg but that's not the defining issue as we already know recharge rates are currently faster than anyone can pull a trigger.

But if you feel better seeing that on paper,that's fine too.

[ezrunner]

triple regging & inverse output

Depending on the reg design, you get an inverse reaction.

Ie, as the input of the reg drops, the output rises. Some tanks seem to "spike" below 1000 psi because of this.

The dual reg getting a higher input pressure will smooth this out.

Tripple regging kills recharge rate as you loose the gradient. The gradient is the difference in the input pressure and the output pressure. Most regs work best with a 200psi or higher gradient. It really seems to have more todo with the output pressure and the reg design than anything else but I don't know the exact answer. The rule of thumb is to use 200psi higher input than output to keep your reg recharging fast.

The new conquest and the SP Maxflo vent when the pressure gets too high. They call this a "balanced" design. These regs reduce spiking. The Palmer stabilizer with the LP kit will vent because the piston has a small relief setup in it that will open at a certain pressure.

If you single reg you can stay close to output by using one of these regs but the dual reg system keeps you from getting hot gun penalties at the end of a game when your tank is low. That is why the higher end players use double regs so they don't get hot guns :)

-rob

[Buff]

PMI (I think) has an interesting volumizer with a piston and spring inside it which is designed to shrink the volume as gas is drawn off during a shot -- hence keeping the pressure constant. Its an interesting idea in theory, but I have no idea how it works in practice.

I have a piranha ProTS with palmer stab, LP at ~270psi, and an eforce frame with PD eye. It can ffire up to 20bps, but since I use an evoII w/o the new board, it shoots around 17bps. The Ram Air chamber is the volumizer that has the piston, and it isn't noticable when shooting slowely. However, under rapid fire it does improve consistency.
Buff

[lamby]

This is what I expected. I was always under the impression, from an engineering standpoint, that dual regs will be more consistant shot to shot. With that being said, and the known recharge time of different valves, is there a way to determain if a diffence in pressure from regulator one (the tank) of 1-4% will affect the output of the second regulator if the output of the second regulator is half of the input?

Is the only factor in this case the recharge rate of the second regulator?

[athomas]

You will get a recharge delay for each regulator in the system. Basically, it takes time for the regulators to react to any pressure change.

As previously stated, a regulator needs a pressure differential from input to output to regulate properly. A higher differential will allow for increased flow rate.

Volumizers work by having a large volume available for each shot. This allows the lower pressure guns to use less percentage of the available regulated air for each shot. While this can reduce fluctuation and starving, it can cause the regulator to not respond as quickly as it normally would if the volume is too large. A large volumizer volume can mean that not enough of the air volume is used to allow the regulator to respond properly. The other side of the coin would be no excess volume at all and all used air would have to be replaced by the regulator. At low gun pressures, the amount of regulated air required for each shot is critical so any regulator that didn't fully cause the volume to be recharged before the next shot would result in dropoff. These would be an extreme cases. Either extreme would be bad but I suspect that there is an ideal volume per pressure for any setup.

[lamby]

thank you for the input, there is some good data here.

I will have to find out what the recharge time is for different regulators. does anyone have any data for the recharge properties of different inline regs like the cp, palmer, torpido, messiah, vigilate, ect?

[Redkey]

recharge rates

the recharge rate of most regulators depends on the pressure differential on either side of the regs "valve". Large pressure differences mean there is less back pressure on the reg so the valve opens further allowing more air to flow through. As the pressure beings to equalize, the valve is pushed closed, reducing the air path and slowing the reg recharge rate. The plot below is an old stainless unireg running on a 99ish slide trigger cocker (transducer in gage port on reg) You're looking at almost .9 seconds to get back up to full pressure.



this plot shows what happens at about 10 balls a second. The pressure drops, but eventually levels off at some value where the reg flow matches the air requirements of the gun. The slope of the line can be used to determine the recharge rates at different pressure ranges. Notice how the line between 520 and 540 psi is much steeper than the line between 570 and 580. The first shot was taken at 600 psi... the next at 580, 560 and then a whole string at about 550 psi, where the reg holds pretty steady. Personally, I think the biggest thing is how well the gun functions with the differences in input pressures. I don't quite have the chrono working to track each of these shots but it will be interesting to see how the velocity behaves as the pressure drops. It will also be interesting to see what happens when the input pressure is 450 instead of 600.



oh yeah... the little hump you see on all the recharge upswings is the cocker cycling and using a little bit of air to push the ram/bolt forward. And, I think the little spike after the firing pulse is the ram pushing the bolt back... but I still need to confirm that.

The accuracy of the pressure values is probably +/- 2 psi or better.

[lamby]

sweet... Thank you very much.

Very good data there as well. I wich I had the equipment to do these measurements to find out what kind of reg is the most efficient at stabilizing a fixed pressure based on time. This data would be great to determain what the BEST main reg is. Throw all that hype out the window.