Heatsink on a pistol mag?

[Sonic Reducer]

the problem every GBB has is cooldown. the only way so far to avoid it is shooting slowly, but thats no fun!

 

why not have fins on the back of the mag or bottom? increasing the surface area available to (comparatively) warm air will make the mag warm faster. a grid of cuts might weaken the structural integrity (grid like a pineapple hand grenade) but fins shouldn't weaken the body too much

[Punkypink]

I have a better idea. A variable volume gas reservoir. With gas filling it, the pressure forces the reservoir to expand to its max capacity, as the gas is used up, the volume decreases, helping to maintain a more constant gas pressure.

 

Question is, how to turn that idea into reality?

[Sonic Reducer]

I have a better idea. A variable volume gas reservoir. With gas filling it, the pressure forces the reservoir to expand to its max capacity, as the gas is used up, the volume decreases, helping to maintain a more constant gas pressure.

 

Question is, how to turn that idea into reality?

paintball guns have something like that called an expansion tank or something. basically it's a chamber after the regulator so the gas can evap without shooting liquid (liquid is a lot of gas).

 

i can see it working on like a gas M-60 or something, but it wouldn't really have anywhere to go on a GBB

[Punkypink]

I had an idea for GBB pistols for a sort of deformable bladder with a spring under tension when the bladder is full pushing a baseplate up against the deformable bladder in the mag. As the gas is used up, the movable baseplate pushes up against the bladder.

[ED-SKaR]

I had an idea for GBB pistols for a sort of deformable bladder with a spring under tension when the bladder is full pushing a baseplate up against the deformable bladder in the mag. As the gas is used up, the movable baseplate pushes up against the bladder.

 

 

Clearly you do not understand how GIM guns work!!

 

 

The gas self regulates by evaporating from liquid to gas form. green gas and 134a are both highly suseptible to temprature change, made worse by the fact that when the liquid gas evaporates it takes heat from its surroundings to do so. The only way to make a GIM gun using green or 134a more consistant is to keep the temperature of the gas chamber constant.

 

I have considered fitting a mini heater into the grips of my 1911, but there isn't enough space .

[scorch]

Heating systems use a similar sounding principle to keep a minimum working pressure, except its a vessel with a rubber diaphragm halfway down it, with pressurised air in one half instead of a spring.

[Seraphim989]

paintball guns have something like that called an expansion tank or something. basically it's a chamber after the regulator so the gas can evap without shooting liquid (liquid is a lot of gas).

 

i can see it working on like a gas M-60 or something, but it wouldn't really have anywhere to go on a GBB

 

 

An expansion chamber isn't a variable volume chamber. It just allows the liquid more time and space to expand before entering the gun. But since paintball guns use externals rigs, to fit it in a normal GBB youd REALLY have to shrink things. And since the principle work son giving the gas more space...it kinda defeats the purpose. But on external rig classics, you can do similar things.

[snowman]

Lots of the early external gas gun systems used an expansion tank.

 

If you look at photos of MGC's Beretta M12S, you'll see two tanks on the gas rig - One is 134a, the other an expansion tank.

 

 

Cheers.

[Punkypink]

Clearly you do not understand how GIM guns work!!

 

 

The gas self regulates by evaporating from liquid to gas form. green gas and 134a are both highly suseptible to temprature change, made worse by the fact that when the liquid gas evaporates it takes heat from its surroundings to do so. The only way to make a GIM gun using green or 134a more consistant is to keep the temperature of the gas chamber constant.

 

I have considered fitting a mini heater into the grips of my 1911, but there isn't enough space .

Er, having done thermodynamics at university level, it is my understanding that cool down occurs as a result of the mass of gas decreasing but being forced to stay at the same volume?

 

I'm not that good at explaining it, but this page seems to sum up my understanding of why cooldown occurs.

 

http://resources.schoolscience.co.uk/BAMA/...erosch2pg5.html

 

If the volume of the gas reservoir is variable, and is reduced as the gas is depleted, the gas molecues do not need to take in as much energy. Assuming the same amount of molecues in 2 examples, the example with the smaller volume would require less kinetic energy since the volume for the gas molecues to travel around is smaller. As a result, it draws less energy from the surrounding system, and thus, cools down less.

 

If anything, the reason the gas HAS to self regulate is because the volume is fixed despite a diminishing mass. If volume was variable and could correspondingly vary in accordance to mass, there will be a lot less of the "cool-down" effect because the gas molecues now need to draw a lot less energy from the system, and have more potential energy to expend in cycling the system.

 

Pressure exerted by gas is, at a molecular level, due to gas molecues moving and bouncing off a surface. The larger the volume the gas molecues need to travel, the more kinetic energy it requires for pressure to remain constant. In order to obtain a constant pressure as the number of gas molecues are decreased without the molecues needing an increase in kinetic energy, the volume and hence "ground" that each molecue needs to cover, is reduced in proportion to the amount of molecues left.

