Super Soaker Central forums

Drenchenator · 05-13-2008, 05:53 PM

I'm sorry to be blunt, but that's the formula for the volume of a cylinder. A cylinder is a three dimensional object and therefore has volume, not area. And the important thing is not the volume anyway; it's the area of the base of the cylinder where the force is applied to build pressure.

Area is a units of length squared, and it's always going to be that by definition. Volume is units of length cubed. The formula pi(r^2)h has units of length cubed. r has units of length and is squared. h has units of length and is multiplied by r^2, making units of length cubed. Pi has no units, so the end answer will have units of length cubed and be a volume.

CROC · 05-13-2008, 06:06 PM

Alright. Would a reducer right after it be a problem with force, or not?

Drenchenator · 05-13-2008, 06:16 PM

No, it wouldn't matter at all. It won't change the area at the end of the pump rod, so it doesn't change anything.

Edit: I'm thinking right now that I might have not explained the whole thing well enough in the article. Too many equations, too few pictures or something. I'll get to it next week after finals.

aEx155 · 05-13-2008, 06:25 PM

So the CPVC is pressure rated?

Technically, the pump is subjected to the same force as the pressure champers, isn't it? When you pump, you have to get the pressure in the pump cylinder equal to that of the pressure chambers before the check valve leading to the pressure chambers opens, which would mean that the pump it subjected to the same pressure. It is, of course, intermittent and building (on a CPS gun it would be constant.) when you pump.

Drenchenator · 05-13-2008, 06:34 PM

Quote:

So the CPVC is pressure rated?

It seems from what CROC said that it is rated for some pressure. I know that it's mostly used for hot water though, so it has to deal with much more than just pressure. It looks like it takes 400 psi at 73.4 degrees F, which is good enough I suppose.

Quote:

Technically, the pump is subjected to the same force as the pressure champers, isn't it? When you pump, you have to get the pressure in the pump cylinder equal to that of the pressure chambers before the check valve leading to the pressure chambers opens, which would mean that the pump it subjected to the same pressure. It is, of course, intermittent and building (on a CPS gun it would be constant.) when you pump.

Yes, the pump feels the same pressure that the is in the chambers, not force. The force is the force the user needs to use to push in the pump at a given pressure. If you want to get technical, the force actually increases as you pump in a air pressure gun because the pressure will increase as the water flows in, but in this case since the pressure is constant we don't need to worry about that.

CROC · 05-13-2008, 07:09 PM

Wouldn't the pump only have to withstand the pressures of the PC for a while, with the check valves and all?? I know with LRT, it's only a certain pressure, so I may have the pump explode in between the two parts of my gun.

Random question, but would you guys (Admin) be able to merge this and my "Idea for a Homemade" thread? It would be a good refresher for those who have not seen my plans (Besides, I don't really want to revive my topic that's been dead for a year or so)

Drenchenator · 05-13-2008, 07:19 PM

Well, there really is only pressure in the pump area while it is being compressed. The check valves prevent backflow, so the pressure is only transferred through the water while they are open and the water flows from pump to chamber.

Is this the thread you are talking about? Just want to make sure before I do it.

CROC · 05-13-2008, 07:37 PM

I thought as much, that it would only be subjected to pressure once in a while.

Yes, that is the thread.

Drenchenator · 05-13-2008, 07:41 PM

Okay. Threads merged.

I really think now that I rewrite or update that article. It's important stuff, but I really didn't dive into many details and didn't provide any visuals of what's going on. As I said, I'll to get an updated version out next week.

Silence · 05-13-2008, 07:47 PM

Yes, the pump area is only pressurized while you're pumping, but that doesn't make a big difference in the end. Too much pressure is too much pressure, and it only takes a split second for the pipe to shatter. So it doesn't really matter how long the area is pressurized.

Also, Drenchenator, dimensional analysis isn't very widely known. To those that don't know, it's basically doing math with units to check formulas for consistency. Although it's only done rigorously in college, you might have encountered it in chemistry:
kg * moles/kg = moles
because the kilograms in the numerator and denominator cancel out. Using ratios like that to cancel out units is a good way to make sure certain physical quantities aren't magically appearing and disappearing.

So if you know that pressure is measured in PSI, or pounds per square inch, or force/area, then you can assume that you can take a quantity of force (whatever you apply to the pump) and divide it by the pump's cross-sectional area. Things do get more complicated with vectors - for example, torque=force*distance and work=force*distance, but in one case the two vectors are perpendicular, but in the other they are parallel.

CROC · 05-14-2008, 03:58 PM

I have to purchase my materials, but I will try the 3/4" pump, and if it is indeed too hard, I will just switch to a 1/2" pump, since the whole piping will be done in 1/2" anyways.