 

Fitting a heatsink or a mini heater, as you suggest, seems to be to be akin to taking painkillers for a headache. You're addressing the symptom of cooldown, and providing the gas molecues with the extra energy input it needs for them to get to the required level of kinetic energy in order to maintain constant pressure. Varying the volume of the gas reservoir on the other hand, is to tackle the problem at the root: reducing the amount of kinetic energy the remaining gas molecues need in order to maintain constant pressure, by reducing the amount of volume of the reservoir they're trapped in.

 

Heating systems use a similar sounding principle to keep a minimum working pressure, except its a vessel with a rubber diaphragm halfway down it, with pressurised air in one half instead of a spring.

Yes that concept is similiar to what I had in mind. 2 years Make that 3 years(including doing the 1st year twice) of torture sitting thru thermodynamic modules in engineering better be of some use!

[Danke]

You could probably find the bladder you're after in a bicycle rear shock. That's got a small chamber so a small gas cell.

[tome]

for other wacky ideas.... how you about introducing a hand pump inlet to the magazine so that you can put intoduce more energy into the system to off set the temperature drop?

[Yuri]

I'm no expert since I just barely passed my university thermodynamics, but to me it seems that the variable volume gas reservoir might not help. Most of the cooling happens when the liquid propellant turns into gaseous form. The expansion of the gas itself is so fast that it can be considered adiabatic, ie. the amount of heat it draws from it's surroundings is negligible. Also I'm fairly sure that when there's both gas and liquid propellant inside the gas reservoir, the internal pressure stays constant. When gas is taken out, some liquid turns into gas and the pressure stays the same.

[suicidalsnowman]

A variable pressure chamber could increase gas efficiency and the number of shots in a magazine as there is less energy loss, from the gas, in maintaining a constant pressure in the vessel. However, it wouldn't stop the cooldown caused by the phase change in the propane/134a as this is where the energy comes from. Energy has to be conserved, and in this case a rapid increase in volume and reduction of pressure in the gas for each shot will cause a drop in temperature.

[ED-SKaR]

Also I'm fairly sure that when there's both gas and liquid propellant inside the gas reservoir, the internal pressure stays constant.

 

 

This

 

 

 

Plus the fact that the gas needs to be in gas form to make the gun work. This is why green/134a GIM guns dont work upside down and why co2 bottles dont like beeing inverted.

 

 

The ONLY way you can keep a GIM gun with liquid pressure at the ranges we 'softers use stable is to keep the temperature of the gas chamber, and therfore the gas, stable. The only way to do this is to introduce more heat as the gun is fired.

 

The origonal idea of increasing the surface area of the outside of the gas chamber(magazine) is actually, from a scientific point of view, a rather good idea. Practically i don't believe you could increase the surface area enough to make a difference.

 

Having a heating unit hidden in the grips could be a workable idea, but you would need space for a battery somewhere on the gun. You would want a low voltage batery conected to a paralel series of small resistors fixed into the grip. You would have to do some heavy maths to make the batery last for a decent ammount of time (yay for discharge rates :s)

All in all its above my skill set. Plus i dont think it will make a practical difference, even in colder weather.

 

 

 

 

 

 

[Punkypink]

I'm no expert since I just barely passed my university thermodynamics, but to me it seems that the variable volume gas reservoir might not help. Most of the cooling happens when the liquid propellant turns into gaseous form. The expansion of the gas itself is so fast that it can be considered adiabatic, ie. the amount of heat it draws from it's surroundings is negligible. Also I'm fairly sure that when there's both gas and liquid propellant inside the gas reservoir, the internal pressure stays constant. When gas is taken out, some liquid turns into gas and the pressure stays the same.

I don't think pressure stays the same unless the gas and liquid molecues are able to obtain sufficient kinetic energy to allow them to continue hitting the sides of the reservoir as hard as they did when there were more molecues in the reservoir. That occurs when the gas cools beyond a certain point. Thermal energy simply cannot enter the system fast enough given how much has already been taken from the surrounding.

 

That is why some have proposed a system to inject more thermal energy into the area surrounding the magazine where it can then be absorbed by the gas molecues and converted into kinetic energy to maintain the pressure. The reason the internal pressure stays constant because energy is entering the system. If the system existed in a vaccum, then the pressure will drop when gas is taken out, even if volume stays the same.

 

I'm pretty sure that it is not needed for the sort of extreme temperature drop experienced in GBB under rapid firing conditions in order for it to work. The propellent, even if it IS stored in a liquid form, should only gain enough energy to transition to a gaseous state near the top of the mag, if not just after leaving the reservoir. I don't see there to be any reason for majority propellent to exist in a gaseous state well before a shot is fired, and if the propellent turns into a gaseous state only after leaving the valve, the thermal imbalance it thus introduces when energy for a state change is absorbed, will affect the system less.