Drenchenator · 05-14-2008, 04:45 PM

Well, I thought we did the calculations to see if it would be too hard to pump! The numbers won't lie--as long as you put in the right ones. Now that I think of it, is 3/4" CPVC really have a 7/16" ID? That seems awfully too small, but perhaps about where 1/2" CPVC is in ID. What kind of 3/4" pipe are we talking about?

CROC · 05-14-2008, 05:04 PM

I was going to do the pump in 3/4", but the rest of it in 1/2", to clarify that statement.

We are talking about 3/4" CPVC (They were very crude measurements. I just measured it, its more like 5/8" ID)

Oops. My bad.

Drenchenator · 05-14-2008, 05:11 PM

Okay, I just want to get this straight: The rest of the gun is make from 1/2" CPVC, correct? Not 1/2" schedule 40 PVC?

With that diameter the pump force will be 9.2039 lbs, which it definitely well within the limits of human power.

CROC · 05-15-2008, 10:14 PM

I think the rest of the gun will be SCH 40, with some iron and copper pieces on it. I have a metal adaptor for it to fit my pump. (Most of the gun will be made with threaded PVC)

05-13-2008, 05:53 PM	#76
Drenchenator Administrator Join Date: Jun 2004 Location: Maryland Posts: 718 UserID: 320	Re: Question I'm sorry to be blunt, but that's the formula for the volume of a cylinder. A cylinder is a three dimensional object and therefore has volume, not area. And the important thing is not the volume anyway; it's the area of the base of the cylinder where the force is applied to build pressure. Area is a units of length squared, and it's always going to be that by definition. Volume is units of length cubed. The formula pi(r^2)h has units of length cubed. r has units of length and is squared. h has units of length and is multiplied by r^2, making units of length cubed. Pi has no units, so the end answer will have units of length cubed and be a volume. __________________ The Drenchenator, also known as Lt. Col. Drench. Last edited by Drenchenator : 05-13-2008 at 06:00 PM.

05-13-2008, 06:06 PM	#77
CROC Senior Member Join Date: Mar 2006 Location: Ontario, Canada (GTA) Posts: 289 UserID: 569	Re: Question Alright. Would a reducer right after it be a problem with force, or not? __________________ ~CROC~(c 'rock)n. -The master of ideas, and the occasional mod (Works with mr. dude) Mods: 3xA combat - CPS Turbine - Super Flash Flood - (working on CPH)

05-13-2008, 06:16 PM	#78
Drenchenator Administrator Join Date: Jun 2004 Location: Maryland Posts: 718 UserID: 320	Re: Question No, it wouldn't matter at all. It won't change the area at the end of the pump rod, so it doesn't change anything. Edit: I'm thinking right now that I might have not explained the whole thing well enough in the article. Too many equations, too few pictures or something. I'll get to it next week after finals. __________________ The Drenchenator, also known as Lt. Col. Drench. Last edited by Drenchenator : 05-13-2008 at 06:22 PM.

05-13-2008, 06:25 PM	#79
aEx155 Senior Member Join Date: Apr 2008 Posts: 305 UserID: 1517	Re: Question So the CPVC is pressure rated? Technically, the pump is subjected to the same force as the pressure champers, isn't it? When you pump, you have to get the pressure in the pump cylinder equal to that of the pressure chambers before the check valve leading to the pressure chambers opens, which would mean that the pump it subjected to the same pressure. It is, of course, intermittent and building (on a CPS gun it would be constant.) when you pump.

05-13-2008, 07:09 PM	#81
CROC Senior Member Join Date: Mar 2006 Location: Ontario, Canada (GTA) Posts: 289 UserID: 569	Re: Question Wouldn't the pump only have to withstand the pressures of the PC for a while, with the check valves and all?? I know with LRT, it's only a certain pressure, so I may have the pump explode in between the two parts of my gun. Random question, but would you guys (Admin) be able to merge this and my "Idea for a Homemade" thread? It would be a good refresher for those who have not seen my plans (Besides, I don't really want to revive my topic that's been dead for a year or so) __________________ ~CROC~(c 'rock)n. -The master of ideas, and the occasional mod (Works with mr. dude) Mods: 3xA combat - CPS Turbine - Super Flash Flood - (working on CPH)

05-13-2008, 07:19 PM	#82
Drenchenator Administrator Join Date: Jun 2004 Location: Maryland Posts: 718 UserID: 320	Re: Question Well, there really is only pressure in the pump area while it is being compressed. The check valves prevent backflow, so the pressure is only transferred through the water while they are open and the water flows from pump to chamber. Is this the thread you are talking about? Just want to make sure before I do it. __________________ The Drenchenator, also known as Lt. Col. Drench.

05-13-2008, 07:37 PM	#83
CROC Senior Member Join Date: Mar 2006 Location: Ontario, Canada (GTA) Posts: 289 UserID: 569	Re: Question I thought as much, that it would only be subjected to pressure once in a while. Yes, that is the thread. __________________ ~CROC~(c 'rock)n. -The master of ideas, and the occasional mod (Works with mr. dude) Mods: 3xA combat - CPS Turbine - Super Flash Flood - (working on CPH)

05-13-2008, 07:41 PM	#84
Drenchenator Administrator Join Date: Jun 2004 Location: Maryland Posts: 718 UserID: 320	Re: An idea for a homemade Okay. Threads merged. I really think now that I rewrite or update that article. It's important stuff, but I really didn't dive into many details and didn't provide any visuals of what's going on. As I said, I'll to get an updated version out next week. __________________ The Drenchenator, also known as Lt. Col. Drench.

05-13-2008, 07:47 PM	#85
Silence Administrator Join Date: Apr 2006 Location: Virginia Posts: 3,264 UserID: 576	Re: An idea for a homemade Yes, the pump area is only pressurized while you're pumping, but that doesn't make a big difference in the end. Too much pressure is too much pressure, and it only takes a split second for the pipe to shatter. So it doesn't really matter how long the area is pressurized. Also, Drenchenator, dimensional analysis isn't very widely known. To those that don't know, it's basically doing math with units to check formulas for consistency. Although it's only done rigorously in college, you might have encountered it in chemistry: *kg moles/kg = moles** because the kilograms in the numerator and denominator cancel out. Using ratios like that to cancel out units is a good way to make sure certain physical quantities aren't magically appearing and disappearing. So if you know that pressure is measured in PSI, or pounds per square inch, or force/area, then you can assume that you can take a quantity of force (whatever you apply to the pump) and divide it by the pump's cross-sectional area. Things do get more complicated with vectors - for example, torque=forcedistance and work=forcedistance, but in one case the two vectors are perpendicular, but in the other they are parallel. __________________ Forum Rules

05-14-2008, 03:58 PM	#86
CROC Senior Member Join Date: Mar 2006 Location: Ontario, Canada (GTA) Posts: 289 UserID: 569	Re: An idea for a homemade I have to purchase my materials, but I will try the 3/4" pump, and if it is indeed too hard, I will just switch to a 1/2" pump, since the whole piping will be done in 1/2" anyways. __________________ ~CROC~(c 'rock)n. -The master of ideas, and the occasional mod (Works with mr. dude) Mods: 3xA combat - CPS Turbine - Super Flash Flood - (working on CPH)

05-14-2008, 04:45 PM	#87
Drenchenator Administrator Join Date: Jun 2004 Location: Maryland Posts: 718 UserID: 320	Re: An idea for a homemade Well, I thought we did the calculations to see if it would be too hard to pump! The numbers won't lie--as long as you put in the right ones. Now that I think of it, is 3/4" CPVC really have a 7/16" ID? That seems awfully too small, but perhaps about where 1/2" CPVC is in ID. What kind of 3/4" pipe are we talking about? __________________ The Drenchenator, also known as Lt. Col. Drench.

05-14-2008, 05:04 PM	#88
CROC Senior Member Join Date: Mar 2006 Location: Ontario, Canada (GTA) Posts: 289 UserID: 569	Re: An idea for a homemade I was going to do the pump in 3/4", but the rest of it in 1/2", to clarify that statement. We are talking about 3/4" CPVC (They were very crude measurements. I just measured it, its more like 5/8" ID) Oops. My bad. __________________ ~CROC~(c 'rock)n. -The master of ideas, and the occasional mod (Works with mr. dude) Mods: 3xA combat - CPS Turbine - Super Flash Flood - (working on CPH)

05-14-2008, 05:11 PM	#89
Drenchenator Administrator Join Date: Jun 2004 Location: Maryland Posts: 718 UserID: 320	Re: An idea for a homemade Okay, I just want to get this straight: The rest of the gun is make from 1/2" CPVC, correct? Not 1/2" schedule 40 PVC? With that diameter the pump force will be 9.2039 lbs, which it definitely well within the limits of human power. __________________ The Drenchenator, also known as Lt. Col. Drench.

05-15-2008, 10:14 PM	#90
CROC Senior Member Join Date: Mar 2006 Location: Ontario, Canada (GTA) Posts: 289 UserID: 569	Re: An idea for a homemade I think the rest of the gun will be SCH 40, with some iron and copper pieces on it. I have a metal adaptor for it to fit my pump. (Most of the gun will be made with threaded PVC) __________________ ~CROC~(c 'rock)n. -The master of ideas, and the occasional mod (Works with mr. dude) Mods: 3xA combat - CPS Turbine - Super Flash Flood - (working on CPH)

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