 

Assuming it IS indeed true that propellents stay in a liquid form inside the magazine, I simply cannot see any good for the propellent to be in a gaseous state inside the chamber, since the reason it stays in a liquid form, is because it is subject to a high pressure in the 1st place. For the gas to change into a gaseous state surely means that pressure acting on the propellent has decreased. Thus a variable size reservoir only serves to maintain the propellent's pressure regardless of it being in a liquid or gaseous state.

 

 

A variable pressure chamber could increase gas efficiency and the number of shots in a magazine as there is less energy loss, from the gas, in maintaining a constant pressure in the vessel. However, it wouldn't stop the cooldown caused by the phase change in the propane/134a as this is where the energy comes from. Energy has to be conserved, and in this case a rapid increase in volume and reduction of pressure in the gas for each shot will cause a drop in temperature.

Hence a rapid decrease in volume? It doesn't have to reduce so that pressure stays exactly constant, but just enough to allow the liquid propellent to turn into a gaseous state, but reduce the amount of energy that the gas needs to remain at a similiar pressure.

 

[Stealthbomber]

FWIW, to make this workable you'd not only have to build a heat-sink onto the outside of the mag but you'd probably have to create something similar inside the mag as well.

 

It's all to do with surface area and thermal conductivity.

The mag can only conduct a certain amount of heat and simply fitting a heatsink to the outside isn't going to increase the rate that the heat (or lack of it) can be radiated through the metal.

The only way to conduct more heat is to have a larger surface area inside the mag to absorb the cold as well as an increased surface area outside to absorb heat.

 

All seems like a bit of a dead end to me.

Anything mechanical will take up so much space inside the mag that it will almost certainly offset any advantage it yields.

And increase cost significantly too.

 

no passive system (such as a heatsink) can be made small enough and effective enough that it'll have a significant impact without substantially altering the way the gun looks.

[Punkypink]

no passive system (such as a heatsink) can be made small enough and effective enough that it'll have a significant impact without substantially altering the way the gun looks.

not in our lifetime anyway. Give it another 100 years maybe. Who knows what nanotech will bring about.

[Sonic Reducer]

not in our lifetime anyway. Give it another 100 years maybe. Who knows what nanotech will bring about.

but by then we'll either be using laser pistols and lightsabers or sticks and stones

[Stealthbomber]

not in our lifetime anyway. Give it another 100 years maybe. Who knows what nanotech will bring about.

To be pedantic, anything using nano technology wouldn't be passive. It'd just be too small for us to see it working.

[Punkypink]

To be pedantic, anything using nano technology wouldn't be passive. It'd just be too small for us to see it working.

True that.

 

Man I wonder what airsoft will be like in 100 years. An idea for a new thread there...

[renegadecow]

The problem with a physical heat sink is that it can work just as well the other way around. Wear them in pouches outside your clothes and they'll be subjected to windchill and could possibly even lower your mags temperature. The only solution I could think of is having a dump pouch to hold your mags and have a couple thermal socks in to keep them warm. The cheaper ones go for $20 and can last for 12 hours. Do that plus tactical reloads.

[xlizer]

This is not the point of this thread, but being a physicist, I feel compelled to point this out. Punky, what you say about gas pressure and temperature relations is true, but (fortunately) not applicable to this system.

 

It's been said before, but when there is both gas and liquid in the mag, the pressure is self-regulating. That is, it relies solely on the vapor pressure of the liquid, which is a function of temperature. When gas escapes from the mag, the pressure lowers, so some of the liquid evaporates to fill the "void," as the gas obviously has a lower density than the liquid. This will happen until the vapor pressure is reached (very, very quickly).

 

The cooling comes form when the gas rapidly expands while leaving the mag/entering the blowback chamber.

 

All of these principles have been stated in this thread, but I wanted to straighten things out since there was some confusion as to what's going on.

[Punkypink]

What happens if you have a variable reservoir that is pressurised to decrease in size as the propellent is used up? What effect will that have on the performance of the propellent cycling the system itself?

[DrKalinka]

What i believe punky meant was that with a variable gas chamber, you try to keep the propellant in its liquid state inside the tank in the magazine. When firing, you let some of that liquid outside the tank to expand so it does not happen in the enclosed system. Changing the state away from the magazine will probably not cool down the mag that much.

 

The variable pressure chamber would be there to maintain the liquid form so that the propellant don't change state.

[dealingaces]

Just to throw my two cents in, agitating the cold liquid-soon-to-be-gas seems to help (shaking, etc). I opened my mags up and dropped two bearings into each to kinda rattle about and knock the gas up and it's allowed my P226 to shoot even with my apartment freezing (seriously, I'm wearing a turtleneck indoors. ARGH.). It seems to have upped the power a -bit-. I'll note, it's only by a little, and I can't be sure as I'm not chrono-ing, it just -feels- harder.